TABLESAMPLE patch

*** /home/jcasanov/Documentos/2ndQuadrant/postgresql/src/test/regress/expected/tablesample.out	2014-12-16 01:10:00.229590530 -0500
--- /home/jcasanov/Documentos/2ndQuadrant/postgresql/src/test/regress/results/tablesample.out	2014-12-16 02:18:43.262035533 -0500
***************
*** 55,62 ****
    3
    4
    5
!   9
! (6 rows)
  
  SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
   id 
--- 55,61 ----
    3
    4
    5
! (5 rows)
  
  SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
   id 
***************
*** 65,68 ****
    5
  (2 rows)
  
- DROP TABLE test_tablesample;
--- 64,66 ----

======================================================================

diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 01d24a5..250ae29 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,38 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        one of:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of those sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability.
+        The optional numeric parameter <literal>REPEATABLE</literal> is used
+        as random seed for sampling.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..595737c 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  transam tsm
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/tsm/Makefile b/src/backend/access/tsm/Makefile
new file mode 100644
index 0000000..73bbbd7
--- /dev/null
+++ b/src/backend/access/tsm/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for access/tsm
+#
+# IDENTIFICATION
+#    src/backend/access/tsm/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/access/tsm
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = tsm_system.o tsm_bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/tsm/tsm_bernoulli.c b/src/backend/access/tsm/tsm_bernoulli.c
new file mode 100644
index 0000000..ad419b9
--- /dev/null
+++ b/src/backend/access/tsm/tsm_bernoulli.c
@@ -0,0 +1,174 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_bernoulli.c
+ *	  interface routines for BERNOULLI table sample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/access/tsm/tsm_bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tsm_bernoulli.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+
+
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	long seed;
+	BlockNumber tblocks;
+	BlockNumber blockno;
+	float percent;
+	OffsetNumber lt;			/* last tuple returned from current block */
+} BernoulliSamplerData;
+
+
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	long			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_GETARG_FLOAT4(2);
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size can be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks = RelationGetNumberOfBlocks(rel);
+	sampler->blockno = InvalidBlockNumber;
+	sampler->percent = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+
+	sampler_setseed(seed);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler = (BernoulliSamplerData *) scanstate->tsmdata;
+
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = 0;
+	else if (++sampler->blockno >= sampler->tblocks)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData *sampler = (BernoulliSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+	double			percent = sampler->percent;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/* Every tuple has percent chance of being returned */
+	while (sampler_random_fract() > percent)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler = (BernoulliSamplerData *) scanstate->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_setseed(sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	SamplePath	   *path = (SamplePath *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+	List		   *args = path->tsmargs;
+	Node		   *pctnode;
+	float4			percent;
+
+	SamplerAccessStrategy *strategy = (SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_SEQUENTIAL;
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (!IsA(pctnode, Const))
+	{
+		*tuples = baserel->tuples * 0.1;
+		PG_RETURN_VOID();
+	}
+
+	percent = DatumGetFloat4(((Const *) pctnode)->constvalue);
+	percent /= 100.0;
+
+	*tuples = baserel->tuples * percent;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/access/tsm/tsm_system.c b/src/backend/access/tsm/tsm_system.c
new file mode 100644
index 0000000..733e2ae
--- /dev/null
+++ b/src/backend/access/tsm/tsm_system.c
@@ -0,0 +1,164 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_system.c
+ *	  interface routines for system table sample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/access/tsm/tsm_system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tsm_system.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+
+
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockSamplerData bs;
+	long seed;
+	BlockNumber tblocks;
+	int samplesize;
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	long			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_GETARG_FLOAT4(2);
+	SystemSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size can be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks = RelationGetNumberOfBlocks(scanstate->ss.ss_currentRelation);
+	sampler->samplesize = 1 + (int) (sampler->tblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	sampler_setseed(seed);
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	BlockNumber		blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	sampler_setseed(sampler->seed);
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize);
+
+	PG_RETURN_VOID();
+}
+
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	SamplePath	   *path = (SamplePath *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+	List		   *args = path->tsmargs;
+	Node		   *pctnode;
+	float4			percent;
+
+	SamplerAccessStrategy *strategy = (SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_RANDOM;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (!IsA(pctnode, Const))
+	{
+		*pages = baserel->pages * 0.1;
+		*tuples = baserel->tuples * 0.1;
+		PG_RETURN_VOID();
+	}
+
+	percent = DatumGetFloat4(((Const *) pctnode)->constvalue);
+	percent /= 100.0;
+
+	*pages = baserel->pages * percent;
+	*tuples = baserel->tuples * percent;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..5598244 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesamplemethod.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 732ab22..4b011c7 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -88,10 +78,6 @@ static BufferAccessStrategy vac_strategy;
 static void do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -947,94 +933,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1089,6 +987,8 @@ acquire_sample_rows(Relation onerel, int elevel,
 	/* Need a cutoff xmin for HeapTupleSatisfiesVacuum */
 	OldestXmin = GetOldestXmin(onerel, true);
 
+	/* Seed the sampler random number generator */
+	sampler_setseed(random());
 	/* Prepare for sampling block numbers */
 	BlockSampler_Init(&bs, totalblocks, targrows);
 	/* Prepare for sampling rows */
@@ -1249,7 +1149,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1308,13 +1208,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
 /*
  * These two routines embody Algorithm Z from "Random sampling with a
  * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
@@ -1333,7 +1226,7 @@ double
 anl_init_selection_state(int n)
 {
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
+	return exp(-log(sampler_random_fract()) / n);
 }
 
 double
@@ -1348,7 +1241,7 @@ anl_get_next_S(double t, int n, double *stateptr)
 		double		V,
 					quot;
 
-		V = anl_random_fract(); /* Generate V */
+		V = sampler_random_fract(); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -1380,7 +1273,7 @@ anl_get_next_S(double t, int n, double *stateptr)
 						tmp;
 
 			/* Generate U and X */
-			U = anl_random_fract();
+			U = sampler_random_fract();
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -1409,7 +1302,7 @@ anl_get_next_S(double t, int n, double *stateptr)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 064f880..d5d703d 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -724,6 +724,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -950,6 +951,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			pname = sname = "Sample Scan";
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1067,6 +1071,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1319,6 +1324,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2147,6 +2153,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 7027d7f..1826059 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index d5079ef..613f799 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index e27c062..a1cba97 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..13af326
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,405 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "catalog/pg_tablesamplemethod.h"
+#include "executor/executor.h"
+#include "access/relscan.h"
+#include "executor/nodeSamplescan.h"
+#include "parser/parsetree.h"
+#include "storage/bufmgr.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate, int eflags);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+
+/*
+ * Initialize the sampling method - loads function info and
+ * calls the tsminit function.
+ *
+ * We need special handling for this because the tsminit function
+ * is allowed to take optional additional arguments.
+ */
+static void
+InitSamplingMethod(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(scanstate->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(scanstate->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(scanstate->tsmnexttuple));
+	fmgr_info(tablesample->tsmend, &(scanstate->tsmend));
+	fmgr_info(tablesample->tsmreset, &(scanstate->tsmreset));
+
+	InitFunctionCallInfoData(fcinfo, &scanstate->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	/* First arg is always SampleScanState */
+	fcinfo.arg[0] = PointerGetDatum(scanstate);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause cannot be NULL")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+}
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	EState	   *estate;
+	TupleTableSlot *slot;
+	BlockNumber	blockno = InvalidBlockNumber;
+	Snapshot	snapshot;
+	Relation	relation;
+	bool		found = false;
+	bool		retry = false;
+	OffsetNumber tupoffset, maxoffset;
+	Buffer		buffer;
+	Page		page;
+	HeapTuple	tuple = &(node->tup);
+
+	/*
+	 * get information from the estate and scan state
+	 */
+	estate = node->ss.ps.state;
+	snapshot = estate->es_snapshot;
+	slot = node->ss.ss_ScanTupleSlot;
+	relation = node->ss.ss_currentRelation;
+	buffer = node->openbuffer;
+
+	if (BufferIsValid(buffer))
+	{
+		blockno = BufferGetBlockNumber(buffer);
+		page = BufferGetPage(buffer);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	/*
+	 * get the next tuple from the table
+	 */
+	for (;;)
+	{
+		ItemId			itemid;
+
+		/* Load next block if needed. */
+		if (!BufferIsValid(buffer))
+		{
+			blockno = DatumGetInt32(FunctionCall2(&node->tsmnextblock,
+												  PointerGetDatum(node),
+												  BoolGetDatum(retry)));
+			/* No more blocks to fetch */
+			if (!BlockNumberIsValid(blockno))
+				break;
+
+			buffer = ReadBufferExtended(relation, MAIN_FORKNUM, blockno,
+										RBM_NORMAL, NULL);
+			LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+			node->openbuffer = buffer;
+			page = BufferGetPage(buffer);
+			maxoffset = PageGetMaxOffsetNumber(page);
+		}
+
+		tupoffset = DatumGetUInt16(FunctionCall4(&node->tsmnexttuple,
+												 PointerGetDatum(node),
+												 UInt32GetDatum(blockno),
+												 UInt16GetDatum(maxoffset),
+												 BoolGetDatum(retry)));
+		/* Go to next block. */
+		if (!OffsetNumberIsValid(tupoffset))
+		{
+			UnlockReleaseBuffer(buffer);
+			node->openbuffer = buffer = InvalidBuffer;
+			continue;
+		}
+		retry = true;
+
+		/* Skip invalid tuple pointers. */
+		itemid = PageGetItemId(page, tupoffset);
+		if (!ItemIdIsNormal(itemid))
+			continue;
+
+		tuple->t_tableOid = RelationGetRelid(relation);
+		tuple->t_data = (HeapTupleHeader) PageGetItem(page, itemid);
+		tuple->t_len = ItemIdGetLength(itemid);
+		ItemPointerSet(&tuple->t_self, blockno, tupoffset);
+
+		/* Found visible tuple, return it. */
+		if (HeapTupleSatisfiesVisibility(tuple, snapshot, buffer))
+		{
+			found = true;
+			break;
+		}
+	}
+
+	if (found)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   buffer,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation sequentially and returns the next qualifying
+ *		tuple while calling the sampling method functions.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+	node->ss.ss_currentScanDesc = NULL;
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	/*
+	 * Once upon a time it was possible to have an outerPlan of a SanpleScan, but
+	 * not any more.
+	 */
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	scanstate->openbuffer = InvalidBuffer;
+
+	InitSamplingMethod(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished thes can.
+	 */
+	FunctionCall1(&node->tsmend, PointerGetDatum(node));
+
+	if (BufferIsValid(node->openbuffer))
+	{
+		UnlockReleaseBuffer(node->openbuffer);
+		node->openbuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *node)
+{
+	if (BufferIsValid(node->openbuffer))
+	{
+		UnlockReleaseBuffer(node->openbuffer);
+		node->openbuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	FunctionCall1(&node->tsmreset, PointerGetDatum(node));
+
+	ExecReScan((PlanState *) node);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 491e4db..d69cc4e 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -628,6 +628,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2006,6 +2022,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2138,6 +2155,37 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4077,6 +4125,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4725,6 +4776,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_PrivGrantee:
 			retval = _copyPrivGrantee(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 0803674..83c5a25 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2325,6 +2325,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2444,6 +2445,33 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3152,6 +3180,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_PrivGrantee:
 			retval = _equalPrivGrantee(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index ae857a0..66b40dc 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3209,6 +3209,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index e3e29f5..7018512 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -578,6 +578,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -1589,6 +1597,17 @@ _outTidPath(StringInfo str, const TidPath *node)
 }
 
 static void
+_outSamplePath(StringInfo str, const SamplePath *node)
+{
+	WRITE_NODE_TYPE("SAMPLEPATH");
+
+	_outPathInfo(str, (const Path *) node);
+
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(tsmargs);
+}
+
+static void
 _outForeignPath(StringInfo str, const ForeignPath *node)
 {
 	WRITE_NODE_TYPE("FOREIGNPATH");
@@ -2391,6 +2410,33 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2420,6 +2466,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2887,6 +2934,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3092,6 +3142,8 @@ _outNode(StringInfo str, const void *obj)
 			case T_TidPath:
 				_outTidPath(str, obj);
 				break;
+			case T_SamplePath:
+				_outSamplePath(str, obj);
 			case T_ForeignPath:
 				_outForeignPath(str, obj);
 				break;
@@ -3228,6 +3280,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index a3efdd4..3a510dd 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,43 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1216,6 +1253,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1311,6 +1349,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 449fdc3..dffab29 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,8 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -332,6 +334,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +425,34 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids		required_outer;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	add_path(rel, (Path *) create_samplescan_path(root, rel, required_outer));
+
+	/*
+	 * There is only one plan to consider but we still need to set
+	 * parameters for RelOptInfo.
+	 */
+	set_cheapest(rel);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 659daa2..d0741f0 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -88,6 +88,7 @@
 #include "optimizer/restrictinfo.h"
 #include "parser/parsetree.h"
 #include "utils/lsyscache.h"
+#include "utils/sampling.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
 #include "utils/tuplesort.h"
@@ -219,6 +220,72 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we dont't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(SamplePath *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	SamplerAccessStrategy strategy;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(path->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples),
+					 PointerGetDatum(&strategy));
+
+	/* Mark the path with the correct row estimate */
+	if (path->path.param_info)
+		path->path.rows = path->path.param_info->ppi_rows;
+	else
+		path->path.rows = tuples;
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = strategy == SAS_RANDOM ?
+		spc_random_page_cost : spc_seq_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->path.param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->path.startup_cost = startup_cost;
+	path->path.total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 8f9ae4f..1056885 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3318,6 +3369,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 4d3fbca..0d78f27 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -446,6 +446,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 579d021..7da1a44 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2163,6 +2163,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 319e8b2..3c2c1b8 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,33 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+SamplePath *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	SamplePath	   *pathnode = makeNode(SamplePath);
+	RangeTblEntry  *rte = planner_rt_fetch(rel->relid, root);
+	TableSampleClause *tablesample = rte->tablesample;
+
+	Assert(tablesample);
+
+	pathnode->path.pathtype = T_SampleScan;
+	pathnode->path.parent = rel;
+	pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->path.pathkeys = NIL;	/* samplescan has unordered result */
+
+	pathnode->tsmcost = tablesample->tsmcost;
+	pathnode->tsmargs = tablesample->args;
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1921,6 +1948,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 1f4fe9d..9d0e05f 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -447,6 +447,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -611,8 +612,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10137,6 +10138,12 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample opt_alias_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10432,7 +10439,6 @@ relation_expr_list:
 			| relation_expr_list ',' relation_expr	{ $$ = lappend($1, $3); }
 		;
 
-
 /*
  * Given "UPDATE foo set set ...", we have to decide without looking any
  * further ahead whether the first "set" is an alias or the UPDATE's SET
@@ -10462,6 +10468,31 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $2;
+					n->relation = $1;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' func_arg_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' Iconst ')'	{ $$ = makeIntConst($3, @3); }
+			| /*EMPTY*/					{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13244,7 +13275,6 @@ unreserved_keyword:
 			| RELATIVE_P
 			| RELEASE
 			| RENAME
-			| REPEATABLE
 			| REPLACE
 			| REPLICA
 			| RESET
@@ -13419,6 +13449,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
@@ -13487,6 +13518,7 @@ reserved_keyword:
 			| PLACING
 			| PRIMARY
 			| REFERENCES
+			| REPEATABLE
 			| RETURNING
 			| SELECT
 			| SESSION_USER
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 4931dca..6d64a84 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -413,6 +416,19 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *r)
+{
+	RangeTblEntry  *rte;
+	TableSampleClause *tablesample = NULL;
+
+	rte = transformTableEntry(pstate, r->relation);
+	tablesample = ParseTableSample(pstate, r->method, r->repeatable, r->args);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -421,7 +437,7 @@ transformTableEntry(ParseState *pstate, RangeVar *r)
 {
 	RangeTblEntry *rte;
 
-	/* We need only build a range table entry */
+	/* We first need to build a range table entry */
 	rte = addRangeTableEntry(pstate, r, r->alias,
 							 interpretInhOption(r->inhOpt), true);
 
@@ -1121,6 +1137,26 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 9ebd3fd..cc91af2 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesamplemethod.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -760,6 +762,120 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+extern TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesamplemethod tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				actual_arg_types[FUNC_MAX_ARGS];
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the table sample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("table sample method \"%s\" does not exist",
+						samplemethod)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesamplemethod) GETSTRUCT(tuple);
+
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 * XXX: maybe make this ereport?
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = transformExpr(pstate, repeatable, EXPR_KIND_FROM_FUNCTION);
+
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Transform the rest of arguments ... */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *arg = transformExpr(pstate, (Node *) lfirst(larg), EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		fargs = lappend(fargs, arg);
+
+		actual_arg_types[nargs++] = argtype;
+	}
+
+	/*
+	 * Check if parameters are correct.
+	 *
+	 * XXX: can we do better at hinting here?
+	 */
+	if (initnargs != nargs ||
+			!can_coerce_type(initnargs, actual_arg_types, init_arg_types,
+						COERCION_IMPLICIT))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("wrong parameters for TABLESAMPLE method \"%s\"",
+						samplemethod)));
+
+	/* perform the necessary typecasting of arguments */
+	make_fn_arguments(pstate, fargs, actual_arg_types, init_arg_types);
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 24ade6c..56d1266 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -31,6 +31,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesamplemethod.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -343,6 +344,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4157,6 +4160,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesamplemethod tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the table sample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for table sample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesamplemethod) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+	}
+	appendStringInfoChar(buf, ')');
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8384,6 +8431,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index 94d951c..6832e0b 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesamplemethod.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesamplemethod_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index c7b745e..f311c74 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o rbtree.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..c07f01e
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,131 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Block sampling routines shared by ANALYZE and TABLESAMPLE.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+static unsigned short _sampler_seed[3] = { 0x330e, 0xabcd, 0x1234 };
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler is used for stage one of our new two-stage tuple
+ * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
+ * "Large DB").  It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table.  If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+
+void
+sampler_setseed(long seed)
+{
+	_sampler_seed[0] = 0x330e;
+	_sampler_seed[1] = (unsigned short) seed;
+	_sampler_seed[2] = (unsigned short) (seed >> 16);
+}
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract(void)
+{
+	return pg_erand48(_sampler_seed);
+}
diff --git a/src/include/access/tsm_bernoulli.h b/src/include/access/tsm_bernoulli.h
new file mode 100644
index 0000000..00cd069
--- /dev/null
+++ b/src/include/access/tsm_bernoulli.h
@@ -0,0 +1,20 @@
+/*--------------------------------------------------------------------------
+ * tsm_bernoulli.h
+ *	  Header file for BERNOULLI table sampling method.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/access/tsm_bernoulli.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TSM_BERNOULLI_H
+#define TSM_BERNOULLI_H
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TSM_SYSTEM_H */
diff --git a/src/include/access/tsm_system.h b/src/include/access/tsm_system.h
new file mode 100644
index 0000000..4021470
--- /dev/null
+++ b/src/include/access/tsm_system.h
@@ -0,0 +1,20 @@
+/*--------------------------------------------------------------------------
+ * tsm_system.h
+ *	  Header file for SYSTEM table sampling method.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/access/tsm_system.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TSM_SYSTEM_H
+#define TSM_SYSTEM_H
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TSM_SYSTEM_H */
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index bde1a84..5eb4811 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesamplemethod_name_index, 3281, on pg_tablesamplemethod using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3281
+DECLARE_UNIQUE_INDEX(pg_tablesamplemethod_oid_index, 3282, on pg_tablesamplemethod using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3282
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index eace352..54359f7 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5136,6 +5136,31 @@ DESCR("rank of hypothetical row without gaps");
 DATA(insert OID = 3993 ( dense_rank_final	PGNSP PGUID 12 1 0 2276 0 f f f f f f i 2 0 20 "2281 2276" "{2281,2276}" "{i,v}" _null_ _null_	hypothetical_dense_rank_final _null_ _null_ _null_ ));
 DESCR("aggregate final function");
 
+DATA(insert OID = 3285 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3286 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 23 "2281" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3287 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 21 "2281" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3288 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3289 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3290 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "700" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3291 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3292 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 23 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3293 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 21 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3294 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3296 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3297 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "700" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesamplemethod.h b/src/include/catalog/pg_tablesamplemethod.h
new file mode 100644
index 0000000..a0ce3ab
--- /dev/null
+++ b/src/include/catalog/pg_tablesamplemethod.h
@@ -0,0 +1,70 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesamplemethod.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesamplemethod.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLEMETHOD_H
+#define PG_TABLESAMPLEMETHOD_H
+
+#include "catalog/genbki.h"
+
+/* ----------------
+ *		pg_tablesamplemethod definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesamplemethod
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3280
+
+CATALOG(pg_tablesamplemethod,3280)
+{
+	NameData	tsmname;		/* tablescan method name */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesamplemethod;
+
+/* ----------------
+ *		Form_pg_tablesamplemethod corresponds to a pointer to a tuple with
+ *		the format of pg_tablesamplemethod relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesamplemethod *Form_pg_tablesamplemethod;
+
+/* ----------------
+ *		compiler constants for pg_tablesamplemethod
+ * ----------------
+ */
+#define Natts_pg_tablesamplemethod				7
+#define Anum_pg_tablesamplemethod_tsmname		1
+#define Anum_pg_tablesamplemethod_tsminit		2
+#define Anum_pg_tablesamplemethod_tsmnextblock	3
+#define Anum_pg_tablesamplemethod_tsmnexttuple	4
+#define Anum_pg_tablesamplemethod_tsmend		5
+#define Anum_pg_tablesamplemethod_tsmreset		6
+#define Anum_pg_tablesamplemethod_tsmcost		7
+
+/* ----------------
+ *		initial contents of pg_tablesamplemethod
+ * ----------------
+ */
+
+DATA(insert OID = 3283 ( system tsm_system_init tsm_system_nextblock tsm_system_nexttuple tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3284 ( bernoulli tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLEMETHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 41b13b2..b7f3129 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1212,6 +1212,26 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState		ss;
+
+	/* Sampling method functions. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmend;
+	FmgrInfo		tsmreset;
+
+	Buffer			openbuffer;		/* currently open buffer */
+	HeapTupleData	tup;			/* last tuple */
+
+	void		   *tsmdata;		/* for use by table scan method */
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index bc71fea..01d4795 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -225,6 +227,7 @@ typedef enum NodeTag
 	T_MergePath,
 	T_HashPath,
 	T_TidPath,
+	T_SamplePath,
 	T_ForeignPath,
 	T_CustomPath,
 	T_AppendPath,
@@ -413,6 +416,8 @@ typedef enum NodeTag
 	T_XmlSerialize,
 	T_WithClause,
 	T_CommonTableExpr,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 458eeb0..62c2c57 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -307,6 +307,23 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -507,6 +524,21 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * We are more generic than SQL Standard so we pass generic function
+ * arguments to the sampling method.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -751,6 +783,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 48203a0..8427b44 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -278,6 +278,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 7116496..064e336 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -870,6 +870,18 @@ typedef struct TidPath
 } TidPath;
 
 /*
+ * SamplePath represents a sample sacn
+ *
+ * args is list of parameters for the the TABLESAMPLE clause
+ */
+typedef struct SamplePath
+{
+	Path		path;
+	Oid			tsmcost;		/* table sample method costing function */
+	List	   *tsmargs;		/* arguments to a TABLESAMPLE clause */
+} SamplePath;
+
+/*
  * ForeignPath represents a potential scan of a foreign table
  *
  * fdw_private stores FDW private data about the scan.  While fdw_private is
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 75e2afb..97bc0ba 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(SamplePath *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 26b17f5..6c0a6cf 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern SamplePath *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+										  Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index e14dc9a..e565082 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -312,7 +312,7 @@ PG_KEYWORD("reindex", REINDEX, UNRESERVED_KEYWORD)
 PG_KEYWORD("relative", RELATIVE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("release", RELEASE, UNRESERVED_KEYWORD)
 PG_KEYWORD("rename", RENAME, UNRESERVED_KEYWORD)
-PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
+PG_KEYWORD("repeatable", REPEATABLE, RESERVED_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 4423bc0..0ba9768 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,10 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 48ebf59..1ba06b6 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..734cdc0
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,49 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+typedef enum SamplerAccessStrategy
+{
+	SAS_RANDOM,
+	SAS_SEQUENTIAL
+} SamplerAccessStrategy;
+
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Vitter reservoir sampling functions */
+extern double vitter_init_selection_state(int n);
+extern double vitter_get_next_S(double t, int n, double *stateptr);
+
+/* Random generator */
+extern void sampler_setseed(long seed);
+extern double sampler_random_fract(void);
+
+#endif /* SAMPLING_H */
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index f97229f..29244c7 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..970d4da 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesamplemethod|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..3d23ca1
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,67 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  6
+  7
+  8
+  9
+(10 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+DROP TABLE test_tablesample;
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index 62cc198..cf789dc 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 07fc827..852fed9 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -151,3 +151,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..5f6e828
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,12 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+DROP TABLE test_tablesample;

diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 01d24a5..250ae29 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,38 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        one of:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of those sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability.
+        The optional numeric parameter <literal>REPEATABLE</literal> is used
+        as random seed for sampling.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..595737c 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  transam tsm
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/tsm/Makefile b/src/backend/access/tsm/Makefile
new file mode 100644
index 0000000..73bbbd7
--- /dev/null
+++ b/src/backend/access/tsm/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for access/tsm
+#
+# IDENTIFICATION
+#    src/backend/access/tsm/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/access/tsm
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = tsm_system.o tsm_bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/tsm/tsm_bernoulli.c b/src/backend/access/tsm/tsm_bernoulli.c
new file mode 100644
index 0000000..fd87fab
--- /dev/null
+++ b/src/backend/access/tsm/tsm_bernoulli.c
@@ -0,0 +1,200 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_bernoulli.c
+ *	  interface routines for BERNOULLI table sample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/access/tsm/tsm_bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tsm_bernoulli.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+
+
+/* State */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	float4 samplesize;			/* percentage of tuples to return (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks = RelationGetNumberOfBlocks(rel);
+	sampler->blockno = InvalidBlockNumber;
+	sampler->samplesize = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+
+	sampler_setseed(seed);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler = (BernoulliSamplerData *) scanstate->tsmdata;
+
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = 0;
+	else if (++sampler->blockno >= sampler->tblocks)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData *sampler = (BernoulliSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+	double			samplesize = sampler->samplesize;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/* Every tuple has percent chance of being returned */
+	while (sampler_random_fract() > samplesize)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler = (BernoulliSamplerData *) scanstate->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_setseed(sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	SamplePath	   *path = (SamplePath *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+	List		   *args = path->tsmargs;
+	Node		   *pctnode;
+	float4			samplesize;
+
+	SamplerAccessStrategy *strategy = (SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_SEQUENTIAL;
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (!IsA(pctnode, Const))
+	{
+		*tuples = baserel->tuples * 0.1;
+		PG_RETURN_VOID();
+	}
+
+	samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+	samplesize /= 100.0;
+
+	*tuples = baserel->tuples * samplesize;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/access/tsm/tsm_system.c b/src/backend/access/tsm/tsm_system.c
new file mode 100644
index 0000000..dff7765
--- /dev/null
+++ b/src/backend/access/tsm/tsm_system.c
@@ -0,0 +1,187 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_system.c
+ *	  interface routines for system table sample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/access/tsm/tsm_system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tsm_system.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	SystemSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks = RelationGetNumberOfBlocks(scanstate->ss.ss_currentRelation);
+	sampler->samplesize = 1 + (int) (sampler->tblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	sampler_setseed(seed);
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as VACUUM for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	BlockNumber		blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	sampler_setseed(sampler->seed);
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	SamplePath	   *path = (SamplePath *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+	List		   *args = path->tsmargs;
+	Node		   *pctnode;
+	float4			percent;
+
+	SamplerAccessStrategy *strategy = (SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_RANDOM;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (!IsA(pctnode, Const))
+	{
+		*pages = baserel->pages * 0.1;
+		*tuples = baserel->tuples * 0.1;
+		PG_RETURN_VOID();
+	}
+
+	percent = DatumGetFloat4(((Const *) pctnode)->constvalue);
+	percent /= 100.0;
+
+	*pages = baserel->pages * percent;
+	*tuples = baserel->tuples * percent;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..34db3e6 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesample_method.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 732ab22..4b011c7 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -88,10 +78,6 @@ static BufferAccessStrategy vac_strategy;
 static void do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -947,94 +933,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1089,6 +987,8 @@ acquire_sample_rows(Relation onerel, int elevel,
 	/* Need a cutoff xmin for HeapTupleSatisfiesVacuum */
 	OldestXmin = GetOldestXmin(onerel, true);
 
+	/* Seed the sampler random number generator */
+	sampler_setseed(random());
 	/* Prepare for sampling block numbers */
 	BlockSampler_Init(&bs, totalblocks, targrows);
 	/* Prepare for sampling rows */
@@ -1249,7 +1149,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1308,13 +1208,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
 /*
  * These two routines embody Algorithm Z from "Random sampling with a
  * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
@@ -1333,7 +1226,7 @@ double
 anl_init_selection_state(int n)
 {
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
+	return exp(-log(sampler_random_fract()) / n);
 }
 
 double
@@ -1348,7 +1241,7 @@ anl_get_next_S(double t, int n, double *stateptr)
 		double		V,
 					quot;
 
-		V = anl_random_fract(); /* Generate V */
+		V = sampler_random_fract(); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -1380,7 +1273,7 @@ anl_get_next_S(double t, int n, double *stateptr)
 						tmp;
 
 			/* Generate U and X */
-			U = anl_random_fract();
+			U = sampler_random_fract();
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -1409,7 +1302,7 @@ anl_get_next_S(double t, int n, double *stateptr)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 064f880..d5d703d 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -724,6 +724,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -950,6 +951,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			pname = sname = "Sample Scan";
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1067,6 +1071,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1319,6 +1324,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2147,6 +2153,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 7027d7f..1826059 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index d5079ef..613f799 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index e27c062..a1cba97 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..27f5f05
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,404 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "catalog/pg_tablesample_method.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "storage/bufmgr.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate, int eflags);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+
+/*
+ * Initialize the sampling method - loads function info and
+ * calls the tsminit function.
+ *
+ * We need special handling for this because the tsminit function
+ * is allowed to take optional additional arguments.
+ */
+static void
+InitSamplingMethod(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(scanstate->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(scanstate->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(scanstate->tsmnexttuple));
+	fmgr_info(tablesample->tsmend, &(scanstate->tsmend));
+	fmgr_info(tablesample->tsmreset, &(scanstate->tsmreset));
+
+	InitFunctionCallInfoData(fcinfo, &scanstate->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	/* First arg is always SampleScanState */
+	fcinfo.arg[0] = PointerGetDatum(scanstate);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause cannot be NULL")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+}
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	EState	   *estate;
+	TupleTableSlot *slot;
+	BlockNumber	blockno = InvalidBlockNumber;
+	Snapshot	snapshot;
+	Relation	relation;
+	bool		found = false;
+	bool		retry = false;
+	OffsetNumber tupoffset, maxoffset;
+	Buffer		buffer;
+	Page		page;
+	HeapTuple	tuple = &(node->tup);
+
+	/*
+	 * get information from the estate and scan state
+	 */
+	estate = node->ss.ps.state;
+	snapshot = estate->es_snapshot;
+	slot = node->ss.ss_ScanTupleSlot;
+	relation = node->ss.ss_currentRelation;
+	buffer = node->openbuffer;
+
+	if (BufferIsValid(buffer))
+	{
+		blockno = BufferGetBlockNumber(buffer);
+		page = BufferGetPage(buffer);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	/*
+	 * get the next tuple from the table
+	 */
+	for (;;)
+	{
+		ItemId			itemid;
+
+		CHECK_FOR_INTERRUPTS();
+
+		/* Load next block if needed. */
+		if (!BufferIsValid(buffer))
+		{
+			blockno = DatumGetInt32(FunctionCall2(&node->tsmnextblock,
+												  PointerGetDatum(node),
+												  BoolGetDatum(retry)));
+			/* No more blocks to fetch */
+			if (!BlockNumberIsValid(blockno))
+				break;
+
+			buffer = ReadBufferExtended(relation, MAIN_FORKNUM, blockno,
+										RBM_NORMAL, NULL);
+			LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+			node->openbuffer = buffer;
+			page = BufferGetPage(buffer);
+			maxoffset = PageGetMaxOffsetNumber(page);
+		}
+
+		tupoffset = DatumGetUInt16(FunctionCall4(&node->tsmnexttuple,
+												 PointerGetDatum(node),
+												 UInt32GetDatum(blockno),
+												 UInt16GetDatum(maxoffset),
+												 BoolGetDatum(retry)));
+		/* Go to next block. */
+		if (!OffsetNumberIsValid(tupoffset))
+		{
+			UnlockReleaseBuffer(buffer);
+			node->openbuffer = buffer = InvalidBuffer;
+			continue;
+		}
+		retry = true;
+
+		/* Skip invalid tuple pointers. */
+		itemid = PageGetItemId(page, tupoffset);
+		if (!ItemIdIsNormal(itemid))
+			continue;
+
+		tuple->t_tableOid = RelationGetRelid(relation);
+		tuple->t_data = (HeapTupleHeader) PageGetItem(page, itemid);
+		tuple->t_len = ItemIdGetLength(itemid);
+		ItemPointerSet(&tuple->t_self, blockno, tupoffset);
+
+		/* Found visible tuple, return it. */
+		if (HeapTupleSatisfiesVisibility(tuple, snapshot, buffer))
+		{
+			found = true;
+			break;
+		}
+	}
+
+	if (found)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   buffer,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+	node->ss.ss_currentScanDesc = NULL;
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	scanstate->openbuffer = InvalidBuffer;
+
+	InitSamplingMethod(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished thes can.
+	 */
+	FunctionCall1(&node->tsmend, PointerGetDatum(node));
+
+	if (BufferIsValid(node->openbuffer))
+	{
+		UnlockReleaseBuffer(node->openbuffer);
+		node->openbuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *scanstate)
+{
+	if (BufferIsValid(scanstate->openbuffer))
+	{
+		UnlockReleaseBuffer(scanstate->openbuffer);
+		scanstate->openbuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	FunctionCall1(&scanstate->tsmreset, PointerGetDatum(scanstate));
+
+	ExecScanReScan(&scanstate->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 491e4db..d69cc4e 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -628,6 +628,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2006,6 +2022,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2138,6 +2155,37 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4077,6 +4125,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4725,6 +4776,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_PrivGrantee:
 			retval = _copyPrivGrantee(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 0803674..83c5a25 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2325,6 +2325,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2444,6 +2445,33 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3152,6 +3180,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_PrivGrantee:
 			retval = _equalPrivGrantee(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index ae857a0..66b40dc 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3209,6 +3209,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index e3e29f5..7018512 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -578,6 +578,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -1589,6 +1597,17 @@ _outTidPath(StringInfo str, const TidPath *node)
 }
 
 static void
+_outSamplePath(StringInfo str, const SamplePath *node)
+{
+	WRITE_NODE_TYPE("SAMPLEPATH");
+
+	_outPathInfo(str, (const Path *) node);
+
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(tsmargs);
+}
+
+static void
 _outForeignPath(StringInfo str, const ForeignPath *node)
 {
 	WRITE_NODE_TYPE("FOREIGNPATH");
@@ -2391,6 +2410,33 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2420,6 +2466,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2887,6 +2934,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3092,6 +3142,8 @@ _outNode(StringInfo str, const void *obj)
 			case T_TidPath:
 				_outTidPath(str, obj);
 				break;
+			case T_SamplePath:
+				_outSamplePath(str, obj);
 			case T_ForeignPath:
 				_outForeignPath(str, obj);
 				break;
@@ -3228,6 +3280,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index a3efdd4..3a510dd 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,43 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1216,6 +1253,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1311,6 +1349,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 449fdc3..dffab29 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,8 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -332,6 +334,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +425,34 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids		required_outer;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	add_path(rel, (Path *) create_samplescan_path(root, rel, required_outer));
+
+	/*
+	 * There is only one plan to consider but we still need to set
+	 * parameters for RelOptInfo.
+	 */
+	set_cheapest(rel);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 659daa2..d0741f0 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -88,6 +88,7 @@
 #include "optimizer/restrictinfo.h"
 #include "parser/parsetree.h"
 #include "utils/lsyscache.h"
+#include "utils/sampling.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
 #include "utils/tuplesort.h"
@@ -219,6 +220,72 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we dont't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(SamplePath *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	SamplerAccessStrategy strategy;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(path->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples),
+					 PointerGetDatum(&strategy));
+
+	/* Mark the path with the correct row estimate */
+	if (path->path.param_info)
+		path->path.rows = path->path.param_info->ppi_rows;
+	else
+		path->path.rows = tuples;
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = strategy == SAS_RANDOM ?
+		spc_random_page_cost : spc_seq_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->path.param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->path.startup_cost = startup_cost;
+	path->path.total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 8f9ae4f..1056885 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3318,6 +3369,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 4d3fbca..0d78f27 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -446,6 +446,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 579d021..7da1a44 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2163,6 +2163,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 319e8b2..3c2c1b8 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,33 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+SamplePath *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	SamplePath	   *pathnode = makeNode(SamplePath);
+	RangeTblEntry  *rte = planner_rt_fetch(rel->relid, root);
+	TableSampleClause *tablesample = rte->tablesample;
+
+	Assert(tablesample);
+
+	pathnode->path.pathtype = T_SampleScan;
+	pathnode->path.parent = rel;
+	pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->path.pathkeys = NIL;	/* samplescan has unordered result */
+
+	pathnode->tsmcost = tablesample->tsmcost;
+	pathnode->tsmargs = tablesample->args;
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1921,6 +1948,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 1f4fe9d..0eb81ae 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -447,6 +447,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -611,8 +612,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10137,6 +10138,12 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample opt_alias_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10432,7 +10439,6 @@ relation_expr_list:
 			| relation_expr_list ',' relation_expr	{ $$ = lappend($1, $3); }
 		;
 
-
 /*
  * Given "UPDATE foo set set ...", we have to decide without looking any
  * further ahead whether the first "set" is an alias or the UPDATE's SET
@@ -10462,6 +10468,31 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $2;
+					n->relation = $1;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' func_arg_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' AexprConst ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/						{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13244,7 +13275,6 @@ unreserved_keyword:
 			| RELATIVE_P
 			| RELEASE
 			| RENAME
-			| REPEATABLE
 			| REPLACE
 			| REPLICA
 			| RESET
@@ -13419,6 +13449,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
@@ -13487,6 +13518,7 @@ reserved_keyword:
 			| PLACING
 			| PRIMARY
 			| REFERENCES
+			| REPEATABLE
 			| RETURNING
 			| SELECT
 			| SESSION_USER
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 4931dca..6d64a84 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -413,6 +416,19 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *r)
+{
+	RangeTblEntry  *rte;
+	TableSampleClause *tablesample = NULL;
+
+	rte = transformTableEntry(pstate, r->relation);
+	tablesample = ParseTableSample(pstate, r->method, r->repeatable, r->args);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -421,7 +437,7 @@ transformTableEntry(ParseState *pstate, RangeVar *r)
 {
 	RangeTblEntry *rte;
 
-	/* We need only build a range table entry */
+	/* We first need to build a range table entry */
 	rte = addRangeTableEntry(pstate, r, r->alias,
 							 interpretInhOption(r->inhOpt), true);
 
@@ -1121,6 +1137,26 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 9ebd3fd..b4ef9b8 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -760,6 +762,133 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+extern TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				actual_arg_types[FUNC_MAX_ARGS];
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the table sample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("table sample method \"%s\" does not exist",
+						samplemethod)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 * XXX: maybe make this ereport?
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Transform the rest of arguments ... */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *arg = transformExpr(pstate, (Node *) lfirst(larg), EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		fargs = lappend(fargs, arg);
+
+		actual_arg_types[nargs++] = argtype;
+	}
+
+	/*
+	 * Check if parameters are correct.
+	 *
+	 * XXX: can we do better at hinting here?
+	 */
+	if (initnargs != nargs ||
+			!can_coerce_type(initnargs, actual_arg_types, init_arg_types,
+						COERCION_IMPLICIT))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("wrong parameters for TABLESAMPLE method \"%s\"",
+						samplemethod)));
+
+	/* perform the necessary typecasting of arguments */
+	make_fn_arguments(pstate, fargs, actual_arg_types, init_arg_types);
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 24ade6c..65ca5bf 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -31,6 +31,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -343,6 +344,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4157,6 +4160,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the table sample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for table sample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8384,6 +8431,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index 94d951c..11d560e 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index 449d5b4..848ba29 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..71a91f9
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,130 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Block sampling routines shared by ANALYZE and TABLESAMPLE.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+static unsigned short _sampler_seed[3] = { 0x330e, 0xabcd, 0x1234 };
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler is used for stage one of our new two-stage tuple
+ * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
+ * "Large DB").  It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table.  If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+void
+sampler_setseed(long seed)
+{
+	_sampler_seed[0] = 0x330e;
+	_sampler_seed[1] = (unsigned short) seed;
+	_sampler_seed[2] = (unsigned short) (seed >> 16);
+}
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract(void)
+{
+	return pg_erand48(_sampler_seed);
+}
diff --git a/src/include/access/tsm_bernoulli.h b/src/include/access/tsm_bernoulli.h
new file mode 100644
index 0000000..00cd069
--- /dev/null
+++ b/src/include/access/tsm_bernoulli.h
@@ -0,0 +1,20 @@
+/*--------------------------------------------------------------------------
+ * tsm_bernoulli.h
+ *	  Header file for BERNOULLI table sampling method.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/access/tsm_bernoulli.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TSM_BERNOULLI_H
+#define TSM_BERNOULLI_H
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TSM_SYSTEM_H */
diff --git a/src/include/access/tsm_system.h b/src/include/access/tsm_system.h
new file mode 100644
index 0000000..4021470
--- /dev/null
+++ b/src/include/access/tsm_system.h
@@ -0,0 +1,20 @@
+/*--------------------------------------------------------------------------
+ * tsm_system.h
+ *	  Header file for SYSTEM table sampling method.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/access/tsm_system.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TSM_SYSTEM_H
+#define TSM_SYSTEM_H
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TSM_SYSTEM_H */
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index bde1a84..b06a791 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3281, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3281
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3282, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3282
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index f766ed7..9c77957 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5136,6 +5136,31 @@ DESCR("rank of hypothetical row without gaps");
 DATA(insert OID = 3993 ( dense_rank_final	PGNSP PGUID 12 1 0 2276 0 f f f f f f i 2 0 20 "2281 2276" "{2281,2276}" "{i,v}" _null_ _null_	hypothetical_dense_rank_final _null_ _null_ _null_ ));
 DESCR("aggregate final function");
 
+DATA(insert OID = 3285 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3286 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 23 "2281" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3287 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 21 "2281" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3288 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3289 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3290 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "700" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3291 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3292 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 23 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3293 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 21 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3294 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3296 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3297 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "700" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 0000000..0e4a716
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,70 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3280
+
+CATALOG(pg_tablesample_method,3280)
+{
+	NameData	tsmname;		/* tablescan method name */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method				7
+#define Anum_pg_tablesample_method_tsmname		1
+#define Anum_pg_tablesample_method_tsminit		2
+#define Anum_pg_tablesample_method_tsmnextblock	3
+#define Anum_pg_tablesample_method_tsmnexttuple	4
+#define Anum_pg_tablesample_method_tsmend		5
+#define Anum_pg_tablesample_method_tsmreset		6
+#define Anum_pg_tablesample_method_tsmcost		7
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3283 ( system tsm_system_init tsm_system_nextblock tsm_system_nexttuple tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3284 ( bernoulli tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 41b13b2..b7f3129 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1212,6 +1212,26 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState		ss;
+
+	/* Sampling method functions. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmend;
+	FmgrInfo		tsmreset;
+
+	Buffer			openbuffer;		/* currently open buffer */
+	HeapTupleData	tup;			/* last tuple */
+
+	void		   *tsmdata;		/* for use by table scan method */
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index bc71fea..01d4795 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -225,6 +227,7 @@ typedef enum NodeTag
 	T_MergePath,
 	T_HashPath,
 	T_TidPath,
+	T_SamplePath,
 	T_ForeignPath,
 	T_CustomPath,
 	T_AppendPath,
@@ -413,6 +416,8 @@ typedef enum NodeTag
 	T_XmlSerialize,
 	T_WithClause,
 	T_CommonTableExpr,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 458eeb0..62c2c57 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -307,6 +307,23 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -507,6 +524,21 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * We are more generic than SQL Standard so we pass generic function
+ * arguments to the sampling method.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -751,6 +783,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 48203a0..8427b44 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -278,6 +278,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 7116496..064e336 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -870,6 +870,18 @@ typedef struct TidPath
 } TidPath;
 
 /*
+ * SamplePath represents a sample sacn
+ *
+ * args is list of parameters for the the TABLESAMPLE clause
+ */
+typedef struct SamplePath
+{
+	Path		path;
+	Oid			tsmcost;		/* table sample method costing function */
+	List	   *tsmargs;		/* arguments to a TABLESAMPLE clause */
+} SamplePath;
+
+/*
  * ForeignPath represents a potential scan of a foreign table
  *
  * fdw_private stores FDW private data about the scan.  While fdw_private is
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 75e2afb..97bc0ba 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(SamplePath *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 26b17f5..6c0a6cf 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern SamplePath *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+										  Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index e14dc9a..e565082 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -312,7 +312,7 @@ PG_KEYWORD("reindex", REINDEX, UNRESERVED_KEYWORD)
 PG_KEYWORD("relative", RELATIVE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("release", RELEASE, UNRESERVED_KEYWORD)
 PG_KEYWORD("rename", RENAME, UNRESERVED_KEYWORD)
-PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
+PG_KEYWORD("repeatable", REPEATABLE, RESERVED_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 4423bc0..0ba9768 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,10 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 48ebf59..1ba06b6 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..734cdc0
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,49 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+typedef enum SamplerAccessStrategy
+{
+	SAS_RANDOM,
+	SAS_SEQUENTIAL
+} SamplerAccessStrategy;
+
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Vitter reservoir sampling functions */
+extern double vitter_init_selection_state(int n);
+extern double vitter_get_next_S(double t, int n, double *stateptr);
+
+/* Random generator */
+extern void sampler_setseed(long seed);
+extern double sampler_random_fract(void);
+
+#endif /* SAMPLING_H */
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index f97229f..29244c7 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..5946edf 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..436b754
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,77 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index 62cc198..cf789dc 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 07fc827..852fed9 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -151,3 +151,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..e8313a3
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,17 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+DROP TABLE test_tablesample CASCADE;

>From d799c85e65346615f9fa102890e3c6c6156ce92f Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:36:56 +0100
Subject: [PATCH 1/3] separate block sampling functions

---
 src/backend/commands/analyze.c    | 123 +++---------------------------------
 src/backend/utils/misc/Makefile   |   2 +-
 src/backend/utils/misc/sampling.c | 130 ++++++++++++++++++++++++++++++++++++++
 src/include/utils/sampling.h      |  49 ++++++++++++++
 4 files changed, 188 insertions(+), 116 deletions(-)
 create mode 100644 src/backend/utils/misc/sampling.c
 create mode 100644 src/include/utils/sampling.h

diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 5de2b39..0e770b7 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -88,10 +78,6 @@ static BufferAccessStrategy vac_strategy;
 static void do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -947,94 +933,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1089,6 +987,8 @@ acquire_sample_rows(Relation onerel, int elevel,
 	/* Need a cutoff xmin for HeapTupleSatisfiesVacuum */
 	OldestXmin = GetOldestXmin(onerel, true);
 
+	/* Seed the sampler random number generator */
+	sampler_setseed(random());
 	/* Prepare for sampling block numbers */
 	BlockSampler_Init(&bs, totalblocks, targrows);
 	/* Prepare for sampling rows */
@@ -1249,7 +1149,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1308,13 +1208,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
 /*
  * These two routines embody Algorithm Z from "Random sampling with a
  * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
@@ -1333,7 +1226,7 @@ double
 anl_init_selection_state(int n)
 {
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
+	return exp(-log(sampler_random_fract()) / n);
 }
 
 double
@@ -1348,7 +1241,7 @@ anl_get_next_S(double t, int n, double *stateptr)
 		double		V,
 					quot;
 
-		V = anl_random_fract(); /* Generate V */
+		V = sampler_random_fract(); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -1380,7 +1273,7 @@ anl_get_next_S(double t, int n, double *stateptr)
 						tmp;
 
 			/* Generate U and X */
-			U = anl_random_fract();
+			U = sampler_random_fract();
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -1409,7 +1302,7 @@ anl_get_next_S(double t, int n, double *stateptr)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index 449d5b4..848ba29 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..71a91f9
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,130 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Block sampling routines shared by ANALYZE and TABLESAMPLE.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+static unsigned short _sampler_seed[3] = { 0x330e, 0xabcd, 0x1234 };
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler is used for stage one of our new two-stage tuple
+ * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
+ * "Large DB").  It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table.  If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+void
+sampler_setseed(long seed)
+{
+	_sampler_seed[0] = 0x330e;
+	_sampler_seed[1] = (unsigned short) seed;
+	_sampler_seed[2] = (unsigned short) (seed >> 16);
+}
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract(void)
+{
+	return pg_erand48(_sampler_seed);
+}
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..734cdc0
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,49 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+typedef enum SamplerAccessStrategy
+{
+	SAS_RANDOM,
+	SAS_SEQUENTIAL
+} SamplerAccessStrategy;
+
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Vitter reservoir sampling functions */
+extern double vitter_init_selection_state(int n);
+extern double vitter_get_next_S(double t, int n, double *stateptr);
+
+/* Random generator */
+extern void sampler_setseed(long seed);
+extern double sampler_random_fract(void);
+
+#endif /* SAMPLING_H */
-- 
1.9.1

>From 19b0cde3a84841790eb8e10c3eacd21b581aa4a3 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:37:55 +0100
Subject: [PATCH 2/3] tablesample v4

---
 doc/src/sgml/ref/select.sgml                |  34 ++-
 src/backend/access/Makefile                 |   3 +-
 src/backend/catalog/Makefile                |   2 +-
 src/backend/commands/explain.c              |   7 +
 src/backend/executor/Makefile               |   2 +-
 src/backend/executor/execAmi.c              |   8 +
 src/backend/executor/execCurrent.c          |   1 +
 src/backend/executor/execProcnode.c         |  14 +
 src/backend/executor/nodeSamplescan.c       | 404 ++++++++++++++++++++++++++++
 src/backend/nodes/copyfuncs.c               |  57 ++++
 src/backend/nodes/equalfuncs.c              |  34 +++
 src/backend/nodes/nodeFuncs.c               |  12 +
 src/backend/nodes/outfuncs.c                |  58 ++++
 src/backend/nodes/readfuncs.c               |  42 +++
 src/backend/optimizer/path/allpaths.c       |  35 +++
 src/backend/optimizer/path/costsize.c       |  67 +++++
 src/backend/optimizer/plan/createplan.c     |  69 +++++
 src/backend/optimizer/plan/setrefs.c        |  11 +
 src/backend/optimizer/plan/subselect.c      |   1 +
 src/backend/optimizer/util/pathnode.c       |  29 ++
 src/backend/parser/gram.y                   |  40 ++-
 src/backend/parser/parse_clause.c           |  38 ++-
 src/backend/parser/parse_func.c             | 128 +++++++++
 src/backend/utils/Makefile                  |   3 +-
 src/backend/utils/adt/ruleutils.c           |  50 ++++
 src/backend/utils/cache/syscache.c          |  23 ++
 src/backend/utils/tablesample/Makefile      |  17 ++
 src/backend/utils/tablesample/bernoulli.c   | 199 ++++++++++++++
 src/backend/utils/tablesample/system.c      | 186 +++++++++++++
 src/include/catalog/indexing.h              |   5 +
 src/include/catalog/pg_proc.h               |  25 ++
 src/include/catalog/pg_tablesample_method.h |  70 +++++
 src/include/executor/nodeSamplescan.h       |  24 ++
 src/include/nodes/execnodes.h               |  20 ++
 src/include/nodes/nodes.h                   |   5 +
 src/include/nodes/parsenodes.h              |  33 +++
 src/include/nodes/plannodes.h               |   6 +
 src/include/nodes/relation.h                |  12 +
 src/include/optimizer/cost.h                |   1 +
 src/include/optimizer/pathnode.h            |   2 +
 src/include/parser/kwlist.h                 |   3 +-
 src/include/parser/parse_func.h             |   4 +
 src/include/utils/rel.h                     |   1 -
 src/include/utils/sampling.h                |   4 -
 src/include/utils/syscache.h                |   2 +
 src/include/utils/tablesample.h             |  27 ++
 src/test/regress/expected/sanity_check.out  |   1 +
 src/test/regress/expected/tablesample.out   |  77 ++++++
 src/test/regress/parallel_schedule          |   2 +-
 src/test/regress/serial_schedule            |   1 +
 src/test/regress/sql/tablesample.sql        |  17 ++
 51 files changed, 1899 insertions(+), 17 deletions(-)
 create mode 100644 src/backend/executor/nodeSamplescan.c
 create mode 100644 src/backend/utils/tablesample/Makefile
 create mode 100644 src/backend/utils/tablesample/bernoulli.c
 create mode 100644 src/backend/utils/tablesample/system.c
 create mode 100644 src/include/catalog/pg_tablesample_method.h
 create mode 100644 src/include/executor/nodeSamplescan.h
 create mode 100644 src/include/utils/tablesample.h
 create mode 100644 src/test/regress/expected/tablesample.out
 create mode 100644 src/test/regress/sql/tablesample.sql

diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 01d24a5..250ae29 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,38 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        one of:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of those sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability.
+        The optional numeric parameter <literal>REPEATABLE</literal> is used
+        as random seed for sampling.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..238057a 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  transam
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..34db3e6 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesample_method.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 8a0be5d..5152964 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -724,6 +724,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -950,6 +951,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			pname = sname = "Sample Scan";
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1067,6 +1071,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1319,6 +1324,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2147,6 +2153,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 6ebad2f..4948a26 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index 1c8be25..5cfe549 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 9892499..03c2feb 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..27f5f05
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,404 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "catalog/pg_tablesample_method.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "storage/bufmgr.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate, int eflags);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+
+/*
+ * Initialize the sampling method - loads function info and
+ * calls the tsminit function.
+ *
+ * We need special handling for this because the tsminit function
+ * is allowed to take optional additional arguments.
+ */
+static void
+InitSamplingMethod(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(scanstate->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(scanstate->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(scanstate->tsmnexttuple));
+	fmgr_info(tablesample->tsmend, &(scanstate->tsmend));
+	fmgr_info(tablesample->tsmreset, &(scanstate->tsmreset));
+
+	InitFunctionCallInfoData(fcinfo, &scanstate->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	/* First arg is always SampleScanState */
+	fcinfo.arg[0] = PointerGetDatum(scanstate);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause cannot be NULL")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+}
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	EState	   *estate;
+	TupleTableSlot *slot;
+	BlockNumber	blockno = InvalidBlockNumber;
+	Snapshot	snapshot;
+	Relation	relation;
+	bool		found = false;
+	bool		retry = false;
+	OffsetNumber tupoffset, maxoffset;
+	Buffer		buffer;
+	Page		page;
+	HeapTuple	tuple = &(node->tup);
+
+	/*
+	 * get information from the estate and scan state
+	 */
+	estate = node->ss.ps.state;
+	snapshot = estate->es_snapshot;
+	slot = node->ss.ss_ScanTupleSlot;
+	relation = node->ss.ss_currentRelation;
+	buffer = node->openbuffer;
+
+	if (BufferIsValid(buffer))
+	{
+		blockno = BufferGetBlockNumber(buffer);
+		page = BufferGetPage(buffer);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	/*
+	 * get the next tuple from the table
+	 */
+	for (;;)
+	{
+		ItemId			itemid;
+
+		CHECK_FOR_INTERRUPTS();
+
+		/* Load next block if needed. */
+		if (!BufferIsValid(buffer))
+		{
+			blockno = DatumGetInt32(FunctionCall2(&node->tsmnextblock,
+												  PointerGetDatum(node),
+												  BoolGetDatum(retry)));
+			/* No more blocks to fetch */
+			if (!BlockNumberIsValid(blockno))
+				break;
+
+			buffer = ReadBufferExtended(relation, MAIN_FORKNUM, blockno,
+										RBM_NORMAL, NULL);
+			LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+			node->openbuffer = buffer;
+			page = BufferGetPage(buffer);
+			maxoffset = PageGetMaxOffsetNumber(page);
+		}
+
+		tupoffset = DatumGetUInt16(FunctionCall4(&node->tsmnexttuple,
+												 PointerGetDatum(node),
+												 UInt32GetDatum(blockno),
+												 UInt16GetDatum(maxoffset),
+												 BoolGetDatum(retry)));
+		/* Go to next block. */
+		if (!OffsetNumberIsValid(tupoffset))
+		{
+			UnlockReleaseBuffer(buffer);
+			node->openbuffer = buffer = InvalidBuffer;
+			continue;
+		}
+		retry = true;
+
+		/* Skip invalid tuple pointers. */
+		itemid = PageGetItemId(page, tupoffset);
+		if (!ItemIdIsNormal(itemid))
+			continue;
+
+		tuple->t_tableOid = RelationGetRelid(relation);
+		tuple->t_data = (HeapTupleHeader) PageGetItem(page, itemid);
+		tuple->t_len = ItemIdGetLength(itemid);
+		ItemPointerSet(&tuple->t_self, blockno, tupoffset);
+
+		/* Found visible tuple, return it. */
+		if (HeapTupleSatisfiesVisibility(tuple, snapshot, buffer))
+		{
+			found = true;
+			break;
+		}
+	}
+
+	if (found)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   buffer,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+	node->ss.ss_currentScanDesc = NULL;
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	scanstate->openbuffer = InvalidBuffer;
+
+	InitSamplingMethod(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished thes can.
+	 */
+	FunctionCall1(&node->tsmend, PointerGetDatum(node));
+
+	if (BufferIsValid(node->openbuffer))
+	{
+		UnlockReleaseBuffer(node->openbuffer);
+		node->openbuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *scanstate)
+{
+	if (BufferIsValid(scanstate->openbuffer))
+	{
+		UnlockReleaseBuffer(scanstate->openbuffer);
+		scanstate->openbuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	FunctionCall1(&scanstate->tsmreset, PointerGetDatum(scanstate));
+
+	ExecScanReScan(&scanstate->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index f1a24f5..8861512 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -628,6 +628,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2006,6 +2022,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2138,6 +2155,37 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4075,6 +4123,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4723,6 +4774,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_PrivGrantee:
 			retval = _copyPrivGrantee(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 6e8b308..1e7ebbf 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2323,6 +2323,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2442,6 +2443,33 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3150,6 +3178,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_PrivGrantee:
 			retval = _equalPrivGrantee(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 21dfda7..bd9ce09 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3209,6 +3209,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index dd1278b..684cd7e 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -578,6 +578,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -1589,6 +1597,17 @@ _outTidPath(StringInfo str, const TidPath *node)
 }
 
 static void
+_outSamplePath(StringInfo str, const SamplePath *node)
+{
+	WRITE_NODE_TYPE("SAMPLEPATH");
+
+	_outPathInfo(str, (const Path *) node);
+
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(tsmargs);
+}
+
+static void
 _outForeignPath(StringInfo str, const ForeignPath *node)
 {
 	WRITE_NODE_TYPE("FOREIGNPATH");
@@ -2391,6 +2410,33 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2420,6 +2466,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2887,6 +2934,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3092,6 +3142,8 @@ _outNode(StringInfo str, const void *obj)
 			case T_TidPath:
 				_outTidPath(str, obj);
 				break;
+			case T_SamplePath:
+				_outSamplePath(str, obj);
 			case T_ForeignPath:
 				_outForeignPath(str, obj);
 				break;
@@ -3228,6 +3280,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index ae24d05..fe08107 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,43 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1216,6 +1253,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1311,6 +1349,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 58d78e6..c18973c 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,8 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -332,6 +334,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +425,34 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids		required_outer;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	add_path(rel, (Path *) create_samplescan_path(root, rel, required_outer));
+
+	/*
+	 * There is only one plan to consider but we still need to set
+	 * parameters for RelOptInfo.
+	 */
+	set_cheapest(rel);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 020558b..8f9d41e 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -88,6 +88,7 @@
 #include "optimizer/restrictinfo.h"
 #include "parser/parsetree.h"
 #include "utils/lsyscache.h"
+#include "utils/sampling.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
 #include "utils/tuplesort.h"
@@ -219,6 +220,72 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we dont't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(SamplePath *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	SamplerAccessStrategy strategy;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(path->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples),
+					 PointerGetDatum(&strategy));
+
+	/* Mark the path with the correct row estimate */
+	if (path->path.param_info)
+		path->path.rows = path->path.param_info->ppi_rows;
+	else
+		path->path.rows = tuples;
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = strategy == SAS_RANDOM ?
+		spc_random_page_cost : spc_seq_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->path.param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->path.startup_cost = startup_cost;
+	path->path.total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 655be81..10a5e02 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3318,6 +3369,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 7703946..de33fc6 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -446,6 +446,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 78fb6b1..191624c 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2163,6 +2163,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 1395a21..6206c60 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,33 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+SamplePath *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	SamplePath	   *pathnode = makeNode(SamplePath);
+	RangeTblEntry  *rte = planner_rt_fetch(rel->relid, root);
+	TableSampleClause *tablesample = rte->tablesample;
+
+	Assert(tablesample);
+
+	pathnode->path.pathtype = T_SampleScan;
+	pathnode->path.parent = rel;
+	pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->path.pathkeys = NIL;	/* samplescan has unordered result */
+
+	pathnode->tsmcost = tablesample->tsmcost;
+	pathnode->tsmargs = tablesample->args;
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1921,6 +1948,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 679e1bb..01d72d4 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -447,6 +447,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -611,8 +612,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10227,6 +10228,12 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample opt_alias_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10522,7 +10529,6 @@ relation_expr_list:
 			| relation_expr_list ',' relation_expr	{ $$ = lappend($1, $3); }
 		;
 
-
 /*
  * Given "UPDATE foo set set ...", we have to decide without looking any
  * further ahead whether the first "set" is an alias or the UPDATE's SET
@@ -10552,6 +10558,31 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $2;
+					n->relation = $1;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' func_arg_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' AexprConst ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/						{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13334,7 +13365,6 @@ unreserved_keyword:
 			| RELATIVE_P
 			| RELEASE
 			| RENAME
-			| REPEATABLE
 			| REPLACE
 			| REPLICA
 			| RESET
@@ -13509,6 +13539,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
@@ -13577,6 +13608,7 @@ reserved_keyword:
 			| PLACING
 			| PRIMARY
 			| REFERENCES
+			| REPEATABLE
 			| RETURNING
 			| SELECT
 			| SESSION_USER
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 654dce6..03632d2 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -413,6 +416,19 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *r)
+{
+	RangeTblEntry  *rte;
+	TableSampleClause *tablesample = NULL;
+
+	rte = transformTableEntry(pstate, r->relation);
+	tablesample = ParseTableSample(pstate, r->method, r->repeatable, r->args);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -421,7 +437,7 @@ transformTableEntry(ParseState *pstate, RangeVar *r)
 {
 	RangeTblEntry *rte;
 
-	/* We need only build a range table entry */
+	/* We first need to build a range table entry */
 	rte = addRangeTableEntry(pstate, r, r->alias,
 							 interpretInhOption(r->inhOpt), true);
 
@@ -1121,6 +1137,26 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index a200804..690d0fa 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -760,6 +762,132 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+extern TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				actual_arg_types[FUNC_MAX_ARGS];
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						samplemethod)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Transform the rest of arguments ... */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *arg = transformExpr(pstate, (Node *) lfirst(larg), EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		fargs = lappend(fargs, arg);
+
+		actual_arg_types[nargs++] = argtype;
+	}
+
+	/*
+	 * Check if parameters are correct.
+	 *
+	 * XXX: can we do better at hinting here?
+	 */
+	if (initnargs != nargs ||
+			!can_coerce_type(initnargs, actual_arg_types, init_arg_types,
+						COERCION_IMPLICIT))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("wrong parameters for tablesample method \"%s\"",
+						samplemethod)));
+
+	/* perform the necessary typecasting of arguments */
+	make_fn_arguments(pstate, fargs, actual_arg_types, init_arg_types);
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/utils/Makefile b/src/backend/utils/Makefile
index 8374533..9daa2ae 100644
--- a/src/backend/utils/Makefile
+++ b/src/backend/utils/Makefile
@@ -9,7 +9,8 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS        = fmgrtab.o
-SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time
+SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time \
+			  tablesample
 
 # location of Catalog.pm
 catalogdir  = $(top_srcdir)/src/backend/catalog
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index dd748ac..4f1c534 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -31,6 +31,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -343,6 +344,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4157,6 +4160,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for tablesample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8384,6 +8431,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index bd27168..3a8f01e 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/tablesample/Makefile b/src/backend/utils/tablesample/Makefile
new file mode 100644
index 0000000..df92939
--- /dev/null
+++ b/src/backend/utils/tablesample/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for utils/tablesample
+#
+# IDENTIFICATION
+#    src/backend/utils/tablesample/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/utils/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = system.o bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/tablesample/bernoulli.c b/src/backend/utils/tablesample/bernoulli.c
new file mode 100644
index 0000000..1c7808d
--- /dev/null
+++ b/src/backend/utils/tablesample/bernoulli.c
@@ -0,0 +1,199 @@
+/*-------------------------------------------------------------------------
+ *
+ * bernoulli.c
+ *	  interface routines for BERNOULLI tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/* State */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	float4 samplesize;			/* percentage of tuples to return (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks = RelationGetNumberOfBlocks(rel);
+	sampler->blockno = InvalidBlockNumber;
+	sampler->samplesize = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+
+	sampler_setseed(seed);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler = (BernoulliSamplerData *) scanstate->tsmdata;
+
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = 0;
+	else if (++sampler->blockno >= sampler->tblocks)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData *sampler = (BernoulliSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+	double			samplesize = sampler->samplesize;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/* Every tuple has percent chance of being returned */
+	while (sampler_random_fract() > samplesize)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler = (BernoulliSamplerData *) scanstate->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_setseed(sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	SamplePath	   *path = (SamplePath *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+	List		   *args = path->tsmargs;
+	Node		   *pctnode;
+	float4			samplesize;
+
+	SamplerAccessStrategy *strategy = (SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_SEQUENTIAL;
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (!IsA(pctnode, Const))
+	{
+		*tuples = baserel->tuples * 0.1;
+		PG_RETURN_VOID();
+	}
+
+	samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+	samplesize /= 100.0;
+
+	*tuples = baserel->tuples * samplesize;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/utils/tablesample/system.c b/src/backend/utils/tablesample/system.c
new file mode 100644
index 0000000..83a7ccf
--- /dev/null
+++ b/src/backend/utils/tablesample/system.c
@@ -0,0 +1,186 @@
+/*-------------------------------------------------------------------------
+ *
+ * system.c
+ *	  interface routines for system tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	SystemSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks = RelationGetNumberOfBlocks(scanstate->ss.ss_currentRelation);
+	sampler->samplesize = 1 + (int) (sampler->tblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	sampler_setseed(seed);
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as VACUUM for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	BlockNumber		blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	sampler_setseed(sampler->seed);
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	SamplePath	   *path = (SamplePath *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+	List		   *args = path->tsmargs;
+	Node		   *pctnode;
+	float4			percent;
+
+	SamplerAccessStrategy *strategy = (SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_RANDOM;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (!IsA(pctnode, Const))
+	{
+		*pages = baserel->pages * 0.1;
+		*tuples = baserel->tuples * 0.1;
+		PG_RETURN_VOID();
+	}
+
+	percent = DatumGetFloat4(((Const *) pctnode)->constvalue);
+	percent /= 100.0;
+
+	*pages = baserel->pages * percent;
+	*tuples = baserel->tuples * percent;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index a680229..c711cca 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3281, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3281
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3282, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3282
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 9edfdb8..a0f97ac 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5143,6 +5143,31 @@ DESCR("rank of hypothetical row without gaps");
 DATA(insert OID = 3993 ( dense_rank_final	PGNSP PGUID 12 1 0 2276 0 f f f f f f i 2 0 20 "2281 2276" "{2281,2276}" "{i,v}" _null_ _null_	hypothetical_dense_rank_final _null_ _null_ _null_ ));
 DESCR("aggregate final function");
 
+DATA(insert OID = 3285 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3286 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3287 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3288 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3289 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3290 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 6 0 2278 "2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3291 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3292 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3293 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3294 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3296 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3297 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 6 0 2278 "2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 0000000..0e4a716
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,70 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3280
+
+CATALOG(pg_tablesample_method,3280)
+{
+	NameData	tsmname;		/* tablescan method name */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method				7
+#define Anum_pg_tablesample_method_tsmname		1
+#define Anum_pg_tablesample_method_tsminit		2
+#define Anum_pg_tablesample_method_tsmnextblock	3
+#define Anum_pg_tablesample_method_tsmnexttuple	4
+#define Anum_pg_tablesample_method_tsmend		5
+#define Anum_pg_tablesample_method_tsmreset		6
+#define Anum_pg_tablesample_method_tsmcost		7
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3283 ( system tsm_system_init tsm_system_nextblock tsm_system_nexttuple tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3284 ( bernoulli tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 41288ed..43e1a30 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1212,6 +1212,26 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState		ss;
+
+	/* Sampling method functions. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmend;
+	FmgrInfo		tsmreset;
+
+	Buffer			openbuffer;		/* currently open buffer */
+	HeapTupleData	tup;			/* last tuple */
+
+	void		   *tsmdata;		/* for use by table scan method */
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 97ef0fc..99ac985 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -225,6 +227,7 @@ typedef enum NodeTag
 	T_MergePath,
 	T_HashPath,
 	T_TidPath,
+	T_SamplePath,
 	T_ForeignPath,
 	T_CustomPath,
 	T_AppendPath,
@@ -413,6 +416,8 @@ typedef enum NodeTag
 	T_XmlSerialize,
 	T_WithClause,
 	T_CommonTableExpr,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index b1dfa85..d87343f 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -307,6 +307,23 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -507,6 +524,21 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * We are more generic than SQL Standard so we pass generic function
+ * arguments to the sampling method.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -751,6 +783,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 316c9ce..8a2a146 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -278,6 +278,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 6845a40..67c3b1f 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -870,6 +870,18 @@ typedef struct TidPath
 } TidPath;
 
 /*
+ * SamplePath represents a sample sacn
+ *
+ * args is list of parameters for the the TABLESAMPLE clause
+ */
+typedef struct SamplePath
+{
+	Path		path;
+	Oid			tsmcost;		/* table sample method costing function */
+	List	   *tsmargs;		/* arguments to a TABLESAMPLE clause */
+} SamplePath;
+
+/*
  * ForeignPath represents a potential scan of a foreign table
  *
  * fdw_private stores FDW private data about the scan.  While fdw_private is
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 9c2000b..3777054 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(SamplePath *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 9923f0e..dfb580e 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern SamplePath *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+										  Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 7c243ec..6ff7b44 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -312,7 +312,7 @@ PG_KEYWORD("reindex", REINDEX, UNRESERVED_KEYWORD)
 PG_KEYWORD("relative", RELATIVE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("release", RELEASE, UNRESERVED_KEYWORD)
 PG_KEYWORD("rename", RENAME, UNRESERVED_KEYWORD)
-PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
+PG_KEYWORD("repeatable", REPEATABLE, RESERVED_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 3264691..6727e55 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,10 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 6bd786d..185bd81 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
index 734cdc0..3098ab4 100644
--- a/src/include/utils/sampling.h
+++ b/src/include/utils/sampling.h
@@ -38,10 +38,6 @@ extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
 extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
-/* Vitter reservoir sampling functions */
-extern double vitter_init_selection_state(int n);
-extern double vitter_get_next_S(double t, int n, double *stateptr);
-
 /* Random generator */
 extern void sampler_setseed(long seed);
 extern double sampler_random_fract(void);
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index ba0b090..6b628f6 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/include/utils/tablesample.h b/src/include/utils/tablesample.h
new file mode 100644
index 0000000..1a24cb6
--- /dev/null
+++ b/src/include/utils/tablesample.h
@@ -0,0 +1,27 @@
+/*--------------------------------------------------------------------------
+ * tablesample.h
+ *	  Header file for builtin table sampling methods.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/utils/tablesample.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TABLESAMPLE_H
+#define TABLESAMPLE_H
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TABLESAMPLE_H */
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..5946edf 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..436b754
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,77 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index 62ef6ec..2e1b200 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity object_address tablesample
 
 # rowsecurity creates an event trigger, so don't run it in parallel
 test: rowsecurity
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index b491b97..2d74c9f 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -152,3 +152,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..e8313a3
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,17 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+DROP TABLE test_tablesample CASCADE;
-- 
1.9.1

>From ec16f7e1dfe75f4f019a42801f60818c7c37bdcd Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:51:44 +0100
Subject: [PATCH 3/3] tablesample-ddl

---
 doc/src/sgml/ref/allfiles.sgml                     |   2 +
 doc/src/sgml/ref/create_tablesamplemethod.sgml     | 149 ++++++++
 doc/src/sgml/ref/drop_tablesamplemethod.sgml       |  87 +++++
 doc/src/sgml/reference.sgml                        |   2 +
 src/backend/catalog/dependency.c                   |  15 +-
 src/backend/catalog/objectaddress.c                |  65 +++-
 src/backend/commands/Makefile                      |   6 +-
 src/backend/commands/dropcmds.c                    |   4 +
 src/backend/commands/event_trigger.c               |   3 +
 src/backend/commands/tablecmds.c                   |   1 +
 src/backend/commands/tablesample.c                 | 398 +++++++++++++++++++++
 src/backend/parser/gram.y                          |  14 +-
 src/backend/tcop/utility.c                         |  12 +
 src/include/catalog/dependency.h                   |   1 +
 src/include/catalog/pg_tablesample_method.h        |  11 +
 src/include/nodes/parsenodes.h                     |   1 +
 src/include/nodes/relation.h                       |   2 +-
 src/include/parser/kwlist.h                        |   1 +
 src/test/modules/Makefile                          |   3 +-
 src/test/modules/tablesample/.gitignore            |   4 +
 src/test/modules/tablesample/Makefile              |  21 ++
 .../modules/tablesample/expected/tablesample.out   |  39 ++
 src/test/modules/tablesample/sql/tablesample.sql   |  14 +
 src/test/modules/tablesample/tsm_test--1.0.sql     |  44 +++
 src/test/modules/tablesample/tsm_test.c            | 179 +++++++++
 src/test/modules/tablesample/tsm_test.control      |   5 +
 26 files changed, 1074 insertions(+), 9 deletions(-)
 create mode 100644 doc/src/sgml/ref/create_tablesamplemethod.sgml
 create mode 100644 doc/src/sgml/ref/drop_tablesamplemethod.sgml
 create mode 100644 src/backend/commands/tablesample.c
 create mode 100644 src/test/modules/tablesample/.gitignore
 create mode 100644 src/test/modules/tablesample/Makefile
 create mode 100644 src/test/modules/tablesample/expected/tablesample.out
 create mode 100644 src/test/modules/tablesample/sql/tablesample.sql
 create mode 100644 src/test/modules/tablesample/tsm_test--1.0.sql
 create mode 100644 src/test/modules/tablesample/tsm_test.c
 create mode 100644 src/test/modules/tablesample/tsm_test.control

diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index 7aa3128..2fad084 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -78,6 +78,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY createServer       SYSTEM "create_server.sgml">
 <!ENTITY createTable        SYSTEM "create_table.sgml">
 <!ENTITY createTableAs      SYSTEM "create_table_as.sgml">
+<!ENTITY createTablesampleMethod SYSTEM "create_tablesamplemethod.sgml">
 <!ENTITY createTableSpace   SYSTEM "create_tablespace.sgml">
 <!ENTITY createTrigger      SYSTEM "create_trigger.sgml">
 <!ENTITY createTSConfig     SYSTEM "create_tsconfig.sgml">
@@ -119,6 +120,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY dropSequence       SYSTEM "drop_sequence.sgml">
 <!ENTITY dropServer         SYSTEM "drop_server.sgml">
 <!ENTITY dropTable          SYSTEM "drop_table.sgml">
+<!ENTITY dropTablesampleMethod SYSTEM "drop_tablesamplemethod.sgml">
 <!ENTITY dropTableSpace     SYSTEM "drop_tablespace.sgml">
 <!ENTITY dropTrigger        SYSTEM "drop_trigger.sgml">
 <!ENTITY dropTSConfig       SYSTEM "drop_tsconfig.sgml">
diff --git a/doc/src/sgml/ref/create_tablesamplemethod.sgml b/doc/src/sgml/ref/create_tablesamplemethod.sgml
new file mode 100644
index 0000000..70720e5
--- /dev/null
+++ b/doc/src/sgml/ref/create_tablesamplemethod.sgml
@@ -0,0 +1,149 @@
+<!--
+doc/src/sgml/ref/create_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-CREATETABLESAMPLEMETHOD">
+ <indexterm zone="sql-createtablesamplemethod">
+  <primary>CREATE TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE TABLESAMPLE METHOD</refname>
+  <refpurpose>define custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE TABLESAMPLE METHOD <replaceable class="parameter">name</replaceable> (
+    INIT = <replaceable class="parameter">init_function</replaceable> ,
+    NEXTBLOCK = <replaceable class="parameter">nextblock_function</replaceable> ,
+    NEXTTUPLE = <replaceable class="parameter">nexttuple_function</replaceable> ,
+    END = <replaceable class="parameter">end_function</replaceable> ,
+    RESET = <replaceable class="parameter">reset_function</replaceable> ,
+    COST = <replaceable class="parameter">cost_function</replaceable>
+)
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE TABLESAMPLE METHOD</command> creates a tablesample method.
+   A tablesample method provides alrorithm for reading sample part of a table
+   when used in <command>TABLESAMPLE</> clause of a <command>SELECT</>
+   statement.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the tablesample method to be created. This name must be
+      unique within the database.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">init_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the init function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nextblock_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-block function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nexttuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-tuple function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">end_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the end function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">reset_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the reset function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">cost_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the costing function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+  <para>
+   The function names can be schema-qualified if necessary.  Argument types
+   are not given, since the argument list for each type of function is
+   predetermined.  All functions are required.
+  </para>
+
+  <para>
+   The arguments can appear in any order, not only the one shown above.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>CREATE TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-droptablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/ref/drop_tablesamplemethod.sgml b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
new file mode 100644
index 0000000..dffd2ec
--- /dev/null
+++ b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
@@ -0,0 +1,87 @@
+<!--
+doc/src/sgml/ref/drop_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-DROPTABLESAMPLEMETHOD">
+ <indexterm zone="sql-droptablesamplemethod">
+  <primary>DROP TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DROP TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP TABLESAMPLE METHOD</refname>
+  <refpurpose>remove a custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP TABLESAMPLE METHOD [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>DROP TABLESAMPLE METHOD</command> drop an existing tablesample
+   method.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the tablesample method does not exist.
+      A notice is issued in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of an existing tablesample method to be removed.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>DROP TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createtablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index 10c9a6d..2c09a3c 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -106,6 +106,7 @@
    &createServer;
    &createTable;
    &createTableAs;
+   &createTablesampleMethod;
    &createTableSpace;
    &createTSConfig;
    &createTSDictionary;
@@ -147,6 +148,7 @@
    &dropSequence;
    &dropServer;
    &dropTable;
+   &dropTablesampleMethod;
    &dropTableSpace;
    &dropTSConfig;
    &dropTSDictionary;
diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index bacb242..6acb5b3 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -46,6 +46,7 @@
 #include "catalog/pg_policy.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -157,7 +158,8 @@ static const Oid object_classes[MAX_OCLASS] = {
 	DefaultAclRelationId,		/* OCLASS_DEFACL */
 	ExtensionRelationId,		/* OCLASS_EXTENSION */
 	EventTriggerRelationId,		/* OCLASS_EVENT_TRIGGER */
-	PolicyRelationId			/* OCLASS_POLICY */
+	PolicyRelationId,			/* OCLASS_POLICY */
+	TableSampleMethodRelationId			/* OCLASS_TABLESAMPLEMETHOD */
 };
 
 
@@ -1265,6 +1267,10 @@ doDeletion(const ObjectAddress *object, int flags)
 			RemovePolicyById(object->objectId);
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			RemoveTablesampleMethodById(object->objectId);
+			break;
+
 		default:
 			elog(ERROR, "unrecognized object class: %u",
 				 object->classId);
@@ -1794,6 +1800,10 @@ find_expr_references_walker(Node *node,
 				case RTE_RELATION:
 					add_object_address(OCLASS_CLASS, rte->relid, 0,
 									   context->addrs);
+					if (rte->tablesample)
+						add_object_address(OCLASS_TABLESAMPLEMETHOD,
+										   rte->tablesample->tsmid, 0,
+										   context->addrs);
 					break;
 				default:
 					break;
@@ -2373,6 +2383,9 @@ getObjectClass(const ObjectAddress *object)
 
 		case PolicyRelationId:
 			return OCLASS_POLICY;
+
+		case TableSampleMethodRelationId:
+			return OCLASS_TABLESAMPLEMETHOD;
 	}
 
 	/* shouldn't get here */
diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index 825d8b2..02edc0a 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -44,6 +44,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_policy.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -429,7 +430,19 @@ static const ObjectPropertyType ObjectProperty[] =
 		Anum_pg_type_typacl,
 		ACL_KIND_TYPE,
 		true
-	}
+	},
+	{
+		TableSampleMethodRelationId,
+		TableSampleMethodOidIndexId,
+		TABLESAMPLEMETHODOID,
+		TABLESAMPLEMETHODNAME,
+		Anum_pg_tablesample_method_tsmname,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		-1,
+		true
+	},
 };
 
 /*
@@ -528,7 +541,9 @@ ObjectTypeMap[] =
 	/* OCLASS_EVENT_TRIGGER */
 	{ "event trigger", OBJECT_EVENT_TRIGGER },
 	/* OCLASS_POLICY */
-	{ "policy", OBJECT_POLICY }
+	{ "policy", OBJECT_POLICY },
+	/* OCLASS_TABLESAMPLEMETHOD */
+	{ "tablesample method", OBJECT_TABLESAMPLEMETHOD }
 };
 
 
@@ -670,6 +685,7 @@ get_object_address(ObjectType objtype, List *objname, List *objargs,
 			case OBJECT_FDW:
 			case OBJECT_FOREIGN_SERVER:
 			case OBJECT_EVENT_TRIGGER:
+			case OBJECT_TABLESAMPLEMETHOD:
 				address = get_object_address_unqualified(objtype,
 														 objname, missing_ok);
 				break;
@@ -896,6 +912,9 @@ get_object_address_unqualified(ObjectType objtype,
 			case OBJECT_EVENT_TRIGGER:
 				msg = gettext_noop("event trigger name cannot be qualified");
 				break;
+			case OBJECT_TABLESAMPLEMETHOD:
+				msg = gettext_noop("tablesample method name cannot be qualified");
+				break;
 			default:
 				elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 				msg = NULL;		/* placate compiler */
@@ -956,6 +975,11 @@ get_object_address_unqualified(ObjectType objtype,
 			address.objectId = get_event_trigger_oid(name, missing_ok);
 			address.objectSubId = 0;
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			address.classId = TableSampleMethodRelationId;
+			address.objectId = get_tablesample_method_oid(name, missing_ok);
+			address.objectSubId = 0;
+			break;
 		default:
 			elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 			/* placate compiler, which doesn't know elog won't return */
@@ -1720,6 +1744,7 @@ check_object_ownership(Oid roleid, ObjectType objtype, ObjectAddress address,
 			break;
 		case OBJECT_TSPARSER:
 		case OBJECT_TSTEMPLATE:
+		case OBJECT_TABLESAMPLEMETHOD:
 			/* We treat these object types as being owned by superusers */
 			if (!superuser_arg(roleid))
 				ereport(ERROR,
@@ -2654,6 +2679,21 @@ getObjectDescription(const ObjectAddress *object)
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				appendStringInfo(&buffer, _("tablesample method %s"),
+					 NameStr(((Form_pg_tablesample_method) GETSTRUCT(tup))->tsmname));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
@@ -3131,6 +3171,10 @@ getObjectTypeDescription(const ObjectAddress *object)
 			appendStringInfoString(&buffer, "policy");
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			appendStringInfoString(&buffer, "tablesample method");
+			break;
+
 		default:
 			appendStringInfo(&buffer, "unrecognized %u", object->classId);
 			break;
@@ -4025,6 +4069,23 @@ getObjectIdentityParts(const ObjectAddress *object,
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+				Form_pg_tablesample_method tsmForm;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				tsmForm = (Form_pg_tablesample_method) GETSTRUCT(tup);
+				appendStringInfoString(&buffer,
+							   quote_identifier(NameStr(tsmForm->tsmname)));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index b1ac704..04fcd8c 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -18,8 +18,8 @@ OBJS = aggregatecmds.o alter.o analyze.o async.o cluster.o comment.o  \
 	event_trigger.o explain.o extension.o foreigncmds.o functioncmds.o \
 	indexcmds.o lockcmds.o matview.o operatorcmds.o opclasscmds.o \
 	policy.o portalcmds.o prepare.o proclang.o \
-	schemacmds.o seclabel.o sequence.o tablecmds.o tablespace.o trigger.o \
-	tsearchcmds.o typecmds.o user.o vacuum.o vacuumlazy.o \
-	variable.o view.o
+	schemacmds.o seclabel.o sequence.o tablecmds.o tablesample.o \
+	tablespace.o trigger.o tsearchcmds.o typecmds.o user.o vacuum.o \
+	vacuumlazy.o variable.o view.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/commands/dropcmds.c b/src/backend/commands/dropcmds.c
index e5185ba..04d29a2 100644
--- a/src/backend/commands/dropcmds.c
+++ b/src/backend/commands/dropcmds.c
@@ -421,6 +421,10 @@ does_not_exist_skipping(ObjectType objtype, List *objname, List *objargs)
 				args = strVal(linitial(objargs));
 			}
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			msg = gettext_noop("tablesample method \"%s\" does not exist, skipping");
+			name = NameListToString(objname);
+			break;
 		default:
 			elog(ERROR, "unexpected object type (%d)", (int) objtype);
 			break;
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index a33a5ad..f20e9f7 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -97,6 +97,7 @@ static event_trigger_support_data event_trigger_support[] = {
 	{"SEQUENCE", true},
 	{"SERVER", true},
 	{"TABLE", true},
+	{"TABLESAMPLE METHOD", true},
 	{"TABLESPACE", false},
 	{"TRIGGER", true},
 	{"TEXT SEARCH CONFIGURATION", true},
@@ -1078,6 +1079,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_SEQUENCE:
 		case OBJECT_TABCONSTRAINT:
 		case OBJECT_TABLE:
+		case OBJECT_TABLESAMPLEMETHOD:
 		case OBJECT_TRIGGER:
 		case OBJECT_TSCONFIGURATION:
 		case OBJECT_TSDICTIONARY:
@@ -1134,6 +1136,7 @@ EventTriggerSupportsObjectClass(ObjectClass objclass)
 		case OCLASS_DEFACL:
 		case OCLASS_EXTENSION:
 		case OCLASS_POLICY:
+		case OCLASS_TABLESAMPLEMETHOD:
 			return true;
 
 		case MAX_OCLASS:
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 66d5083..b67c560 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8059,6 +8059,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 			case OCLASS_USER_MAPPING:
 			case OCLASS_DEFACL:
 			case OCLASS_EXTENSION:
+			case OCLASS_TABLESAMPLEMETHOD:
 
 				/*
 				 * We don't expect any of these sorts of objects to depend on
diff --git a/src/backend/commands/tablesample.c b/src/backend/commands/tablesample.c
new file mode 100644
index 0000000..58cddf5
--- /dev/null
+++ b/src/backend/commands/tablesample.c
@@ -0,0 +1,398 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *	  Commands to manipulate tablesample methods
+ *
+ * Table sampling methods provide algorithms for doing sample scan over
+ * the table.
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/tablesample.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "access/heapam.h"
+#include "access/htup_details.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/objectaccess.h"
+#include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
+#include "catalog/pg_type.h"
+#include "commands/defrem.h"
+#include "miscadmin.h"
+#include "parser/parse_func.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+
+static Datum
+get_tabmesample_method_func(DefElem *defel, int attnum)
+{
+	List	   *funcName = defGetQualifiedName(defel);
+	/* Big enough size for our needs. */
+	Oid		   *typeId = palloc0(6 * sizeof(Oid));
+	Oid			retTypeId;
+	int			nargs;
+	Oid			procOid = InvalidOid;
+	FuncCandidateList clist;
+
+	switch (attnum)
+	{
+		case Anum_pg_tablesample_method_tsminit:
+			/*
+			 * tsminit needs special handling because it is defined as function
+			 * with 3 or more arguments and only first two arguments must have
+			 * specific type, the rest is up to the tablesample method creator.
+			 */
+			{
+				nargs = 2;
+				typeId[0] = INTERNALOID;
+				typeId[1] = INT4OID;
+				retTypeId = VOIDOID;
+
+				clist = FuncnameGetCandidates(funcName, -1, NIL, false, false, false);
+
+				while (clist)
+				{
+					if (clist->nargs >= 3 &&
+						memcmp(typeId, clist->args, nargs * sizeof(Oid)) == 0)
+					{
+						procOid = clist->oid;
+						/* Save real function signature for future errors. */
+						nargs = clist->nargs;
+						pfree(typeId);
+						typeId = clist->args;
+						break;
+					}
+					clist = clist->next;
+				}
+
+				if (!OidIsValid(procOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_UNDEFINED_FUNCTION),
+							 errmsg("function \"%s\" does not exist or does not have valid signature",
+									NameListToString(funcName)),
+							 errhint("The tamplesample method init function "
+									 "must have at least 3 input parameters "
+									 "with first one of type INTERNAL and second of type INTEGER.")));
+			}
+			break;
+
+		case Anum_pg_tablesample_method_tsmnextblock:
+			nargs = 2;
+			typeId[0] = INTERNALOID;
+			typeId[1] = BOOLOID;
+			retTypeId = INT4OID;
+			break;
+		case Anum_pg_tablesample_method_tsmnexttuple:
+			nargs = 4;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INT2OID;
+			typeId[3] = BOOLOID;
+			retTypeId = INT2OID;
+			break;
+		case Anum_pg_tablesample_method_tsmend:
+		case Anum_pg_tablesample_method_tsmreset:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		case Anum_pg_tablesample_method_tsmcost:
+			nargs = 6;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INTERNALOID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = INTERNALOID;
+			typeId[4] = INTERNALOID;
+			typeId[5] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		default:
+			/* should not be here */
+			elog(ERROR, "unrecognized attribute for tablesample method: %d",
+				 attnum);
+			nargs = 0;			/* keep compiler quiet */
+	}
+
+	if (!OidIsValid(procOid))
+		procOid = LookupFuncName(funcName, nargs, typeId, false);
+	if (get_func_rettype(procOid) != retTypeId)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("function %s should return type %s",
+						func_signature_string(funcName, nargs, NIL, typeId),
+						format_type_be(retTypeId))));
+
+	return ObjectIdGetDatum(procOid);
+}
+
+/*
+ * make pg_depend entries for a new pg_tablsample_method entry
+ */
+static void
+makeParserDependencies(HeapTuple tuple)
+{
+	Form_pg_tablesample_method tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	ObjectAddress	myself,
+					referenced;
+
+	myself.classId = TableSampleMethodRelationId;
+	myself.objectId = HeapTupleGetOid(tuple);
+	myself.objectSubId = 0;
+
+	/* dependency on extension */
+	recordDependencyOnCurrentExtension(&myself, false);
+
+	/* dependencies on functions */
+	referenced.classId = ProcedureRelationId;
+	referenced.objectSubId = 0;
+
+	referenced.objectId = tsm->tsminit;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnextblock;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnexttuple;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmend;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmreset;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmcost;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+}
+
+/*
+ * Create a table sampling method
+ *
+ * Only superusers can create a table sampling methods.
+ */
+Oid
+DefineTablesampleMethod(List *names, List *parameters)
+{
+	char	   *tsmname = strVal(linitial(names));
+	Oid			tsmoid;
+	ListCell   *pl;
+	Relation	rel;
+	Datum		values[Natts_pg_tablesample_method];
+	bool		nulls[Natts_pg_tablesample_method];
+	HeapTuple	tuple;
+
+	/* Must be super user. */
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied to create tablesample method \"%s\"",
+						tsmname),
+				 errhint("Must be superuser to create a tablesample method.")));
+
+	/* Must not already exist. */
+	tsmoid = get_tablesample_method_oid(tsmname, true);
+	if (OidIsValid(tsmoid))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" already exists",
+						tsmname)));
+
+	/* Initialize the values. */
+	memset(values, 0, sizeof(values));
+	memset(nulls, false, sizeof(nulls));
+
+	values[Anum_pg_tablesample_method_tsmname - 1] =
+		DirectFunctionCall1(namein, CStringGetDatum(tsmname));
+
+	/*
+	 * loop over the definition list and extract the information we need.
+	 */
+	foreach(pl, parameters)
+	{
+		DefElem    *defel = (DefElem *) lfirst(pl);
+
+		if (pg_strcasecmp(defel->defname, "init") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsminit - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsminit);
+		}
+		else if (pg_strcasecmp(defel->defname, "nextblock") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnextblock - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnextblock);
+		}
+		else if (pg_strcasecmp(defel->defname, "nexttuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnexttuple - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnexttuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "end") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmend - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmend);
+		}
+		else if (pg_strcasecmp(defel->defname, "reset") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmreset - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmreset);
+		}
+		else if (pg_strcasecmp(defel->defname, "cost") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmcost - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmcost);
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("tablesample method parameter \"%s\" not recognized",
+						defel->defname)));
+	}
+
+	/*
+	 * Validation.
+	 */
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsminit - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method init function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnextblock - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nextblock function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnexttuple - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nexttuple function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmend - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method end function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmreset - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method reset function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmcost - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method cost function is required")));
+
+	/*
+	 * Insert tuple into pg_tablesample_method.
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = heap_form_tuple(rel->rd_att, values, nulls);
+
+	tsmoid = simple_heap_insert(rel, tuple);
+
+	CatalogUpdateIndexes(rel, tuple);
+
+	makeParserDependencies(tuple);
+
+	heap_freetuple(tuple);
+
+	/* Post creation hook for new tablesample method */
+	InvokeObjectPostCreateHook(TableSampleMethodRelationId, tsmoid, 0);
+
+	heap_close(rel, RowExclusiveLock);
+
+	return tsmoid;
+}
+
+/*
+ * Drop a tablesample method.
+ */
+void
+RemoveTablesampleMethodById(Oid tsmoid)
+{
+	Relation	rel;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+
+	/*
+	 * Find the target tuple
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmoid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for tablesample method %u",
+			 tsmoid);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	/* Can't drop builtin tablesample methods. */
+	if (tsmoid == TABLESAMPLE_METHOD_SYSTEM_OID ||
+		tsmoid == TABLESAMPLE_METHOD_BERNOULLI_OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied for tablesample method %s",
+						NameStr(tsm->tsmname))));
+
+	/*
+	 * Remove the pg_tablespace tuple (this will roll back if we fail below)
+	 */
+	simple_heap_delete(rel, &tuple->t_self);
+
+	ReleaseSysCache(tuple);
+
+	heap_close(rel, RowExclusiveLock);
+}
+
+/*
+ * get_tablesample_method_oid - given a tablesample method name,
+ * look up the OID
+ *
+ * If missing_ok is false, throw an error if tablesample method name not found.
+ * If true, just return InvalidOid.
+ */
+Oid
+get_tablesample_method_oid(const char *tsmname, bool missing_ok)
+{
+	Oid			result;
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(tsmname));
+	if (HeapTupleIsValid(tuple))
+	{
+		result = HeapTupleGetOid(tuple);
+		ReleaseSysCache(tuple);
+	}
+	else
+		result = InvalidOid;
+
+	if (!OidIsValid(result) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						tsmname)));
+
+	return result;
+}
+
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 01d72d4..4bf4aff 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -586,7 +586,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATERIALIZED MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
+	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P
+	MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEXT NO NONE
 	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
@@ -5094,6 +5095,15 @@ DefineStmt:
 					n->definition = list_make1(makeDefElem("from", (Node *) $5));
 					$$ = (Node *)n;
 				}
+			| CREATE TABLESAMPLE METHOD name definition
+				{
+					DefineStmt *n = makeNode(DefineStmt);
+					n->kind = OBJECT_TABLESAMPLEMETHOD;
+					n->args = NIL;
+					n->defnames = list_make1(makeString($4));
+					n->definition = $5;
+					$$ = (Node *)n;
+				}
 		;
 
 definition: '(' def_list ')'						{ $$ = $2; }
@@ -5552,6 +5562,7 @@ drop_type:	TABLE									{ $$ = OBJECT_TABLE; }
 			| TEXT_P SEARCH DICTIONARY				{ $$ = OBJECT_TSDICTIONARY; }
 			| TEXT_P SEARCH TEMPLATE				{ $$ = OBJECT_TSTEMPLATE; }
 			| TEXT_P SEARCH CONFIGURATION			{ $$ = OBJECT_TSCONFIGURATION; }
+			| TABLESAMPLE METHOD					{ $$ = OBJECT_TABLESAMPLEMETHOD; }
 		;
 
 any_name_list:
@@ -13313,6 +13324,7 @@ unreserved_keyword:
 			| MATCH
 			| MATERIALIZED
 			| MAXVALUE
+			| METHOD
 			| MINUTE_P
 			| MINVALUE
 			| MODE
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 3533cfa..532256d 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -23,6 +23,7 @@
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/toasting.h"
 #include "commands/alter.h"
 #include "commands/async.h"
@@ -1106,6 +1107,11 @@ ProcessUtilitySlow(Node *parsetree,
 							Assert(stmt->args == NIL);
 							DefineCollation(stmt->defnames, stmt->definition);
 							break;
+						case OBJECT_TABLESAMPLEMETHOD:
+							Assert(stmt->args == NIL);
+							Assert(list_length(stmt->defnames) == 1);
+							DefineTablesampleMethod(stmt->defnames, stmt->definition);
+							break;
 						default:
 							elog(ERROR, "unrecognized define stmt type: %d",
 								 (int) stmt->kind);
@@ -1960,6 +1966,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_POLICY:
 					tag = "DROP POLICY";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "DROP TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
@@ -2056,6 +2065,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_COLLATION:
 					tag = "CREATE COLLATION";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "CREATE TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 6481ac8..30653f8 100644
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -148,6 +148,7 @@ typedef enum ObjectClass
 	OCLASS_EXTENSION,			/* pg_extension */
 	OCLASS_EVENT_TRIGGER,		/* pg_event_trigger */
 	OCLASS_POLICY,				/* pg_policy */
+	OCLASS_TABLESAMPLEMETHOD,	/* pg_tablesample_method */
 	MAX_OCLASS					/* MUST BE LAST */
 } ObjectClass;
 
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
index 0e4a716..4ae8364 100644
--- a/src/include/catalog/pg_tablesample_method.h
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -64,7 +64,18 @@ typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
 
 DATA(insert OID = 3283 ( system tsm_system_init tsm_system_nextblock tsm_system_nexttuple tsm_system_end tsm_system_reset tsm_system_cost ));
 DESCR("SYSTEM table sampling method");
+#define TABLESAMPLE_METHOD_SYSTEM_OID 3283
 DATA(insert OID = 3284 ( bernoulli tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
 DESCR("BERNOULLI table sampling method");
+#define TABLESAMPLE_METHOD_BERNOULLI_OID 3284
+
+/* ----------------
+ *		functions for manipulation of pg_tablesample_method
+ * ----------------
+ */
+
+extern Oid DefineTablesampleMethod(List *names, List *parameters);
+extern void RemoveTablesampleMethodById(Oid tsmoid);
+extern Oid get_tablesample_method_oid(const char *tsmname, bool missing_ok);
 
 #endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index d87343f..54c4ba5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1267,6 +1267,7 @@ typedef enum ObjectType
 	OBJECT_SEQUENCE,
 	OBJECT_TABCONSTRAINT,
 	OBJECT_TABLE,
+	OBJECT_TABLESAMPLEMETHOD,
 	OBJECT_TABLESPACE,
 	OBJECT_TRIGGER,
 	OBJECT_TSCONFIGURATION,
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 67c3b1f..33c0f3d 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -877,7 +877,7 @@ typedef struct TidPath
 typedef struct SamplePath
 {
 	Path		path;
-	Oid			tsmcost;		/* table sample method costing function */
+	Oid			tsmcost;		/* tablesample method costing function */
 	List	   *tsmargs;		/* arguments to a TABLESAMPLE clause */
 } SamplePath;
 
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 6ff7b44..c3269c0 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -236,6 +236,7 @@ PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("mode", MODE, UNRESERVED_KEYWORD)
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 93d93af..37ea524 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -9,7 +9,8 @@ SUBDIRS = \
 		  worker_spi \
 		  dummy_seclabel \
 		  test_shm_mq \
-		  test_parser
+		  test_parser \
+		  tablesample
 
 all: submake-errcodes
 
diff --git a/src/test/modules/tablesample/.gitignore b/src/test/modules/tablesample/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/src/test/modules/tablesample/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/src/test/modules/tablesample/Makefile b/src/test/modules/tablesample/Makefile
new file mode 100644
index 0000000..f5220a9
--- /dev/null
+++ b/src/test/modules/tablesample/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/test_parser/Makefile
+
+MODULE_big = tsm_test
+OBJS = tsm_test.o $(WIN32RES)
+PGFILEDESC = "tsn_test - example of a custom tablesample method"
+
+EXTENSION = tsm_test
+DATA = tsm_test--1.0.sql
+
+REGRESS = tablesample
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/tablesample/expected/tablesample.out b/src/test/modules/tablesample/expected/tablesample.out
new file mode 100644
index 0000000..95c8036
--- /dev/null
+++ b/src/test/modules/tablesample/expected/tablesample.out
@@ -0,0 +1,39 @@
+CREATE EXTENSION tsm_test;
+CREATE TABLE test_tsm AS SELECT md5(i::text) a FROM generate_series(1,10) g(i);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test(true);
+                a                 
+----------------------------------
+ c4ca4238a0b923820dcc509a6f75849b
+ c81e728d9d4c2f636f067f89cc14862c
+ eccbc87e4b5ce2fe28308fd9f2a7baf3
+ a87ff679a2f3e71d9181a67b7542122c
+ e4da3b7fbbce2345d7772b0674a318d5
+ 1679091c5a880faf6fb5e6087eb1b2dc
+ 8f14e45fceea167a5a36dedd4bea2543
+ c9f0f895fb98ab9159f51fd0297e236d
+ 45c48cce2e2d7fbdea1afc51c7c6ad26
+ d3d9446802a44259755d38e6d163e820
+(10 rows)
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test(false);
+ a 
+---
+(0 rows)
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test(true);
+DROP TABLESAMPLE METHOD tsm_test;
+ERROR:  cannot drop tablesample method tsm_test because extension tsm_test requires it
+HINT:  You can drop extension tsm_test instead.
+DROP EXTENSION tsm_test;
+ERROR:  cannot drop extension tsm_test because other objects depend on it
+DETAIL:  view test_tsm_v depends on tablesample method tsm_test
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+DROP EXTENSION tsm_test CASCADE;
+NOTICE:  drop cascades to view test_tsm_v
+SELECT * FROM pg_tablesample_method;
+  tsmname  |      tsminit       |      tsmnextblock       |      tsmnexttuple       |      tsmend       |      tsmreset       |      tsmcost       
+-----------+--------------------+-------------------------+-------------------------+-------------------+---------------------+--------------------
+ system    | tsm_system_init    | tsm_system_nextblock    | tsm_system_nexttuple    | tsm_system_end    | tsm_system_reset    | tsm_system_cost
+ bernoulli | tsm_bernoulli_init | tsm_bernoulli_nextblock | tsm_bernoulli_nexttuple | tsm_bernoulli_end | tsm_bernoulli_reset | tsm_bernoulli_cost
+(2 rows)
+
diff --git a/src/test/modules/tablesample/sql/tablesample.sql b/src/test/modules/tablesample/sql/tablesample.sql
new file mode 100644
index 0000000..70997bd
--- /dev/null
+++ b/src/test/modules/tablesample/sql/tablesample.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_test;
+
+CREATE TABLE test_tsm AS SELECT md5(i::text) a FROM generate_series(1,10) g(i);
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test(true);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test(false);
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test(true);
+
+DROP TABLESAMPLE METHOD tsm_test;
+DROP EXTENSION tsm_test;
+DROP EXTENSION tsm_test CASCADE;
+
+SELECT * FROM pg_tablesample_method;
diff --git a/src/test/modules/tablesample/tsm_test--1.0.sql b/src/test/modules/tablesample/tsm_test--1.0.sql
new file mode 100644
index 0000000..6cfa014
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test--1.0.sql
@@ -0,0 +1,44 @@
+/* src/test/modules/tablesample/tsm_test--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_test" to load this file. \quit
+
+CREATE FUNCTION tsm_test_init(internal, int4, bool)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nextblock(internal, bool)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nexttuple(internal, int4, int2, bool)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_cost(internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+
+CREATE TABLESAMPLE METHOD tsm_test (
+    INIT		= tsm_test_init,
+    NEXTBLOCK	= tsm_test_nextblock,
+    NEXTTUPLE	= tsm_test_nexttuple,
+	END			= tsm_test_end,
+    RESET		= tsm_test_reset,
+	COST		= tsm_test_cost
+);
diff --git a/src/test/modules/tablesample/tsm_test.c b/src/test/modules/tablesample/tsm_test.c
new file mode 100644
index 0000000..98d5721
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.c
@@ -0,0 +1,179 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_test.c
+ *	  Simple example of a custom tablesample method
+ *
+ * Copyright (c) 2007-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/test/modules/tablesample/tsm_test.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+
+PG_MODULE_MAGIC;
+
+/* State */
+typedef struct
+{
+	bool ret;
+	BlockNumber tblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} tsm_test_state;
+
+
+PG_FUNCTION_INFO_V1(tsm_test_init);
+PG_FUNCTION_INFO_V1(tsm_test_nextblock);
+PG_FUNCTION_INFO_V1(tsm_test_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_test_end);
+PG_FUNCTION_INFO_V1(tsm_test_reset);
+PG_FUNCTION_INFO_V1(tsm_test_cost);
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_test_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	bool			ret;
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	tsm_test_state *state;
+
+	if (PG_ARGISNULL(2))
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("Return has cannot be NULL.")));
+
+	ret = PG_GETARG_BOOL(2);
+
+	state = palloc0(sizeof(tsm_test_state));
+
+	/* Remember initial values for reinit */
+	state->ret = ret;
+	state->tblocks = RelationGetNumberOfBlocks(rel);
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+	scanstate->tsmdata = (void *) state;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_test_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (!state->ret)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	if (state->blockno == InvalidBlockNumber)
+		state->blockno = 0;
+	else if (++state->blockno >= state->tblocks)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	PG_RETURN_UINT32(state->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ */
+Datum
+tsm_test_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (!state->ret)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	if (state->lt == InvalidOffsetNumber)
+		state->lt = FirstOffsetNumber;
+	else if (++state->lt > maxoffset)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	PG_RETURN_UINT16(state->lt);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_test_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_test_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_test_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	SamplePath	   *path = (SamplePath *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+	List		   *args = path->tsmargs;
+	Node		   *pctnode;
+	bool			ret;
+
+	SamplerAccessStrategy *strategy = (SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_SEQUENTIAL;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+		ret = DatumGetBool(((Const *) pctnode)->constvalue);
+	else
+		ret = true;
+
+	*pages = ret ? baserel->pages : 0;
+	*tuples = ret ? baserel->tuples : 0;
+
+	PG_RETURN_VOID();
+}
+
diff --git a/src/test/modules/tablesample/tsm_test.control b/src/test/modules/tablesample/tsm_test.control
new file mode 100644
index 0000000..a7b2741
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.control
@@ -0,0 +1,5 @@
+# tsm_test extension
+comment = 'test module for custom tablesample method'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_test'
+relocatable = true
-- 
1.9.1

>From 0d61cf71bd65ea054f0b80a12fb5c70bf652a0dc Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:36:56 +0100
Subject: [PATCH 1/3] separate block sampling functions v2

---
 contrib/file_fdw/file_fdw.c         |   9 +-
 contrib/postgres_fdw/postgres_fdw.c |  10 +-
 src/backend/commands/analyze.c      | 225 +----------------------------------
 src/backend/utils/misc/Makefile     |   2 +-
 src/backend/utils/misc/sampling.c   | 226 ++++++++++++++++++++++++++++++++++++
 src/include/commands/vacuum.h       |   3 -
 src/include/utils/sampling.h        |  44 +++++++
 7 files changed, 287 insertions(+), 232 deletions(-)
 create mode 100644 src/backend/utils/misc/sampling.c
 create mode 100644 src/include/utils/sampling.h

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index d569760..df732c0 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -34,6 +34,7 @@
 #include "optimizer/var.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -1005,7 +1006,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 {
 	int			numrows = 0;
 	double		rowstoskip = -1;	/* -1 means not set yet */
-	double		rstate;
+	ReservoirStateData rstate;
 	TupleDesc	tupDesc;
 	Datum	   *values;
 	bool	   *nulls;
@@ -1043,7 +1044,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 									   ALLOCSET_DEFAULT_MAXSIZE);
 
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Set up callback to identify error line number. */
 	errcallback.callback = CopyFromErrorCallback;
@@ -1087,7 +1088,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 			 * not-yet-incremented value of totalrows as t.
 			 */
 			if (rowstoskip < 0)
-				rowstoskip = anl_get_next_S(*totalrows, targrows, &rstate);
+				rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
 
 			if (rowstoskip <= 0)
 			{
@@ -1095,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * anl_random_fract());
+				int			k = (int) (targrows * sampler_random_fract());
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index d76e739..cbcba6e 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -37,6 +37,7 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -202,7 +203,7 @@ typedef struct PgFdwAnalyzeState
 	/* for random sampling */
 	double		samplerows;		/* # of rows fetched */
 	double		rowstoskip;		/* # of rows to skip before next sample */
-	double		rstate;			/* random state */
+	ReservoirStateData rstate;		/* state for reservoir sampling*/
 
 	/* working memory contexts */
 	MemoryContext anl_cxt;		/* context for per-analyze lifespan data */
@@ -2393,7 +2394,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 	astate.numrows = 0;
 	astate.samplerows = 0;
 	astate.rowstoskip = -1;		/* -1 means not set yet */
-	astate.rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&astate.rstate, targrows);
 
 	/* Remember ANALYZE context, and create a per-tuple temp context */
 	astate.anl_cxt = CurrentMemoryContext;
@@ -2533,13 +2534,12 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		 * analyze.c; see Jeff Vitter's paper.
 		 */
 		if (astate->rowstoskip < 0)
-			astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
-												&astate->rstate);
+			astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
 
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * anl_random_fract());
+			pos = (int) (targrows * sampler_random_fract());
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 5de2b39..ae44d22 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -88,10 +78,6 @@ static BufferAccessStrategy vac_strategy;
 static void do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -947,94 +933,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1080,7 +978,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	BlockNumber totalblocks;
 	TransactionId OldestXmin;
 	BlockSamplerData bs;
-	double		rstate;
+	ReservoirStateData rstate;
 
 	Assert(targrows > 0);
 
@@ -1090,9 +988,9 @@ acquire_sample_rows(Relation onerel, int elevel,
 	OldestXmin = GetOldestXmin(onerel, true);
 
 	/* Prepare for sampling block numbers */
-	BlockSampler_Init(&bs, totalblocks, targrows);
+	BlockSampler_Init(&bs, totalblocks, targrows, random());
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Outer loop over blocks to sample */
 	while (BlockSampler_HasMore(&bs))
@@ -1240,8 +1138,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 					 * t.
 					 */
 					if (rowstoskip < 0)
-						rowstoskip = anl_get_next_S(samplerows, targrows,
-													&rstate);
+						rowstoskip = reservoir_get_next_S(&rstate, samplerows, targrows);
 
 					if (rowstoskip <= 0)
 					{
@@ -1249,7 +1146,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1308,116 +1205,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
-/*
- * These two routines embody Algorithm Z from "Random sampling with a
- * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
- * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
- * of the count S of records to skip before processing another record.
- * It is computed primarily based on t, the number of records already read.
- * The only extra state needed between calls is W, a random state variable.
- *
- * anl_init_selection_state computes the initial W value.
- *
- * Given that we've already read t records (t >= n), anl_get_next_S
- * determines the number of records to skip before the next record is
- * processed.
- */
-double
-anl_init_selection_state(int n)
-{
-	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
-}
-
-double
-anl_get_next_S(double t, int n, double *stateptr)
-{
-	double		S;
-
-	/* The magic constant here is T from Vitter's paper */
-	if (t <= (22.0 * n))
-	{
-		/* Process records using Algorithm X until t is large enough */
-		double		V,
-					quot;
-
-		V = anl_random_fract(); /* Generate V */
-		S = 0;
-		t += 1;
-		/* Note: "num" in Vitter's code is always equal to t - n */
-		quot = (t - (double) n) / t;
-		/* Find min S satisfying (4.1) */
-		while (quot > V)
-		{
-			S += 1;
-			t += 1;
-			quot *= (t - (double) n) / t;
-		}
-	}
-	else
-	{
-		/* Now apply Algorithm Z */
-		double		W = *stateptr;
-		double		term = t - (double) n + 1;
-
-		for (;;)
-		{
-			double		numer,
-						numer_lim,
-						denom;
-			double		U,
-						X,
-						lhs,
-						rhs,
-						y,
-						tmp;
-
-			/* Generate U and X */
-			U = anl_random_fract();
-			X = t * (W - 1.0);
-			S = floor(X);		/* S is tentatively set to floor(X) */
-			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
-			tmp = (t + 1) / term;
-			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
-			rhs = (((t + X) / (term + S)) * term) / t;
-			if (lhs <= rhs)
-			{
-				W = rhs / lhs;
-				break;
-			}
-			/* Test if U <= f(S)/cg(X) */
-			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
-			if ((double) n < S)
-			{
-				denom = t;
-				numer_lim = term + S;
-			}
-			else
-			{
-				denom = t - (double) n + S;
-				numer_lim = t + 1;
-			}
-			for (numer = t + S; numer >= numer_lim; numer -= 1)
-			{
-				y *= numer / denom;
-				denom -= 1;
-			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
-			if (exp(log(y) / n) <= (t + X) / t)
-				break;
-		}
-		*stateptr = W;
-	}
-	return S;
-}
-
 /*
  * qsort comparator for sorting rows[] array
  */
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index 449d5b4..848ba29 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..1eeabaf
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,226 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Relation block sampling routines.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler provides algorithm for block level sampling of a relation
+ * as discussed on pgsql-hackers 2004-04-02 (subject "Large DB")
+ * It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table. If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
+				  long randseed)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+/*
+ * These two routines embody Algorithm Z from "Random sampling with a
+ * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
+ * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
+ * of the count S of records to skip before processing another record.
+ * It is computed primarily based on t, the number of records already read.
+ * The only extra state needed between calls is W, a random state variable.
+ *
+ * reservoir_init_selection_state computes the initial W value.
+ *
+ * Given that we've already read t records (t >= n), reservoir_get_next_S
+ * determines the number of records to skip before the next record is
+ * processed.
+ */
+void
+reservoir_init_selection_state(ReservoirState rs, int n)
+{
+	/* Initial value of W (for use when Algorithm Z is first applied) */
+	*rs = exp(-log(sampler_random_fract()) / n);
+}
+
+double
+reservoir_get_next_S(ReservoirState rs, double t, int n)
+{
+	double		S;
+
+	/* The magic constant here is T from Vitter's paper */
+	if (t <= (22.0 * n))
+	{
+		/* Process records using Algorithm X until t is large enough */
+		double		V,
+					quot;
+
+		V = sampler_random_fract(); /* Generate V */
+		S = 0;
+		t += 1;
+		/* Note: "num" in Vitter's code is always equal to t - n */
+		quot = (t - (double) n) / t;
+		/* Find min S satisfying (4.1) */
+		while (quot > V)
+		{
+			S += 1;
+			t += 1;
+			quot *= (t - (double) n) / t;
+		}
+	}
+	else
+	{
+		/* Now apply Algorithm Z */
+		double		W = *rs;
+		double		term = t - (double) n + 1;
+
+		for (;;)
+		{
+			double		numer,
+						numer_lim,
+						denom;
+			double		U,
+						X,
+						lhs,
+						rhs,
+						y,
+						tmp;
+
+			/* Generate U and X */
+			U = sampler_random_fract();
+			X = t * (W - 1.0);
+			S = floor(X);		/* S is tentatively set to floor(X) */
+			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
+			tmp = (t + 1) / term;
+			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
+			rhs = (((t + X) / (term + S)) * term) / t;
+			if (lhs <= rhs)
+			{
+				W = rhs / lhs;
+				break;
+			}
+			/* Test if U <= f(S)/cg(X) */
+			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
+			if ((double) n < S)
+			{
+				denom = t;
+				numer_lim = term + S;
+			}
+			else
+			{
+				denom = t - (double) n + S;
+				numer_lim = t + 1;
+			}
+			for (numer = t + S; numer >= numer_lim; numer -= 1)
+			{
+				y *= numer / denom;
+				denom -= 1;
+			}
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			if (exp(log(y) / n) <= (t + X) / t)
+				break;
+		}
+		*rs = W;
+	}
+	return S;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract()
+{
+	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+}
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 4275484..d38fead 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -178,8 +178,5 @@ extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 extern void analyze_rel(Oid relid, VacuumStmt *vacstmt,
 			bool in_outer_xact, BufferAccessStrategy bstrategy);
 extern bool std_typanalyze(VacAttrStats *stats);
-extern double anl_random_fract(void);
-extern double anl_init_selection_state(int n);
-extern double anl_get_next_S(double t, int n, double *stateptr);
 
 #endif   /* VACUUM_H */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..e3e7f9c
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,44 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+extern double sampler_random_fract(void);
+
+/* Block sampling methods */
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize, long randseed);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Reservoid sampling methods */
+typedef double ReservoirStateData;
+typedef ReservoirStateData *ReservoirState;
+
+extern void reservoir_init_selection_state(ReservoirState rs, int n);
+extern double reservoir_get_next_S(ReservoirState rs, double t, int n);
+
+#endif /* SAMPLING_H */
-- 
1.9.1

>From 5efa4aaab144ac31a4b5a419747de72a0a788348 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:37:55 +0100
Subject: [PATCH 2/3] tablesample v5

---
 contrib/file_fdw/file_fdw.c                 |   2 +-
 contrib/postgres_fdw/postgres_fdw.c         |   2 +-
 doc/src/sgml/ref/select.sgml                |  38 ++-
 src/backend/access/Makefile                 |   3 +-
 src/backend/catalog/Makefile                |   2 +-
 src/backend/commands/analyze.c              |   2 +-
 src/backend/commands/explain.c              |   7 +
 src/backend/executor/Makefile               |   2 +-
 src/backend/executor/execAmi.c              |   8 +
 src/backend/executor/execCurrent.c          |   1 +
 src/backend/executor/execProcnode.c         |  14 +
 src/backend/executor/nodeSamplescan.c       | 404 ++++++++++++++++++++++++++++
 src/backend/nodes/copyfuncs.c               |  57 ++++
 src/backend/nodes/equalfuncs.c              |  34 +++
 src/backend/nodes/nodeFuncs.c               |  12 +
 src/backend/nodes/outfuncs.c                |  58 ++++
 src/backend/nodes/readfuncs.c               |  42 +++
 src/backend/optimizer/path/allpaths.c       |  35 +++
 src/backend/optimizer/path/costsize.c       |  67 +++++
 src/backend/optimizer/plan/createplan.c     |  69 +++++
 src/backend/optimizer/plan/setrefs.c        |  11 +
 src/backend/optimizer/plan/subselect.c      |   1 +
 src/backend/optimizer/util/pathnode.c       |  29 ++
 src/backend/parser/gram.y                   |  40 ++-
 src/backend/parser/parse_clause.c           |  38 ++-
 src/backend/parser/parse_func.c             | 128 +++++++++
 src/backend/utils/Makefile                  |   3 +-
 src/backend/utils/adt/ruleutils.c           |  50 ++++
 src/backend/utils/cache/syscache.c          |  23 ++
 src/backend/utils/misc/sampling.c           |  33 ++-
 src/backend/utils/tablesample/Makefile      |  17 ++
 src/backend/utils/tablesample/bernoulli.c   | 203 ++++++++++++++
 src/backend/utils/tablesample/system.c      | 188 +++++++++++++
 src/include/catalog/indexing.h              |   5 +
 src/include/catalog/pg_proc.h               |  25 ++
 src/include/catalog/pg_tablesample_method.h |  70 +++++
 src/include/executor/nodeSamplescan.h       |  24 ++
 src/include/nodes/execnodes.h               |  20 ++
 src/include/nodes/nodes.h                   |   5 +
 src/include/nodes/parsenodes.h              |  33 +++
 src/include/nodes/plannodes.h               |   6 +
 src/include/nodes/relation.h                |  12 +
 src/include/optimizer/cost.h                |   1 +
 src/include/optimizer/pathnode.h            |   2 +
 src/include/parser/kwlist.h                 |   3 +-
 src/include/parser/parse_func.h             |   4 +
 src/include/utils/rel.h                     |   1 -
 src/include/utils/sampling.h                |  15 +-
 src/include/utils/syscache.h                |   2 +
 src/include/utils/tablesample.h             |  33 +++
 src/test/regress/expected/sanity_check.out  |   1 +
 src/test/regress/expected/tablesample.out   | 165 ++++++++++++
 src/test/regress/parallel_schedule          |   2 +-
 src/test/regress/serial_schedule            |   1 +
 src/test/regress/sql/tablesample.sql        |  39 +++
 55 files changed, 2065 insertions(+), 27 deletions(-)
 create mode 100644 src/backend/executor/nodeSamplescan.c
 create mode 100644 src/backend/utils/tablesample/Makefile
 create mode 100644 src/backend/utils/tablesample/bernoulli.c
 create mode 100644 src/backend/utils/tablesample/system.c
 create mode 100644 src/include/catalog/pg_tablesample_method.h
 create mode 100644 src/include/executor/nodeSamplescan.h
 create mode 100644 src/include/utils/tablesample.h
 create mode 100644 src/test/regress/expected/tablesample.out
 create mode 100644 src/test/regress/sql/tablesample.sql

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index df732c0..3fc3962 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -1096,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * sampler_random_fract());
+				int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index cbcba6e..95f196e 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -2539,7 +2539,7 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * sampler_random_fract());
+			pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 01d24a5..407bf9d 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,42 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        one of:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of those sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability.
+        The optional numeric parameter <literal>REPEATABLE</literal> is used
+        as random seed for sampling. Note that subsequent commands may return
+        different results even if same <literal>REPEATABLE</literal> clause
+        was specified. This happens because <acronym>DML</acronym> statements
+        and maintenance operations such as <command>VACUUM</> affect physical
+        distribution of data.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..238057a 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  transam
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..34db3e6 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesample_method.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index ae44d22..1dd4dcb 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1146,7 +1146,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * sampler_random_fract());
+						int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 8a0be5d..5152964 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -724,6 +724,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -950,6 +951,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			pname = sname = "Sample Scan";
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1067,6 +1071,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1319,6 +1324,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2147,6 +2153,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 6ebad2f..4948a26 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index 1c8be25..5cfe549 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 9892499..03c2feb 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..27f5f05
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,404 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "catalog/pg_tablesample_method.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "storage/bufmgr.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate, int eflags);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+
+/*
+ * Initialize the sampling method - loads function info and
+ * calls the tsminit function.
+ *
+ * We need special handling for this because the tsminit function
+ * is allowed to take optional additional arguments.
+ */
+static void
+InitSamplingMethod(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(scanstate->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(scanstate->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(scanstate->tsmnexttuple));
+	fmgr_info(tablesample->tsmend, &(scanstate->tsmend));
+	fmgr_info(tablesample->tsmreset, &(scanstate->tsmreset));
+
+	InitFunctionCallInfoData(fcinfo, &scanstate->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	/* First arg is always SampleScanState */
+	fcinfo.arg[0] = PointerGetDatum(scanstate);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause cannot be NULL")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+}
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	EState	   *estate;
+	TupleTableSlot *slot;
+	BlockNumber	blockno = InvalidBlockNumber;
+	Snapshot	snapshot;
+	Relation	relation;
+	bool		found = false;
+	bool		retry = false;
+	OffsetNumber tupoffset, maxoffset;
+	Buffer		buffer;
+	Page		page;
+	HeapTuple	tuple = &(node->tup);
+
+	/*
+	 * get information from the estate and scan state
+	 */
+	estate = node->ss.ps.state;
+	snapshot = estate->es_snapshot;
+	slot = node->ss.ss_ScanTupleSlot;
+	relation = node->ss.ss_currentRelation;
+	buffer = node->openbuffer;
+
+	if (BufferIsValid(buffer))
+	{
+		blockno = BufferGetBlockNumber(buffer);
+		page = BufferGetPage(buffer);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	/*
+	 * get the next tuple from the table
+	 */
+	for (;;)
+	{
+		ItemId			itemid;
+
+		CHECK_FOR_INTERRUPTS();
+
+		/* Load next block if needed. */
+		if (!BufferIsValid(buffer))
+		{
+			blockno = DatumGetInt32(FunctionCall2(&node->tsmnextblock,
+												  PointerGetDatum(node),
+												  BoolGetDatum(retry)));
+			/* No more blocks to fetch */
+			if (!BlockNumberIsValid(blockno))
+				break;
+
+			buffer = ReadBufferExtended(relation, MAIN_FORKNUM, blockno,
+										RBM_NORMAL, NULL);
+			LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+			node->openbuffer = buffer;
+			page = BufferGetPage(buffer);
+			maxoffset = PageGetMaxOffsetNumber(page);
+		}
+
+		tupoffset = DatumGetUInt16(FunctionCall4(&node->tsmnexttuple,
+												 PointerGetDatum(node),
+												 UInt32GetDatum(blockno),
+												 UInt16GetDatum(maxoffset),
+												 BoolGetDatum(retry)));
+		/* Go to next block. */
+		if (!OffsetNumberIsValid(tupoffset))
+		{
+			UnlockReleaseBuffer(buffer);
+			node->openbuffer = buffer = InvalidBuffer;
+			continue;
+		}
+		retry = true;
+
+		/* Skip invalid tuple pointers. */
+		itemid = PageGetItemId(page, tupoffset);
+		if (!ItemIdIsNormal(itemid))
+			continue;
+
+		tuple->t_tableOid = RelationGetRelid(relation);
+		tuple->t_data = (HeapTupleHeader) PageGetItem(page, itemid);
+		tuple->t_len = ItemIdGetLength(itemid);
+		ItemPointerSet(&tuple->t_self, blockno, tupoffset);
+
+		/* Found visible tuple, return it. */
+		if (HeapTupleSatisfiesVisibility(tuple, snapshot, buffer))
+		{
+			found = true;
+			break;
+		}
+	}
+
+	if (found)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   buffer,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+	node->ss.ss_currentScanDesc = NULL;
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	scanstate->openbuffer = InvalidBuffer;
+
+	InitSamplingMethod(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished thes can.
+	 */
+	FunctionCall1(&node->tsmend, PointerGetDatum(node));
+
+	if (BufferIsValid(node->openbuffer))
+	{
+		UnlockReleaseBuffer(node->openbuffer);
+		node->openbuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *scanstate)
+{
+	if (BufferIsValid(scanstate->openbuffer))
+	{
+		UnlockReleaseBuffer(scanstate->openbuffer);
+		scanstate->openbuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	FunctionCall1(&scanstate->tsmreset, PointerGetDatum(scanstate));
+
+	ExecScanReScan(&scanstate->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index f1a24f5..8861512 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -628,6 +628,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2006,6 +2022,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2138,6 +2155,37 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4075,6 +4123,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4723,6 +4774,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_PrivGrantee:
 			retval = _copyPrivGrantee(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 6e8b308..1e7ebbf 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2323,6 +2323,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2442,6 +2443,33 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3150,6 +3178,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_PrivGrantee:
 			retval = _equalPrivGrantee(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 21dfda7..bd9ce09 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3209,6 +3209,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index dd1278b..684cd7e 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -578,6 +578,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -1589,6 +1597,17 @@ _outTidPath(StringInfo str, const TidPath *node)
 }
 
 static void
+_outSamplePath(StringInfo str, const SamplePath *node)
+{
+	WRITE_NODE_TYPE("SAMPLEPATH");
+
+	_outPathInfo(str, (const Path *) node);
+
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(tsmargs);
+}
+
+static void
 _outForeignPath(StringInfo str, const ForeignPath *node)
 {
 	WRITE_NODE_TYPE("FOREIGNPATH");
@@ -2391,6 +2410,33 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2420,6 +2466,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2887,6 +2934,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3092,6 +3142,8 @@ _outNode(StringInfo str, const void *obj)
 			case T_TidPath:
 				_outTidPath(str, obj);
 				break;
+			case T_SamplePath:
+				_outSamplePath(str, obj);
 			case T_ForeignPath:
 				_outForeignPath(str, obj);
 				break;
@@ -3228,6 +3280,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index ae24d05..fe08107 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,43 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1216,6 +1253,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1311,6 +1349,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 58d78e6..c18973c 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,8 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -332,6 +334,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +425,34 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids		required_outer;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	add_path(rel, (Path *) create_samplescan_path(root, rel, required_outer));
+
+	/*
+	 * There is only one plan to consider but we still need to set
+	 * parameters for RelOptInfo.
+	 */
+	set_cheapest(rel);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 020558b..e4025a8 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -90,6 +90,7 @@
 #include "utils/lsyscache.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
+#include "utils/tablesample.h"
 #include "utils/tuplesort.h"
 
 
@@ -219,6 +220,72 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we dont't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(SamplePath *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	SamplerAccessStrategy strategy;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(path->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples),
+					 PointerGetDatum(&strategy));
+
+	/* Mark the path with the correct row estimate */
+	if (path->path.param_info)
+		path->path.rows = path->path.param_info->ppi_rows;
+	else
+		path->path.rows = tuples;
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = strategy == SAS_RANDOM ?
+		spc_random_page_cost : spc_seq_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->path.param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->path.startup_cost = startup_cost;
+	path->path.total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 655be81..10a5e02 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3318,6 +3369,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 7703946..de33fc6 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -446,6 +446,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 78fb6b1..191624c 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2163,6 +2163,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 1395a21..6206c60 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,33 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+SamplePath *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	SamplePath	   *pathnode = makeNode(SamplePath);
+	RangeTblEntry  *rte = planner_rt_fetch(rel->relid, root);
+	TableSampleClause *tablesample = rte->tablesample;
+
+	Assert(tablesample);
+
+	pathnode->path.pathtype = T_SampleScan;
+	pathnode->path.parent = rel;
+	pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->path.pathkeys = NIL;	/* samplescan has unordered result */
+
+	pathnode->tsmcost = tablesample->tsmcost;
+	pathnode->tsmargs = tablesample->args;
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1921,6 +1948,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 679e1bb..01d72d4 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -447,6 +447,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -611,8 +612,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10227,6 +10228,12 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample opt_alias_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10522,7 +10529,6 @@ relation_expr_list:
 			| relation_expr_list ',' relation_expr	{ $$ = lappend($1, $3); }
 		;
 
-
 /*
  * Given "UPDATE foo set set ...", we have to decide without looking any
  * further ahead whether the first "set" is an alias or the UPDATE's SET
@@ -10552,6 +10558,31 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $2;
+					n->relation = $1;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' func_arg_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' AexprConst ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/						{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13334,7 +13365,6 @@ unreserved_keyword:
 			| RELATIVE_P
 			| RELEASE
 			| RENAME
-			| REPEATABLE
 			| REPLACE
 			| REPLICA
 			| RESET
@@ -13509,6 +13539,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
@@ -13577,6 +13608,7 @@ reserved_keyword:
 			| PLACING
 			| PRIMARY
 			| REFERENCES
+			| REPEATABLE
 			| RETURNING
 			| SELECT
 			| SESSION_USER
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 654dce6..03632d2 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -413,6 +416,19 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *r)
+{
+	RangeTblEntry  *rte;
+	TableSampleClause *tablesample = NULL;
+
+	rte = transformTableEntry(pstate, r->relation);
+	tablesample = ParseTableSample(pstate, r->method, r->repeatable, r->args);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -421,7 +437,7 @@ transformTableEntry(ParseState *pstate, RangeVar *r)
 {
 	RangeTblEntry *rte;
 
-	/* We need only build a range table entry */
+	/* We first need to build a range table entry */
 	rte = addRangeTableEntry(pstate, r, r->alias,
 							 interpretInhOption(r->inhOpt), true);
 
@@ -1121,6 +1137,26 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index a200804..690d0fa 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -760,6 +762,132 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+extern TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				actual_arg_types[FUNC_MAX_ARGS];
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						samplemethod)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Transform the rest of arguments ... */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *arg = transformExpr(pstate, (Node *) lfirst(larg), EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		fargs = lappend(fargs, arg);
+
+		actual_arg_types[nargs++] = argtype;
+	}
+
+	/*
+	 * Check if parameters are correct.
+	 *
+	 * XXX: can we do better at hinting here?
+	 */
+	if (initnargs != nargs ||
+			!can_coerce_type(initnargs, actual_arg_types, init_arg_types,
+						COERCION_IMPLICIT))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("wrong parameters for tablesample method \"%s\"",
+						samplemethod)));
+
+	/* perform the necessary typecasting of arguments */
+	make_fn_arguments(pstate, fargs, actual_arg_types, init_arg_types);
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/utils/Makefile b/src/backend/utils/Makefile
index 8374533..9daa2ae 100644
--- a/src/backend/utils/Makefile
+++ b/src/backend/utils/Makefile
@@ -9,7 +9,8 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS        = fmgrtab.o
-SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time
+SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time \
+			  tablesample
 
 # location of Catalog.pm
 catalogdir  = $(top_srcdir)/src/backend/catalog
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index dd748ac..4f1c534 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -31,6 +31,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -343,6 +344,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4157,6 +4160,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for tablesample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8384,6 +8431,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index bd27168..3a8f01e 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
index 1eeabaf..f213c46 100644
--- a/src/backend/utils/misc/sampling.c
+++ b/src/backend/utils/misc/sampling.c
@@ -46,6 +46,8 @@ BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
 	bs->n = samplesize;
 	bs->t = 0;					/* blocks scanned so far */
 	bs->m = 0;					/* blocks selected so far */
+
+	sampler_random_init_state(randseed, bs->randstate);
 }
 
 bool
@@ -92,7 +94,7 @@ BlockSampler_Next(BlockSampler bs)
 	 * less than k, which means that we cannot fail to select enough blocks.
 	 *----------
 	 */
-	V = sampler_random_fract();
+	V = sampler_random_fract(bs->randstate);
 	p = 1.0 - (double) k / (double) K;
 	while (V < p)
 	{
@@ -126,8 +128,14 @@ BlockSampler_Next(BlockSampler bs)
 void
 reservoir_init_selection_state(ReservoirState rs, int n)
 {
+	/*
+	 * Reservoir sampling is not used anywhere where it would need to return
+	 * repeatable results so we can initialize it randomly.
+	 */
+	sampler_random_init_state(random(), rs->randstate);
+
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	*rs = exp(-log(sampler_random_fract()) / n);
+	rs->W = exp(-log(sampler_random_fract(rs->randstate)) / n);
 }
 
 double
@@ -142,7 +150,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 		double		V,
 					quot;
 
-		V = sampler_random_fract(); /* Generate V */
+		V = sampler_random_fract(rs->randstate); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -158,7 +166,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 	else
 	{
 		/* Now apply Algorithm Z */
-		double		W = *rs;
+		double		W = rs->W;
 		double		term = t - (double) n + 1;
 
 		for (;;)
@@ -174,7 +182,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 						tmp;
 
 			/* Generate U and X */
-			U = sampler_random_fract();
+			U = sampler_random_fract(rs->randstate);
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -203,11 +211,11 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract(rs->randstate)) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
-		*rs = W;
+		rs->W = W;
 	}
 	return S;
 }
@@ -217,10 +225,17 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
  * Random number generator used by sampling
  *----------
  */
+void
+sampler_random_init_state(long seed, SamplerRandomState randstate)
+{
+	randstate[0] = 0x330e;
+	randstate[1] = (unsigned short) seed;
+	randstate[2] = (unsigned short) (seed >> 16);
+}
 
 /* Select a random value R uniformly distributed in (0 - 1) */
 double
-sampler_random_fract()
+sampler_random_fract(SamplerRandomState randstate)
 {
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+	return pg_erand48(randstate);
 }
diff --git a/src/backend/utils/tablesample/Makefile b/src/backend/utils/tablesample/Makefile
new file mode 100644
index 0000000..df92939
--- /dev/null
+++ b/src/backend/utils/tablesample/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for utils/tablesample
+#
+# IDENTIFICATION
+#    src/backend/utils/tablesample/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/utils/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = system.o bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/tablesample/bernoulli.c b/src/backend/utils/tablesample/bernoulli.c
new file mode 100644
index 0000000..3720b87
--- /dev/null
+++ b/src/backend/utils/tablesample/bernoulli.c
@@ -0,0 +1,203 @@
+/*-------------------------------------------------------------------------
+ *
+ * bernoulli.c
+ *	  interface routines for BERNOULLI tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/* State */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	float4 samplesize;			/* percentage of tuples to return (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks = RelationGetNumberOfBlocks(rel);
+	sampler->blockno = InvalidBlockNumber;
+	sampler->samplesize = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = 0;
+	else if (++sampler->blockno >= sampler->tblocks)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+	double			samplesize = sampler->samplesize;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/* Every tuple has percent chance of being returned */
+	while (sampler_random_fract(sampler->randstate) > samplesize)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	SamplePath	   *path = (SamplePath *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+	List		   *args = path->tsmargs;
+	Node		   *pctnode;
+	float4			samplesize;
+
+	SamplerAccessStrategy *strategy =
+		(SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_SEQUENTIAL;
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (!IsA(pctnode, Const))
+	{
+		*tuples = baserel->tuples * 0.1;
+		PG_RETURN_VOID();
+	}
+
+	samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+	samplesize /= 100.0;
+
+	*tuples = baserel->tuples * samplesize;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/utils/tablesample/system.c b/src/backend/utils/tablesample/system.c
new file mode 100644
index 0000000..1899e84
--- /dev/null
+++ b/src/backend/utils/tablesample/system.c
@@ -0,0 +1,188 @@
+/*-------------------------------------------------------------------------
+ *
+ * system.c
+ *	  interface routines for system tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	SystemSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks =
+		RelationGetNumberOfBlocks(scanstate->ss.ss_currentRelation);
+	sampler->samplesize = 1 + (int) (sampler->tblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as VACUUM for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	BlockNumber		blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	SamplePath	   *path = (SamplePath *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+	List		   *args = path->tsmargs;
+	Node		   *pctnode;
+	float4			percent;
+
+	SamplerAccessStrategy *strategy =
+		(SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_RANDOM;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (!IsA(pctnode, Const))
+	{
+		*pages = baserel->pages * 0.1;
+		*tuples = baserel->tuples * 0.1;
+		PG_RETURN_VOID();
+	}
+
+	percent = DatumGetFloat4(((Const *) pctnode)->constvalue);
+	percent /= 100.0;
+
+	*pages = baserel->pages * percent;
+	*tuples = baserel->tuples * percent;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index a680229..c711cca 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3281, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3281
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3282, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3282
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 9edfdb8..a0f97ac 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5143,6 +5143,31 @@ DESCR("rank of hypothetical row without gaps");
 DATA(insert OID = 3993 ( dense_rank_final	PGNSP PGUID 12 1 0 2276 0 f f f f f f i 2 0 20 "2281 2276" "{2281,2276}" "{i,v}" _null_ _null_	hypothetical_dense_rank_final _null_ _null_ _null_ ));
 DESCR("aggregate final function");
 
+DATA(insert OID = 3285 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3286 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3287 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3288 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3289 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3290 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 6 0 2278 "2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3291 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3292 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3293 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3294 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3296 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3297 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 6 0 2278 "2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 0000000..0e4a716
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,70 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3280
+
+CATALOG(pg_tablesample_method,3280)
+{
+	NameData	tsmname;		/* tablescan method name */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method				7
+#define Anum_pg_tablesample_method_tsmname		1
+#define Anum_pg_tablesample_method_tsminit		2
+#define Anum_pg_tablesample_method_tsmnextblock	3
+#define Anum_pg_tablesample_method_tsmnexttuple	4
+#define Anum_pg_tablesample_method_tsmend		5
+#define Anum_pg_tablesample_method_tsmreset		6
+#define Anum_pg_tablesample_method_tsmcost		7
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3283 ( system tsm_system_init tsm_system_nextblock tsm_system_nexttuple tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3284 ( bernoulli tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 41288ed..43e1a30 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1212,6 +1212,26 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState		ss;
+
+	/* Sampling method functions. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmend;
+	FmgrInfo		tsmreset;
+
+	Buffer			openbuffer;		/* currently open buffer */
+	HeapTupleData	tup;			/* last tuple */
+
+	void		   *tsmdata;		/* for use by table scan method */
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 97ef0fc..99ac985 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -225,6 +227,7 @@ typedef enum NodeTag
 	T_MergePath,
 	T_HashPath,
 	T_TidPath,
+	T_SamplePath,
 	T_ForeignPath,
 	T_CustomPath,
 	T_AppendPath,
@@ -413,6 +416,8 @@ typedef enum NodeTag
 	T_XmlSerialize,
 	T_WithClause,
 	T_CommonTableExpr,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index b1dfa85..d87343f 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -307,6 +307,23 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -507,6 +524,21 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * We are more generic than SQL Standard so we pass generic function
+ * arguments to the sampling method.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -751,6 +783,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 316c9ce..8a2a146 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -278,6 +278,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 6845a40..67c3b1f 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -870,6 +870,18 @@ typedef struct TidPath
 } TidPath;
 
 /*
+ * SamplePath represents a sample sacn
+ *
+ * args is list of parameters for the the TABLESAMPLE clause
+ */
+typedef struct SamplePath
+{
+	Path		path;
+	Oid			tsmcost;		/* table sample method costing function */
+	List	   *tsmargs;		/* arguments to a TABLESAMPLE clause */
+} SamplePath;
+
+/*
  * ForeignPath represents a potential scan of a foreign table
  *
  * fdw_private stores FDW private data about the scan.  While fdw_private is
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 9c2000b..3777054 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(SamplePath *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 9923f0e..dfb580e 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern SamplePath *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+										  Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 7c243ec..6ff7b44 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -312,7 +312,7 @@ PG_KEYWORD("reindex", REINDEX, UNRESERVED_KEYWORD)
 PG_KEYWORD("relative", RELATIVE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("release", RELEASE, UNRESERVED_KEYWORD)
 PG_KEYWORD("rename", RENAME, UNRESERVED_KEYWORD)
-PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
+PG_KEYWORD("repeatable", REPEATABLE, RESERVED_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 3264691..6727e55 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,10 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 6bd786d..185bd81 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
index e3e7f9c..4ac208d 100644
--- a/src/include/utils/sampling.h
+++ b/src/include/utils/sampling.h
@@ -15,7 +15,12 @@
 
 #include "storage/bufmgr.h"
 
-extern double sampler_random_fract(void);
+/* Random generator for sampling code */
+typedef unsigned short SamplerRandomState[3];
+
+extern void sampler_random_init_state(long seed,
+									  SamplerRandomState randstate);
+extern double sampler_random_fract(SamplerRandomState randstate);
 
 /* Block sampling methods */
 /* Data structure for Algorithm S from Knuth 3.4.2 */
@@ -25,6 +30,7 @@ typedef struct
 	int			n;				/* desired sample size */
 	BlockNumber t;				/* current block number */
 	int			m;				/* blocks selected so far */
+	SamplerRandomState randstate; /* random generator state */
 } BlockSamplerData;
 
 typedef BlockSamplerData *BlockSampler;
@@ -35,7 +41,12 @@ extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
 /* Reservoid sampling methods */
-typedef double ReservoirStateData;
+typedef struct
+{
+	double	W;
+	SamplerRandomState randstate; /* random generator state */
+} ReservoirStateData;
+
 typedef ReservoirStateData *ReservoirState;
 
 extern void reservoir_init_selection_state(ReservoirState rs, int n);
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index ba0b090..6b628f6 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/include/utils/tablesample.h b/src/include/utils/tablesample.h
new file mode 100644
index 0000000..3c97a04
--- /dev/null
+++ b/src/include/utils/tablesample.h
@@ -0,0 +1,33 @@
+/*--------------------------------------------------------------------------
+ * tablesample.h
+ *	  Header file for builtin table sampling methods.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/utils/tablesample.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TABLESAMPLE_H
+#define TABLESAMPLE_H
+
+typedef enum SamplerAccessStrategy
+{
+	SAS_RANDOM,
+	SAS_SEQUENTIAL
+} SamplerAccessStrategy;
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TABLESAMPLE_H */
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..5946edf 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..9b387a2
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,165 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+CLOSE tablesample_cur;
+END;
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index e0ae2f2..e0240ac 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 7f762bd..9a7611b 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -152,3 +152,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..2b89b55
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,39 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+CLOSE tablesample_cur;
+END;
+
+DROP TABLE test_tablesample CASCADE;
-- 
1.9.1

>From 4c7282395650bd1f158fba4d0f8508b5eef84f9c Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:51:44 +0100
Subject: [PATCH 3/3] tablesample-ddl v2

---
 doc/src/sgml/ref/allfiles.sgml                     |   2 +
 doc/src/sgml/ref/create_tablesamplemethod.sgml     | 149 ++++++++
 doc/src/sgml/ref/drop_tablesamplemethod.sgml       |  87 +++++
 doc/src/sgml/reference.sgml                        |   2 +
 src/backend/catalog/dependency.c                   |  15 +-
 src/backend/catalog/objectaddress.c                |  65 +++-
 src/backend/commands/Makefile                      |   6 +-
 src/backend/commands/dropcmds.c                    |   4 +
 src/backend/commands/event_trigger.c               |   3 +
 src/backend/commands/tablecmds.c                   |   1 +
 src/backend/commands/tablesample.c                 | 398 +++++++++++++++++++++
 src/backend/parser/gram.y                          |  14 +-
 src/backend/tcop/utility.c                         |  12 +
 src/include/catalog/dependency.h                   |   1 +
 src/include/catalog/pg_tablesample_method.h        |  11 +
 src/include/nodes/parsenodes.h                     |   1 +
 src/include/nodes/relation.h                       |   2 +-
 src/include/parser/kwlist.h                        |   1 +
 src/test/modules/Makefile                          |   3 +-
 src/test/modules/tablesample/.gitignore            |   4 +
 src/test/modules/tablesample/Makefile              |  21 ++
 .../modules/tablesample/expected/tablesample.out   |  39 ++
 src/test/modules/tablesample/sql/tablesample.sql   |  14 +
 src/test/modules/tablesample/tsm_test--1.0.sql     |  44 +++
 src/test/modules/tablesample/tsm_test.c            | 180 ++++++++++
 src/test/modules/tablesample/tsm_test.control      |   5 +
 26 files changed, 1075 insertions(+), 9 deletions(-)
 create mode 100644 doc/src/sgml/ref/create_tablesamplemethod.sgml
 create mode 100644 doc/src/sgml/ref/drop_tablesamplemethod.sgml
 create mode 100644 src/backend/commands/tablesample.c
 create mode 100644 src/test/modules/tablesample/.gitignore
 create mode 100644 src/test/modules/tablesample/Makefile
 create mode 100644 src/test/modules/tablesample/expected/tablesample.out
 create mode 100644 src/test/modules/tablesample/sql/tablesample.sql
 create mode 100644 src/test/modules/tablesample/tsm_test--1.0.sql
 create mode 100644 src/test/modules/tablesample/tsm_test.c
 create mode 100644 src/test/modules/tablesample/tsm_test.control

diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index 7aa3128..2fad084 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -78,6 +78,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY createServer       SYSTEM "create_server.sgml">
 <!ENTITY createTable        SYSTEM "create_table.sgml">
 <!ENTITY createTableAs      SYSTEM "create_table_as.sgml">
+<!ENTITY createTablesampleMethod SYSTEM "create_tablesamplemethod.sgml">
 <!ENTITY createTableSpace   SYSTEM "create_tablespace.sgml">
 <!ENTITY createTrigger      SYSTEM "create_trigger.sgml">
 <!ENTITY createTSConfig     SYSTEM "create_tsconfig.sgml">
@@ -119,6 +120,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY dropSequence       SYSTEM "drop_sequence.sgml">
 <!ENTITY dropServer         SYSTEM "drop_server.sgml">
 <!ENTITY dropTable          SYSTEM "drop_table.sgml">
+<!ENTITY dropTablesampleMethod SYSTEM "drop_tablesamplemethod.sgml">
 <!ENTITY dropTableSpace     SYSTEM "drop_tablespace.sgml">
 <!ENTITY dropTrigger        SYSTEM "drop_trigger.sgml">
 <!ENTITY dropTSConfig       SYSTEM "drop_tsconfig.sgml">
diff --git a/doc/src/sgml/ref/create_tablesamplemethod.sgml b/doc/src/sgml/ref/create_tablesamplemethod.sgml
new file mode 100644
index 0000000..70720e5
--- /dev/null
+++ b/doc/src/sgml/ref/create_tablesamplemethod.sgml
@@ -0,0 +1,149 @@
+<!--
+doc/src/sgml/ref/create_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-CREATETABLESAMPLEMETHOD">
+ <indexterm zone="sql-createtablesamplemethod">
+  <primary>CREATE TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE TABLESAMPLE METHOD</refname>
+  <refpurpose>define custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE TABLESAMPLE METHOD <replaceable class="parameter">name</replaceable> (
+    INIT = <replaceable class="parameter">init_function</replaceable> ,
+    NEXTBLOCK = <replaceable class="parameter">nextblock_function</replaceable> ,
+    NEXTTUPLE = <replaceable class="parameter">nexttuple_function</replaceable> ,
+    END = <replaceable class="parameter">end_function</replaceable> ,
+    RESET = <replaceable class="parameter">reset_function</replaceable> ,
+    COST = <replaceable class="parameter">cost_function</replaceable>
+)
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE TABLESAMPLE METHOD</command> creates a tablesample method.
+   A tablesample method provides alrorithm for reading sample part of a table
+   when used in <command>TABLESAMPLE</> clause of a <command>SELECT</>
+   statement.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the tablesample method to be created. This name must be
+      unique within the database.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">init_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the init function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nextblock_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-block function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nexttuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-tuple function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">end_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the end function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">reset_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the reset function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">cost_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the costing function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+  <para>
+   The function names can be schema-qualified if necessary.  Argument types
+   are not given, since the argument list for each type of function is
+   predetermined.  All functions are required.
+  </para>
+
+  <para>
+   The arguments can appear in any order, not only the one shown above.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>CREATE TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-droptablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/ref/drop_tablesamplemethod.sgml b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
new file mode 100644
index 0000000..dffd2ec
--- /dev/null
+++ b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
@@ -0,0 +1,87 @@
+<!--
+doc/src/sgml/ref/drop_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-DROPTABLESAMPLEMETHOD">
+ <indexterm zone="sql-droptablesamplemethod">
+  <primary>DROP TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DROP TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP TABLESAMPLE METHOD</refname>
+  <refpurpose>remove a custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP TABLESAMPLE METHOD [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>DROP TABLESAMPLE METHOD</command> drop an existing tablesample
+   method.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the tablesample method does not exist.
+      A notice is issued in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of an existing tablesample method to be removed.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>DROP TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createtablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index 10c9a6d..2c09a3c 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -106,6 +106,7 @@
    &createServer;
    &createTable;
    &createTableAs;
+   &createTablesampleMethod;
    &createTableSpace;
    &createTSConfig;
    &createTSDictionary;
@@ -147,6 +148,7 @@
    &dropSequence;
    &dropServer;
    &dropTable;
+   &dropTablesampleMethod;
    &dropTableSpace;
    &dropTSConfig;
    &dropTSDictionary;
diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index bacb242..6acb5b3 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -46,6 +46,7 @@
 #include "catalog/pg_policy.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -157,7 +158,8 @@ static const Oid object_classes[MAX_OCLASS] = {
 	DefaultAclRelationId,		/* OCLASS_DEFACL */
 	ExtensionRelationId,		/* OCLASS_EXTENSION */
 	EventTriggerRelationId,		/* OCLASS_EVENT_TRIGGER */
-	PolicyRelationId			/* OCLASS_POLICY */
+	PolicyRelationId,			/* OCLASS_POLICY */
+	TableSampleMethodRelationId			/* OCLASS_TABLESAMPLEMETHOD */
 };
 
 
@@ -1265,6 +1267,10 @@ doDeletion(const ObjectAddress *object, int flags)
 			RemovePolicyById(object->objectId);
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			RemoveTablesampleMethodById(object->objectId);
+			break;
+
 		default:
 			elog(ERROR, "unrecognized object class: %u",
 				 object->classId);
@@ -1794,6 +1800,10 @@ find_expr_references_walker(Node *node,
 				case RTE_RELATION:
 					add_object_address(OCLASS_CLASS, rte->relid, 0,
 									   context->addrs);
+					if (rte->tablesample)
+						add_object_address(OCLASS_TABLESAMPLEMETHOD,
+										   rte->tablesample->tsmid, 0,
+										   context->addrs);
 					break;
 				default:
 					break;
@@ -2373,6 +2383,9 @@ getObjectClass(const ObjectAddress *object)
 
 		case PolicyRelationId:
 			return OCLASS_POLICY;
+
+		case TableSampleMethodRelationId:
+			return OCLASS_TABLESAMPLEMETHOD;
 	}
 
 	/* shouldn't get here */
diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index 825d8b2..02edc0a 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -44,6 +44,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_policy.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -429,7 +430,19 @@ static const ObjectPropertyType ObjectProperty[] =
 		Anum_pg_type_typacl,
 		ACL_KIND_TYPE,
 		true
-	}
+	},
+	{
+		TableSampleMethodRelationId,
+		TableSampleMethodOidIndexId,
+		TABLESAMPLEMETHODOID,
+		TABLESAMPLEMETHODNAME,
+		Anum_pg_tablesample_method_tsmname,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		-1,
+		true
+	},
 };
 
 /*
@@ -528,7 +541,9 @@ ObjectTypeMap[] =
 	/* OCLASS_EVENT_TRIGGER */
 	{ "event trigger", OBJECT_EVENT_TRIGGER },
 	/* OCLASS_POLICY */
-	{ "policy", OBJECT_POLICY }
+	{ "policy", OBJECT_POLICY },
+	/* OCLASS_TABLESAMPLEMETHOD */
+	{ "tablesample method", OBJECT_TABLESAMPLEMETHOD }
 };
 
 
@@ -670,6 +685,7 @@ get_object_address(ObjectType objtype, List *objname, List *objargs,
 			case OBJECT_FDW:
 			case OBJECT_FOREIGN_SERVER:
 			case OBJECT_EVENT_TRIGGER:
+			case OBJECT_TABLESAMPLEMETHOD:
 				address = get_object_address_unqualified(objtype,
 														 objname, missing_ok);
 				break;
@@ -896,6 +912,9 @@ get_object_address_unqualified(ObjectType objtype,
 			case OBJECT_EVENT_TRIGGER:
 				msg = gettext_noop("event trigger name cannot be qualified");
 				break;
+			case OBJECT_TABLESAMPLEMETHOD:
+				msg = gettext_noop("tablesample method name cannot be qualified");
+				break;
 			default:
 				elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 				msg = NULL;		/* placate compiler */
@@ -956,6 +975,11 @@ get_object_address_unqualified(ObjectType objtype,
 			address.objectId = get_event_trigger_oid(name, missing_ok);
 			address.objectSubId = 0;
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			address.classId = TableSampleMethodRelationId;
+			address.objectId = get_tablesample_method_oid(name, missing_ok);
+			address.objectSubId = 0;
+			break;
 		default:
 			elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 			/* placate compiler, which doesn't know elog won't return */
@@ -1720,6 +1744,7 @@ check_object_ownership(Oid roleid, ObjectType objtype, ObjectAddress address,
 			break;
 		case OBJECT_TSPARSER:
 		case OBJECT_TSTEMPLATE:
+		case OBJECT_TABLESAMPLEMETHOD:
 			/* We treat these object types as being owned by superusers */
 			if (!superuser_arg(roleid))
 				ereport(ERROR,
@@ -2654,6 +2679,21 @@ getObjectDescription(const ObjectAddress *object)
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				appendStringInfo(&buffer, _("tablesample method %s"),
+					 NameStr(((Form_pg_tablesample_method) GETSTRUCT(tup))->tsmname));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
@@ -3131,6 +3171,10 @@ getObjectTypeDescription(const ObjectAddress *object)
 			appendStringInfoString(&buffer, "policy");
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			appendStringInfoString(&buffer, "tablesample method");
+			break;
+
 		default:
 			appendStringInfo(&buffer, "unrecognized %u", object->classId);
 			break;
@@ -4025,6 +4069,23 @@ getObjectIdentityParts(const ObjectAddress *object,
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+				Form_pg_tablesample_method tsmForm;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				tsmForm = (Form_pg_tablesample_method) GETSTRUCT(tup);
+				appendStringInfoString(&buffer,
+							   quote_identifier(NameStr(tsmForm->tsmname)));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index b1ac704..04fcd8c 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -18,8 +18,8 @@ OBJS = aggregatecmds.o alter.o analyze.o async.o cluster.o comment.o  \
 	event_trigger.o explain.o extension.o foreigncmds.o functioncmds.o \
 	indexcmds.o lockcmds.o matview.o operatorcmds.o opclasscmds.o \
 	policy.o portalcmds.o prepare.o proclang.o \
-	schemacmds.o seclabel.o sequence.o tablecmds.o tablespace.o trigger.o \
-	tsearchcmds.o typecmds.o user.o vacuum.o vacuumlazy.o \
-	variable.o view.o
+	schemacmds.o seclabel.o sequence.o tablecmds.o tablesample.o \
+	tablespace.o trigger.o tsearchcmds.o typecmds.o user.o vacuum.o \
+	vacuumlazy.o variable.o view.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/commands/dropcmds.c b/src/backend/commands/dropcmds.c
index e5185ba..04d29a2 100644
--- a/src/backend/commands/dropcmds.c
+++ b/src/backend/commands/dropcmds.c
@@ -421,6 +421,10 @@ does_not_exist_skipping(ObjectType objtype, List *objname, List *objargs)
 				args = strVal(linitial(objargs));
 			}
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			msg = gettext_noop("tablesample method \"%s\" does not exist, skipping");
+			name = NameListToString(objname);
+			break;
 		default:
 			elog(ERROR, "unexpected object type (%d)", (int) objtype);
 			break;
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index a33a5ad..f20e9f7 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -97,6 +97,7 @@ static event_trigger_support_data event_trigger_support[] = {
 	{"SEQUENCE", true},
 	{"SERVER", true},
 	{"TABLE", true},
+	{"TABLESAMPLE METHOD", true},
 	{"TABLESPACE", false},
 	{"TRIGGER", true},
 	{"TEXT SEARCH CONFIGURATION", true},
@@ -1078,6 +1079,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_SEQUENCE:
 		case OBJECT_TABCONSTRAINT:
 		case OBJECT_TABLE:
+		case OBJECT_TABLESAMPLEMETHOD:
 		case OBJECT_TRIGGER:
 		case OBJECT_TSCONFIGURATION:
 		case OBJECT_TSDICTIONARY:
@@ -1134,6 +1136,7 @@ EventTriggerSupportsObjectClass(ObjectClass objclass)
 		case OCLASS_DEFACL:
 		case OCLASS_EXTENSION:
 		case OCLASS_POLICY:
+		case OCLASS_TABLESAMPLEMETHOD:
 			return true;
 
 		case MAX_OCLASS:
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 66d5083..b67c560 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8059,6 +8059,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 			case OCLASS_USER_MAPPING:
 			case OCLASS_DEFACL:
 			case OCLASS_EXTENSION:
+			case OCLASS_TABLESAMPLEMETHOD:
 
 				/*
 				 * We don't expect any of these sorts of objects to depend on
diff --git a/src/backend/commands/tablesample.c b/src/backend/commands/tablesample.c
new file mode 100644
index 0000000..3fcd0bd
--- /dev/null
+++ b/src/backend/commands/tablesample.c
@@ -0,0 +1,398 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *	  Commands to manipulate tablesample methods
+ *
+ * Table sampling methods provide algorithms for doing sample scan over
+ * the table.
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/tablesample.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "access/heapam.h"
+#include "access/htup_details.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/objectaccess.h"
+#include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
+#include "catalog/pg_type.h"
+#include "commands/defrem.h"
+#include "miscadmin.h"
+#include "parser/parse_func.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+
+static Datum
+get_tabmesample_method_func(DefElem *defel, int attnum)
+{
+	List	   *funcName = defGetQualifiedName(defel);
+	/* Big enough size for our needs. */
+	Oid		   *typeId = palloc0(6 * sizeof(Oid));
+	Oid			retTypeId;
+	int			nargs;
+	Oid			procOid = InvalidOid;
+	FuncCandidateList clist;
+
+	switch (attnum)
+	{
+		case Anum_pg_tablesample_method_tsminit:
+			/*
+			 * tsminit needs special handling because it is defined as function
+			 * with 3 or more arguments and only first two arguments must have
+			 * specific type, the rest is up to the tablesample method creator.
+			 */
+			{
+				nargs = 2;
+				typeId[0] = INTERNALOID;
+				typeId[1] = INT4OID;
+				retTypeId = VOIDOID;
+
+				clist = FuncnameGetCandidates(funcName, -1, NIL, false, false, false);
+
+				while (clist)
+				{
+					if (clist->nargs >= 3 &&
+						memcmp(typeId, clist->args, nargs * sizeof(Oid)) == 0)
+					{
+						procOid = clist->oid;
+						/* Save real function signature for future errors. */
+						nargs = clist->nargs;
+						pfree(typeId);
+						typeId = clist->args;
+						break;
+					}
+					clist = clist->next;
+				}
+
+				if (!OidIsValid(procOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_UNDEFINED_FUNCTION),
+							 errmsg("function \"%s\" does not exist or does not have valid signature",
+									NameListToString(funcName)),
+							 errhint("The tamplesample method init function "
+									 "must have at least 3 input parameters "
+									 "with first one of type INTERNAL and second of type INTEGER.")));
+			}
+			break;
+
+		case Anum_pg_tablesample_method_tsmnextblock:
+			nargs = 2;
+			typeId[0] = INTERNALOID;
+			typeId[1] = BOOLOID;
+			retTypeId = INT4OID;
+			break;
+		case Anum_pg_tablesample_method_tsmnexttuple:
+			nargs = 4;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INT2OID;
+			typeId[3] = BOOLOID;
+			retTypeId = INT2OID;
+			break;
+		case Anum_pg_tablesample_method_tsmend:
+		case Anum_pg_tablesample_method_tsmreset:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		case Anum_pg_tablesample_method_tsmcost:
+			nargs = 6;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INTERNALOID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = INTERNALOID;
+			typeId[4] = INTERNALOID;
+			typeId[5] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		default:
+			/* should not be here */
+			elog(ERROR, "unrecognized attribute for tablesample method: %d",
+				 attnum);
+			nargs = 0;			/* keep compiler quiet */
+	}
+
+	if (!OidIsValid(procOid))
+		procOid = LookupFuncName(funcName, nargs, typeId, false);
+	if (get_func_rettype(procOid) != retTypeId)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("function %s should return type %s",
+						func_signature_string(funcName, nargs, NIL, typeId),
+						format_type_be(retTypeId))));
+
+	return ObjectIdGetDatum(procOid);
+}
+
+/*
+ * make pg_depend entries for a new pg_tablesample_method entry
+ */
+static void
+makeTablesampleMethodDeps(HeapTuple tuple)
+{
+	Form_pg_tablesample_method tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	ObjectAddress	myself,
+					referenced;
+
+	myself.classId = TableSampleMethodRelationId;
+	myself.objectId = HeapTupleGetOid(tuple);
+	myself.objectSubId = 0;
+
+	/* dependency on extension */
+	recordDependencyOnCurrentExtension(&myself, false);
+
+	/* dependencies on functions */
+	referenced.classId = ProcedureRelationId;
+	referenced.objectSubId = 0;
+
+	referenced.objectId = tsm->tsminit;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnextblock;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnexttuple;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmend;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmreset;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmcost;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+}
+
+/*
+ * Create a table sampling method
+ *
+ * Only superusers can create a table sampling methods.
+ */
+Oid
+DefineTablesampleMethod(List *names, List *parameters)
+{
+	char	   *tsmname = strVal(linitial(names));
+	Oid			tsmoid;
+	ListCell   *pl;
+	Relation	rel;
+	Datum		values[Natts_pg_tablesample_method];
+	bool		nulls[Natts_pg_tablesample_method];
+	HeapTuple	tuple;
+
+	/* Must be super user. */
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied to create tablesample method \"%s\"",
+						tsmname),
+				 errhint("Must be superuser to create a tablesample method.")));
+
+	/* Must not already exist. */
+	tsmoid = get_tablesample_method_oid(tsmname, true);
+	if (OidIsValid(tsmoid))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" already exists",
+						tsmname)));
+
+	/* Initialize the values. */
+	memset(values, 0, sizeof(values));
+	memset(nulls, false, sizeof(nulls));
+
+	values[Anum_pg_tablesample_method_tsmname - 1] =
+		DirectFunctionCall1(namein, CStringGetDatum(tsmname));
+
+	/*
+	 * loop over the definition list and extract the information we need.
+	 */
+	foreach(pl, parameters)
+	{
+		DefElem    *defel = (DefElem *) lfirst(pl);
+
+		if (pg_strcasecmp(defel->defname, "init") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsminit - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsminit);
+		}
+		else if (pg_strcasecmp(defel->defname, "nextblock") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnextblock - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnextblock);
+		}
+		else if (pg_strcasecmp(defel->defname, "nexttuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnexttuple - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnexttuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "end") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmend - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmend);
+		}
+		else if (pg_strcasecmp(defel->defname, "reset") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmreset - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmreset);
+		}
+		else if (pg_strcasecmp(defel->defname, "cost") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmcost - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmcost);
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("tablesample method parameter \"%s\" not recognized",
+						defel->defname)));
+	}
+
+	/*
+	 * Validation.
+	 */
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsminit - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method init function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnextblock - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nextblock function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnexttuple - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nexttuple function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmend - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method end function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmreset - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method reset function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmcost - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method cost function is required")));
+
+	/*
+	 * Insert tuple into pg_tablesample_method.
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = heap_form_tuple(rel->rd_att, values, nulls);
+
+	tsmoid = simple_heap_insert(rel, tuple);
+
+	CatalogUpdateIndexes(rel, tuple);
+
+	makeTablesampleMethodDeps(tuple);
+
+	heap_freetuple(tuple);
+
+	/* Post creation hook for new tablesample method */
+	InvokeObjectPostCreateHook(TableSampleMethodRelationId, tsmoid, 0);
+
+	heap_close(rel, RowExclusiveLock);
+
+	return tsmoid;
+}
+
+/*
+ * Drop a tablesample method.
+ */
+void
+RemoveTablesampleMethodById(Oid tsmoid)
+{
+	Relation	rel;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+
+	/*
+	 * Find the target tuple
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmoid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for tablesample method %u",
+			 tsmoid);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	/* Can't drop builtin tablesample methods. */
+	if (tsmoid == TABLESAMPLE_METHOD_SYSTEM_OID ||
+		tsmoid == TABLESAMPLE_METHOD_BERNOULLI_OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied for tablesample method %s",
+						NameStr(tsm->tsmname))));
+
+	/*
+	 * Remove the pg_tablespace tuple (this will roll back if we fail below)
+	 */
+	simple_heap_delete(rel, &tuple->t_self);
+
+	ReleaseSysCache(tuple);
+
+	heap_close(rel, RowExclusiveLock);
+}
+
+/*
+ * get_tablesample_method_oid - given a tablesample method name,
+ * look up the OID
+ *
+ * If missing_ok is false, throw an error if tablesample method name not found.
+ * If true, just return InvalidOid.
+ */
+Oid
+get_tablesample_method_oid(const char *tsmname, bool missing_ok)
+{
+	Oid			result;
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(tsmname));
+	if (HeapTupleIsValid(tuple))
+	{
+		result = HeapTupleGetOid(tuple);
+		ReleaseSysCache(tuple);
+	}
+	else
+		result = InvalidOid;
+
+	if (!OidIsValid(result) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						tsmname)));
+
+	return result;
+}
+
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 01d72d4..4bf4aff 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -586,7 +586,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATERIALIZED MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
+	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P
+	MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEXT NO NONE
 	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
@@ -5094,6 +5095,15 @@ DefineStmt:
 					n->definition = list_make1(makeDefElem("from", (Node *) $5));
 					$$ = (Node *)n;
 				}
+			| CREATE TABLESAMPLE METHOD name definition
+				{
+					DefineStmt *n = makeNode(DefineStmt);
+					n->kind = OBJECT_TABLESAMPLEMETHOD;
+					n->args = NIL;
+					n->defnames = list_make1(makeString($4));
+					n->definition = $5;
+					$$ = (Node *)n;
+				}
 		;
 
 definition: '(' def_list ')'						{ $$ = $2; }
@@ -5552,6 +5562,7 @@ drop_type:	TABLE									{ $$ = OBJECT_TABLE; }
 			| TEXT_P SEARCH DICTIONARY				{ $$ = OBJECT_TSDICTIONARY; }
 			| TEXT_P SEARCH TEMPLATE				{ $$ = OBJECT_TSTEMPLATE; }
 			| TEXT_P SEARCH CONFIGURATION			{ $$ = OBJECT_TSCONFIGURATION; }
+			| TABLESAMPLE METHOD					{ $$ = OBJECT_TABLESAMPLEMETHOD; }
 		;
 
 any_name_list:
@@ -13313,6 +13324,7 @@ unreserved_keyword:
 			| MATCH
 			| MATERIALIZED
 			| MAXVALUE
+			| METHOD
 			| MINUTE_P
 			| MINVALUE
 			| MODE
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 3533cfa..532256d 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -23,6 +23,7 @@
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/toasting.h"
 #include "commands/alter.h"
 #include "commands/async.h"
@@ -1106,6 +1107,11 @@ ProcessUtilitySlow(Node *parsetree,
 							Assert(stmt->args == NIL);
 							DefineCollation(stmt->defnames, stmt->definition);
 							break;
+						case OBJECT_TABLESAMPLEMETHOD:
+							Assert(stmt->args == NIL);
+							Assert(list_length(stmt->defnames) == 1);
+							DefineTablesampleMethod(stmt->defnames, stmt->definition);
+							break;
 						default:
 							elog(ERROR, "unrecognized define stmt type: %d",
 								 (int) stmt->kind);
@@ -1960,6 +1966,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_POLICY:
 					tag = "DROP POLICY";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "DROP TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
@@ -2056,6 +2065,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_COLLATION:
 					tag = "CREATE COLLATION";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "CREATE TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 6481ac8..30653f8 100644
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -148,6 +148,7 @@ typedef enum ObjectClass
 	OCLASS_EXTENSION,			/* pg_extension */
 	OCLASS_EVENT_TRIGGER,		/* pg_event_trigger */
 	OCLASS_POLICY,				/* pg_policy */
+	OCLASS_TABLESAMPLEMETHOD,	/* pg_tablesample_method */
 	MAX_OCLASS					/* MUST BE LAST */
 } ObjectClass;
 
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
index 0e4a716..4ae8364 100644
--- a/src/include/catalog/pg_tablesample_method.h
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -64,7 +64,18 @@ typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
 
 DATA(insert OID = 3283 ( system tsm_system_init tsm_system_nextblock tsm_system_nexttuple tsm_system_end tsm_system_reset tsm_system_cost ));
 DESCR("SYSTEM table sampling method");
+#define TABLESAMPLE_METHOD_SYSTEM_OID 3283
 DATA(insert OID = 3284 ( bernoulli tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
 DESCR("BERNOULLI table sampling method");
+#define TABLESAMPLE_METHOD_BERNOULLI_OID 3284
+
+/* ----------------
+ *		functions for manipulation of pg_tablesample_method
+ * ----------------
+ */
+
+extern Oid DefineTablesampleMethod(List *names, List *parameters);
+extern void RemoveTablesampleMethodById(Oid tsmoid);
+extern Oid get_tablesample_method_oid(const char *tsmname, bool missing_ok);
 
 #endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index d87343f..54c4ba5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1267,6 +1267,7 @@ typedef enum ObjectType
 	OBJECT_SEQUENCE,
 	OBJECT_TABCONSTRAINT,
 	OBJECT_TABLE,
+	OBJECT_TABLESAMPLEMETHOD,
 	OBJECT_TABLESPACE,
 	OBJECT_TRIGGER,
 	OBJECT_TSCONFIGURATION,
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 67c3b1f..33c0f3d 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -877,7 +877,7 @@ typedef struct TidPath
 typedef struct SamplePath
 {
 	Path		path;
-	Oid			tsmcost;		/* table sample method costing function */
+	Oid			tsmcost;		/* tablesample method costing function */
 	List	   *tsmargs;		/* arguments to a TABLESAMPLE clause */
 } SamplePath;
 
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 6ff7b44..c3269c0 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -236,6 +236,7 @@ PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("mode", MODE, UNRESERVED_KEYWORD)
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 93d93af..37ea524 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -9,7 +9,8 @@ SUBDIRS = \
 		  worker_spi \
 		  dummy_seclabel \
 		  test_shm_mq \
-		  test_parser
+		  test_parser \
+		  tablesample
 
 all: submake-errcodes
 
diff --git a/src/test/modules/tablesample/.gitignore b/src/test/modules/tablesample/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/src/test/modules/tablesample/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/src/test/modules/tablesample/Makefile b/src/test/modules/tablesample/Makefile
new file mode 100644
index 0000000..469b004
--- /dev/null
+++ b/src/test/modules/tablesample/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/tsm_test/Makefile
+
+MODULE_big = tsm_test
+OBJS = tsm_test.o $(WIN32RES)
+PGFILEDESC = "tsm_test - example of a custom tablesample method"
+
+EXTENSION = tsm_test
+DATA = tsm_test--1.0.sql
+
+REGRESS = tablesample
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/tablesample/expected/tablesample.out b/src/test/modules/tablesample/expected/tablesample.out
new file mode 100644
index 0000000..95c8036
--- /dev/null
+++ b/src/test/modules/tablesample/expected/tablesample.out
@@ -0,0 +1,39 @@
+CREATE EXTENSION tsm_test;
+CREATE TABLE test_tsm AS SELECT md5(i::text) a FROM generate_series(1,10) g(i);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test(true);
+                a                 
+----------------------------------
+ c4ca4238a0b923820dcc509a6f75849b
+ c81e728d9d4c2f636f067f89cc14862c
+ eccbc87e4b5ce2fe28308fd9f2a7baf3
+ a87ff679a2f3e71d9181a67b7542122c
+ e4da3b7fbbce2345d7772b0674a318d5
+ 1679091c5a880faf6fb5e6087eb1b2dc
+ 8f14e45fceea167a5a36dedd4bea2543
+ c9f0f895fb98ab9159f51fd0297e236d
+ 45c48cce2e2d7fbdea1afc51c7c6ad26
+ d3d9446802a44259755d38e6d163e820
+(10 rows)
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test(false);
+ a 
+---
+(0 rows)
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test(true);
+DROP TABLESAMPLE METHOD tsm_test;
+ERROR:  cannot drop tablesample method tsm_test because extension tsm_test requires it
+HINT:  You can drop extension tsm_test instead.
+DROP EXTENSION tsm_test;
+ERROR:  cannot drop extension tsm_test because other objects depend on it
+DETAIL:  view test_tsm_v depends on tablesample method tsm_test
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+DROP EXTENSION tsm_test CASCADE;
+NOTICE:  drop cascades to view test_tsm_v
+SELECT * FROM pg_tablesample_method;
+  tsmname  |      tsminit       |      tsmnextblock       |      tsmnexttuple       |      tsmend       |      tsmreset       |      tsmcost       
+-----------+--------------------+-------------------------+-------------------------+-------------------+---------------------+--------------------
+ system    | tsm_system_init    | tsm_system_nextblock    | tsm_system_nexttuple    | tsm_system_end    | tsm_system_reset    | tsm_system_cost
+ bernoulli | tsm_bernoulli_init | tsm_bernoulli_nextblock | tsm_bernoulli_nexttuple | tsm_bernoulli_end | tsm_bernoulli_reset | tsm_bernoulli_cost
+(2 rows)
+
diff --git a/src/test/modules/tablesample/sql/tablesample.sql b/src/test/modules/tablesample/sql/tablesample.sql
new file mode 100644
index 0000000..70997bd
--- /dev/null
+++ b/src/test/modules/tablesample/sql/tablesample.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_test;
+
+CREATE TABLE test_tsm AS SELECT md5(i::text) a FROM generate_series(1,10) g(i);
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test(true);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test(false);
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test(true);
+
+DROP TABLESAMPLE METHOD tsm_test;
+DROP EXTENSION tsm_test;
+DROP EXTENSION tsm_test CASCADE;
+
+SELECT * FROM pg_tablesample_method;
diff --git a/src/test/modules/tablesample/tsm_test--1.0.sql b/src/test/modules/tablesample/tsm_test--1.0.sql
new file mode 100644
index 0000000..6cfa014
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test--1.0.sql
@@ -0,0 +1,44 @@
+/* src/test/modules/tablesample/tsm_test--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_test" to load this file. \quit
+
+CREATE FUNCTION tsm_test_init(internal, int4, bool)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nextblock(internal, bool)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nexttuple(internal, int4, int2, bool)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_cost(internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+
+CREATE TABLESAMPLE METHOD tsm_test (
+    INIT		= tsm_test_init,
+    NEXTBLOCK	= tsm_test_nextblock,
+    NEXTTUPLE	= tsm_test_nexttuple,
+	END			= tsm_test_end,
+    RESET		= tsm_test_reset,
+	COST		= tsm_test_cost
+);
diff --git a/src/test/modules/tablesample/tsm_test.c b/src/test/modules/tablesample/tsm_test.c
new file mode 100644
index 0000000..77016fd
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.c
@@ -0,0 +1,180 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_test.c
+ *	  Simple example of a custom tablesample method
+ *
+ * Copyright (c) 2007-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/test/modules/tablesample/tsm_test.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/tablesample.h"
+
+PG_MODULE_MAGIC;
+
+/* State */
+typedef struct
+{
+	bool ret;
+	BlockNumber tblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} tsm_test_state;
+
+
+PG_FUNCTION_INFO_V1(tsm_test_init);
+PG_FUNCTION_INFO_V1(tsm_test_nextblock);
+PG_FUNCTION_INFO_V1(tsm_test_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_test_end);
+PG_FUNCTION_INFO_V1(tsm_test_reset);
+PG_FUNCTION_INFO_V1(tsm_test_cost);
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_test_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	bool			ret;
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	tsm_test_state *state;
+
+	if (PG_ARGISNULL(2))
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("Return has cannot be NULL.")));
+
+	ret = PG_GETARG_BOOL(2);
+
+	state = palloc0(sizeof(tsm_test_state));
+
+	/* Remember initial values for reinit */
+	state->ret = ret;
+	state->tblocks = RelationGetNumberOfBlocks(rel);
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+	scanstate->tsmdata = (void *) state;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_test_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (!state->ret)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	if (state->blockno == InvalidBlockNumber)
+		state->blockno = 0;
+	else if (++state->blockno >= state->tblocks)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	PG_RETURN_UINT32(state->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ */
+Datum
+tsm_test_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (!state->ret)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	if (state->lt == InvalidOffsetNumber)
+		state->lt = FirstOffsetNumber;
+	else if (++state->lt > maxoffset)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	PG_RETURN_UINT16(state->lt);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_test_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_test_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_test_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	SamplePath	   *path = (SamplePath *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+	List		   *args = path->tsmargs;
+	Node		   *pctnode;
+	bool			ret;
+
+	SamplerAccessStrategy *strategy =
+		(SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_SEQUENTIAL;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+		ret = DatumGetBool(((Const *) pctnode)->constvalue);
+	else
+		ret = true;
+
+	*pages = ret ? baserel->pages : 0;
+	*tuples = ret ? baserel->tuples : 0;
+
+	PG_RETURN_VOID();
+}
+
diff --git a/src/test/modules/tablesample/tsm_test.control b/src/test/modules/tablesample/tsm_test.control
new file mode 100644
index 0000000..a7b2741
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.control
@@ -0,0 +1,5 @@
+# tsm_test extension
+comment = 'test module for custom tablesample method'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_test'
+relocatable = true
-- 
1.9.1

>From 78afb16082939aa284613a1d57f869a926decaf6 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:51:44 +0100
Subject: [PATCH 3/3] tablesample-ddl v3

---
 doc/src/sgml/ref/allfiles.sgml                     |   2 +
 doc/src/sgml/ref/create_tablesamplemethod.sgml     | 161 ++++++++
 doc/src/sgml/ref/drop_tablesamplemethod.sgml       |  87 +++++
 doc/src/sgml/reference.sgml                        |   2 +
 src/backend/catalog/dependency.c                   |  15 +-
 src/backend/catalog/objectaddress.c                |  65 +++-
 src/backend/commands/Makefile                      |   6 +-
 src/backend/commands/dropcmds.c                    |   4 +
 src/backend/commands/event_trigger.c               |   3 +
 src/backend/commands/tablecmds.c                   |   1 +
 src/backend/commands/tablesample.c                 | 419 +++++++++++++++++++++
 src/backend/parser/gram.y                          |  14 +-
 src/backend/tcop/utility.c                         |  12 +
 src/include/catalog/dependency.h                   |   1 +
 src/include/catalog/pg_tablesample_method.h        |  11 +
 src/include/nodes/parsenodes.h                     |   1 +
 src/include/parser/kwlist.h                        |   1 +
 src/test/modules/Makefile                          |   3 +-
 src/test/modules/tablesample/.gitignore            |   4 +
 src/test/modules/tablesample/Makefile              |  21 ++
 .../modules/tablesample/expected/tablesample.out   |  38 ++
 src/test/modules/tablesample/sql/tablesample.sql   |  14 +
 src/test/modules/tablesample/tsm_test--1.0.sql     |  50 +++
 src/test/modules/tablesample/tsm_test.c            | 218 +++++++++++
 src/test/modules/tablesample/tsm_test.control      |   5 +
 25 files changed, 1150 insertions(+), 8 deletions(-)
 create mode 100644 doc/src/sgml/ref/create_tablesamplemethod.sgml
 create mode 100644 doc/src/sgml/ref/drop_tablesamplemethod.sgml
 create mode 100644 src/backend/commands/tablesample.c
 create mode 100644 src/test/modules/tablesample/.gitignore
 create mode 100644 src/test/modules/tablesample/Makefile
 create mode 100644 src/test/modules/tablesample/expected/tablesample.out
 create mode 100644 src/test/modules/tablesample/sql/tablesample.sql
 create mode 100644 src/test/modules/tablesample/tsm_test--1.0.sql
 create mode 100644 src/test/modules/tablesample/tsm_test.c
 create mode 100644 src/test/modules/tablesample/tsm_test.control

diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index 7aa3128..2fad084 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -78,6 +78,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY createServer       SYSTEM "create_server.sgml">
 <!ENTITY createTable        SYSTEM "create_table.sgml">
 <!ENTITY createTableAs      SYSTEM "create_table_as.sgml">
+<!ENTITY createTablesampleMethod SYSTEM "create_tablesamplemethod.sgml">
 <!ENTITY createTableSpace   SYSTEM "create_tablespace.sgml">
 <!ENTITY createTrigger      SYSTEM "create_trigger.sgml">
 <!ENTITY createTSConfig     SYSTEM "create_tsconfig.sgml">
@@ -119,6 +120,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY dropSequence       SYSTEM "drop_sequence.sgml">
 <!ENTITY dropServer         SYSTEM "drop_server.sgml">
 <!ENTITY dropTable          SYSTEM "drop_table.sgml">
+<!ENTITY dropTablesampleMethod SYSTEM "drop_tablesamplemethod.sgml">
 <!ENTITY dropTableSpace     SYSTEM "drop_tablespace.sgml">
 <!ENTITY dropTrigger        SYSTEM "drop_trigger.sgml">
 <!ENTITY dropTSConfig       SYSTEM "drop_tsconfig.sgml">
diff --git a/doc/src/sgml/ref/create_tablesamplemethod.sgml b/doc/src/sgml/ref/create_tablesamplemethod.sgml
new file mode 100644
index 0000000..566522e
--- /dev/null
+++ b/doc/src/sgml/ref/create_tablesamplemethod.sgml
@@ -0,0 +1,161 @@
+<!--
+doc/src/sgml/ref/create_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-CREATETABLESAMPLEMETHOD">
+ <indexterm zone="sql-createtablesamplemethod">
+  <primary>CREATE TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE TABLESAMPLE METHOD</refname>
+  <refpurpose>define custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE TABLESAMPLE METHOD <replaceable class="parameter">name</replaceable> (
+    INIT = <replaceable class="parameter">init_function</replaceable> ,
+    NEXTBLOCK = <replaceable class="parameter">nextblock_function</replaceable> ,
+    NEXTTUPLE = <replaceable class="parameter">nexttuple_function</replaceable> ,
+    [ RETURNTUPLE = <replaceable class="parameter">returntuple_function</replaceable> , ]
+    END = <replaceable class="parameter">end_function</replaceable> ,
+    RESET = <replaceable class="parameter">reset_function</replaceable> ,
+    COST = <replaceable class="parameter">cost_function</replaceable>
+)
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE TABLESAMPLE METHOD</command> creates a tablesample method.
+   A tablesample method provides alrorithm for reading sample part of a table
+   when used in <command>TABLESAMPLE</> clause of a <command>SELECT</>
+   statement.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the tablesample method to be created. This name must be
+      unique within the database.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">init_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the init function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nextblock_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-block function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nexttuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-tuple function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">returntuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the function for inspecting the tuple contents in orde
+      to make decision if it should be returned or not. This parameter
+      is optional.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">end_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the end function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">reset_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the reset function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">cost_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the costing function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+  <para>
+   The function names can be schema-qualified if necessary.  Argument types
+   are not given, since the argument list for each type of function is
+   predetermined.  All functions are required.
+  </para>
+
+  <para>
+   The arguments can appear in any order, not only the one shown above.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>CREATE TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-droptablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/ref/drop_tablesamplemethod.sgml b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
new file mode 100644
index 0000000..dffd2ec
--- /dev/null
+++ b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
@@ -0,0 +1,87 @@
+<!--
+doc/src/sgml/ref/drop_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-DROPTABLESAMPLEMETHOD">
+ <indexterm zone="sql-droptablesamplemethod">
+  <primary>DROP TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DROP TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP TABLESAMPLE METHOD</refname>
+  <refpurpose>remove a custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP TABLESAMPLE METHOD [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>DROP TABLESAMPLE METHOD</command> drop an existing tablesample
+   method.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the tablesample method does not exist.
+      A notice is issued in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of an existing tablesample method to be removed.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>DROP TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createtablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index 10c9a6d..2c09a3c 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -106,6 +106,7 @@
    &createServer;
    &createTable;
    &createTableAs;
+   &createTablesampleMethod;
    &createTableSpace;
    &createTSConfig;
    &createTSDictionary;
@@ -147,6 +148,7 @@
    &dropSequence;
    &dropServer;
    &dropTable;
+   &dropTablesampleMethod;
    &dropTableSpace;
    &dropTSConfig;
    &dropTSDictionary;
diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index bacb242..6acb5b3 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -46,6 +46,7 @@
 #include "catalog/pg_policy.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -157,7 +158,8 @@ static const Oid object_classes[MAX_OCLASS] = {
 	DefaultAclRelationId,		/* OCLASS_DEFACL */
 	ExtensionRelationId,		/* OCLASS_EXTENSION */
 	EventTriggerRelationId,		/* OCLASS_EVENT_TRIGGER */
-	PolicyRelationId			/* OCLASS_POLICY */
+	PolicyRelationId,			/* OCLASS_POLICY */
+	TableSampleMethodRelationId			/* OCLASS_TABLESAMPLEMETHOD */
 };
 
 
@@ -1265,6 +1267,10 @@ doDeletion(const ObjectAddress *object, int flags)
 			RemovePolicyById(object->objectId);
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			RemoveTablesampleMethodById(object->objectId);
+			break;
+
 		default:
 			elog(ERROR, "unrecognized object class: %u",
 				 object->classId);
@@ -1794,6 +1800,10 @@ find_expr_references_walker(Node *node,
 				case RTE_RELATION:
 					add_object_address(OCLASS_CLASS, rte->relid, 0,
 									   context->addrs);
+					if (rte->tablesample)
+						add_object_address(OCLASS_TABLESAMPLEMETHOD,
+										   rte->tablesample->tsmid, 0,
+										   context->addrs);
 					break;
 				default:
 					break;
@@ -2373,6 +2383,9 @@ getObjectClass(const ObjectAddress *object)
 
 		case PolicyRelationId:
 			return OCLASS_POLICY;
+
+		case TableSampleMethodRelationId:
+			return OCLASS_TABLESAMPLEMETHOD;
 	}
 
 	/* shouldn't get here */
diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index 825d8b2..02edc0a 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -44,6 +44,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_policy.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -429,7 +430,19 @@ static const ObjectPropertyType ObjectProperty[] =
 		Anum_pg_type_typacl,
 		ACL_KIND_TYPE,
 		true
-	}
+	},
+	{
+		TableSampleMethodRelationId,
+		TableSampleMethodOidIndexId,
+		TABLESAMPLEMETHODOID,
+		TABLESAMPLEMETHODNAME,
+		Anum_pg_tablesample_method_tsmname,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		-1,
+		true
+	},
 };
 
 /*
@@ -528,7 +541,9 @@ ObjectTypeMap[] =
 	/* OCLASS_EVENT_TRIGGER */
 	{ "event trigger", OBJECT_EVENT_TRIGGER },
 	/* OCLASS_POLICY */
-	{ "policy", OBJECT_POLICY }
+	{ "policy", OBJECT_POLICY },
+	/* OCLASS_TABLESAMPLEMETHOD */
+	{ "tablesample method", OBJECT_TABLESAMPLEMETHOD }
 };
 
 
@@ -670,6 +685,7 @@ get_object_address(ObjectType objtype, List *objname, List *objargs,
 			case OBJECT_FDW:
 			case OBJECT_FOREIGN_SERVER:
 			case OBJECT_EVENT_TRIGGER:
+			case OBJECT_TABLESAMPLEMETHOD:
 				address = get_object_address_unqualified(objtype,
 														 objname, missing_ok);
 				break;
@@ -896,6 +912,9 @@ get_object_address_unqualified(ObjectType objtype,
 			case OBJECT_EVENT_TRIGGER:
 				msg = gettext_noop("event trigger name cannot be qualified");
 				break;
+			case OBJECT_TABLESAMPLEMETHOD:
+				msg = gettext_noop("tablesample method name cannot be qualified");
+				break;
 			default:
 				elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 				msg = NULL;		/* placate compiler */
@@ -956,6 +975,11 @@ get_object_address_unqualified(ObjectType objtype,
 			address.objectId = get_event_trigger_oid(name, missing_ok);
 			address.objectSubId = 0;
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			address.classId = TableSampleMethodRelationId;
+			address.objectId = get_tablesample_method_oid(name, missing_ok);
+			address.objectSubId = 0;
+			break;
 		default:
 			elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 			/* placate compiler, which doesn't know elog won't return */
@@ -1720,6 +1744,7 @@ check_object_ownership(Oid roleid, ObjectType objtype, ObjectAddress address,
 			break;
 		case OBJECT_TSPARSER:
 		case OBJECT_TSTEMPLATE:
+		case OBJECT_TABLESAMPLEMETHOD:
 			/* We treat these object types as being owned by superusers */
 			if (!superuser_arg(roleid))
 				ereport(ERROR,
@@ -2654,6 +2679,21 @@ getObjectDescription(const ObjectAddress *object)
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				appendStringInfo(&buffer, _("tablesample method %s"),
+					 NameStr(((Form_pg_tablesample_method) GETSTRUCT(tup))->tsmname));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
@@ -3131,6 +3171,10 @@ getObjectTypeDescription(const ObjectAddress *object)
 			appendStringInfoString(&buffer, "policy");
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			appendStringInfoString(&buffer, "tablesample method");
+			break;
+
 		default:
 			appendStringInfo(&buffer, "unrecognized %u", object->classId);
 			break;
@@ -4025,6 +4069,23 @@ getObjectIdentityParts(const ObjectAddress *object,
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+				Form_pg_tablesample_method tsmForm;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				tsmForm = (Form_pg_tablesample_method) GETSTRUCT(tup);
+				appendStringInfoString(&buffer,
+							   quote_identifier(NameStr(tsmForm->tsmname)));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index b1ac704..04fcd8c 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -18,8 +18,8 @@ OBJS = aggregatecmds.o alter.o analyze.o async.o cluster.o comment.o  \
 	event_trigger.o explain.o extension.o foreigncmds.o functioncmds.o \
 	indexcmds.o lockcmds.o matview.o operatorcmds.o opclasscmds.o \
 	policy.o portalcmds.o prepare.o proclang.o \
-	schemacmds.o seclabel.o sequence.o tablecmds.o tablespace.o trigger.o \
-	tsearchcmds.o typecmds.o user.o vacuum.o vacuumlazy.o \
-	variable.o view.o
+	schemacmds.o seclabel.o sequence.o tablecmds.o tablesample.o \
+	tablespace.o trigger.o tsearchcmds.o typecmds.o user.o vacuum.o \
+	vacuumlazy.o variable.o view.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/commands/dropcmds.c b/src/backend/commands/dropcmds.c
index e5185ba..04d29a2 100644
--- a/src/backend/commands/dropcmds.c
+++ b/src/backend/commands/dropcmds.c
@@ -421,6 +421,10 @@ does_not_exist_skipping(ObjectType objtype, List *objname, List *objargs)
 				args = strVal(linitial(objargs));
 			}
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			msg = gettext_noop("tablesample method \"%s\" does not exist, skipping");
+			name = NameListToString(objname);
+			break;
 		default:
 			elog(ERROR, "unexpected object type (%d)", (int) objtype);
 			break;
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index a33a5ad..f20e9f7 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -97,6 +97,7 @@ static event_trigger_support_data event_trigger_support[] = {
 	{"SEQUENCE", true},
 	{"SERVER", true},
 	{"TABLE", true},
+	{"TABLESAMPLE METHOD", true},
 	{"TABLESPACE", false},
 	{"TRIGGER", true},
 	{"TEXT SEARCH CONFIGURATION", true},
@@ -1078,6 +1079,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_SEQUENCE:
 		case OBJECT_TABCONSTRAINT:
 		case OBJECT_TABLE:
+		case OBJECT_TABLESAMPLEMETHOD:
 		case OBJECT_TRIGGER:
 		case OBJECT_TSCONFIGURATION:
 		case OBJECT_TSDICTIONARY:
@@ -1134,6 +1136,7 @@ EventTriggerSupportsObjectClass(ObjectClass objclass)
 		case OCLASS_DEFACL:
 		case OCLASS_EXTENSION:
 		case OCLASS_POLICY:
+		case OCLASS_TABLESAMPLEMETHOD:
 			return true;
 
 		case MAX_OCLASS:
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 66d5083..b67c560 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8059,6 +8059,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 			case OCLASS_USER_MAPPING:
 			case OCLASS_DEFACL:
 			case OCLASS_EXTENSION:
+			case OCLASS_TABLESAMPLEMETHOD:
 
 				/*
 				 * We don't expect any of these sorts of objects to depend on
diff --git a/src/backend/commands/tablesample.c b/src/backend/commands/tablesample.c
new file mode 100644
index 0000000..16882d4
--- /dev/null
+++ b/src/backend/commands/tablesample.c
@@ -0,0 +1,419 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *	  Commands to manipulate tablesample methods
+ *
+ * Table sampling methods provide algorithms for doing sample scan over
+ * the table.
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/tablesample.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "access/heapam.h"
+#include "access/htup_details.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/objectaccess.h"
+#include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
+#include "catalog/pg_type.h"
+#include "commands/defrem.h"
+#include "miscadmin.h"
+#include "parser/parse_func.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+
+static Datum
+get_tabmesample_method_func(DefElem *defel, int attnum)
+{
+	List	   *funcName = defGetQualifiedName(defel);
+	/* Big enough size for our needs. */
+	Oid		   *typeId = palloc0(7 * sizeof(Oid));
+	Oid			retTypeId;
+	int			nargs;
+	Oid			procOid = InvalidOid;
+	FuncCandidateList clist;
+
+	switch (attnum)
+	{
+		case Anum_pg_tablesample_method_tsminit:
+			/*
+			 * tsminit needs special handling because it is defined as function
+			 * with 3 or more arguments and only first two arguments must have
+			 * specific type, the rest is up to the tablesample method creator.
+			 */
+			{
+				nargs = 2;
+				typeId[0] = INTERNALOID;
+				typeId[1] = INT4OID;
+				retTypeId = VOIDOID;
+
+				clist = FuncnameGetCandidates(funcName, -1, NIL, false, false, false);
+
+				while (clist)
+				{
+					if (clist->nargs >= 3 &&
+						memcmp(typeId, clist->args, nargs * sizeof(Oid)) == 0)
+					{
+						procOid = clist->oid;
+						/* Save real function signature for future errors. */
+						nargs = clist->nargs;
+						pfree(typeId);
+						typeId = clist->args;
+						break;
+					}
+					clist = clist->next;
+				}
+
+				if (!OidIsValid(procOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_UNDEFINED_FUNCTION),
+							 errmsg("function \"%s\" does not exist or does not have valid signature",
+									NameListToString(funcName)),
+							 errhint("The tamplesample method init function "
+									 "must have at least 3 input parameters "
+									 "with first one of type INTERNAL and second of type INTEGER.")));
+			}
+			break;
+
+		case Anum_pg_tablesample_method_tsmnextblock:
+			nargs = 2;
+			typeId[0] = INTERNALOID;
+			typeId[1] = BOOLOID;
+			retTypeId = INT4OID;
+			break;
+		case Anum_pg_tablesample_method_tsmnexttuple:
+			nargs = 4;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INT2OID;
+			typeId[3] = BOOLOID;
+			retTypeId = INT2OID;
+			break;
+		case Anum_pg_tablesample_method_tsmreturntuple:
+			nargs = 4;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = BOOLOID;
+			retTypeId = BOOLOID;
+			break;
+		case Anum_pg_tablesample_method_tsmend:
+		case Anum_pg_tablesample_method_tsmreset:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		case Anum_pg_tablesample_method_tsmcost:
+			nargs = 7;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INTERNALOID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = INTERNALOID;
+			typeId[4] = INTERNALOID;
+			typeId[5] = INTERNALOID;
+			typeId[6] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		default:
+			/* should not be here */
+			elog(ERROR, "unrecognized attribute for tablesample method: %d",
+				 attnum);
+			nargs = 0;			/* keep compiler quiet */
+	}
+
+	if (!OidIsValid(procOid))
+		procOid = LookupFuncName(funcName, nargs, typeId, false);
+	if (get_func_rettype(procOid) != retTypeId)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("function %s should return type %s",
+						func_signature_string(funcName, nargs, NIL, typeId),
+						format_type_be(retTypeId))));
+
+	return ObjectIdGetDatum(procOid);
+}
+
+/*
+ * make pg_depend entries for a new pg_tablesample_method entry
+ */
+static void
+makeTablesampleMethodDeps(HeapTuple tuple)
+{
+	Form_pg_tablesample_method tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	ObjectAddress	myself,
+					referenced;
+
+	myself.classId = TableSampleMethodRelationId;
+	myself.objectId = HeapTupleGetOid(tuple);
+	myself.objectSubId = 0;
+
+	/* dependency on extension */
+	recordDependencyOnCurrentExtension(&myself, false);
+
+	/* dependencies on functions */
+	referenced.classId = ProcedureRelationId;
+	referenced.objectSubId = 0;
+
+	referenced.objectId = tsm->tsminit;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnextblock;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnexttuple;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	if (OidIsValid(tsm->tsmreturntuple))
+	{
+		referenced.objectId = tsm->tsmreturntuple;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
+
+	referenced.objectId = tsm->tsmend;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmreset;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmcost;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+}
+
+/*
+ * Create a table sampling method
+ *
+ * Only superusers can create a table sampling methods.
+ */
+Oid
+DefineTablesampleMethod(List *names, List *parameters)
+{
+	char	   *tsmname = strVal(linitial(names));
+	Oid			tsmoid;
+	ListCell   *pl;
+	Relation	rel;
+	Datum		values[Natts_pg_tablesample_method];
+	bool		nulls[Natts_pg_tablesample_method];
+	HeapTuple	tuple;
+
+	/* Must be super user. */
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied to create tablesample method \"%s\"",
+						tsmname),
+				 errhint("Must be superuser to create a tablesample method.")));
+
+	/* Must not already exist. */
+	tsmoid = get_tablesample_method_oid(tsmname, true);
+	if (OidIsValid(tsmoid))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" already exists",
+						tsmname)));
+
+	/* Initialize the values. */
+	memset(values, 0, sizeof(values));
+	memset(nulls, false, sizeof(nulls));
+
+	values[Anum_pg_tablesample_method_tsmname - 1] =
+		DirectFunctionCall1(namein, CStringGetDatum(tsmname));
+
+	/*
+	 * loop over the definition list and extract the information we need.
+	 */
+	foreach(pl, parameters)
+	{
+		DefElem    *defel = (DefElem *) lfirst(pl);
+
+		if (pg_strcasecmp(defel->defname, "init") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsminit - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsminit);
+		}
+		else if (pg_strcasecmp(defel->defname, "nextblock") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnextblock - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnextblock);
+		}
+		else if (pg_strcasecmp(defel->defname, "nexttuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnexttuple - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnexttuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "returntuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmreturntuple - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmreturntuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "end") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmend - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmend);
+		}
+		else if (pg_strcasecmp(defel->defname, "reset") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmreset - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmreset);
+		}
+		else if (pg_strcasecmp(defel->defname, "cost") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmcost - 1] =
+				get_tabmesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmcost);
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("tablesample method parameter \"%s\" not recognized",
+						defel->defname)));
+	}
+
+	/*
+	 * Validation.
+	 */
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsminit - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method init function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnextblock - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nextblock function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnexttuple - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nexttuple function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmend - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method end function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmreset - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method reset function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmcost - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method cost function is required")));
+
+	/*
+	 * Insert tuple into pg_tablesample_method.
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = heap_form_tuple(rel->rd_att, values, nulls);
+
+	tsmoid = simple_heap_insert(rel, tuple);
+
+	CatalogUpdateIndexes(rel, tuple);
+
+	makeTablesampleMethodDeps(tuple);
+
+	heap_freetuple(tuple);
+
+	/* Post creation hook for new tablesample method */
+	InvokeObjectPostCreateHook(TableSampleMethodRelationId, tsmoid, 0);
+
+	heap_close(rel, RowExclusiveLock);
+
+	return tsmoid;
+}
+
+/*
+ * Drop a tablesample method.
+ */
+void
+RemoveTablesampleMethodById(Oid tsmoid)
+{
+	Relation	rel;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+
+	/*
+	 * Find the target tuple
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmoid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for tablesample method %u",
+			 tsmoid);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	/* Can't drop builtin tablesample methods. */
+	if (tsmoid == TABLESAMPLE_METHOD_SYSTEM_OID ||
+		tsmoid == TABLESAMPLE_METHOD_BERNOULLI_OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied for tablesample method %s",
+						NameStr(tsm->tsmname))));
+
+	/*
+	 * Remove the pg_tablespace tuple (this will roll back if we fail below)
+	 */
+	simple_heap_delete(rel, &tuple->t_self);
+
+	ReleaseSysCache(tuple);
+
+	heap_close(rel, RowExclusiveLock);
+}
+
+/*
+ * get_tablesample_method_oid - given a tablesample method name,
+ * look up the OID
+ *
+ * If missing_ok is false, throw an error if tablesample method name not found.
+ * If true, just return InvalidOid.
+ */
+Oid
+get_tablesample_method_oid(const char *tsmname, bool missing_ok)
+{
+	Oid			result;
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(tsmname));
+	if (HeapTupleIsValid(tuple))
+	{
+		result = HeapTupleGetOid(tuple);
+		ReleaseSysCache(tuple);
+	}
+	else
+		result = InvalidOid;
+
+	if (!OidIsValid(result) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						tsmname)));
+
+	return result;
+}
+
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index ac5e095..4578b5e 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -586,7 +586,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATERIALIZED MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
+	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P
+	MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEXT NO NONE
 	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
@@ -5094,6 +5095,15 @@ DefineStmt:
 					n->definition = list_make1(makeDefElem("from", (Node *) $5));
 					$$ = (Node *)n;
 				}
+			| CREATE TABLESAMPLE METHOD name definition
+				{
+					DefineStmt *n = makeNode(DefineStmt);
+					n->kind = OBJECT_TABLESAMPLEMETHOD;
+					n->args = NIL;
+					n->defnames = list_make1(makeString($4));
+					n->definition = $5;
+					$$ = (Node *)n;
+				}
 		;
 
 definition: '(' def_list ')'						{ $$ = $2; }
@@ -5552,6 +5562,7 @@ drop_type:	TABLE									{ $$ = OBJECT_TABLE; }
 			| TEXT_P SEARCH DICTIONARY				{ $$ = OBJECT_TSDICTIONARY; }
 			| TEXT_P SEARCH TEMPLATE				{ $$ = OBJECT_TSTEMPLATE; }
 			| TEXT_P SEARCH CONFIGURATION			{ $$ = OBJECT_TSCONFIGURATION; }
+			| TABLESAMPLE METHOD					{ $$ = OBJECT_TABLESAMPLEMETHOD; }
 		;
 
 any_name_list:
@@ -13313,6 +13324,7 @@ unreserved_keyword:
 			| MATCH
 			| MATERIALIZED
 			| MAXVALUE
+			| METHOD
 			| MINUTE_P
 			| MINVALUE
 			| MODE
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 3533cfa..532256d 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -23,6 +23,7 @@
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/toasting.h"
 #include "commands/alter.h"
 #include "commands/async.h"
@@ -1106,6 +1107,11 @@ ProcessUtilitySlow(Node *parsetree,
 							Assert(stmt->args == NIL);
 							DefineCollation(stmt->defnames, stmt->definition);
 							break;
+						case OBJECT_TABLESAMPLEMETHOD:
+							Assert(stmt->args == NIL);
+							Assert(list_length(stmt->defnames) == 1);
+							DefineTablesampleMethod(stmt->defnames, stmt->definition);
+							break;
 						default:
 							elog(ERROR, "unrecognized define stmt type: %d",
 								 (int) stmt->kind);
@@ -1960,6 +1966,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_POLICY:
 					tag = "DROP POLICY";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "DROP TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
@@ -2056,6 +2065,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_COLLATION:
 					tag = "CREATE COLLATION";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "CREATE TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 6481ac8..30653f8 100644
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -148,6 +148,7 @@ typedef enum ObjectClass
 	OCLASS_EXTENSION,			/* pg_extension */
 	OCLASS_EVENT_TRIGGER,		/* pg_event_trigger */
 	OCLASS_POLICY,				/* pg_policy */
+	OCLASS_TABLESAMPLEMETHOD,	/* pg_tablesample_method */
 	MAX_OCLASS					/* MUST BE LAST */
 } ObjectClass;
 
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
index ea11f45..db1e7eb 100644
--- a/src/include/catalog/pg_tablesample_method.h
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -67,7 +67,18 @@ typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
 
 DATA(insert OID = 3283 ( system tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
 DESCR("SYSTEM table sampling method");
+#define TABLESAMPLE_METHOD_SYSTEM_OID 3283
 DATA(insert OID = 3284 ( bernoulli tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
 DESCR("BERNOULLI table sampling method");
+#define TABLESAMPLE_METHOD_BERNOULLI_OID 3284
+
+/* ----------------
+ *		functions for manipulation of pg_tablesample_method
+ * ----------------
+ */
+
+extern Oid DefineTablesampleMethod(List *names, List *parameters);
+extern void RemoveTablesampleMethodById(Oid tsmoid);
+extern Oid get_tablesample_method_oid(const char *tsmname, bool missing_ok);
 
 #endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 7927a82..a3cf011 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1268,6 +1268,7 @@ typedef enum ObjectType
 	OBJECT_SEQUENCE,
 	OBJECT_TABCONSTRAINT,
 	OBJECT_TABLE,
+	OBJECT_TABLESAMPLEMETHOD,
 	OBJECT_TABLESPACE,
 	OBJECT_TRIGGER,
 	OBJECT_TSCONFIGURATION,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 6ff7b44..c3269c0 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -236,6 +236,7 @@ PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("mode", MODE, UNRESERVED_KEYWORD)
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 93d93af..37ea524 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -9,7 +9,8 @@ SUBDIRS = \
 		  worker_spi \
 		  dummy_seclabel \
 		  test_shm_mq \
-		  test_parser
+		  test_parser \
+		  tablesample
 
 all: submake-errcodes
 
diff --git a/src/test/modules/tablesample/.gitignore b/src/test/modules/tablesample/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/src/test/modules/tablesample/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/src/test/modules/tablesample/Makefile b/src/test/modules/tablesample/Makefile
new file mode 100644
index 0000000..469b004
--- /dev/null
+++ b/src/test/modules/tablesample/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/tsm_test/Makefile
+
+MODULE_big = tsm_test
+OBJS = tsm_test.o $(WIN32RES)
+PGFILEDESC = "tsm_test - example of a custom tablesample method"
+
+EXTENSION = tsm_test
+DATA = tsm_test--1.0.sql
+
+REGRESS = tablesample
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/tablesample/expected/tablesample.out b/src/test/modules/tablesample/expected/tablesample.out
new file mode 100644
index 0000000..970b765
--- /dev/null
+++ b/src/test/modules/tablesample/expected/tablesample.out
@@ -0,0 +1,38 @@
+CREATE EXTENSION tsm_test;
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ c81e728d9d4c2f636f067f89cc14862c | 0.5
+ a87ff679a2f3e71d9181a67b7542122c | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ d3d9446802a44259755d38e6d163e820 | 0.5
+(6 rows)
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ e4da3b7fbbce2345d7772b0674a318d5 | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ c9f0f895fb98ab9159f51fd0297e236d | 0.5
+(5 rows)
+
+DROP TABLESAMPLE METHOD tsm_test;
+ERROR:  cannot drop tablesample method tsm_test because extension tsm_test requires it
+HINT:  You can drop extension tsm_test instead.
+DROP EXTENSION tsm_test;
+ERROR:  cannot drop extension tsm_test because other objects depend on it
+DETAIL:  view test_tsm_v depends on tablesample method tsm_test
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+DROP EXTENSION tsm_test CASCADE;
+NOTICE:  drop cascades to view test_tsm_v
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
+ tsmname | tsminit | tsmnextblock | tsmnexttuple | tsmreturntuple | tsmend | tsmreset | tsmcost 
+---------+---------+--------------+--------------+----------------+--------+----------+---------
+(0 rows)
+
diff --git a/src/test/modules/tablesample/sql/tablesample.sql b/src/test/modules/tablesample/sql/tablesample.sql
new file mode 100644
index 0000000..b1104d6
--- /dev/null
+++ b/src/test/modules/tablesample/sql/tablesample.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_test;
+
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+
+DROP TABLESAMPLE METHOD tsm_test;
+DROP EXTENSION tsm_test;
+DROP EXTENSION tsm_test CASCADE;
+
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
diff --git a/src/test/modules/tablesample/tsm_test--1.0.sql b/src/test/modules/tablesample/tsm_test--1.0.sql
new file mode 100644
index 0000000..2814e37
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test--1.0.sql
@@ -0,0 +1,50 @@
+/* src/test/modules/tablesample/tsm_test--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_test" to load this file. \quit
+
+CREATE FUNCTION tsm_test_init(internal, int4, text)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nextblock(internal, bool)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nexttuple(internal, int4, int2, bool)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_returntuple(internal, int4, internal, bool)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_cost(internal, internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+
+CREATE TABLESAMPLE METHOD tsm_test (
+	INIT		= tsm_test_init,
+	NEXTBLOCK	= tsm_test_nextblock,
+	NEXTTUPLE	= tsm_test_nexttuple,
+	RETURNTUPLE	= tsm_test_returntuple,
+	END			= tsm_test_end,
+	RESET		= tsm_test_reset,
+	COST		= tsm_test_cost
+);
diff --git a/src/test/modules/tablesample/tsm_test.c b/src/test/modules/tablesample/tsm_test.c
new file mode 100644
index 0000000..110322a
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.c
@@ -0,0 +1,218 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_test.c
+ *	  Simple example of a custom tablesample method
+ *
+ * Copyright (c) 2007-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/test/modules/tablesample/tsm_test.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/htup_details.h"
+#include "access/tupdesc.h"
+#include "catalog/pg_type.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/builtins.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+PG_MODULE_MAGIC;
+
+/* State */
+typedef struct
+{
+	uint32		seed;			/* random seed */
+	AttrNumber	attnum;			/* column to check */
+	TupleDesc	tupDesc;		/* tuple descriptor of table */
+	BlockNumber tblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} tsm_test_state;
+
+
+PG_FUNCTION_INFO_V1(tsm_test_init);
+PG_FUNCTION_INFO_V1(tsm_test_nextblock);
+PG_FUNCTION_INFO_V1(tsm_test_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_test_returntuple);
+PG_FUNCTION_INFO_V1(tsm_test_end);
+PG_FUNCTION_INFO_V1(tsm_test_reset);
+PG_FUNCTION_INFO_V1(tsm_test_cost);
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_test_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	char		   *attname;
+	AttrNumber		attnum;
+	Oid				atttype;
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	tsm_test_state *state;
+	TupleDesc		tupDesc = RelationGetDescr(rel);
+
+	if (PG_ARGISNULL(2))
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("attnum cannot be NULL.")));
+
+	attname = text_to_cstring(PG_GETARG_TEXT_P(2));
+
+	attnum = get_attnum(rel->rd_id, attname);
+	if (!AttrNumberIsForUserDefinedAttr(attnum))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s does not exist", attname)));
+
+	atttype = get_atttype(rel->rd_id, attnum);
+	if (atttype != FLOAT8OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s is not of type float.", attname)));
+
+	state = palloc0(sizeof(tsm_test_state));
+
+	/* Remember initial values for reinit */
+	state->seed = seed;
+	state->attnum = attnum;
+	state->tupDesc = tupDesc;
+	state->tblocks = RelationGetNumberOfBlocks(rel);
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+	sampler_random_init_state(state->seed, state->randstate);
+
+	scanstate->tsmdata = (void *) state;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_test_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (state->blockno == InvalidBlockNumber)
+		state->blockno = 0;
+	else if (++state->blockno >= state->tblocks)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	PG_RETURN_UINT32(state->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ */
+Datum
+tsm_test_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (state->lt == InvalidOffsetNumber)
+		state->lt = FirstOffsetNumber;
+	else if (++state->lt > maxoffset)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	PG_RETURN_UINT16(state->lt);
+}
+
+/*
+ * Examine tuple and decide if it should be returned.
+ */
+Datum
+tsm_test_returntuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	HeapTuple		tuple = (HeapTuple) PG_GETARG_POINTER(2);
+	bool			visible = PG_GETARG_BOOL(3);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+	bool			isnull;
+	float8			val, rand;
+
+	if (!visible)
+		PG_RETURN_BOOL(false);
+
+	val = DatumGetFloat8(heap_getattr(tuple, state->attnum, state->tupDesc, &isnull));
+	rand = sampler_random_fract(state->randstate);
+	if (isnull || val < rand)
+		PG_RETURN_BOOL(false);
+	else
+		PG_RETURN_BOOL(true);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_test_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_test_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+
+	sampler_random_init_state(state->seed, state->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_test_cost(PG_FUNCTION_ARGS)
+{
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(3);
+	double		   *tuples = (double *) PG_GETARG_POINTER(4);
+
+	SamplerAccessStrategy *strategy =
+		(SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_SEQUENTIAL;
+
+	*pages = baserel->pages;
+	/* This is very bad estimation */
+	*tuples = baserel->tuples/2;
+
+	PG_RETURN_VOID();
+}
+
diff --git a/src/test/modules/tablesample/tsm_test.control b/src/test/modules/tablesample/tsm_test.control
new file mode 100644
index 0000000..a7b2741
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.control
@@ -0,0 +1,5 @@
+# tsm_test extension
+comment = 'test module for custom tablesample method'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_test'
+relocatable = true
-- 
1.9.1

>From 92959256c7dd892e9aa0f6921ffb2dfd552e28b4 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:36:56 +0100
Subject: [PATCH 1/3] separate block sampling functions v2

---
 contrib/file_fdw/file_fdw.c         |   9 +-
 contrib/postgres_fdw/postgres_fdw.c |  10 +-
 src/backend/commands/analyze.c      | 225 +----------------------------------
 src/backend/utils/misc/Makefile     |   2 +-
 src/backend/utils/misc/sampling.c   | 226 ++++++++++++++++++++++++++++++++++++
 src/include/commands/vacuum.h       |   3 -
 src/include/utils/sampling.h        |  44 +++++++
 7 files changed, 287 insertions(+), 232 deletions(-)
 create mode 100644 src/backend/utils/misc/sampling.c
 create mode 100644 src/include/utils/sampling.h

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index d569760..df732c0 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -34,6 +34,7 @@
 #include "optimizer/var.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -1005,7 +1006,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 {
 	int			numrows = 0;
 	double		rowstoskip = -1;	/* -1 means not set yet */
-	double		rstate;
+	ReservoirStateData rstate;
 	TupleDesc	tupDesc;
 	Datum	   *values;
 	bool	   *nulls;
@@ -1043,7 +1044,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 									   ALLOCSET_DEFAULT_MAXSIZE);
 
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Set up callback to identify error line number. */
 	errcallback.callback = CopyFromErrorCallback;
@@ -1087,7 +1088,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 			 * not-yet-incremented value of totalrows as t.
 			 */
 			if (rowstoskip < 0)
-				rowstoskip = anl_get_next_S(*totalrows, targrows, &rstate);
+				rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
 
 			if (rowstoskip <= 0)
 			{
@@ -1095,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * anl_random_fract());
+				int			k = (int) (targrows * sampler_random_fract());
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index d76e739..cbcba6e 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -37,6 +37,7 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -202,7 +203,7 @@ typedef struct PgFdwAnalyzeState
 	/* for random sampling */
 	double		samplerows;		/* # of rows fetched */
 	double		rowstoskip;		/* # of rows to skip before next sample */
-	double		rstate;			/* random state */
+	ReservoirStateData rstate;		/* state for reservoir sampling*/
 
 	/* working memory contexts */
 	MemoryContext anl_cxt;		/* context for per-analyze lifespan data */
@@ -2393,7 +2394,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 	astate.numrows = 0;
 	astate.samplerows = 0;
 	astate.rowstoskip = -1;		/* -1 means not set yet */
-	astate.rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&astate.rstate, targrows);
 
 	/* Remember ANALYZE context, and create a per-tuple temp context */
 	astate.anl_cxt = CurrentMemoryContext;
@@ -2533,13 +2534,12 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		 * analyze.c; see Jeff Vitter's paper.
 		 */
 		if (astate->rowstoskip < 0)
-			astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
-												&astate->rstate);
+			astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
 
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * anl_random_fract());
+			pos = (int) (targrows * sampler_random_fract());
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index d2856a3..fc9dd44 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -88,10 +78,6 @@ static BufferAccessStrategy vac_strategy;
 static void do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -947,94 +933,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1080,7 +978,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	BlockNumber totalblocks;
 	TransactionId OldestXmin;
 	BlockSamplerData bs;
-	double		rstate;
+	ReservoirStateData rstate;
 
 	Assert(targrows > 0);
 
@@ -1090,9 +988,9 @@ acquire_sample_rows(Relation onerel, int elevel,
 	OldestXmin = GetOldestXmin(onerel, true);
 
 	/* Prepare for sampling block numbers */
-	BlockSampler_Init(&bs, totalblocks, targrows);
+	BlockSampler_Init(&bs, totalblocks, targrows, random());
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Outer loop over blocks to sample */
 	while (BlockSampler_HasMore(&bs))
@@ -1240,8 +1138,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 					 * t.
 					 */
 					if (rowstoskip < 0)
-						rowstoskip = anl_get_next_S(samplerows, targrows,
-													&rstate);
+						rowstoskip = reservoir_get_next_S(&rstate, samplerows, targrows);
 
 					if (rowstoskip <= 0)
 					{
@@ -1249,7 +1146,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1308,116 +1205,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
-/*
- * These two routines embody Algorithm Z from "Random sampling with a
- * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
- * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
- * of the count S of records to skip before processing another record.
- * It is computed primarily based on t, the number of records already read.
- * The only extra state needed between calls is W, a random state variable.
- *
- * anl_init_selection_state computes the initial W value.
- *
- * Given that we've already read t records (t >= n), anl_get_next_S
- * determines the number of records to skip before the next record is
- * processed.
- */
-double
-anl_init_selection_state(int n)
-{
-	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
-}
-
-double
-anl_get_next_S(double t, int n, double *stateptr)
-{
-	double		S;
-
-	/* The magic constant here is T from Vitter's paper */
-	if (t <= (22.0 * n))
-	{
-		/* Process records using Algorithm X until t is large enough */
-		double		V,
-					quot;
-
-		V = anl_random_fract(); /* Generate V */
-		S = 0;
-		t += 1;
-		/* Note: "num" in Vitter's code is always equal to t - n */
-		quot = (t - (double) n) / t;
-		/* Find min S satisfying (4.1) */
-		while (quot > V)
-		{
-			S += 1;
-			t += 1;
-			quot *= (t - (double) n) / t;
-		}
-	}
-	else
-	{
-		/* Now apply Algorithm Z */
-		double		W = *stateptr;
-		double		term = t - (double) n + 1;
-
-		for (;;)
-		{
-			double		numer,
-						numer_lim,
-						denom;
-			double		U,
-						X,
-						lhs,
-						rhs,
-						y,
-						tmp;
-
-			/* Generate U and X */
-			U = anl_random_fract();
-			X = t * (W - 1.0);
-			S = floor(X);		/* S is tentatively set to floor(X) */
-			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
-			tmp = (t + 1) / term;
-			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
-			rhs = (((t + X) / (term + S)) * term) / t;
-			if (lhs <= rhs)
-			{
-				W = rhs / lhs;
-				break;
-			}
-			/* Test if U <= f(S)/cg(X) */
-			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
-			if ((double) n < S)
-			{
-				denom = t;
-				numer_lim = term + S;
-			}
-			else
-			{
-				denom = t - (double) n + S;
-				numer_lim = t + 1;
-			}
-			for (numer = t + S; numer >= numer_lim; numer -= 1)
-			{
-				y *= numer / denom;
-				denom -= 1;
-			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
-			if (exp(log(y) / n) <= (t + X) / t)
-				break;
-		}
-		*stateptr = W;
-	}
-	return S;
-}
-
 /*
  * qsort comparator for sorting rows[] array
  */
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index 449d5b4..848ba29 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..1eeabaf
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,226 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Relation block sampling routines.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler provides algorithm for block level sampling of a relation
+ * as discussed on pgsql-hackers 2004-04-02 (subject "Large DB")
+ * It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table. If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
+				  long randseed)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+/*
+ * These two routines embody Algorithm Z from "Random sampling with a
+ * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
+ * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
+ * of the count S of records to skip before processing another record.
+ * It is computed primarily based on t, the number of records already read.
+ * The only extra state needed between calls is W, a random state variable.
+ *
+ * reservoir_init_selection_state computes the initial W value.
+ *
+ * Given that we've already read t records (t >= n), reservoir_get_next_S
+ * determines the number of records to skip before the next record is
+ * processed.
+ */
+void
+reservoir_init_selection_state(ReservoirState rs, int n)
+{
+	/* Initial value of W (for use when Algorithm Z is first applied) */
+	*rs = exp(-log(sampler_random_fract()) / n);
+}
+
+double
+reservoir_get_next_S(ReservoirState rs, double t, int n)
+{
+	double		S;
+
+	/* The magic constant here is T from Vitter's paper */
+	if (t <= (22.0 * n))
+	{
+		/* Process records using Algorithm X until t is large enough */
+		double		V,
+					quot;
+
+		V = sampler_random_fract(); /* Generate V */
+		S = 0;
+		t += 1;
+		/* Note: "num" in Vitter's code is always equal to t - n */
+		quot = (t - (double) n) / t;
+		/* Find min S satisfying (4.1) */
+		while (quot > V)
+		{
+			S += 1;
+			t += 1;
+			quot *= (t - (double) n) / t;
+		}
+	}
+	else
+	{
+		/* Now apply Algorithm Z */
+		double		W = *rs;
+		double		term = t - (double) n + 1;
+
+		for (;;)
+		{
+			double		numer,
+						numer_lim,
+						denom;
+			double		U,
+						X,
+						lhs,
+						rhs,
+						y,
+						tmp;
+
+			/* Generate U and X */
+			U = sampler_random_fract();
+			X = t * (W - 1.0);
+			S = floor(X);		/* S is tentatively set to floor(X) */
+			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
+			tmp = (t + 1) / term;
+			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
+			rhs = (((t + X) / (term + S)) * term) / t;
+			if (lhs <= rhs)
+			{
+				W = rhs / lhs;
+				break;
+			}
+			/* Test if U <= f(S)/cg(X) */
+			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
+			if ((double) n < S)
+			{
+				denom = t;
+				numer_lim = term + S;
+			}
+			else
+			{
+				denom = t - (double) n + S;
+				numer_lim = t + 1;
+			}
+			for (numer = t + S; numer >= numer_lim; numer -= 1)
+			{
+				y *= numer / denom;
+				denom -= 1;
+			}
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			if (exp(log(y) / n) <= (t + X) / t)
+				break;
+		}
+		*rs = W;
+	}
+	return S;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract()
+{
+	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+}
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 4275484..d38fead 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -178,8 +178,5 @@ extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 extern void analyze_rel(Oid relid, VacuumStmt *vacstmt,
 			bool in_outer_xact, BufferAccessStrategy bstrategy);
 extern bool std_typanalyze(VacAttrStats *stats);
-extern double anl_random_fract(void);
-extern double anl_init_selection_state(int n);
-extern double anl_get_next_S(double t, int n, double *stateptr);
 
 #endif   /* VACUUM_H */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..e3e7f9c
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,44 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+extern double sampler_random_fract(void);
+
+/* Block sampling methods */
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize, long randseed);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Reservoid sampling methods */
+typedef double ReservoirStateData;
+typedef ReservoirStateData *ReservoirState;
+
+extern void reservoir_init_selection_state(ReservoirState rs, int n);
+extern double reservoir_get_next_S(ReservoirState rs, double t, int n);
+
+#endif /* SAMPLING_H */
-- 
1.9.1

>From f7a4c015a74ff0c8cfe5bc76b3a67d134d277d6b Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:37:55 +0100
Subject: [PATCH 2/3] tablesample v7

---
 contrib/file_fdw/file_fdw.c                 |   2 +-
 contrib/postgres_fdw/postgres_fdw.c         |   2 +-
 doc/src/sgml/ref/select.sgml                |  38 ++-
 src/backend/access/Makefile                 |   3 +-
 src/backend/catalog/Makefile                |   2 +-
 src/backend/commands/analyze.c              |   2 +-
 src/backend/commands/explain.c              |   7 +
 src/backend/executor/Makefile               |   2 +-
 src/backend/executor/execAmi.c              |   8 +
 src/backend/executor/execCurrent.c          |   1 +
 src/backend/executor/execProcnode.c         |  14 +
 src/backend/executor/nodeSamplescan.c       | 448 ++++++++++++++++++++++++++++
 src/backend/nodes/copyfuncs.c               |  58 ++++
 src/backend/nodes/equalfuncs.c              |  35 +++
 src/backend/nodes/nodeFuncs.c               |  12 +
 src/backend/nodes/outfuncs.c                |  46 +++
 src/backend/nodes/readfuncs.c               |  43 +++
 src/backend/optimizer/path/allpaths.c       |  31 ++
 src/backend/optimizer/path/costsize.c       |  70 +++++
 src/backend/optimizer/plan/createplan.c     |  69 +++++
 src/backend/optimizer/plan/setrefs.c        |  11 +
 src/backend/optimizer/plan/subselect.c      |   1 +
 src/backend/optimizer/util/pathnode.c       |  22 ++
 src/backend/parser/gram.y                   |  40 ++-
 src/backend/parser/parse_clause.c           |  38 ++-
 src/backend/parser/parse_func.c             | 129 ++++++++
 src/backend/utils/Makefile                  |   3 +-
 src/backend/utils/adt/ruleutils.c           |  50 ++++
 src/backend/utils/cache/syscache.c          |  23 ++
 src/backend/utils/misc/sampling.c           |  33 +-
 src/backend/utils/tablesample/Makefile      |  17 ++
 src/backend/utils/tablesample/bernoulli.c   | 206 +++++++++++++
 src/backend/utils/tablesample/system.c      | 187 ++++++++++++
 src/include/catalog/indexing.h              |   5 +
 src/include/catalog/pg_proc.h               |  25 ++
 src/include/catalog/pg_tablesample_method.h |  73 +++++
 src/include/executor/nodeSamplescan.h       |  24 ++
 src/include/nodes/execnodes.h               |  21 ++
 src/include/nodes/nodes.h                   |   4 +
 src/include/nodes/parsenodes.h              |  34 +++
 src/include/nodes/plannodes.h               |   6 +
 src/include/optimizer/cost.h                |   1 +
 src/include/optimizer/pathnode.h            |   2 +
 src/include/parser/kwlist.h                 |   3 +-
 src/include/parser/parse_func.h             |   4 +
 src/include/utils/rel.h                     |   1 -
 src/include/utils/sampling.h                |  15 +-
 src/include/utils/syscache.h                |   2 +
 src/include/utils/tablesample.h             |  33 ++
 src/test/regress/expected/sanity_check.out  |   1 +
 src/test/regress/expected/tablesample.out   | 165 ++++++++++
 src/test/regress/parallel_schedule          |   2 +-
 src/test/regress/serial_schedule            |   1 +
 src/test/regress/sql/tablesample.sql        |  39 +++
 54 files changed, 2087 insertions(+), 27 deletions(-)
 create mode 100644 src/backend/executor/nodeSamplescan.c
 create mode 100644 src/backend/utils/tablesample/Makefile
 create mode 100644 src/backend/utils/tablesample/bernoulli.c
 create mode 100644 src/backend/utils/tablesample/system.c
 create mode 100644 src/include/catalog/pg_tablesample_method.h
 create mode 100644 src/include/executor/nodeSamplescan.h
 create mode 100644 src/include/utils/tablesample.h
 create mode 100644 src/test/regress/expected/tablesample.out
 create mode 100644 src/test/regress/sql/tablesample.sql

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index df732c0..3fc3962 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -1096,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * sampler_random_fract());
+				int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index cbcba6e..95f196e 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -2539,7 +2539,7 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * sampler_random_fract());
+			pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 01d24a5..407bf9d 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,42 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        one of:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of those sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability.
+        The optional numeric parameter <literal>REPEATABLE</literal> is used
+        as random seed for sampling. Note that subsequent commands may return
+        different results even if same <literal>REPEATABLE</literal> clause
+        was specified. This happens because <acronym>DML</acronym> statements
+        and maintenance operations such as <command>VACUUM</> affect physical
+        distribution of data.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..238057a 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  transam
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..34db3e6 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesample_method.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index fc9dd44..63feb07 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1146,7 +1146,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * sampler_random_fract());
+						int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 7cfc9bb..22525af 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -732,6 +732,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -958,6 +959,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			pname = sname = "Sample Scan";
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1075,6 +1079,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1327,6 +1332,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2230,6 +2236,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 6ebad2f..4948a26 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index 1c8be25..5cfe549 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 9892499..03c2feb 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..1b9f366
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,448 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "catalog/pg_tablesample_method.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "storage/bufmgr.h"
+#include "storage/predicate.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate, int eflags);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+
+/*
+ * Initialize the sampling method - loads function info and
+ * calls the tsminit function.
+ *
+ * We need special handling for this because the tsminit function
+ * is allowed to take optional additional arguments.
+ */
+static void
+InitSamplingMethod(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(scanstate->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(scanstate->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(scanstate->tsmnexttuple));
+	if (OidIsValid(tablesample->tsmreturntuple))
+		fmgr_info(tablesample->tsmreturntuple, &(scanstate->tsmreturntuple));
+	else
+		scanstate->tsmreturntuple.fn_oid = InvalidOid;
+	fmgr_info(tablesample->tsmend, &(scanstate->tsmend));
+	fmgr_info(tablesample->tsmreset, &(scanstate->tsmreset));
+
+	InitFunctionCallInfoData(fcinfo, &scanstate->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	/* First arg is always SampleScanState */
+	fcinfo.arg[0] = PointerGetDatum(scanstate);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause cannot be NULL")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+}
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	EState	   *estate;
+	TupleTableSlot *slot;
+	BlockNumber	blockno = InvalidBlockNumber;
+	Snapshot	snapshot;
+	Relation	relation;
+	bool		found = false;
+	bool		retry = false;
+	Buffer		buffer;
+	Page		page;
+	HeapTuple	tuple = &(node->tup);
+	OffsetNumber tupoffset,
+				 maxoffset,
+				 all_visible;
+
+	/*
+	 * get information from the estate and scan state
+	 */
+	estate = node->ss.ps.state;
+	snapshot = estate->es_snapshot;
+	slot = node->ss.ss_ScanTupleSlot;
+	relation = node->ss.ss_currentRelation;
+	buffer = node->openbuffer;
+
+	if (BufferIsValid(buffer))
+	{
+		blockno = BufferGetBlockNumber(buffer);
+		page = BufferGetPage(buffer);
+		maxoffset = PageGetMaxOffsetNumber(page);
+		all_visible = PageIsAllVisible(page) && !snapshot->takenDuringRecovery;
+	}
+
+	/*
+	 * get the next tuple from the table
+	 */
+	for (;;)
+	{
+		ItemId	itemid;
+		bool	visible;
+
+		CHECK_FOR_INTERRUPTS();
+
+		/* Load next block if needed. */
+		if (!BufferIsValid(buffer))
+		{
+			blockno = DatumGetInt32(FunctionCall2(&node->tsmnextblock,
+												  PointerGetDatum(node),
+												  BoolGetDatum(retry)));
+			/* No more blocks to fetch */
+			if (!BlockNumberIsValid(blockno))
+				break;
+
+			buffer = ReadBufferExtended(relation, MAIN_FORKNUM, blockno,
+										RBM_NORMAL, NULL);
+			/*
+			 * Prune and repair fragmentation for the whole page, if possible.
+			 */
+			heap_page_prune_opt(relation, buffer);
+
+			/*
+			 * Lock the buffer so we can safely assess tuple
+			 * visibility later.
+			 */
+			LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+			node->openbuffer = buffer;
+			page = BufferGetPage(buffer);
+			maxoffset = PageGetMaxOffsetNumber(page);
+			all_visible = PageIsAllVisible(page) && !snapshot->takenDuringRecovery;
+		}
+
+		tupoffset = DatumGetUInt16(FunctionCall4(&node->tsmnexttuple,
+												 PointerGetDatum(node),
+												 UInt32GetDatum(blockno),
+												 UInt16GetDatum(maxoffset),
+												 BoolGetDatum(retry)));
+		/* Go to next block. */
+		if (!OffsetNumberIsValid(tupoffset))
+		{
+			UnlockReleaseBuffer(buffer);
+			node->openbuffer = buffer = InvalidBuffer;
+			continue;
+		}
+		retry = true;
+
+		/* Skip invalid tuple pointers. */
+		itemid = PageGetItemId(page, tupoffset);
+		if (!ItemIdIsNormal(itemid))
+			continue;
+
+		tuple->t_tableOid = RelationGetRelid(relation);
+		tuple->t_data = (HeapTupleHeader) PageGetItem(page, itemid);
+		tuple->t_len = ItemIdGetLength(itemid);
+		ItemPointerSet(&tuple->t_self, blockno, tupoffset);
+
+		/* Check visibility. */
+		if (all_visible)
+			visible = true;
+		else
+			visible = HeapTupleSatisfiesVisibility(tuple, snapshot, buffer);
+
+		CheckForSerializableConflictOut(found, relation, tuple, buffer, snapshot);
+
+		/*
+		 * Let the sampling method examine the actual tuple and decide if we
+		 * should return it.
+		 *
+		 * Note that we let it examine even invisible tuples.
+		 */
+		if (OidIsValid(node->tsmreturntuple.fn_oid))
+		{
+			found = DatumGetBool(FunctionCall4(&node->tsmreturntuple,
+											   PointerGetDatum(node),
+											   UInt32GetDatum(blockno),
+											   PointerGetDatum(tuple),
+											   BoolGetDatum(visible)));
+			/* XXX: better error */
+			if (found && !visible)
+				elog(ERROR, "Sampling method wanted to return invisible tuple");
+		}
+		else
+			found = visible;
+
+		/* Found visible tuple, return it. */
+		if (found)
+			break;
+	}
+
+	if (found)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   buffer,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+	node->ss.ss_currentScanDesc = NULL;
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	scanstate->openbuffer = InvalidBuffer;
+
+	InitSamplingMethod(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished thes can.
+	 */
+	FunctionCall1(&node->tsmend, PointerGetDatum(node));
+
+	if (BufferIsValid(node->openbuffer))
+	{
+		UnlockReleaseBuffer(node->openbuffer);
+		node->openbuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *scanstate)
+{
+	if (BufferIsValid(scanstate->openbuffer))
+	{
+		UnlockReleaseBuffer(scanstate->openbuffer);
+		scanstate->openbuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	FunctionCall1(&scanstate->tsmreset, PointerGetDatum(scanstate));
+
+	ExecScanReScan(&scanstate->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index f1a24f5..383bbf6 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -628,6 +628,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2006,6 +2022,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2138,6 +2155,38 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmreturntuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4075,6 +4124,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4723,6 +4775,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_PrivGrantee:
 			retval = _copyPrivGrantee(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 6e8b308..07c69c9 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2323,6 +2323,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2442,6 +2443,34 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmreturntuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3150,6 +3179,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_PrivGrantee:
 			retval = _equalPrivGrantee(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 21dfda7..bd9ce09 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3209,6 +3209,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index dd1278b..c343732 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -578,6 +578,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -2391,6 +2399,34 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmreturntuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2420,6 +2456,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2887,6 +2924,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3228,6 +3268,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index ae24d05..d08d8e9 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,44 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmreturntuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1216,6 +1254,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1311,6 +1350,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 58d78e6..9a16e46 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,8 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -332,6 +334,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +425,30 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids	required_outer;
+	Path   *path;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	path = create_samplescan_path(root, rel, required_outer);
+	rel->pathlist = list_make1(path);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 020558b..8342392a 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -90,6 +90,7 @@
 #include "utils/lsyscache.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
+#include "utils/tablesample.h"
 #include "utils/tuplesort.h"
 
 
@@ -219,6 +220,75 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we dont't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	RangeTblEntry		   *rte = planner_rt_fetch(baserel->relid, root);
+	TableSampleClause	   *tablesample = rte->tablesample;
+	SamplerAccessStrategy	strategy;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall7(tablesample->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(tablesample->args),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples),
+					 PointerGetDatum(&strategy));
+
+	/* Mark the path with the correct row estimate */
+	if (path->param_info)
+		path->rows = path->param_info->ppi_rows;
+	else
+		path->rows = tuples;
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = strategy == SAS_RANDOM ?
+		spc_random_page_cost : spc_seq_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->startup_cost = startup_cost;
+	path->total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 655be81..10a5e02 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3318,6 +3369,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 7703946..de33fc6 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -446,6 +446,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 78fb6b1..191624c 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2163,6 +2163,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 1395a21..014d670 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,26 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+Path *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	Path		   *pathnode = makeNode(Path);
+
+	pathnode->pathtype = T_SampleScan;
+	pathnode->parent = rel;
+	pathnode->param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->pathkeys = NIL;	/* samplescan has unordered result */
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1921,6 +1941,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 36dac29..ac5e095 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -447,6 +447,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -611,8 +612,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10227,6 +10228,12 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample opt_alias_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10522,7 +10529,6 @@ relation_expr_list:
 			| relation_expr_list ',' relation_expr	{ $$ = lappend($1, $3); }
 		;
 
-
 /*
  * Given "UPDATE foo set set ...", we have to decide without looking any
  * further ahead whether the first "set" is an alias or the UPDATE's SET
@@ -10552,6 +10558,31 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $2;
+					n->relation = $1;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' func_arg_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' AexprConst ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/						{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13334,7 +13365,6 @@ unreserved_keyword:
 			| RELATIVE_P
 			| RELEASE
 			| RENAME
-			| REPEATABLE
 			| REPLACE
 			| REPLICA
 			| RESET
@@ -13509,6 +13539,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
@@ -13577,6 +13608,7 @@ reserved_keyword:
 			| PLACING
 			| PRIMARY
 			| REFERENCES
+			| REPEATABLE
 			| RETURNING
 			| SELECT
 			| SESSION_USER
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 654dce6..03632d2 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -413,6 +416,19 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *r)
+{
+	RangeTblEntry  *rte;
+	TableSampleClause *tablesample = NULL;
+
+	rte = transformTableEntry(pstate, r->relation);
+	tablesample = ParseTableSample(pstate, r->method, r->repeatable, r->args);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -421,7 +437,7 @@ transformTableEntry(ParseState *pstate, RangeVar *r)
 {
 	RangeTblEntry *rte;
 
-	/* We need only build a range table entry */
+	/* We first need to build a range table entry */
 	rte = addRangeTableEntry(pstate, r, r->alias,
 							 interpretInhOption(r->inhOpt), true);
 
@@ -1121,6 +1137,26 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index a200804..7ca1268 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -760,6 +762,133 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+extern TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				actual_arg_types[FUNC_MAX_ARGS];
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						samplemethod)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmreturntuple = tsm->tsmreturntuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Transform the rest of arguments ... */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *arg = transformExpr(pstate, (Node *) lfirst(larg), EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		fargs = lappend(fargs, arg);
+
+		actual_arg_types[nargs++] = argtype;
+	}
+
+	/*
+	 * Check if parameters are correct.
+	 *
+	 * XXX: can we do better at hinting here?
+	 */
+	if (initnargs != nargs ||
+			!can_coerce_type(initnargs, actual_arg_types, init_arg_types,
+						COERCION_IMPLICIT))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("wrong parameters for tablesample method \"%s\"",
+						samplemethod)));
+
+	/* perform the necessary typecasting of arguments */
+	make_fn_arguments(pstate, fargs, actual_arg_types, init_arg_types);
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/utils/Makefile b/src/backend/utils/Makefile
index 8374533..9daa2ae 100644
--- a/src/backend/utils/Makefile
+++ b/src/backend/utils/Makefile
@@ -9,7 +9,8 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS        = fmgrtab.o
-SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time
+SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time \
+			  tablesample
 
 # location of Catalog.pm
 catalogdir  = $(top_srcdir)/src/backend/catalog
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index c1d860c..8198fc7 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -31,6 +31,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -343,6 +344,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4184,6 +4187,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for tablesample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8411,6 +8458,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index bd27168..3a8f01e 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
index 1eeabaf..f213c46 100644
--- a/src/backend/utils/misc/sampling.c
+++ b/src/backend/utils/misc/sampling.c
@@ -46,6 +46,8 @@ BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
 	bs->n = samplesize;
 	bs->t = 0;					/* blocks scanned so far */
 	bs->m = 0;					/* blocks selected so far */
+
+	sampler_random_init_state(randseed, bs->randstate);
 }
 
 bool
@@ -92,7 +94,7 @@ BlockSampler_Next(BlockSampler bs)
 	 * less than k, which means that we cannot fail to select enough blocks.
 	 *----------
 	 */
-	V = sampler_random_fract();
+	V = sampler_random_fract(bs->randstate);
 	p = 1.0 - (double) k / (double) K;
 	while (V < p)
 	{
@@ -126,8 +128,14 @@ BlockSampler_Next(BlockSampler bs)
 void
 reservoir_init_selection_state(ReservoirState rs, int n)
 {
+	/*
+	 * Reservoir sampling is not used anywhere where it would need to return
+	 * repeatable results so we can initialize it randomly.
+	 */
+	sampler_random_init_state(random(), rs->randstate);
+
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	*rs = exp(-log(sampler_random_fract()) / n);
+	rs->W = exp(-log(sampler_random_fract(rs->randstate)) / n);
 }
 
 double
@@ -142,7 +150,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 		double		V,
 					quot;
 
-		V = sampler_random_fract(); /* Generate V */
+		V = sampler_random_fract(rs->randstate); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -158,7 +166,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 	else
 	{
 		/* Now apply Algorithm Z */
-		double		W = *rs;
+		double		W = rs->W;
 		double		term = t - (double) n + 1;
 
 		for (;;)
@@ -174,7 +182,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 						tmp;
 
 			/* Generate U and X */
-			U = sampler_random_fract();
+			U = sampler_random_fract(rs->randstate);
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -203,11 +211,11 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract(rs->randstate)) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
-		*rs = W;
+		rs->W = W;
 	}
 	return S;
 }
@@ -217,10 +225,17 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
  * Random number generator used by sampling
  *----------
  */
+void
+sampler_random_init_state(long seed, SamplerRandomState randstate)
+{
+	randstate[0] = 0x330e;
+	randstate[1] = (unsigned short) seed;
+	randstate[2] = (unsigned short) (seed >> 16);
+}
 
 /* Select a random value R uniformly distributed in (0 - 1) */
 double
-sampler_random_fract()
+sampler_random_fract(SamplerRandomState randstate)
 {
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+	return pg_erand48(randstate);
 }
diff --git a/src/backend/utils/tablesample/Makefile b/src/backend/utils/tablesample/Makefile
new file mode 100644
index 0000000..df92939
--- /dev/null
+++ b/src/backend/utils/tablesample/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for utils/tablesample
+#
+# IDENTIFICATION
+#    src/backend/utils/tablesample/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/utils/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = system.o bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/tablesample/bernoulli.c b/src/backend/utils/tablesample/bernoulli.c
new file mode 100644
index 0000000..15e29d8
--- /dev/null
+++ b/src/backend/utils/tablesample/bernoulli.c
@@ -0,0 +1,206 @@
+/*-------------------------------------------------------------------------
+ *
+ * bernoulli.c
+ *	  interface routines for BERNOULLI tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/* State */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	float4 probability;			/* probabilty that tuple will be returned (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks = RelationGetNumberOfBlocks(rel);
+	sampler->blockno = InvalidBlockNumber;
+	sampler->probability = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = 0;
+	else if (++sampler->blockno >= sampler->tblocks)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+	float4			probability = sampler->probability;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/*
+	 * Loop over tuple offsets until the random generator returns value that
+	 * is within the probability of returning the tuple or until we reach
+	 * end of the block.
+	 */
+	while (sampler_random_fract(sampler->randstate) > probability)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	SamplerAccessStrategy *strategy =
+		(SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_SEQUENTIAL;
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (!IsA(pctnode, Const))
+	{
+		*tuples = baserel->tuples * 0.1;
+		PG_RETURN_VOID();
+	}
+
+	samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+	samplesize /= 100.0;
+
+	*tuples = baserel->tuples * samplesize;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/utils/tablesample/system.c b/src/backend/utils/tablesample/system.c
new file mode 100644
index 0000000..9d410d2
--- /dev/null
+++ b/src/backend/utils/tablesample/system.c
@@ -0,0 +1,187 @@
+/*-------------------------------------------------------------------------
+ *
+ * system.c
+ *	  interface routines for system tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	SystemSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks =
+		RelationGetNumberOfBlocks(scanstate->ss.ss_currentRelation);
+	sampler->samplesize = 1 + (int) (sampler->tblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as VACUUM for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	BlockNumber		blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			percent;
+
+	SamplerAccessStrategy *strategy =
+		(SamplerAccessStrategy *) PG_GETARG_POINTER(5);
+
+	*strategy = SAS_RANDOM;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (!IsA(pctnode, Const))
+	{
+		*pages = baserel->pages * 0.1;
+		*tuples = baserel->tuples * 0.1;
+		PG_RETURN_VOID();
+	}
+
+	percent = DatumGetFloat4(((Const *) pctnode)->constvalue);
+	percent /= 100.0;
+
+	*pages = baserel->pages * percent;
+	*tuples = baserel->tuples * percent;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index a680229..c711cca 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3281, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3281
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3282, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3282
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 9edfdb8..e6d821d 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5143,6 +5143,31 @@ DESCR("rank of hypothetical row without gaps");
 DATA(insert OID = 3993 ( dense_rank_final	PGNSP PGUID 12 1 0 2276 0 f f f f f f i 2 0 20 "2281 2276" "{2281,2276}" "{i,v}" _null_ _null_	hypothetical_dense_rank_final _null_ _null_ _null_ ));
 DESCR("aggregate final function");
 
+DATA(insert OID = 3285 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3286 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3287 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3288 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3289 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3290 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3291 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3292 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3293 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3294 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3296 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3297 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 0000000..ea11f45
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,73 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3280
+
+CATALOG(pg_tablesample_method,3280)
+{
+	NameData	tsmname;		/* tablescan method name */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmreturntuple;	/* optional function which can examine tuple contents and
+								   decide if tuple should be returned or not */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method					8
+#define Anum_pg_tablesample_method_tsmname			1
+#define Anum_pg_tablesample_method_tsminit			2
+#define Anum_pg_tablesample_method_tsmnextblock		3
+#define Anum_pg_tablesample_method_tsmnexttuple		4
+#define Anum_pg_tablesample_method_tsmreturntuple	5
+#define Anum_pg_tablesample_method_tsmend			6
+#define Anum_pg_tablesample_method_tsmreset			7
+#define Anum_pg_tablesample_method_tsmcost			8
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3283 ( system tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3284 ( bernoulli tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 41288ed..526be4c 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1212,6 +1212,27 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState		ss;
+
+	/* Sampling method functions. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmreturntuple;
+	FmgrInfo		tsmend;
+	FmgrInfo		tsmreset;
+
+	Buffer			openbuffer;		/* currently open buffer */
+	HeapTupleData	tup;			/* last tuple */
+
+	void		   *tsmdata;		/* for use by table scan method */
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 97ef0fc..3276be8 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -413,6 +415,8 @@ typedef enum NodeTag
 	T_XmlSerialize,
 	T_WithClause,
 	T_CommonTableExpr,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index b1dfa85..7927a82 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -307,6 +307,24 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmreturntuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -507,6 +525,21 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * We are more generic than SQL Standard so we pass generic function
+ * arguments to the sampling method.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -751,6 +784,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 316c9ce..8a2a146 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -278,6 +278,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 9c2000b..24003ae 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 9923f0e..89c8ded 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern Path *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+									Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 7c243ec..6ff7b44 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -312,7 +312,7 @@ PG_KEYWORD("reindex", REINDEX, UNRESERVED_KEYWORD)
 PG_KEYWORD("relative", RELATIVE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("release", RELEASE, UNRESERVED_KEYWORD)
 PG_KEYWORD("rename", RENAME, UNRESERVED_KEYWORD)
-PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
+PG_KEYWORD("repeatable", REPEATABLE, RESERVED_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 3264691..6727e55 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,10 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 6bd786d..185bd81 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
index e3e7f9c..4ac208d 100644
--- a/src/include/utils/sampling.h
+++ b/src/include/utils/sampling.h
@@ -15,7 +15,12 @@
 
 #include "storage/bufmgr.h"
 
-extern double sampler_random_fract(void);
+/* Random generator for sampling code */
+typedef unsigned short SamplerRandomState[3];
+
+extern void sampler_random_init_state(long seed,
+									  SamplerRandomState randstate);
+extern double sampler_random_fract(SamplerRandomState randstate);
 
 /* Block sampling methods */
 /* Data structure for Algorithm S from Knuth 3.4.2 */
@@ -25,6 +30,7 @@ typedef struct
 	int			n;				/* desired sample size */
 	BlockNumber t;				/* current block number */
 	int			m;				/* blocks selected so far */
+	SamplerRandomState randstate; /* random generator state */
 } BlockSamplerData;
 
 typedef BlockSamplerData *BlockSampler;
@@ -35,7 +41,12 @@ extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
 /* Reservoid sampling methods */
-typedef double ReservoirStateData;
+typedef struct
+{
+	double	W;
+	SamplerRandomState randstate; /* random generator state */
+} ReservoirStateData;
+
 typedef ReservoirStateData *ReservoirState;
 
 extern void reservoir_init_selection_state(ReservoirState rs, int n);
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index ba0b090..6b628f6 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/include/utils/tablesample.h b/src/include/utils/tablesample.h
new file mode 100644
index 0000000..3c97a04
--- /dev/null
+++ b/src/include/utils/tablesample.h
@@ -0,0 +1,33 @@
+/*--------------------------------------------------------------------------
+ * tablesample.h
+ *	  Header file for builtin table sampling methods.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/utils/tablesample.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TABLESAMPLE_H
+#define TABLESAMPLE_H
+
+typedef enum SamplerAccessStrategy
+{
+	SAS_RANDOM,
+	SAS_SEQUENTIAL
+} SamplerAccessStrategy;
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TABLESAMPLE_H */
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..5946edf 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..9b387a2
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,165 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+CLOSE tablesample_cur;
+END;
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index e0ae2f2..e0240ac 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 7f762bd..9a7611b 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -152,3 +152,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..2b89b55
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,39 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+CLOSE tablesample_cur;
+END;
+
+DROP TABLE test_tablesample CASCADE;
-- 
1.9.1

>From de3bfeb6275228b03944fdf39cee0277d97c4449 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:36:56 +0100
Subject: [PATCH 1/3] separate block sampling functions v2

---
 contrib/file_fdw/file_fdw.c         |   9 +-
 contrib/postgres_fdw/postgres_fdw.c |  10 +-
 src/backend/commands/analyze.c      | 225 +----------------------------------
 src/backend/utils/misc/Makefile     |   2 +-
 src/backend/utils/misc/sampling.c   | 226 ++++++++++++++++++++++++++++++++++++
 src/include/commands/vacuum.h       |   3 -
 src/include/utils/sampling.h        |  44 +++++++
 7 files changed, 287 insertions(+), 232 deletions(-)
 create mode 100644 src/backend/utils/misc/sampling.c
 create mode 100644 src/include/utils/sampling.h

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index d569760..df732c0 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -34,6 +34,7 @@
 #include "optimizer/var.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -1005,7 +1006,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 {
 	int			numrows = 0;
 	double		rowstoskip = -1;	/* -1 means not set yet */
-	double		rstate;
+	ReservoirStateData rstate;
 	TupleDesc	tupDesc;
 	Datum	   *values;
 	bool	   *nulls;
@@ -1043,7 +1044,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 									   ALLOCSET_DEFAULT_MAXSIZE);
 
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Set up callback to identify error line number. */
 	errcallback.callback = CopyFromErrorCallback;
@@ -1087,7 +1088,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 			 * not-yet-incremented value of totalrows as t.
 			 */
 			if (rowstoskip < 0)
-				rowstoskip = anl_get_next_S(*totalrows, targrows, &rstate);
+				rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
 
 			if (rowstoskip <= 0)
 			{
@@ -1095,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * anl_random_fract());
+				int			k = (int) (targrows * sampler_random_fract());
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index d76e739..cbcba6e 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -37,6 +37,7 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -202,7 +203,7 @@ typedef struct PgFdwAnalyzeState
 	/* for random sampling */
 	double		samplerows;		/* # of rows fetched */
 	double		rowstoskip;		/* # of rows to skip before next sample */
-	double		rstate;			/* random state */
+	ReservoirStateData rstate;		/* state for reservoir sampling*/
 
 	/* working memory contexts */
 	MemoryContext anl_cxt;		/* context for per-analyze lifespan data */
@@ -2393,7 +2394,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 	astate.numrows = 0;
 	astate.samplerows = 0;
 	astate.rowstoskip = -1;		/* -1 means not set yet */
-	astate.rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&astate.rstate, targrows);
 
 	/* Remember ANALYZE context, and create a per-tuple temp context */
 	astate.anl_cxt = CurrentMemoryContext;
@@ -2533,13 +2534,12 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		 * analyze.c; see Jeff Vitter's paper.
 		 */
 		if (astate->rowstoskip < 0)
-			astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
-												&astate->rstate);
+			astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
 
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * anl_random_fract());
+			pos = (int) (targrows * sampler_random_fract());
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index d2856a3..fc9dd44 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -88,10 +78,6 @@ static BufferAccessStrategy vac_strategy;
 static void do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -947,94 +933,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1080,7 +978,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	BlockNumber totalblocks;
 	TransactionId OldestXmin;
 	BlockSamplerData bs;
-	double		rstate;
+	ReservoirStateData rstate;
 
 	Assert(targrows > 0);
 
@@ -1090,9 +988,9 @@ acquire_sample_rows(Relation onerel, int elevel,
 	OldestXmin = GetOldestXmin(onerel, true);
 
 	/* Prepare for sampling block numbers */
-	BlockSampler_Init(&bs, totalblocks, targrows);
+	BlockSampler_Init(&bs, totalblocks, targrows, random());
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Outer loop over blocks to sample */
 	while (BlockSampler_HasMore(&bs))
@@ -1240,8 +1138,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 					 * t.
 					 */
 					if (rowstoskip < 0)
-						rowstoskip = anl_get_next_S(samplerows, targrows,
-													&rstate);
+						rowstoskip = reservoir_get_next_S(&rstate, samplerows, targrows);
 
 					if (rowstoskip <= 0)
 					{
@@ -1249,7 +1146,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1308,116 +1205,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
-/*
- * These two routines embody Algorithm Z from "Random sampling with a
- * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
- * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
- * of the count S of records to skip before processing another record.
- * It is computed primarily based on t, the number of records already read.
- * The only extra state needed between calls is W, a random state variable.
- *
- * anl_init_selection_state computes the initial W value.
- *
- * Given that we've already read t records (t >= n), anl_get_next_S
- * determines the number of records to skip before the next record is
- * processed.
- */
-double
-anl_init_selection_state(int n)
-{
-	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
-}
-
-double
-anl_get_next_S(double t, int n, double *stateptr)
-{
-	double		S;
-
-	/* The magic constant here is T from Vitter's paper */
-	if (t <= (22.0 * n))
-	{
-		/* Process records using Algorithm X until t is large enough */
-		double		V,
-					quot;
-
-		V = anl_random_fract(); /* Generate V */
-		S = 0;
-		t += 1;
-		/* Note: "num" in Vitter's code is always equal to t - n */
-		quot = (t - (double) n) / t;
-		/* Find min S satisfying (4.1) */
-		while (quot > V)
-		{
-			S += 1;
-			t += 1;
-			quot *= (t - (double) n) / t;
-		}
-	}
-	else
-	{
-		/* Now apply Algorithm Z */
-		double		W = *stateptr;
-		double		term = t - (double) n + 1;
-
-		for (;;)
-		{
-			double		numer,
-						numer_lim,
-						denom;
-			double		U,
-						X,
-						lhs,
-						rhs,
-						y,
-						tmp;
-
-			/* Generate U and X */
-			U = anl_random_fract();
-			X = t * (W - 1.0);
-			S = floor(X);		/* S is tentatively set to floor(X) */
-			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
-			tmp = (t + 1) / term;
-			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
-			rhs = (((t + X) / (term + S)) * term) / t;
-			if (lhs <= rhs)
-			{
-				W = rhs / lhs;
-				break;
-			}
-			/* Test if U <= f(S)/cg(X) */
-			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
-			if ((double) n < S)
-			{
-				denom = t;
-				numer_lim = term + S;
-			}
-			else
-			{
-				denom = t - (double) n + S;
-				numer_lim = t + 1;
-			}
-			for (numer = t + S; numer >= numer_lim; numer -= 1)
-			{
-				y *= numer / denom;
-				denom -= 1;
-			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
-			if (exp(log(y) / n) <= (t + X) / t)
-				break;
-		}
-		*stateptr = W;
-	}
-	return S;
-}
-
 /*
  * qsort comparator for sorting rows[] array
  */
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index 378b77e..7889101 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o rls.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..1eeabaf
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,226 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Relation block sampling routines.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler provides algorithm for block level sampling of a relation
+ * as discussed on pgsql-hackers 2004-04-02 (subject "Large DB")
+ * It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table. If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
+				  long randseed)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+/*
+ * These two routines embody Algorithm Z from "Random sampling with a
+ * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
+ * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
+ * of the count S of records to skip before processing another record.
+ * It is computed primarily based on t, the number of records already read.
+ * The only extra state needed between calls is W, a random state variable.
+ *
+ * reservoir_init_selection_state computes the initial W value.
+ *
+ * Given that we've already read t records (t >= n), reservoir_get_next_S
+ * determines the number of records to skip before the next record is
+ * processed.
+ */
+void
+reservoir_init_selection_state(ReservoirState rs, int n)
+{
+	/* Initial value of W (for use when Algorithm Z is first applied) */
+	*rs = exp(-log(sampler_random_fract()) / n);
+}
+
+double
+reservoir_get_next_S(ReservoirState rs, double t, int n)
+{
+	double		S;
+
+	/* The magic constant here is T from Vitter's paper */
+	if (t <= (22.0 * n))
+	{
+		/* Process records using Algorithm X until t is large enough */
+		double		V,
+					quot;
+
+		V = sampler_random_fract(); /* Generate V */
+		S = 0;
+		t += 1;
+		/* Note: "num" in Vitter's code is always equal to t - n */
+		quot = (t - (double) n) / t;
+		/* Find min S satisfying (4.1) */
+		while (quot > V)
+		{
+			S += 1;
+			t += 1;
+			quot *= (t - (double) n) / t;
+		}
+	}
+	else
+	{
+		/* Now apply Algorithm Z */
+		double		W = *rs;
+		double		term = t - (double) n + 1;
+
+		for (;;)
+		{
+			double		numer,
+						numer_lim,
+						denom;
+			double		U,
+						X,
+						lhs,
+						rhs,
+						y,
+						tmp;
+
+			/* Generate U and X */
+			U = sampler_random_fract();
+			X = t * (W - 1.0);
+			S = floor(X);		/* S is tentatively set to floor(X) */
+			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
+			tmp = (t + 1) / term;
+			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
+			rhs = (((t + X) / (term + S)) * term) / t;
+			if (lhs <= rhs)
+			{
+				W = rhs / lhs;
+				break;
+			}
+			/* Test if U <= f(S)/cg(X) */
+			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
+			if ((double) n < S)
+			{
+				denom = t;
+				numer_lim = term + S;
+			}
+			else
+			{
+				denom = t - (double) n + S;
+				numer_lim = t + 1;
+			}
+			for (numer = t + S; numer >= numer_lim; numer -= 1)
+			{
+				y *= numer / denom;
+				denom -= 1;
+			}
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			if (exp(log(y) / n) <= (t + X) / t)
+				break;
+		}
+		*rs = W;
+	}
+	return S;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract()
+{
+	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+}
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 4275484..d38fead 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -178,8 +178,5 @@ extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 extern void analyze_rel(Oid relid, VacuumStmt *vacstmt,
 			bool in_outer_xact, BufferAccessStrategy bstrategy);
 extern bool std_typanalyze(VacAttrStats *stats);
-extern double anl_random_fract(void);
-extern double anl_init_selection_state(int n);
-extern double anl_get_next_S(double t, int n, double *stateptr);
 
 #endif   /* VACUUM_H */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..e3e7f9c
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,44 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+extern double sampler_random_fract(void);
+
+/* Block sampling methods */
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize, long randseed);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Reservoid sampling methods */
+typedef double ReservoirStateData;
+typedef ReservoirStateData *ReservoirState;
+
+extern void reservoir_init_selection_state(ReservoirState rs, int n);
+extern double reservoir_get_next_S(ReservoirState rs, double t, int n);
+
+#endif /* SAMPLING_H */
-- 
1.9.1

>From 7ccd2dcbd95a8c759068bd034f810b22e93748d8 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:37:55 +0100
Subject: [PATCH 2/3] tablesample v8

---
 contrib/file_fdw/file_fdw.c                 |   2 +-
 contrib/postgres_fdw/postgres_fdw.c         |   2 +-
 doc/src/sgml/catalogs.sgml                  | 112 +++++++
 doc/src/sgml/ref/select.sgml                |  38 ++-
 src/backend/access/Makefile                 |   3 +-
 src/backend/access/heap/heapam.c            |   7 +-
 src/backend/catalog/Makefile                |   2 +-
 src/backend/commands/analyze.c              |   2 +-
 src/backend/commands/explain.c              |   7 +
 src/backend/executor/Makefile               |   2 +-
 src/backend/executor/execAmi.c              |   8 +
 src/backend/executor/execCurrent.c          |   1 +
 src/backend/executor/execProcnode.c         |  14 +
 src/backend/executor/nodeSamplescan.c       | 500 ++++++++++++++++++++++++++++
 src/backend/nodes/copyfuncs.c               |  59 ++++
 src/backend/nodes/equalfuncs.c              |  36 ++
 src/backend/nodes/nodeFuncs.c               |  12 +
 src/backend/nodes/outfuncs.c                |  47 +++
 src/backend/nodes/readfuncs.c               |  44 +++
 src/backend/optimizer/path/allpaths.c       |  49 +++
 src/backend/optimizer/path/costsize.c       |  68 ++++
 src/backend/optimizer/plan/createplan.c     |  69 ++++
 src/backend/optimizer/plan/setrefs.c        |  11 +
 src/backend/optimizer/plan/subselect.c      |   1 +
 src/backend/optimizer/util/pathnode.c       |  22 ++
 src/backend/parser/gram.y                   |  40 ++-
 src/backend/parser/parse_clause.c           |  38 ++-
 src/backend/parser/parse_func.c             | 130 ++++++++
 src/backend/utils/Makefile                  |   3 +-
 src/backend/utils/adt/ruleutils.c           |  50 +++
 src/backend/utils/cache/syscache.c          |  23 ++
 src/backend/utils/misc/sampling.c           |  33 +-
 src/backend/utils/tablesample/Makefile      |  17 +
 src/backend/utils/tablesample/bernoulli.c   | 224 +++++++++++++
 src/backend/utils/tablesample/system.c      | 185 ++++++++++
 src/include/access/heapam.h                 |   1 +
 src/include/access/relscan.h                |   1 +
 src/include/catalog/indexing.h              |   5 +
 src/include/catalog/pg_proc.h               |  25 ++
 src/include/catalog/pg_tablesample_method.h |  75 +++++
 src/include/executor/nodeSamplescan.h       |  24 ++
 src/include/nodes/execnodes.h               |  18 +
 src/include/nodes/nodes.h                   |   4 +
 src/include/nodes/parsenodes.h              |  35 ++
 src/include/nodes/plannodes.h               |   6 +
 src/include/optimizer/cost.h                |   1 +
 src/include/optimizer/pathnode.h            |   2 +
 src/include/parser/kwlist.h                 |   3 +-
 src/include/parser/parse_func.h             |   4 +
 src/include/utils/rel.h                     |   1 -
 src/include/utils/sampling.h                |  15 +-
 src/include/utils/syscache.h                |   2 +
 src/include/utils/tablesample.h             |  27 ++
 src/test/regress/expected/sanity_check.out  |   1 +
 src/test/regress/expected/tablesample.out   | 165 +++++++++
 src/test/regress/parallel_schedule          |   2 +-
 src/test/regress/serial_schedule            |   1 +
 src/test/regress/sql/tablesample.sql        |  39 +++
 58 files changed, 2288 insertions(+), 30 deletions(-)
 create mode 100644 src/backend/executor/nodeSamplescan.c
 create mode 100644 src/backend/utils/tablesample/Makefile
 create mode 100644 src/backend/utils/tablesample/bernoulli.c
 create mode 100644 src/backend/utils/tablesample/system.c
 create mode 100644 src/include/catalog/pg_tablesample_method.h
 create mode 100644 src/include/executor/nodeSamplescan.h
 create mode 100644 src/include/utils/tablesample.h
 create mode 100644 src/test/regress/expected/tablesample.out
 create mode 100644 src/test/regress/sql/tablesample.sql

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index df732c0..3fc3962 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -1096,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * sampler_random_fract());
+				int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index cbcba6e..95f196e 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -2539,7 +2539,7 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * sampler_random_fract());
+			pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 515a40e..6b4e32b 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -269,6 +269,11 @@
      </row>
 
      <row>
+      <entry><link linkend="catalog-pg-tablesample-method"><structname>pg_tablesample_method</structname></link></entry>
+      <entry>table sampling methods</entry>
+     </row>
+
+     <row>
       <entry><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link></entry>
       <entry>tablespaces within this database cluster</entry>
      </row>
@@ -5989,6 +5994,113 @@
  </sect1>
 
 
+ <sect1 id="catalog-pg-tablesample-method">
+  <title><structname>pg_tabesample_method</structname></title>
+
+  <indexterm zone="catalog-pg-tablesample-method">
+   <primary>pg_am</primary>
+  </indexterm>
+
+  <para>
+   The catalog <structname>pg_tablesample_method</structname> stores
+   information about table sampling methods which can be used in
+   <command>TABLESAMPLE</command> clause of a <command>SELECT</command>
+   statement.
+  </para>
+
+  <table>
+   <title><structname>pg_tablesample_method</> Columns</title>
+
+   <tgroup cols="4">
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Type</entry>
+      <entry>References</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+    <tbody>
+
+     <row>
+      <entry><structfield>oid</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry></entry>
+      <entry>Row identifier (hidden attribute; must be explicitly selected)</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmname</structfield></entry>
+      <entry><type>name</type></entry>
+      <entry></entry>
+      <entry>Name of the sampling method</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmseqscan</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry></entry>
+      <entry>Does the sampling method scan the whole table sequentially?
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsminit</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Initialize the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnextblock</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next block number</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnexttuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next tuple offset</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmexaminetuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Function which examines the tuple contents and decides if to
+        return in, or zero if none</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmend</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>End the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmreset</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Restart the state of sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmcost</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Costing function</entry>
+     </row>
+
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect1>
+
+
  <sect1 id="catalog-pg-tablespace">
   <title><structname>pg_tablespace</structname></title>
 
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 01d24a5..407bf9d 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,42 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        one of:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of those sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability.
+        The optional numeric parameter <literal>REPEATABLE</literal> is used
+        as random seed for sampling. Note that subsequent commands may return
+        different results even if same <literal>REPEATABLE</literal> clause
+        was specified. This happens because <acronym>DML</acronym> statements
+        and maintenance operations such as <command>VACUUM</> affect physical
+        distribution of data.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..238057a 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  transam
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 46060bc..e847ece 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -293,9 +293,10 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
 
 	/*
 	 * Currently, we don't have a stats counter for bitmap heap scans (but the
-	 * underlying bitmap index scans will be counted).
+	 * underlying bitmap index scans will be counted) or sample scans (we only
+	 * update stats for tuple fetches there)
 	 */
-	if (!scan->rs_bitmapscan)
+	if (!scan->rs_bitmapscan && !scan->rs_samplescan)
 		pgstat_count_heap_scan(scan->rs_rd);
 }
 
@@ -314,7 +315,7 @@ heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk, BlockNumber numBlks)
  * In page-at-a-time mode it performs additional work, namely determining
  * which tuples on the page are visible.
  */
-static void
+void
 heapgetpage(HeapScanDesc scan, BlockNumber page)
 {
 	Buffer		buffer;
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..34db3e6 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesample_method.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index fc9dd44..63feb07 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1146,7 +1146,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * sampler_random_fract());
+						int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 7cfc9bb..22525af 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -732,6 +732,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -958,6 +959,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			pname = sname = "Sample Scan";
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1075,6 +1079,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1327,6 +1332,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2230,6 +2236,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 6ebad2f..4948a26 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index 1c8be25..5cfe549 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 9892499..03c2feb 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..34ea4ab
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,500 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "catalog/pg_tablesample_method.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "pgstat.h"
+#include "storage/bufmgr.h"
+#include "storage/predicate.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate,
+							 int eflags, TableSampleClause *tablesample);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+static HeapTuple samplenexttup(SampleScanState *node, HeapScanDesc scan);
+
+
+/*
+ * Initialize the sampling method - loads function info and
+ * calls the tsminit function.
+ *
+ * We need special handling for this because the tsminit function
+ * is allowed to take optional additional arguments.
+ */
+static void
+InitSamplingMethod(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(scanstate->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(scanstate->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(scanstate->tsmnexttuple));
+	if (OidIsValid(tablesample->tsmexaminetuple))
+		fmgr_info(tablesample->tsmexaminetuple, &(scanstate->tsmexaminetuple));
+	else
+		scanstate->tsmexaminetuple.fn_oid = InvalidOid;
+	fmgr_info(tablesample->tsmend, &(scanstate->tsmend));
+	fmgr_info(tablesample->tsmreset, &(scanstate->tsmreset));
+
+	InitFunctionCallInfoData(fcinfo, &scanstate->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	/* First arg is always SampleScanState */
+	fcinfo.arg[0] = PointerGetDatum(scanstate);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause cannot be NULL")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+}
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	TupleTableSlot *slot;
+	HeapScanDesc	scan;
+	HeapTuple		tuple;
+
+	/*
+	 * get information from the scan state
+	 */
+	slot = node->ss.ss_ScanTupleSlot;
+	scan = node->ss.ss_currentScanDesc;
+
+	tuple = samplenexttup(node, scan);
+
+	if (tuple)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   scan->rs_cbuf,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+static HeapTuple
+samplenexttup(SampleScanState *node, HeapScanDesc scan)
+{
+	HeapTuple		tuple = &(scan->rs_ctup);
+	Snapshot		snapshot = scan->rs_snapshot;
+	BlockNumber		blockno;
+	Page			page;
+	ItemId			itemid;
+	OffsetNumber	tupoffset,
+					maxoffset;
+
+	if (!scan->rs_inited)
+	{
+		/*
+		 * return null immediately if relation is empty
+		 */
+		if (scan->rs_nblocks == 0)
+		{
+			Assert(!BufferIsValid(scan->rs_cbuf));
+			tuple->t_data = NULL;
+			return NULL;
+		}
+		blockno = DatumGetInt32(FunctionCall1(&node->tsmnextblock,
+											  PointerGetDatum(node)));
+		if (!BlockNumberIsValid(blockno))
+		{
+			tuple->t_data = NULL;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+		scan->rs_inited = true;
+	}
+	else
+	{
+		/* continue from previously returned page/tuple */
+		blockno = scan->rs_cblock;		/* current page */
+	}
+
+	LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+	page = (Page) BufferGetPage(scan->rs_cbuf);
+	maxoffset = PageGetMaxOffsetNumber(page);
+
+	for (;;)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		tupoffset = DatumGetUInt16(FunctionCall3(&node->tsmnexttuple,
+												 PointerGetDatum(node),
+												 UInt32GetDatum(blockno),
+												 UInt16GetDatum(maxoffset)));
+
+		if (OffsetNumberIsValid(tupoffset))
+		{
+			bool	visible;
+			bool	found;
+
+			/* Skip invalid tuple pointers. */
+			itemid = PageGetItemId(page, tupoffset);
+			if (!ItemIdIsNormal(itemid))
+				continue;
+
+			tuple->t_data = (HeapTupleHeader) PageGetItem((Page) page, itemid);
+			tuple->t_len = ItemIdGetLength(itemid);
+			ItemPointerSet(&(tuple->t_self), blockno, tupoffset);
+
+			visible = HeapTupleSatisfiesVisibility(tuple, snapshot, scan->rs_cbuf);
+
+			CheckForSerializableConflictOut(visible, scan->rs_rd, tuple,
+											scan->rs_cbuf, snapshot);
+
+			/*
+			 * Let the sampling method examine the actual tuple and decide if we
+			 * should return it.
+			 *
+			 * Note that we let it examine even invisible tuples for
+			 * statistical purposes, but not return them since user should
+			 * never see invisible tuples.
+			 */
+			if (OidIsValid(node->tsmexaminetuple.fn_oid))
+			{
+				found = DatumGetBool(FunctionCall4(&node->tsmexaminetuple,
+												   PointerGetDatum(node),
+												   UInt32GetDatum(blockno),
+												   PointerGetDatum(tuple),
+												   BoolGetDatum(visible)));
+				/* Should not happen if sampling method is well written. */
+				if (found && !visible)
+					elog(ERROR, "Sampling method wanted to return invisible tuple");
+			}
+			else
+				found = visible;
+
+			/* Found visible tuple, return it. */
+			if (found)
+			{
+				LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+				break;
+			}
+			else
+			{
+				/* Try next tuple from same page. */
+				continue;
+			}
+		}
+
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+		blockno = DatumGetInt32(FunctionCall1(&node->tsmnextblock,
+											  PointerGetDatum(node)));
+
+		/*
+		 * Report our new scan position for synchronization purposes. We
+		 * don't do that when moving backwards, however. That would just
+		 * mess up any other forward-moving scanners.
+		 *
+		 * Note: we do this before checking for end of scan so that the
+		 * final state of the position hint is back at the start of the
+		 * rel.  That's not strictly necessary, but otherwise when you run
+		 * the same query multiple times the starting position would shift
+		 * a little bit backwards on every invocation, which is confusing.
+		 * We don't guarantee any specific ordering in general, though.
+		 */
+		if (scan->rs_syncscan)
+			ss_report_location(scan->rs_rd, BlockNumberIsValid(blockno) ?
+							   blockno : scan->rs_startblock);
+
+		/*
+		 * Reached end of scan.
+		 */
+		if (!BlockNumberIsValid(blockno))
+		{
+			if (BufferIsValid(scan->rs_cbuf))
+				ReleaseBuffer(scan->rs_cbuf);
+			scan->rs_cbuf = InvalidBuffer;
+			scan->rs_cblock = InvalidBlockNumber;
+			tuple->t_data = NULL;
+			scan->rs_inited = false;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+		page = (Page) BufferGetPage(scan->rs_cbuf);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	pgstat_count_heap_getnext(scan->rs_rd);
+
+	return &(scan->rs_ctup);
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags,
+				 TableSampleClause *tablesample)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+
+	/*
+	 * Even though we aren't going to do a conventional seqscan, it is useful
+	 * to create a HeapScanDesc --- many of the fields in it are usable.
+	 */
+	node->ss.ss_currentScanDesc =
+		heap_beginscan_strat(currentRelation,
+							 estate->es_snapshot,
+							 0, NULL, false,
+							 tablesample->tsmseqscan);
+
+	/*
+	 * Page at a time mode is useless for us as we need to check visibility
+	 * of tuples individually because tuple offsets returned by sampling
+	 * methods map to rs_vistuples values and not to its indexes.
+	 */
+	node->ss.ss_currentScanDesc->rs_pageatatime = false;
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags, rte->tablesample);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	InitSamplingMethod(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished thes can.
+	 */
+	FunctionCall1(&node->tsmend, PointerGetDatum(node));
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close heap scan
+	 */
+	heap_endscan(node->ss.ss_currentScanDesc);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *node)
+{
+	heap_rescan(node->ss.ss_currentScanDesc, NULL);
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	FunctionCall1(&node->tsmreset, PointerGetDatum(node));
+
+	ExecScanReScan(&node->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index f1a24f5..9cff63e 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -628,6 +628,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2006,6 +2022,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2138,6 +2155,39 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsmseqscan);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmexaminetuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4075,6 +4125,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4723,6 +4776,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_PrivGrantee:
 			retval = _copyPrivGrantee(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 6e8b308..165c4e5 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2323,6 +2323,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2442,6 +2443,35 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsmseqscan);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmexaminetuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3150,6 +3180,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_PrivGrantee:
 			retval = _equalPrivGrantee(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 21dfda7..bd9ce09 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3209,6 +3209,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index dd1278b..8dcd02a 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -578,6 +578,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -2391,6 +2399,35 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_BOOL_FIELD(tsmseqscan);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmexaminetuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2420,6 +2457,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2887,6 +2925,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3228,6 +3269,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index ae24d05..076c958 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,45 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_BOOL_FIELD(tsmseqscan);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmexaminetuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1216,6 +1255,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1311,6 +1351,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 58d78e6..5f12477 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,10 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
+				   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -265,6 +269,11 @@ set_rel_size(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_size(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Sampled relation */
+					set_tablesample_rel_size(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -332,6 +341,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +432,41 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_size
+ *	  Set size estimates for a sampled relation.
+ */
+static void
+set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	/* Mark rel with estimated output rows, width, etc */
+	set_baserel_size_estimates(root, rel);
+}
+
+/*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids	required_outer;
+	Path   *path;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	path = create_samplescan_path(root, rel, required_outer);
+	rel->pathlist = list_make1(path);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 020558b..2167716 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -90,6 +90,7 @@
 #include "utils/lsyscache.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
+#include "utils/tablesample.h"
 #include "utils/tuplesort.h"
 
 
@@ -219,6 +220,73 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we dont't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	RangeTblEntry		   *rte = planner_rt_fetch(baserel->relid, root);
+	TableSampleClause	   *tablesample = rte->tablesample;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Mark the path with the correct row estimate */
+	if (path->param_info)
+		path->rows = path->param_info->ppi_rows;
+	else
+		path->rows = baserel->rows;
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(tablesample->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(tablesample->args),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples));
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = tablesample->tsmseqscan ? spc_seq_page_cost :
+					spc_random_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->startup_cost = startup_cost;
+	path->total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 655be81..10a5e02 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3318,6 +3369,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 7703946..de33fc6 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -446,6 +446,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 78fb6b1..191624c 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2163,6 +2163,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 1395a21..014d670 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,26 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+Path *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	Path		   *pathnode = makeNode(Path);
+
+	pathnode->pathtype = T_SampleScan;
+	pathnode->parent = rel;
+	pathnode->param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->pathkeys = NIL;	/* samplescan has unordered result */
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1921,6 +1941,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 36dac29..ac5e095 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -447,6 +447,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -611,8 +612,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10227,6 +10228,12 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample opt_alias_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10522,7 +10529,6 @@ relation_expr_list:
 			| relation_expr_list ',' relation_expr	{ $$ = lappend($1, $3); }
 		;
 
-
 /*
  * Given "UPDATE foo set set ...", we have to decide without looking any
  * further ahead whether the first "set" is an alias or the UPDATE's SET
@@ -10552,6 +10558,31 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $2;
+					n->relation = $1;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' func_arg_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' AexprConst ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/						{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13334,7 +13365,6 @@ unreserved_keyword:
 			| RELATIVE_P
 			| RELEASE
 			| RENAME
-			| REPEATABLE
 			| REPLACE
 			| REPLICA
 			| RESET
@@ -13509,6 +13539,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
@@ -13577,6 +13608,7 @@ reserved_keyword:
 			| PLACING
 			| PRIMARY
 			| REFERENCES
+			| REPEATABLE
 			| RETURNING
 			| SELECT
 			| SESSION_USER
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 654dce6..03632d2 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -413,6 +416,19 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *r)
+{
+	RangeTblEntry  *rte;
+	TableSampleClause *tablesample = NULL;
+
+	rte = transformTableEntry(pstate, r->relation);
+	tablesample = ParseTableSample(pstate, r->method, r->repeatable, r->args);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -421,7 +437,7 @@ transformTableEntry(ParseState *pstate, RangeVar *r)
 {
 	RangeTblEntry *rte;
 
-	/* We need only build a range table entry */
+	/* We first need to build a range table entry */
 	rte = addRangeTableEntry(pstate, r, r->alias,
 							 interpretInhOption(r->inhOpt), true);
 
@@ -1121,6 +1137,26 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index a200804..541f415 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -760,6 +762,134 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+extern TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				actual_arg_types[FUNC_MAX_ARGS];
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						samplemethod)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsmseqscan = tsm->tsmseqscan;
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmexaminetuple = tsm->tsmexaminetuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Transform the rest of arguments ... */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *arg = transformExpr(pstate, (Node *) lfirst(larg), EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		fargs = lappend(fargs, arg);
+
+		actual_arg_types[nargs++] = argtype;
+	}
+
+	/*
+	 * Check if parameters are correct.
+	 *
+	 * XXX: can we do better at hinting here?
+	 */
+	if (initnargs != nargs ||
+			!can_coerce_type(initnargs, actual_arg_types, init_arg_types,
+						COERCION_IMPLICIT))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("wrong parameters for tablesample method \"%s\"",
+						samplemethod)));
+
+	/* perform the necessary typecasting of arguments */
+	make_fn_arguments(pstate, fargs, actual_arg_types, init_arg_types);
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/utils/Makefile b/src/backend/utils/Makefile
index 8374533..9daa2ae 100644
--- a/src/backend/utils/Makefile
+++ b/src/backend/utils/Makefile
@@ -9,7 +9,8 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS        = fmgrtab.o
-SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time
+SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time \
+			  tablesample
 
 # location of Catalog.pm
 catalogdir  = $(top_srcdir)/src/backend/catalog
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index c1d860c..8198fc7 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -31,6 +31,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -343,6 +344,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4184,6 +4187,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for tablesample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8411,6 +8458,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index bd27168..3a8f01e 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
index 1eeabaf..f213c46 100644
--- a/src/backend/utils/misc/sampling.c
+++ b/src/backend/utils/misc/sampling.c
@@ -46,6 +46,8 @@ BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
 	bs->n = samplesize;
 	bs->t = 0;					/* blocks scanned so far */
 	bs->m = 0;					/* blocks selected so far */
+
+	sampler_random_init_state(randseed, bs->randstate);
 }
 
 bool
@@ -92,7 +94,7 @@ BlockSampler_Next(BlockSampler bs)
 	 * less than k, which means that we cannot fail to select enough blocks.
 	 *----------
 	 */
-	V = sampler_random_fract();
+	V = sampler_random_fract(bs->randstate);
 	p = 1.0 - (double) k / (double) K;
 	while (V < p)
 	{
@@ -126,8 +128,14 @@ BlockSampler_Next(BlockSampler bs)
 void
 reservoir_init_selection_state(ReservoirState rs, int n)
 {
+	/*
+	 * Reservoir sampling is not used anywhere where it would need to return
+	 * repeatable results so we can initialize it randomly.
+	 */
+	sampler_random_init_state(random(), rs->randstate);
+
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	*rs = exp(-log(sampler_random_fract()) / n);
+	rs->W = exp(-log(sampler_random_fract(rs->randstate)) / n);
 }
 
 double
@@ -142,7 +150,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 		double		V,
 					quot;
 
-		V = sampler_random_fract(); /* Generate V */
+		V = sampler_random_fract(rs->randstate); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -158,7 +166,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 	else
 	{
 		/* Now apply Algorithm Z */
-		double		W = *rs;
+		double		W = rs->W;
 		double		term = t - (double) n + 1;
 
 		for (;;)
@@ -174,7 +182,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 						tmp;
 
 			/* Generate U and X */
-			U = sampler_random_fract();
+			U = sampler_random_fract(rs->randstate);
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -203,11 +211,11 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract(rs->randstate)) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
-		*rs = W;
+		rs->W = W;
 	}
 	return S;
 }
@@ -217,10 +225,17 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
  * Random number generator used by sampling
  *----------
  */
+void
+sampler_random_init_state(long seed, SamplerRandomState randstate)
+{
+	randstate[0] = 0x330e;
+	randstate[1] = (unsigned short) seed;
+	randstate[2] = (unsigned short) (seed >> 16);
+}
 
 /* Select a random value R uniformly distributed in (0 - 1) */
 double
-sampler_random_fract()
+sampler_random_fract(SamplerRandomState randstate)
 {
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+	return pg_erand48(randstate);
 }
diff --git a/src/backend/utils/tablesample/Makefile b/src/backend/utils/tablesample/Makefile
new file mode 100644
index 0000000..df92939
--- /dev/null
+++ b/src/backend/utils/tablesample/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for utils/tablesample
+#
+# IDENTIFICATION
+#    src/backend/utils/tablesample/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/utils/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = system.o bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/tablesample/bernoulli.c b/src/backend/utils/tablesample/bernoulli.c
new file mode 100644
index 0000000..f7e9688
--- /dev/null
+++ b/src/backend/utils/tablesample/bernoulli.c
@@ -0,0 +1,224 @@
+/*-------------------------------------------------------------------------
+ *
+ * bernoulli.c
+ *	  interface routines for BERNOULLI tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/relscan.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/* State */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* number of blocks */
+	BlockNumber blockno;		/* current block */
+	float4 probability;			/* probabilty that tuple will be returned (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	HeapScanDesc	scan = scanstate->ss.ss_currentScanDesc;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->startblock = scan->rs_startblock;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->blockno = InvalidBlockNumber;
+	sampler->probability = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	/*
+	 * Bernoulli sampling scans all blocks on the table and supports
+	 * syncscan so loop from startblock to startblock instead of
+	 * from 0 to nblocks.
+	 */
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = sampler->startblock;
+	else
+	{
+		sampler->blockno++;
+
+		if (sampler->blockno >= sampler->nblocks)
+			sampler->blockno = 0;
+
+		if (sampler->blockno == sampler->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+	float4			probability = sampler->probability;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/*
+	 * Loop over tuple offsets until the random generator returns value that
+	 * is within the probability of returning the tuple or until we reach
+	 * end of the block.
+	 *
+	 * (This is our implementation of bernoulli trial)
+	 */
+	while (sampler_random_fract(sampler->randstate) > probability)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1;
+	}
+
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/utils/tablesample/system.c b/src/backend/utils/tablesample/system.c
new file mode 100644
index 0000000..0c4da28
--- /dev/null
+++ b/src/backend/utils/tablesample/system.c
@@ -0,0 +1,185 @@
+/*-------------------------------------------------------------------------
+ *
+ * system.c
+ *	  interface routines for system tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	SystemSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks =
+		RelationGetNumberOfBlocks(scanstate->ss.ss_currentRelation);
+	sampler->samplesize = 1 + (int) (sampler->tblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as VACUUM for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	BlockNumber		blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1;
+	}
+
+	*pages = baserel->pages * samplesize;
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 939d93d..9dabcb0 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -115,6 +115,7 @@ extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key);
 extern void heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk,
 		   BlockNumber endBlk);
+extern void heapgetpage(HeapScanDesc scan, BlockNumber page);
 extern void heap_rescan(HeapScanDesc scan, ScanKey key);
 extern void heap_endscan(HeapScanDesc scan);
 extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 9bb6362..e2b2b4f 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -29,6 +29,7 @@ typedef struct HeapScanDescData
 	int			rs_nkeys;		/* number of scan keys */
 	ScanKey		rs_key;			/* array of scan key descriptors */
 	bool		rs_bitmapscan;	/* true if this is really a bitmap scan */
+	bool		rs_samplescan;	/* true if this is really a sample scan */
 	bool		rs_pageatatime; /* verify visibility page-at-a-time? */
 	bool		rs_allow_strat; /* allow or disallow use of access strategy */
 	bool		rs_allow_sync;	/* allow or disallow use of syncscan */
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index a680229..c711cca 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3281, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3281
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3282, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3282
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 9edfdb8..e6d821d 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5143,6 +5143,31 @@ DESCR("rank of hypothetical row without gaps");
 DATA(insert OID = 3993 ( dense_rank_final	PGNSP PGUID 12 1 0 2276 0 f f f f f f i 2 0 20 "2281 2276" "{2281,2276}" "{i,v}" _null_ _null_	hypothetical_dense_rank_final _null_ _null_ _null_ ));
 DESCR("aggregate final function");
 
+DATA(insert OID = 3285 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3286 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3287 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3288 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3289 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3290 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3291 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3292 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3293 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3294 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3296 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3297 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 0000000..fd76f77
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,75 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3280
+
+CATALOG(pg_tablesample_method,3280)
+{
+	NameData	tsmname;		/* tablesample method name */
+	bool		tsmseqscan;		/* does this method scan whole table sequentially? */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmexaminetuple;	/* optional function which can examine tuple contents and
+								   decide if tuple should be returned or not */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method					9
+#define Anum_pg_tablesample_method_tsmname			1
+#define Anum_pg_tablesample_method_tsmseqscan		2
+#define Anum_pg_tablesample_method_tsminit			3
+#define Anum_pg_tablesample_method_tsmnextblock		4
+#define Anum_pg_tablesample_method_tsmnexttuple		5
+#define Anum_pg_tablesample_method_tsmexaminetuple	6
+#define Anum_pg_tablesample_method_tsmend			7
+#define Anum_pg_tablesample_method_tsmreset			8
+#define Anum_pg_tablesample_method_tsmcost			9
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3283 ( system false tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3284 ( bernoulli true tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 41288ed..e913924 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1212,6 +1212,24 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState		ss;
+
+	/* Sampling method functions. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmexaminetuple;
+	FmgrInfo		tsmend;
+	FmgrInfo		tsmreset;
+
+	void		   *tsmdata;		/* for use by table scan method */
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 97ef0fc..3276be8 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -413,6 +415,8 @@ typedef enum NodeTag
 	T_XmlSerialize,
 	T_WithClause,
 	T_CommonTableExpr,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index b1dfa85..2f4df1d 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -307,6 +307,25 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	bool		tsmseqscan;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmexaminetuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -507,6 +526,21 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * We are more generic than SQL Standard so we pass generic function
+ * arguments to the sampling method.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -751,6 +785,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 316c9ce..8a2a146 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -278,6 +278,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 9c2000b..24003ae 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 9923f0e..89c8ded 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern Path *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+									Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 7c243ec..6ff7b44 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -312,7 +312,7 @@ PG_KEYWORD("reindex", REINDEX, UNRESERVED_KEYWORD)
 PG_KEYWORD("relative", RELATIVE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("release", RELEASE, UNRESERVED_KEYWORD)
 PG_KEYWORD("rename", RENAME, UNRESERVED_KEYWORD)
-PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
+PG_KEYWORD("repeatable", REPEATABLE, RESERVED_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 3264691..6727e55 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,10 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 6bd786d..185bd81 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
index e3e7f9c..4ac208d 100644
--- a/src/include/utils/sampling.h
+++ b/src/include/utils/sampling.h
@@ -15,7 +15,12 @@
 
 #include "storage/bufmgr.h"
 
-extern double sampler_random_fract(void);
+/* Random generator for sampling code */
+typedef unsigned short SamplerRandomState[3];
+
+extern void sampler_random_init_state(long seed,
+									  SamplerRandomState randstate);
+extern double sampler_random_fract(SamplerRandomState randstate);
 
 /* Block sampling methods */
 /* Data structure for Algorithm S from Knuth 3.4.2 */
@@ -25,6 +30,7 @@ typedef struct
 	int			n;				/* desired sample size */
 	BlockNumber t;				/* current block number */
 	int			m;				/* blocks selected so far */
+	SamplerRandomState randstate; /* random generator state */
 } BlockSamplerData;
 
 typedef BlockSamplerData *BlockSampler;
@@ -35,7 +41,12 @@ extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
 /* Reservoid sampling methods */
-typedef double ReservoirStateData;
+typedef struct
+{
+	double	W;
+	SamplerRandomState randstate; /* random generator state */
+} ReservoirStateData;
+
 typedef ReservoirStateData *ReservoirState;
 
 extern void reservoir_init_selection_state(ReservoirState rs, int n);
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index ba0b090..6b628f6 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/include/utils/tablesample.h b/src/include/utils/tablesample.h
new file mode 100644
index 0000000..1a24cb6
--- /dev/null
+++ b/src/include/utils/tablesample.h
@@ -0,0 +1,27 @@
+/*--------------------------------------------------------------------------
+ * tablesample.h
+ *	  Header file for builtin table sampling methods.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/utils/tablesample.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TABLESAMPLE_H
+#define TABLESAMPLE_H
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TABLESAMPLE_H */
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..5946edf 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..9b387a2
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,165 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+CLOSE tablesample_cur;
+END;
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index e0ae2f2..e0240ac 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 7f762bd..9a7611b 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -152,3 +152,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..2b89b55
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,39 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+CLOSE tablesample_cur;
+END;
+
+DROP TABLE test_tablesample CASCADE;
-- 
1.9.1

>From f04d4842d22e18b79a306fa3693bad02106cde2b Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:51:44 +0100
Subject: [PATCH 3/3] tablesample-ddl v4

---
 doc/src/sgml/ref/allfiles.sgml                     |   2 +
 doc/src/sgml/ref/create_tablesamplemethod.sgml     | 173 +++++++++
 doc/src/sgml/ref/drop_tablesamplemethod.sgml       |  87 +++++
 doc/src/sgml/reference.sgml                        |   2 +
 src/backend/catalog/dependency.c                   |  15 +-
 src/backend/catalog/objectaddress.c                |  65 +++-
 src/backend/commands/Makefile                      |   6 +-
 src/backend/commands/dropcmds.c                    |   4 +
 src/backend/commands/event_trigger.c               |   3 +
 src/backend/commands/tablecmds.c                   |   1 +
 src/backend/commands/tablesample.c                 | 422 +++++++++++++++++++++
 src/backend/parser/gram.y                          |  14 +-
 src/backend/tcop/utility.c                         |  12 +
 src/bin/pg_dump/common.c                           |   5 +
 src/bin/pg_dump/pg_dump.c                          | 171 +++++++++
 src/bin/pg_dump/pg_dump.h                          |  10 +-
 src/bin/pg_dump/pg_dump_sort.c                     |  11 +-
 src/include/catalog/dependency.h                   |   1 +
 src/include/catalog/pg_tablesample_method.h        |  11 +
 src/include/nodes/parsenodes.h                     |   1 +
 src/include/parser/kwlist.h                        |   1 +
 src/test/modules/Makefile                          |   3 +-
 src/test/modules/tablesample/.gitignore            |   4 +
 src/test/modules/tablesample/Makefile              |  21 +
 .../modules/tablesample/expected/tablesample.out   |  38 ++
 src/test/modules/tablesample/sql/tablesample.sql   |  14 +
 src/test/modules/tablesample/tsm_test--1.0.sql     |  51 +++
 src/test/modules/tablesample/tsm_test.c            | 228 +++++++++++
 src/test/modules/tablesample/tsm_test.control      |   5 +
 29 files changed, 1370 insertions(+), 11 deletions(-)
 create mode 100644 doc/src/sgml/ref/create_tablesamplemethod.sgml
 create mode 100644 doc/src/sgml/ref/drop_tablesamplemethod.sgml
 create mode 100644 src/backend/commands/tablesample.c
 create mode 100644 src/test/modules/tablesample/.gitignore
 create mode 100644 src/test/modules/tablesample/Makefile
 create mode 100644 src/test/modules/tablesample/expected/tablesample.out
 create mode 100644 src/test/modules/tablesample/sql/tablesample.sql
 create mode 100644 src/test/modules/tablesample/tsm_test--1.0.sql
 create mode 100644 src/test/modules/tablesample/tsm_test.c
 create mode 100644 src/test/modules/tablesample/tsm_test.control

diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index 7aa3128..2fad084 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -78,6 +78,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY createServer       SYSTEM "create_server.sgml">
 <!ENTITY createTable        SYSTEM "create_table.sgml">
 <!ENTITY createTableAs      SYSTEM "create_table_as.sgml">
+<!ENTITY createTablesampleMethod SYSTEM "create_tablesamplemethod.sgml">
 <!ENTITY createTableSpace   SYSTEM "create_tablespace.sgml">
 <!ENTITY createTrigger      SYSTEM "create_trigger.sgml">
 <!ENTITY createTSConfig     SYSTEM "create_tsconfig.sgml">
@@ -119,6 +120,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY dropSequence       SYSTEM "drop_sequence.sgml">
 <!ENTITY dropServer         SYSTEM "drop_server.sgml">
 <!ENTITY dropTable          SYSTEM "drop_table.sgml">
+<!ENTITY dropTablesampleMethod SYSTEM "drop_tablesamplemethod.sgml">
 <!ENTITY dropTableSpace     SYSTEM "drop_tablespace.sgml">
 <!ENTITY dropTrigger        SYSTEM "drop_trigger.sgml">
 <!ENTITY dropTSConfig       SYSTEM "drop_tsconfig.sgml">
diff --git a/doc/src/sgml/ref/create_tablesamplemethod.sgml b/doc/src/sgml/ref/create_tablesamplemethod.sgml
new file mode 100644
index 0000000..62a8ce4
--- /dev/null
+++ b/doc/src/sgml/ref/create_tablesamplemethod.sgml
@@ -0,0 +1,173 @@
+<!--
+doc/src/sgml/ref/create_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-CREATETABLESAMPLEMETHOD">
+ <indexterm zone="sql-createtablesamplemethod">
+  <primary>CREATE TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE TABLESAMPLE METHOD</refname>
+  <refpurpose>define custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE TABLESAMPLE METHOD <replaceable class="parameter">name</replaceable> (
+    INIT = <replaceable class="parameter">init_function</replaceable> ,
+    NEXTBLOCK = <replaceable class="parameter">nextblock_function</replaceable> ,
+    NEXTTUPLE = <replaceable class="parameter">nexttuple_function</replaceable> ,
+    END = <replaceable class="parameter">end_function</replaceable> ,
+    RESET = <replaceable class="parameter">reset_function</replaceable> ,
+    COST = <replaceable class="parameter">cost_function</replaceable>
+    [ , EXAMINETUPLE = <replaceable class="parameter">examinetuple_function</replaceable> ]
+    [ , SEQSCAN = <replaceable class="parameter">seqscan</replaceable> ]
+)
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE TABLESAMPLE METHOD</command> creates a tablesample method.
+   A tablesample method provides alrorithm for reading sample part of a table
+   when used in <command>TABLESAMPLE</> clause of a <command>SELECT</>
+   statement.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the tablesample method to be created. This name must be
+      unique within the database.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">init_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the init function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nextblock_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-block function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nexttuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-tuple function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">end_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the end function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">reset_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the reset function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">cost_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the costing function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">examinetuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the function for inspecting the tuple contents in order
+      to make decision if it should be returned or not. This parameter
+      is optional.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">seqscan</replaceable></term>
+    <listitem>
+     <para>
+      True if the sampling method will do sequential scan of the whole table.
+      Used for cost estimation and syncscan. The default value if not specified
+      is False.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+  <para>
+   The function names can be schema-qualified if necessary.  Argument types
+   are not given, since the argument list for each type of function is
+   predetermined.  All functions are required.
+  </para>
+
+  <para>
+   The arguments can appear in any order, not only the one shown above.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>CREATE TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-droptablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/ref/drop_tablesamplemethod.sgml b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
new file mode 100644
index 0000000..dffd2ec
--- /dev/null
+++ b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
@@ -0,0 +1,87 @@
+<!--
+doc/src/sgml/ref/drop_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-DROPTABLESAMPLEMETHOD">
+ <indexterm zone="sql-droptablesamplemethod">
+  <primary>DROP TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DROP TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP TABLESAMPLE METHOD</refname>
+  <refpurpose>remove a custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP TABLESAMPLE METHOD [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>DROP TABLESAMPLE METHOD</command> drop an existing tablesample
+   method.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the tablesample method does not exist.
+      A notice is issued in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of an existing tablesample method to be removed.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>DROP TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createtablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index 10c9a6d..2c09a3c 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -106,6 +106,7 @@
    &createServer;
    &createTable;
    &createTableAs;
+   &createTablesampleMethod;
    &createTableSpace;
    &createTSConfig;
    &createTSDictionary;
@@ -147,6 +148,7 @@
    &dropSequence;
    &dropServer;
    &dropTable;
+   &dropTablesampleMethod;
    &dropTableSpace;
    &dropTSConfig;
    &dropTSDictionary;
diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index bacb242..6acb5b3 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -46,6 +46,7 @@
 #include "catalog/pg_policy.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -157,7 +158,8 @@ static const Oid object_classes[MAX_OCLASS] = {
 	DefaultAclRelationId,		/* OCLASS_DEFACL */
 	ExtensionRelationId,		/* OCLASS_EXTENSION */
 	EventTriggerRelationId,		/* OCLASS_EVENT_TRIGGER */
-	PolicyRelationId			/* OCLASS_POLICY */
+	PolicyRelationId,			/* OCLASS_POLICY */
+	TableSampleMethodRelationId			/* OCLASS_TABLESAMPLEMETHOD */
 };
 
 
@@ -1265,6 +1267,10 @@ doDeletion(const ObjectAddress *object, int flags)
 			RemovePolicyById(object->objectId);
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			RemoveTablesampleMethodById(object->objectId);
+			break;
+
 		default:
 			elog(ERROR, "unrecognized object class: %u",
 				 object->classId);
@@ -1794,6 +1800,10 @@ find_expr_references_walker(Node *node,
 				case RTE_RELATION:
 					add_object_address(OCLASS_CLASS, rte->relid, 0,
 									   context->addrs);
+					if (rte->tablesample)
+						add_object_address(OCLASS_TABLESAMPLEMETHOD,
+										   rte->tablesample->tsmid, 0,
+										   context->addrs);
 					break;
 				default:
 					break;
@@ -2373,6 +2383,9 @@ getObjectClass(const ObjectAddress *object)
 
 		case PolicyRelationId:
 			return OCLASS_POLICY;
+
+		case TableSampleMethodRelationId:
+			return OCLASS_TABLESAMPLEMETHOD;
 	}
 
 	/* shouldn't get here */
diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index 825d8b2..02edc0a 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -44,6 +44,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_policy.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -429,7 +430,19 @@ static const ObjectPropertyType ObjectProperty[] =
 		Anum_pg_type_typacl,
 		ACL_KIND_TYPE,
 		true
-	}
+	},
+	{
+		TableSampleMethodRelationId,
+		TableSampleMethodOidIndexId,
+		TABLESAMPLEMETHODOID,
+		TABLESAMPLEMETHODNAME,
+		Anum_pg_tablesample_method_tsmname,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		-1,
+		true
+	},
 };
 
 /*
@@ -528,7 +541,9 @@ ObjectTypeMap[] =
 	/* OCLASS_EVENT_TRIGGER */
 	{ "event trigger", OBJECT_EVENT_TRIGGER },
 	/* OCLASS_POLICY */
-	{ "policy", OBJECT_POLICY }
+	{ "policy", OBJECT_POLICY },
+	/* OCLASS_TABLESAMPLEMETHOD */
+	{ "tablesample method", OBJECT_TABLESAMPLEMETHOD }
 };
 
 
@@ -670,6 +685,7 @@ get_object_address(ObjectType objtype, List *objname, List *objargs,
 			case OBJECT_FDW:
 			case OBJECT_FOREIGN_SERVER:
 			case OBJECT_EVENT_TRIGGER:
+			case OBJECT_TABLESAMPLEMETHOD:
 				address = get_object_address_unqualified(objtype,
 														 objname, missing_ok);
 				break;
@@ -896,6 +912,9 @@ get_object_address_unqualified(ObjectType objtype,
 			case OBJECT_EVENT_TRIGGER:
 				msg = gettext_noop("event trigger name cannot be qualified");
 				break;
+			case OBJECT_TABLESAMPLEMETHOD:
+				msg = gettext_noop("tablesample method name cannot be qualified");
+				break;
 			default:
 				elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 				msg = NULL;		/* placate compiler */
@@ -956,6 +975,11 @@ get_object_address_unqualified(ObjectType objtype,
 			address.objectId = get_event_trigger_oid(name, missing_ok);
 			address.objectSubId = 0;
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			address.classId = TableSampleMethodRelationId;
+			address.objectId = get_tablesample_method_oid(name, missing_ok);
+			address.objectSubId = 0;
+			break;
 		default:
 			elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 			/* placate compiler, which doesn't know elog won't return */
@@ -1720,6 +1744,7 @@ check_object_ownership(Oid roleid, ObjectType objtype, ObjectAddress address,
 			break;
 		case OBJECT_TSPARSER:
 		case OBJECT_TSTEMPLATE:
+		case OBJECT_TABLESAMPLEMETHOD:
 			/* We treat these object types as being owned by superusers */
 			if (!superuser_arg(roleid))
 				ereport(ERROR,
@@ -2654,6 +2679,21 @@ getObjectDescription(const ObjectAddress *object)
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				appendStringInfo(&buffer, _("tablesample method %s"),
+					 NameStr(((Form_pg_tablesample_method) GETSTRUCT(tup))->tsmname));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
@@ -3131,6 +3171,10 @@ getObjectTypeDescription(const ObjectAddress *object)
 			appendStringInfoString(&buffer, "policy");
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			appendStringInfoString(&buffer, "tablesample method");
+			break;
+
 		default:
 			appendStringInfo(&buffer, "unrecognized %u", object->classId);
 			break;
@@ -4025,6 +4069,23 @@ getObjectIdentityParts(const ObjectAddress *object,
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+				Form_pg_tablesample_method tsmForm;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				tsmForm = (Form_pg_tablesample_method) GETSTRUCT(tup);
+				appendStringInfoString(&buffer,
+							   quote_identifier(NameStr(tsmForm->tsmname)));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index b1ac704..04fcd8c 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -18,8 +18,8 @@ OBJS = aggregatecmds.o alter.o analyze.o async.o cluster.o comment.o  \
 	event_trigger.o explain.o extension.o foreigncmds.o functioncmds.o \
 	indexcmds.o lockcmds.o matview.o operatorcmds.o opclasscmds.o \
 	policy.o portalcmds.o prepare.o proclang.o \
-	schemacmds.o seclabel.o sequence.o tablecmds.o tablespace.o trigger.o \
-	tsearchcmds.o typecmds.o user.o vacuum.o vacuumlazy.o \
-	variable.o view.o
+	schemacmds.o seclabel.o sequence.o tablecmds.o tablesample.o \
+	tablespace.o trigger.o tsearchcmds.o typecmds.o user.o vacuum.o \
+	vacuumlazy.o variable.o view.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/commands/dropcmds.c b/src/backend/commands/dropcmds.c
index e5185ba..04d29a2 100644
--- a/src/backend/commands/dropcmds.c
+++ b/src/backend/commands/dropcmds.c
@@ -421,6 +421,10 @@ does_not_exist_skipping(ObjectType objtype, List *objname, List *objargs)
 				args = strVal(linitial(objargs));
 			}
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			msg = gettext_noop("tablesample method \"%s\" does not exist, skipping");
+			name = NameListToString(objname);
+			break;
 		default:
 			elog(ERROR, "unexpected object type (%d)", (int) objtype);
 			break;
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index a33a5ad..f20e9f7 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -97,6 +97,7 @@ static event_trigger_support_data event_trigger_support[] = {
 	{"SEQUENCE", true},
 	{"SERVER", true},
 	{"TABLE", true},
+	{"TABLESAMPLE METHOD", true},
 	{"TABLESPACE", false},
 	{"TRIGGER", true},
 	{"TEXT SEARCH CONFIGURATION", true},
@@ -1078,6 +1079,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_SEQUENCE:
 		case OBJECT_TABCONSTRAINT:
 		case OBJECT_TABLE:
+		case OBJECT_TABLESAMPLEMETHOD:
 		case OBJECT_TRIGGER:
 		case OBJECT_TSCONFIGURATION:
 		case OBJECT_TSDICTIONARY:
@@ -1134,6 +1136,7 @@ EventTriggerSupportsObjectClass(ObjectClass objclass)
 		case OCLASS_DEFACL:
 		case OCLASS_EXTENSION:
 		case OCLASS_POLICY:
+		case OCLASS_TABLESAMPLEMETHOD:
 			return true;
 
 		case MAX_OCLASS:
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 66d5083..b67c560 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8059,6 +8059,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 			case OCLASS_USER_MAPPING:
 			case OCLASS_DEFACL:
 			case OCLASS_EXTENSION:
+			case OCLASS_TABLESAMPLEMETHOD:
 
 				/*
 				 * We don't expect any of these sorts of objects to depend on
diff --git a/src/backend/commands/tablesample.c b/src/backend/commands/tablesample.c
new file mode 100644
index 0000000..ed8102d
--- /dev/null
+++ b/src/backend/commands/tablesample.c
@@ -0,0 +1,422 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *	  Commands to manipulate tablesample methods
+ *
+ * Table sampling methods provide algorithms for doing sample scan over
+ * the table.
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/tablesample.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "access/heapam.h"
+#include "access/htup_details.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/objectaccess.h"
+#include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
+#include "catalog/pg_type.h"
+#include "commands/defrem.h"
+#include "miscadmin.h"
+#include "parser/parse_func.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+
+static Datum
+get_tablesample_method_func(DefElem *defel, int attnum)
+{
+	List	   *funcName = defGetQualifiedName(defel);
+	/* Big enough size for our needs. */
+	Oid		   *typeId = palloc0(7 * sizeof(Oid));
+	Oid			retTypeId;
+	int			nargs;
+	Oid			procOid = InvalidOid;
+	FuncCandidateList clist;
+
+	switch (attnum)
+	{
+		case Anum_pg_tablesample_method_tsminit:
+			/*
+			 * tsminit needs special handling because it is defined as function
+			 * with 3 or more arguments and only first two arguments must have
+			 * specific type, the rest is up to the tablesample method creator.
+			 */
+			{
+				nargs = 2;
+				typeId[0] = INTERNALOID;
+				typeId[1] = INT4OID;
+				retTypeId = VOIDOID;
+
+				clist = FuncnameGetCandidates(funcName, -1, NIL, false, false, false);
+
+				while (clist)
+				{
+					if (clist->nargs >= 3 &&
+						memcmp(typeId, clist->args, nargs * sizeof(Oid)) == 0)
+					{
+						procOid = clist->oid;
+						/* Save real function signature for future errors. */
+						nargs = clist->nargs;
+						pfree(typeId);
+						typeId = clist->args;
+						break;
+					}
+					clist = clist->next;
+				}
+
+				if (!OidIsValid(procOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_UNDEFINED_FUNCTION),
+							 errmsg("function \"%s\" does not exist or does not have valid signature",
+									NameListToString(funcName)),
+							 errhint("The tamplesample method init function "
+									 "must have at least 3 input parameters "
+									 "with first one of type INTERNAL and second of type INTEGER.")));
+			}
+			break;
+
+		case Anum_pg_tablesample_method_tsmnextblock:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = INT4OID;
+			break;
+		case Anum_pg_tablesample_method_tsmnexttuple:
+			nargs = 3;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INT2OID;
+			retTypeId = INT2OID;
+			break;
+		case Anum_pg_tablesample_method_tsmexaminetuple:
+			nargs = 4;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = BOOLOID;
+			retTypeId = BOOLOID;
+			break;
+		case Anum_pg_tablesample_method_tsmend:
+		case Anum_pg_tablesample_method_tsmreset:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		case Anum_pg_tablesample_method_tsmcost:
+			nargs = 7;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INTERNALOID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = INTERNALOID;
+			typeId[4] = INTERNALOID;
+			typeId[5] = INTERNALOID;
+			typeId[6] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		default:
+			/* should not be here */
+			elog(ERROR, "unrecognized attribute for tablesample method: %d",
+				 attnum);
+			nargs = 0;			/* keep compiler quiet */
+	}
+
+	if (!OidIsValid(procOid))
+		procOid = LookupFuncName(funcName, nargs, typeId, false);
+	if (get_func_rettype(procOid) != retTypeId)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("function %s should return type %s",
+						func_signature_string(funcName, nargs, NIL, typeId),
+						format_type_be(retTypeId))));
+
+	return ObjectIdGetDatum(procOid);
+}
+
+/*
+ * make pg_depend entries for a new pg_tablesample_method entry
+ */
+static void
+makeTablesampleMethodDeps(HeapTuple tuple)
+{
+	Form_pg_tablesample_method tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	ObjectAddress	myself,
+					referenced;
+
+	myself.classId = TableSampleMethodRelationId;
+	myself.objectId = HeapTupleGetOid(tuple);
+	myself.objectSubId = 0;
+
+	/* dependency on extension */
+	recordDependencyOnCurrentExtension(&myself, false);
+
+	/* dependencies on functions */
+	referenced.classId = ProcedureRelationId;
+	referenced.objectSubId = 0;
+
+	referenced.objectId = tsm->tsminit;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnextblock;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnexttuple;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	if (OidIsValid(tsm->tsmexaminetuple))
+	{
+		referenced.objectId = tsm->tsmexaminetuple;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
+
+	referenced.objectId = tsm->tsmend;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmreset;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmcost;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+}
+
+/*
+ * Create a table sampling method
+ *
+ * Only superusers can create a table sampling methods.
+ */
+Oid
+DefineTablesampleMethod(List *names, List *parameters)
+{
+	char	   *tsmname = strVal(linitial(names));
+	Oid			tsmoid;
+	ListCell   *pl;
+	Relation	rel;
+	Datum		values[Natts_pg_tablesample_method];
+	bool		nulls[Natts_pg_tablesample_method];
+	HeapTuple	tuple;
+
+	/* Must be super user. */
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied to create tablesample method \"%s\"",
+						tsmname),
+				 errhint("Must be superuser to create a tablesample method.")));
+
+	/* Must not already exist. */
+	tsmoid = get_tablesample_method_oid(tsmname, true);
+	if (OidIsValid(tsmoid))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" already exists",
+						tsmname)));
+
+	/* Initialize the values. */
+	memset(values, 0, sizeof(values));
+	memset(nulls, false, sizeof(nulls));
+
+	values[Anum_pg_tablesample_method_tsmname - 1] =
+		DirectFunctionCall1(namein, CStringGetDatum(tsmname));
+
+	/*
+	 * loop over the definition list and extract the information we need.
+	 */
+	foreach(pl, parameters)
+	{
+		DefElem    *defel = (DefElem *) lfirst(pl);
+
+		if (pg_strcasecmp(defel->defname, "seqscan") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmseqscan - 1] =
+				BoolGetDatum(defGetBoolean(defel));
+		}
+		else if (pg_strcasecmp(defel->defname, "init") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsminit - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsminit);
+		}
+		else if (pg_strcasecmp(defel->defname, "nextblock") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnextblock - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnextblock);
+		}
+		else if (pg_strcasecmp(defel->defname, "nexttuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnexttuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnexttuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "examinetuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmexaminetuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmexaminetuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "end") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmend - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmend);
+		}
+		else if (pg_strcasecmp(defel->defname, "reset") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmreset - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmreset);
+		}
+		else if (pg_strcasecmp(defel->defname, "cost") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmcost - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmcost);
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("tablesample method parameter \"%s\" not recognized",
+						defel->defname)));
+	}
+
+	/*
+	 * Validation.
+	 */
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsminit - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method init function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnextblock - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nextblock function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnexttuple - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nexttuple function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmend - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method end function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmreset - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method reset function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmcost - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method cost function is required")));
+
+	/*
+	 * Insert tuple into pg_tablesample_method.
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = heap_form_tuple(rel->rd_att, values, nulls);
+
+	tsmoid = simple_heap_insert(rel, tuple);
+
+	CatalogUpdateIndexes(rel, tuple);
+
+	makeTablesampleMethodDeps(tuple);
+
+	heap_freetuple(tuple);
+
+	/* Post creation hook for new tablesample method */
+	InvokeObjectPostCreateHook(TableSampleMethodRelationId, tsmoid, 0);
+
+	heap_close(rel, RowExclusiveLock);
+
+	return tsmoid;
+}
+
+/*
+ * Drop a tablesample method.
+ */
+void
+RemoveTablesampleMethodById(Oid tsmoid)
+{
+	Relation	rel;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+
+	/*
+	 * Find the target tuple
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmoid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for tablesample method %u",
+			 tsmoid);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	/* Can't drop builtin tablesample methods. */
+	if (tsmoid == TABLESAMPLE_METHOD_SYSTEM_OID ||
+		tsmoid == TABLESAMPLE_METHOD_BERNOULLI_OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied for tablesample method %s",
+						NameStr(tsm->tsmname))));
+
+	/*
+	 * Remove the pg_tablespace tuple (this will roll back if we fail below)
+	 */
+	simple_heap_delete(rel, &tuple->t_self);
+
+	ReleaseSysCache(tuple);
+
+	heap_close(rel, RowExclusiveLock);
+}
+
+/*
+ * get_tablesample_method_oid - given a tablesample method name,
+ * look up the OID
+ *
+ * If missing_ok is false, throw an error if tablesample method name not found.
+ * If true, just return InvalidOid.
+ */
+Oid
+get_tablesample_method_oid(const char *tsmname, bool missing_ok)
+{
+	Oid			result;
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(tsmname));
+	if (HeapTupleIsValid(tuple))
+	{
+		result = HeapTupleGetOid(tuple);
+		ReleaseSysCache(tuple);
+	}
+	else
+		result = InvalidOid;
+
+	if (!OidIsValid(result) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						tsmname)));
+
+	return result;
+}
+
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index ac5e095..4578b5e 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -586,7 +586,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATERIALIZED MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
+	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P
+	MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEXT NO NONE
 	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
@@ -5094,6 +5095,15 @@ DefineStmt:
 					n->definition = list_make1(makeDefElem("from", (Node *) $5));
 					$$ = (Node *)n;
 				}
+			| CREATE TABLESAMPLE METHOD name definition
+				{
+					DefineStmt *n = makeNode(DefineStmt);
+					n->kind = OBJECT_TABLESAMPLEMETHOD;
+					n->args = NIL;
+					n->defnames = list_make1(makeString($4));
+					n->definition = $5;
+					$$ = (Node *)n;
+				}
 		;
 
 definition: '(' def_list ')'						{ $$ = $2; }
@@ -5552,6 +5562,7 @@ drop_type:	TABLE									{ $$ = OBJECT_TABLE; }
 			| TEXT_P SEARCH DICTIONARY				{ $$ = OBJECT_TSDICTIONARY; }
 			| TEXT_P SEARCH TEMPLATE				{ $$ = OBJECT_TSTEMPLATE; }
 			| TEXT_P SEARCH CONFIGURATION			{ $$ = OBJECT_TSCONFIGURATION; }
+			| TABLESAMPLE METHOD					{ $$ = OBJECT_TABLESAMPLEMETHOD; }
 		;
 
 any_name_list:
@@ -13313,6 +13324,7 @@ unreserved_keyword:
 			| MATCH
 			| MATERIALIZED
 			| MAXVALUE
+			| METHOD
 			| MINUTE_P
 			| MINVALUE
 			| MODE
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 3533cfa..532256d 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -23,6 +23,7 @@
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/toasting.h"
 #include "commands/alter.h"
 #include "commands/async.h"
@@ -1106,6 +1107,11 @@ ProcessUtilitySlow(Node *parsetree,
 							Assert(stmt->args == NIL);
 							DefineCollation(stmt->defnames, stmt->definition);
 							break;
+						case OBJECT_TABLESAMPLEMETHOD:
+							Assert(stmt->args == NIL);
+							Assert(list_length(stmt->defnames) == 1);
+							DefineTablesampleMethod(stmt->defnames, stmt->definition);
+							break;
 						default:
 							elog(ERROR, "unrecognized define stmt type: %d",
 								 (int) stmt->kind);
@@ -1960,6 +1966,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_POLICY:
 					tag = "DROP POLICY";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "DROP TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
@@ -2056,6 +2065,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_COLLATION:
 					tag = "CREATE COLLATION";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "CREATE TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
diff --git a/src/bin/pg_dump/common.c b/src/bin/pg_dump/common.c
index 1a0a587..8a64e4b 100644
--- a/src/bin/pg_dump/common.c
+++ b/src/bin/pg_dump/common.c
@@ -103,6 +103,7 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 	int			numForeignServers;
 	int			numDefaultACLs;
 	int			numEventTriggers;
+	int			numTSMs;
 
 	if (g_verbose)
 		write_msg(NULL, "reading schemas\n");
@@ -251,6 +252,10 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 		write_msg(NULL, "reading policies\n");
 	getPolicies(fout, tblinfo, numTables);
 
+	if (g_verbose)
+		write_msg(NULL, "reading tablesample methods\n");
+	getTableSampleMethods(fout, &numTSMs);
+
 	*numTablesPtr = numTables;
 	return tblinfo;
 }
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 7e92b74..9f19799 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -182,6 +182,7 @@ static void dumpSequenceData(Archive *fout, TableDataInfo *tdinfo);
 static void dumpIndex(Archive *fout, DumpOptions *dopt, IndxInfo *indxinfo);
 static void dumpConstraint(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
 static void dumpTableConstraintComment(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
+static void dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tbinfo);
 static void dumpTSParser(Archive *fout, DumpOptions *dopt, TSParserInfo *prsinfo);
 static void dumpTSDictionary(Archive *fout, DumpOptions *dopt, TSDictInfo *dictinfo);
 static void dumpTSTemplate(Archive *fout, DumpOptions *dopt, TSTemplateInfo *tmplinfo);
@@ -7174,6 +7175,75 @@ getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tblinfo, int numTable
 }
 
 /*
+ * getTableSampleMethods:
+ *	  read all tablesample methods in the system catalogs and return them
+ *	  in the TSMInfo* structure
+ *
+ *	numTSMs is set to the number of tablesample methods read in
+ */
+TSMInfo *
+getTableSampleMethods(Archive *fout, int *numTSMs)
+{
+	PGresult   *res;
+	int			ntups;
+	int			i;
+	PQExpBuffer query;
+	TSMInfo	   *tsminfo;
+	int			i_tableoid,
+				i_oid,
+				i_tsmname,
+				i_tsmseqscan;
+
+	/* Before 9.5, there were no tablesample methods */
+	if (fout->remoteVersion < 90500)
+	{
+		*numTSMs = 0;
+		return NULL;
+	}
+
+	query = createPQExpBuffer();
+
+	appendPQExpBuffer(query,
+					  "SELECT tableoid, oid, tsmname, tsmseqscan "
+					  "FROM pg_catalog.pg_tablesample_method "
+					  "WHERE oid >= '%u'::pg_catalog.oid",
+					  FirstNormalObjectId);
+
+	res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
+
+	ntups = PQntuples(res);
+	*numTSMs = ntups;
+
+	tsminfo = (TSMInfo *) pg_malloc(ntups * sizeof(TSMInfo));
+
+	i_tableoid = PQfnumber(res, "tableoid");
+	i_oid = PQfnumber(res, "oid");
+	i_tsmname = PQfnumber(res, "tsmname");
+	i_tsmseqscan = PQfnumber(res, "tsmseqscan");
+
+	for (i = 0; i < ntups; i++)
+	{
+		tsminfo[i].dobj.objType = DO_TABLESAMPLE_METHOD;
+		tsminfo[i].dobj.catId.tableoid = atooid(PQgetvalue(res, i, i_tableoid));
+		tsminfo[i].dobj.catId.oid = atooid(PQgetvalue(res, i, i_oid));
+		AssignDumpId(&tsminfo[i].dobj);
+		tsminfo[i].dobj.name = pg_strdup(PQgetvalue(res, i, i_tsmname));
+		tsminfo[i].dobj.namespace = NULL;
+		tsminfo[i].tsmseqscan = PQgetvalue(res, i, i_tsmseqscan)[0] == 't';
+
+		/* Decide whether we want to dump it */
+		selectDumpableObject(&(tsminfo[i].dobj));
+	}
+
+	PQclear(res);
+
+	destroyPQExpBuffer(query);
+
+	return tsminfo;
+}
+
+
+/*
  * Test whether a column should be printed as part of table's CREATE TABLE.
  * Column number is zero-based.
  *
@@ -8266,6 +8336,9 @@ dumpDumpableObject(Archive *fout, DumpOptions *dopt, DumpableObject *dobj)
 		case DO_POLICY:
 			dumpPolicy(fout, dopt, (PolicyInfo *) dobj);
 			break;
+		case DO_TABLESAMPLE_METHOD:
+			dumpTableSampleMethod(fout, dopt, (TSMInfo *) dobj);
+			break;
 		case DO_PRE_DATA_BOUNDARY:
 		case DO_POST_DATA_BOUNDARY:
 			/* never dumped, nothing to do */
@@ -12266,6 +12339,103 @@ dumpAgg(Archive *fout, DumpOptions *dopt, AggInfo *agginfo)
 }
 
 /*
+ * dumpTableSampleMethod
+ *	  write the declaration of one user-defined tablesample method
+ */
+static void
+dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tsminfo)
+{
+	PGresult   *res;
+	PQExpBuffer q;
+	PQExpBuffer delq;
+	PQExpBuffer labelq;
+	PQExpBuffer query;
+	char	   *tsminit;
+	char	   *tsmnextblock;
+	char	   *tsmnexttuple;
+	char	   *tsmexaminetuple;
+	char	   *tsmend;
+	char	   *tsmreset;
+	char	   *tsmcost;
+
+	/* Skip if not to be dumped */
+	if (!tsminfo->dobj.dump || dopt->dataOnly)
+		return;
+
+	q = createPQExpBuffer();
+	delq = createPQExpBuffer();
+	labelq = createPQExpBuffer();
+	query = createPQExpBuffer();
+
+	/* Make sure we are in proper schema */
+	selectSourceSchema(fout, "pg_catalog");
+
+	appendPQExpBuffer(query, "SELECT tsminit, tsmnextblock, "
+							 "tsmnexttuple, tsmexaminetuple, "
+							 "tsmend, tsmreset, tsmcost "
+							 "FROM pg_catalog.pg_tablesample_method "
+							 "WHERE oid = '%u'::pg_catalog.oid",
+							 tsminfo->dobj.catId.oid);
+
+	res = ExecuteSqlQueryForSingleRow(fout, query->data);
+
+	tsminit = PQgetvalue(res, 0, PQfnumber(res, "tsminit"));
+	tsmnexttuple = PQgetvalue(res, 0, PQfnumber(res, "tsmnexttuple"));
+	tsmnextblock = PQgetvalue(res, 0, PQfnumber(res, "tsmnextblock"));
+	tsmexaminetuple = PQgetvalue(res, 0, PQfnumber(res, "tsmexaminetuple"));
+	tsmend = PQgetvalue(res, 0, PQfnumber(res, "tsmend"));
+	tsmreset = PQgetvalue(res, 0, PQfnumber(res, "tsmreset"));
+	 tsmcost = PQgetvalue(res, 0, PQfnumber(res, "tsmcost"));
+
+	appendPQExpBuffer(q, "CREATE TABLESAMPLE METHOD %s (\n",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(q, "    INIT = %s,\n", tsminit);
+	appendPQExpBuffer(q, "    NEXTTUPLE = %s,\n", tsmnexttuple);
+	appendPQExpBuffer(q, "    NEXTBLOCK = %s,\n", tsmnextblock);
+	appendPQExpBuffer(q, "    END = %s,\n", tsmend);
+	appendPQExpBuffer(q, "    RESET = %s,\n", tsmreset);
+	appendPQExpBuffer(q, "    COST = %s", tsmcost);
+
+	if (strcmp(tsmexaminetuple, "-") != 0)
+		appendPQExpBuffer(q, ",\n    EXAMINETUPLE = %s", tsmexaminetuple);
+
+	if (tsminfo->tsmseqscan)
+		appendPQExpBufferStr(q, ",\n    SEQSCAN = true");
+
+	appendPQExpBufferStr(q, "\n);");
+
+	appendPQExpBuffer(delq, "DROP TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(labelq, "TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	if (dopt->binary_upgrade)
+		binary_upgrade_extension_member(q, &tsminfo->dobj, labelq->data);
+
+	ArchiveEntry(fout, tsminfo->dobj.catId, tsminfo->dobj.dumpId,
+				 tsminfo->dobj.name,
+				 NULL,
+				 NULL,
+				 "",
+				 false, "TABLESAMPLE METHOD", SECTION_PRE_DATA,
+				 q->data, delq->data, NULL,
+				 NULL, 0,
+				 NULL, NULL);
+
+	/* Dump Parser Comments */
+	dumpComment(fout, dopt, labelq->data,
+				NULL, "",
+				tsminfo->dobj.catId, 0, tsminfo->dobj.dumpId);
+
+	PQclear(res);
+	destroyPQExpBuffer(q);
+	destroyPQExpBuffer(delq);
+	destroyPQExpBuffer(labelq);
+}
+
+/*
  * dumpTSParser
  *	  write out a single text search parser
  */
@@ -15619,6 +15789,7 @@ addBoundaryDependencies(DumpableObject **dobjs, int numObjs,
 			case DO_FDW:
 			case DO_FOREIGN_SERVER:
 			case DO_BLOB:
+			case DO_TABLESAMPLE_METHOD:
 				/* Pre-data objects: must come before the pre-data boundary */
 				addObjectDependency(preDataBound, dobj->dumpId);
 				break;
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index f42c42d..645c07c 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -76,7 +76,8 @@ typedef enum
 	DO_POST_DATA_BOUNDARY,
 	DO_EVENT_TRIGGER,
 	DO_REFRESH_MATVIEW,
-	DO_POLICY
+	DO_POLICY,
+	DO_TABLESAMPLE_METHOD
 } DumpableObjectType;
 
 typedef struct _dumpableObject
@@ -384,6 +385,12 @@ typedef struct _inhInfo
 	Oid			inhparent;		/* OID of its parent */
 } InhInfo;
 
+typedef struct _tsmInfo
+{
+	DumpableObject dobj;
+	bool		tsmseqscan;
+} TSMInfo;
+
 typedef struct _prsInfo
 {
 	DumpableObject dobj;
@@ -537,6 +544,7 @@ extern ProcLangInfo *getProcLangs(Archive *fout, int *numProcLangs);
 extern CastInfo *getCasts(Archive *fout, DumpOptions *dopt, int *numCasts);
 extern void getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tbinfo, int numTables);
 extern bool shouldPrintColumn(DumpOptions *dopt, TableInfo *tbinfo, int colno);
+extern TSMInfo *getTableSampleMethods(Archive *fout, int *numTSMs);
 extern TSParserInfo *getTSParsers(Archive *fout, int *numTSParsers);
 extern TSDictInfo *getTSDictionaries(Archive *fout, int *numTSDicts);
 extern TSTemplateInfo *getTSTemplates(Archive *fout, int *numTSTemplates);
diff --git a/src/bin/pg_dump/pg_dump_sort.c b/src/bin/pg_dump/pg_dump_sort.c
index 4b9bba0..cb009ce 100644
--- a/src/bin/pg_dump/pg_dump_sort.c
+++ b/src/bin/pg_dump/pg_dump_sort.c
@@ -73,7 +73,8 @@ static const int oldObjectTypePriority[] =
 	13,							/* DO_POST_DATA_BOUNDARY */
 	20,							/* DO_EVENT_TRIGGER */
 	15,							/* DO_REFRESH_MATVIEW */
-	21							/* DO_POLICY */
+	21,							/* DO_POLICY */
+	5							/* DO_TABLESAMPLE_METHOD */
 };
 
 /*
@@ -122,7 +123,8 @@ static const int newObjectTypePriority[] =
 	25,							/* DO_POST_DATA_BOUNDARY */
 	32,							/* DO_EVENT_TRIGGER */
 	33,							/* DO_REFRESH_MATVIEW */
-	34							/* DO_POLICY */
+	34,							/* DO_POLICY */
+	17							/* DO_TABLESAMPLE_METHOD */
 };
 
 static DumpId preDataBoundId;
@@ -1443,6 +1445,11 @@ describeDumpableObject(DumpableObject *obj, char *buf, int bufsize)
 					 "POLICY (ID %d OID %u)",
 					 obj->dumpId, obj->catId.oid);
 			return;
+		case DO_TABLESAMPLE_METHOD:
+			snprintf(buf, bufsize,
+					 "TABLESAMPLE METHOD %s  (ID %d OID %u)",
+					 obj->name, obj->dumpId, obj->catId.oid);
+			return;
 		case DO_PRE_DATA_BOUNDARY:
 			snprintf(buf, bufsize,
 					 "PRE-DATA BOUNDARY  (ID %d)",
diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 6481ac8..30653f8 100644
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -148,6 +148,7 @@ typedef enum ObjectClass
 	OCLASS_EXTENSION,			/* pg_extension */
 	OCLASS_EVENT_TRIGGER,		/* pg_event_trigger */
 	OCLASS_POLICY,				/* pg_policy */
+	OCLASS_TABLESAMPLEMETHOD,	/* pg_tablesample_method */
 	MAX_OCLASS					/* MUST BE LAST */
 } ObjectClass;
 
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
index fd76f77..6a55669 100644
--- a/src/include/catalog/pg_tablesample_method.h
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -69,7 +69,18 @@ typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
 
 DATA(insert OID = 3283 ( system false tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
 DESCR("SYSTEM table sampling method");
+#define TABLESAMPLE_METHOD_SYSTEM_OID 3283
 DATA(insert OID = 3284 ( bernoulli true tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
 DESCR("BERNOULLI table sampling method");
+#define TABLESAMPLE_METHOD_BERNOULLI_OID 3284
+
+/* ----------------
+ *		functions for manipulation of pg_tablesample_method
+ * ----------------
+ */
+
+extern Oid DefineTablesampleMethod(List *names, List *parameters);
+extern void RemoveTablesampleMethodById(Oid tsmoid);
+extern Oid get_tablesample_method_oid(const char *tsmname, bool missing_ok);
 
 #endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 2f4df1d..bc1fef2 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1269,6 +1269,7 @@ typedef enum ObjectType
 	OBJECT_SEQUENCE,
 	OBJECT_TABCONSTRAINT,
 	OBJECT_TABLE,
+	OBJECT_TABLESAMPLEMETHOD,
 	OBJECT_TABLESPACE,
 	OBJECT_TRIGGER,
 	OBJECT_TSCONFIGURATION,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 6ff7b44..c3269c0 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -236,6 +236,7 @@ PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("mode", MODE, UNRESERVED_KEYWORD)
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 93d93af..37ea524 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -9,7 +9,8 @@ SUBDIRS = \
 		  worker_spi \
 		  dummy_seclabel \
 		  test_shm_mq \
-		  test_parser
+		  test_parser \
+		  tablesample
 
 all: submake-errcodes
 
diff --git a/src/test/modules/tablesample/.gitignore b/src/test/modules/tablesample/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/src/test/modules/tablesample/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/src/test/modules/tablesample/Makefile b/src/test/modules/tablesample/Makefile
new file mode 100644
index 0000000..469b004
--- /dev/null
+++ b/src/test/modules/tablesample/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/tsm_test/Makefile
+
+MODULE_big = tsm_test
+OBJS = tsm_test.o $(WIN32RES)
+PGFILEDESC = "tsm_test - example of a custom tablesample method"
+
+EXTENSION = tsm_test
+DATA = tsm_test--1.0.sql
+
+REGRESS = tablesample
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/tablesample/expected/tablesample.out b/src/test/modules/tablesample/expected/tablesample.out
new file mode 100644
index 0000000..3cb3848
--- /dev/null
+++ b/src/test/modules/tablesample/expected/tablesample.out
@@ -0,0 +1,38 @@
+CREATE EXTENSION tsm_test;
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ c81e728d9d4c2f636f067f89cc14862c | 0.5
+ a87ff679a2f3e71d9181a67b7542122c | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ d3d9446802a44259755d38e6d163e820 | 0.5
+(6 rows)
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ e4da3b7fbbce2345d7772b0674a318d5 | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ c9f0f895fb98ab9159f51fd0297e236d | 0.5
+(5 rows)
+
+DROP TABLESAMPLE METHOD tsm_test;
+ERROR:  cannot drop tablesample method tsm_test because extension tsm_test requires it
+HINT:  You can drop extension tsm_test instead.
+DROP EXTENSION tsm_test;
+ERROR:  cannot drop extension tsm_test because other objects depend on it
+DETAIL:  view test_tsm_v depends on tablesample method tsm_test
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+DROP EXTENSION tsm_test CASCADE;
+NOTICE:  drop cascades to view test_tsm_v
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
+ tsmname | tsmseqscan | tsminit | tsmnextblock | tsmnexttuple | tsmexaminetuple | tsmend | tsmreset | tsmcost 
+---------+------------+---------+--------------+--------------+-----------------+--------+----------+---------
+(0 rows)
+
diff --git a/src/test/modules/tablesample/sql/tablesample.sql b/src/test/modules/tablesample/sql/tablesample.sql
new file mode 100644
index 0000000..b1104d6
--- /dev/null
+++ b/src/test/modules/tablesample/sql/tablesample.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_test;
+
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+
+DROP TABLESAMPLE METHOD tsm_test;
+DROP EXTENSION tsm_test;
+DROP EXTENSION tsm_test CASCADE;
+
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
diff --git a/src/test/modules/tablesample/tsm_test--1.0.sql b/src/test/modules/tablesample/tsm_test--1.0.sql
new file mode 100644
index 0000000..2280ab0
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test--1.0.sql
@@ -0,0 +1,51 @@
+/* src/test/modules/tablesample/tsm_test--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_test" to load this file. \quit
+
+CREATE FUNCTION tsm_test_init(internal, int4, text)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nextblock(internal)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nexttuple(internal, int4, int2)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_examinetuple(internal, int4, internal, bool)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_cost(internal, internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+
+CREATE TABLESAMPLE METHOD tsm_test (
+	SEQSCAN		= true,
+	INIT		= tsm_test_init,
+	NEXTBLOCK	= tsm_test_nextblock,
+	NEXTTUPLE	= tsm_test_nexttuple,
+	EXAMINETUPLE	= tsm_test_examinetuple,
+	END			= tsm_test_end,
+	RESET		= tsm_test_reset,
+	COST		= tsm_test_cost
+);
diff --git a/src/test/modules/tablesample/tsm_test.c b/src/test/modules/tablesample/tsm_test.c
new file mode 100644
index 0000000..be4dcb9
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.c
@@ -0,0 +1,228 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_test.c
+ *	  Simple example of a custom tablesample method
+ *
+ * Copyright (c) 2007-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/test/modules/tablesample/tsm_test.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/htup_details.h"
+#include "access/relscan.h"
+#include "access/tupdesc.h"
+#include "catalog/pg_type.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/builtins.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+PG_MODULE_MAGIC;
+
+/* State */
+typedef struct
+{
+	uint32		seed;			/* random seed */
+	AttrNumber	attnum;			/* column to check */
+	TupleDesc	tupDesc;		/* tuple descriptor of table */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} tsm_test_state;
+
+
+PG_FUNCTION_INFO_V1(tsm_test_init);
+PG_FUNCTION_INFO_V1(tsm_test_nextblock);
+PG_FUNCTION_INFO_V1(tsm_test_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_test_examinetuple);
+PG_FUNCTION_INFO_V1(tsm_test_end);
+PG_FUNCTION_INFO_V1(tsm_test_reset);
+PG_FUNCTION_INFO_V1(tsm_test_cost);
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_test_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	char		   *attname;
+	AttrNumber		attnum;
+	Oid				atttype;
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	HeapScanDesc	scan = scanstate->ss.ss_currentScanDesc;
+	tsm_test_state *state;
+	TupleDesc		tupDesc = RelationGetDescr(rel);
+
+	if (PG_ARGISNULL(2))
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("attnum cannot be NULL.")));
+
+	attname = text_to_cstring(PG_GETARG_TEXT_P(2));
+
+	attnum = get_attnum(rel->rd_id, attname);
+	if (!AttrNumberIsForUserDefinedAttr(attnum))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s does not exist", attname)));
+
+	atttype = get_atttype(rel->rd_id, attnum);
+	if (atttype != FLOAT8OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s is not of type float.", attname)));
+
+	state = palloc0(sizeof(tsm_test_state));
+
+	/* Remember initial values for reinit */
+	state->seed = seed;
+	state->attnum = attnum;
+	state->tupDesc = tupDesc;
+	state->startblock = scan->rs_startblock;
+	state->nblocks = scan->rs_nblocks;
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+	sampler_random_init_state(state->seed, state->randstate);
+
+	scanstate->tsmdata = (void *) state;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_test_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	/* Cycle from startblock to startblock to support syncscan. */
+	if (state->blockno == InvalidBlockNumber)
+		state->blockno = state->startblock;
+	else
+	{
+		state->blockno++;
+
+		if (state->blockno >= state->nblocks)
+			state->blockno = 0;
+
+		if (state->blockno == state->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(state->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ */
+Datum
+tsm_test_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (state->lt == InvalidOffsetNumber)
+		state->lt = FirstOffsetNumber;
+	else if (++state->lt > maxoffset)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	PG_RETURN_UINT16(state->lt);
+}
+
+/*
+ * Examine tuple and decide if it should be returned.
+ */
+Datum
+tsm_test_examinetuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	HeapTuple		tuple = (HeapTuple) PG_GETARG_POINTER(2);
+	bool			visible = PG_GETARG_BOOL(3);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+	bool			isnull;
+	float8			val, rand;
+
+	if (!visible)
+		PG_RETURN_BOOL(false);
+
+	val = DatumGetFloat8(heap_getattr(tuple, state->attnum, state->tupDesc, &isnull));
+	rand = sampler_random_fract(state->randstate);
+	if (isnull || val < rand)
+		PG_RETURN_BOOL(false);
+	else
+		PG_RETURN_BOOL(true);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_test_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_test_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+
+	sampler_random_init_state(state->seed, state->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_test_cost(PG_FUNCTION_ARGS)
+{
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+
+	*pages = baserel->pages;
+
+	/* This is very bad estimation */
+	*tuples = path->rows = path->rows/2;
+
+	PG_RETURN_VOID();
+}
+
diff --git a/src/test/modules/tablesample/tsm_test.control b/src/test/modules/tablesample/tsm_test.control
new file mode 100644
index 0000000..a7b2741
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.control
@@ -0,0 +1,5 @@
+# tsm_test extension
+comment = 'test module for custom tablesample method'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_test'
+relocatable = true
-- 
1.9.1

>From 3d7b57ffca70a067d31ed3a99bc9a07f2b836372 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:36:56 +0100
Subject: [PATCH 1/3] separate block sampling functions v2

---
 contrib/file_fdw/file_fdw.c         |   9 +-
 contrib/postgres_fdw/postgres_fdw.c |  10 +-
 src/backend/commands/analyze.c      | 225 +----------------------------------
 src/backend/utils/misc/Makefile     |   2 +-
 src/backend/utils/misc/sampling.c   | 226 ++++++++++++++++++++++++++++++++++++
 src/include/commands/vacuum.h       |   3 -
 src/include/utils/sampling.h        |  44 +++++++
 7 files changed, 287 insertions(+), 232 deletions(-)
 create mode 100644 src/backend/utils/misc/sampling.c
 create mode 100644 src/include/utils/sampling.h

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 4368897..249d541 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -34,6 +34,7 @@
 #include "optimizer/var.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -1005,7 +1006,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 {
 	int			numrows = 0;
 	double		rowstoskip = -1;	/* -1 means not set yet */
-	double		rstate;
+	ReservoirStateData rstate;
 	TupleDesc	tupDesc;
 	Datum	   *values;
 	bool	   *nulls;
@@ -1043,7 +1044,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 									   ALLOCSET_DEFAULT_MAXSIZE);
 
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Set up callback to identify error line number. */
 	errcallback.callback = CopyFromErrorCallback;
@@ -1087,7 +1088,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 			 * not-yet-incremented value of totalrows as t.
 			 */
 			if (rowstoskip < 0)
-				rowstoskip = anl_get_next_S(*totalrows, targrows, &rstate);
+				rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
 
 			if (rowstoskip <= 0)
 			{
@@ -1095,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * anl_random_fract());
+				int			k = (int) (targrows * sampler_random_fract());
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 63f0577..59aaff7 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -37,6 +37,7 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -202,7 +203,7 @@ typedef struct PgFdwAnalyzeState
 	/* for random sampling */
 	double		samplerows;		/* # of rows fetched */
 	double		rowstoskip;		/* # of rows to skip before next sample */
-	double		rstate;			/* random state */
+	ReservoirStateData rstate;		/* state for reservoir sampling*/
 
 	/* working memory contexts */
 	MemoryContext anl_cxt;		/* context for per-analyze lifespan data */
@@ -2393,7 +2394,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 	astate.numrows = 0;
 	astate.samplerows = 0;
 	astate.rowstoskip = -1;		/* -1 means not set yet */
-	astate.rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&astate.rstate, targrows);
 
 	/* Remember ANALYZE context, and create a per-tuple temp context */
 	astate.anl_cxt = CurrentMemoryContext;
@@ -2533,13 +2534,12 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		 * analyze.c; see Jeff Vitter's paper.
 		 */
 		if (astate->rowstoskip < 0)
-			astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
-												&astate->rstate);
+			astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
 
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * anl_random_fract());
+			pos = (int) (targrows * sampler_random_fract());
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index d2856a3..fc9dd44 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -88,10 +78,6 @@ static BufferAccessStrategy vac_strategy;
 static void do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -947,94 +933,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1080,7 +978,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	BlockNumber totalblocks;
 	TransactionId OldestXmin;
 	BlockSamplerData bs;
-	double		rstate;
+	ReservoirStateData rstate;
 
 	Assert(targrows > 0);
 
@@ -1090,9 +988,9 @@ acquire_sample_rows(Relation onerel, int elevel,
 	OldestXmin = GetOldestXmin(onerel, true);
 
 	/* Prepare for sampling block numbers */
-	BlockSampler_Init(&bs, totalblocks, targrows);
+	BlockSampler_Init(&bs, totalblocks, targrows, random());
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Outer loop over blocks to sample */
 	while (BlockSampler_HasMore(&bs))
@@ -1240,8 +1138,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 					 * t.
 					 */
 					if (rowstoskip < 0)
-						rowstoskip = anl_get_next_S(samplerows, targrows,
-													&rstate);
+						rowstoskip = reservoir_get_next_S(&rstate, samplerows, targrows);
 
 					if (rowstoskip <= 0)
 					{
@@ -1249,7 +1146,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1308,116 +1205,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
-/*
- * These two routines embody Algorithm Z from "Random sampling with a
- * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
- * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
- * of the count S of records to skip before processing another record.
- * It is computed primarily based on t, the number of records already read.
- * The only extra state needed between calls is W, a random state variable.
- *
- * anl_init_selection_state computes the initial W value.
- *
- * Given that we've already read t records (t >= n), anl_get_next_S
- * determines the number of records to skip before the next record is
- * processed.
- */
-double
-anl_init_selection_state(int n)
-{
-	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
-}
-
-double
-anl_get_next_S(double t, int n, double *stateptr)
-{
-	double		S;
-
-	/* The magic constant here is T from Vitter's paper */
-	if (t <= (22.0 * n))
-	{
-		/* Process records using Algorithm X until t is large enough */
-		double		V,
-					quot;
-
-		V = anl_random_fract(); /* Generate V */
-		S = 0;
-		t += 1;
-		/* Note: "num" in Vitter's code is always equal to t - n */
-		quot = (t - (double) n) / t;
-		/* Find min S satisfying (4.1) */
-		while (quot > V)
-		{
-			S += 1;
-			t += 1;
-			quot *= (t - (double) n) / t;
-		}
-	}
-	else
-	{
-		/* Now apply Algorithm Z */
-		double		W = *stateptr;
-		double		term = t - (double) n + 1;
-
-		for (;;)
-		{
-			double		numer,
-						numer_lim,
-						denom;
-			double		U,
-						X,
-						lhs,
-						rhs,
-						y,
-						tmp;
-
-			/* Generate U and X */
-			U = anl_random_fract();
-			X = t * (W - 1.0);
-			S = floor(X);		/* S is tentatively set to floor(X) */
-			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
-			tmp = (t + 1) / term;
-			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
-			rhs = (((t + X) / (term + S)) * term) / t;
-			if (lhs <= rhs)
-			{
-				W = rhs / lhs;
-				break;
-			}
-			/* Test if U <= f(S)/cg(X) */
-			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
-			if ((double) n < S)
-			{
-				denom = t;
-				numer_lim = term + S;
-			}
-			else
-			{
-				denom = t - (double) n + S;
-				numer_lim = t + 1;
-			}
-			for (numer = t + S; numer >= numer_lim; numer -= 1)
-			{
-				y *= numer / denom;
-				denom -= 1;
-			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
-			if (exp(log(y) / n) <= (t + X) / t)
-				break;
-		}
-		*stateptr = W;
-	}
-	return S;
-}
-
 /*
  * qsort comparator for sorting rows[] array
  */
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index 378b77e..7889101 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o rls.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..1eeabaf
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,226 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Relation block sampling routines.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler provides algorithm for block level sampling of a relation
+ * as discussed on pgsql-hackers 2004-04-02 (subject "Large DB")
+ * It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table. If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
+				  long randseed)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+/*
+ * These two routines embody Algorithm Z from "Random sampling with a
+ * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
+ * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
+ * of the count S of records to skip before processing another record.
+ * It is computed primarily based on t, the number of records already read.
+ * The only extra state needed between calls is W, a random state variable.
+ *
+ * reservoir_init_selection_state computes the initial W value.
+ *
+ * Given that we've already read t records (t >= n), reservoir_get_next_S
+ * determines the number of records to skip before the next record is
+ * processed.
+ */
+void
+reservoir_init_selection_state(ReservoirState rs, int n)
+{
+	/* Initial value of W (for use when Algorithm Z is first applied) */
+	*rs = exp(-log(sampler_random_fract()) / n);
+}
+
+double
+reservoir_get_next_S(ReservoirState rs, double t, int n)
+{
+	double		S;
+
+	/* The magic constant here is T from Vitter's paper */
+	if (t <= (22.0 * n))
+	{
+		/* Process records using Algorithm X until t is large enough */
+		double		V,
+					quot;
+
+		V = sampler_random_fract(); /* Generate V */
+		S = 0;
+		t += 1;
+		/* Note: "num" in Vitter's code is always equal to t - n */
+		quot = (t - (double) n) / t;
+		/* Find min S satisfying (4.1) */
+		while (quot > V)
+		{
+			S += 1;
+			t += 1;
+			quot *= (t - (double) n) / t;
+		}
+	}
+	else
+	{
+		/* Now apply Algorithm Z */
+		double		W = *rs;
+		double		term = t - (double) n + 1;
+
+		for (;;)
+		{
+			double		numer,
+						numer_lim,
+						denom;
+			double		U,
+						X,
+						lhs,
+						rhs,
+						y,
+						tmp;
+
+			/* Generate U and X */
+			U = sampler_random_fract();
+			X = t * (W - 1.0);
+			S = floor(X);		/* S is tentatively set to floor(X) */
+			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
+			tmp = (t + 1) / term;
+			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
+			rhs = (((t + X) / (term + S)) * term) / t;
+			if (lhs <= rhs)
+			{
+				W = rhs / lhs;
+				break;
+			}
+			/* Test if U <= f(S)/cg(X) */
+			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
+			if ((double) n < S)
+			{
+				denom = t;
+				numer_lim = term + S;
+			}
+			else
+			{
+				denom = t - (double) n + S;
+				numer_lim = t + 1;
+			}
+			for (numer = t + S; numer >= numer_lim; numer -= 1)
+			{
+				y *= numer / denom;
+				denom -= 1;
+			}
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			if (exp(log(y) / n) <= (t + X) / t)
+				break;
+		}
+		*rs = W;
+	}
+	return S;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract()
+{
+	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+}
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 4275484..d38fead 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -178,8 +178,5 @@ extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 extern void analyze_rel(Oid relid, VacuumStmt *vacstmt,
 			bool in_outer_xact, BufferAccessStrategy bstrategy);
 extern bool std_typanalyze(VacAttrStats *stats);
-extern double anl_random_fract(void);
-extern double anl_init_selection_state(int n);
-extern double anl_get_next_S(double t, int n, double *stateptr);
 
 #endif   /* VACUUM_H */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..e3e7f9c
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,44 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+extern double sampler_random_fract(void);
+
+/* Block sampling methods */
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize, long randseed);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Reservoid sampling methods */
+typedef double ReservoirStateData;
+typedef ReservoirStateData *ReservoirState;
+
+extern void reservoir_init_selection_state(ReservoirState rs, int n);
+extern double reservoir_get_next_S(ReservoirState rs, double t, int n);
+
+#endif /* SAMPLING_H */
-- 
1.9.1

>From 1de801e5e46891389641bfc1303634141839ba01 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:37:55 +0100
Subject: [PATCH 2/3] tablesample v9

---
 contrib/file_fdw/file_fdw.c                 |   2 +-
 contrib/postgres_fdw/postgres_fdw.c         |   2 +-
 doc/src/sgml/catalogs.sgml                  | 112 +++++++
 doc/src/sgml/ref/select.sgml                |  38 ++-
 src/backend/access/Makefile                 |   3 +-
 src/backend/access/heap/heapam.c            |   7 +-
 src/backend/catalog/Makefile                |   2 +-
 src/backend/commands/analyze.c              |   2 +-
 src/backend/commands/explain.c              |   7 +
 src/backend/executor/Makefile               |   2 +-
 src/backend/executor/execAmi.c              |   8 +
 src/backend/executor/execCurrent.c          |   1 +
 src/backend/executor/execProcnode.c         |  14 +
 src/backend/executor/nodeSamplescan.c       | 500 ++++++++++++++++++++++++++++
 src/backend/nodes/copyfuncs.c               |  59 ++++
 src/backend/nodes/equalfuncs.c              |  36 ++
 src/backend/nodes/nodeFuncs.c               |  12 +
 src/backend/nodes/outfuncs.c                |  47 +++
 src/backend/nodes/readfuncs.c               |  44 +++
 src/backend/optimizer/path/allpaths.c       |  49 +++
 src/backend/optimizer/path/costsize.c       |  68 ++++
 src/backend/optimizer/plan/createplan.c     |  69 ++++
 src/backend/optimizer/plan/setrefs.c        |  11 +
 src/backend/optimizer/plan/subselect.c      |   1 +
 src/backend/optimizer/util/pathnode.c       |  22 ++
 src/backend/parser/gram.y                   |  40 ++-
 src/backend/parser/parse_clause.c           |  48 ++-
 src/backend/parser/parse_func.c             | 130 ++++++++
 src/backend/utils/Makefile                  |   3 +-
 src/backend/utils/adt/ruleutils.c           |  50 +++
 src/backend/utils/cache/syscache.c          |  23 ++
 src/backend/utils/misc/sampling.c           |  33 +-
 src/backend/utils/tablesample/Makefile      |  17 +
 src/backend/utils/tablesample/bernoulli.c   | 224 +++++++++++++
 src/backend/utils/tablesample/system.c      | 185 ++++++++++
 src/include/access/heapam.h                 |   1 +
 src/include/access/relscan.h                |   1 +
 src/include/catalog/indexing.h              |   5 +
 src/include/catalog/pg_proc.h               |  25 ++
 src/include/catalog/pg_tablesample_method.h |  75 +++++
 src/include/executor/nodeSamplescan.h       |  24 ++
 src/include/nodes/execnodes.h               |  18 +
 src/include/nodes/nodes.h                   |   4 +
 src/include/nodes/parsenodes.h              |  35 ++
 src/include/nodes/plannodes.h               |   6 +
 src/include/optimizer/cost.h                |   1 +
 src/include/optimizer/pathnode.h            |   2 +
 src/include/parser/kwlist.h                 |   3 +-
 src/include/parser/parse_func.h             |   4 +
 src/include/utils/rel.h                     |   1 -
 src/include/utils/sampling.h                |  15 +-
 src/include/utils/syscache.h                |   2 +
 src/include/utils/tablesample.h             |  27 ++
 src/test/regress/expected/sanity_check.out  |   1 +
 src/test/regress/expected/tablesample.out   | 168 ++++++++++
 src/test/regress/parallel_schedule          |   2 +-
 src/test/regress/serial_schedule            |   1 +
 src/test/regress/sql/tablesample.sql        |  42 +++
 58 files changed, 2304 insertions(+), 30 deletions(-)
 create mode 100644 src/backend/executor/nodeSamplescan.c
 create mode 100644 src/backend/utils/tablesample/Makefile
 create mode 100644 src/backend/utils/tablesample/bernoulli.c
 create mode 100644 src/backend/utils/tablesample/system.c
 create mode 100644 src/include/catalog/pg_tablesample_method.h
 create mode 100644 src/include/executor/nodeSamplescan.h
 create mode 100644 src/include/utils/tablesample.h
 create mode 100644 src/test/regress/expected/tablesample.out
 create mode 100644 src/test/regress/sql/tablesample.sql

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 249d541..6a813a3 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -1096,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * sampler_random_fract());
+				int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 59aaff7..5b2335f 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -2539,7 +2539,7 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * sampler_random_fract());
+			pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 515a40e..6b4e32b 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -269,6 +269,11 @@
      </row>
 
      <row>
+      <entry><link linkend="catalog-pg-tablesample-method"><structname>pg_tablesample_method</structname></link></entry>
+      <entry>table sampling methods</entry>
+     </row>
+
+     <row>
       <entry><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link></entry>
       <entry>tablespaces within this database cluster</entry>
      </row>
@@ -5989,6 +5994,113 @@
  </sect1>
 
 
+ <sect1 id="catalog-pg-tablesample-method">
+  <title><structname>pg_tabesample_method</structname></title>
+
+  <indexterm zone="catalog-pg-tablesample-method">
+   <primary>pg_am</primary>
+  </indexterm>
+
+  <para>
+   The catalog <structname>pg_tablesample_method</structname> stores
+   information about table sampling methods which can be used in
+   <command>TABLESAMPLE</command> clause of a <command>SELECT</command>
+   statement.
+  </para>
+
+  <table>
+   <title><structname>pg_tablesample_method</> Columns</title>
+
+   <tgroup cols="4">
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Type</entry>
+      <entry>References</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+    <tbody>
+
+     <row>
+      <entry><structfield>oid</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry></entry>
+      <entry>Row identifier (hidden attribute; must be explicitly selected)</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmname</structfield></entry>
+      <entry><type>name</type></entry>
+      <entry></entry>
+      <entry>Name of the sampling method</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmseqscan</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry></entry>
+      <entry>Does the sampling method scan the whole table sequentially?
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsminit</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Initialize the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnextblock</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next block number</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnexttuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next tuple offset</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmexaminetuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Function which examines the tuple contents and decides if to
+        return in, or zero if none</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmend</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>End the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmreset</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Restart the state of sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmcost</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Costing function</entry>
+     </row>
+
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect1>
+
+
  <sect1 id="catalog-pg-tablespace">
   <title><structname>pg_tablespace</structname></title>
 
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 01d24a5..407bf9d 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,42 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        one of:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of those sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability.
+        The optional numeric parameter <literal>REPEATABLE</literal> is used
+        as random seed for sampling. Note that subsequent commands may return
+        different results even if same <literal>REPEATABLE</literal> clause
+        was specified. This happens because <acronym>DML</acronym> statements
+        and maintenance operations such as <command>VACUUM</> affect physical
+        distribution of data.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..238057a 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  transam
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index cb6f8a3..4cd3223 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -293,9 +293,10 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
 
 	/*
 	 * Currently, we don't have a stats counter for bitmap heap scans (but the
-	 * underlying bitmap index scans will be counted).
+	 * underlying bitmap index scans will be counted) or sample scans (we only
+	 * update stats for tuple fetches there)
 	 */
-	if (!scan->rs_bitmapscan)
+	if (!scan->rs_bitmapscan && !scan->rs_samplescan)
 		pgstat_count_heap_scan(scan->rs_rd);
 }
 
@@ -314,7 +315,7 @@ heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk, BlockNumber numBlks)
  * In page-at-a-time mode it performs additional work, namely determining
  * which tuples on the page are visible.
  */
-static void
+void
 heapgetpage(HeapScanDesc scan, BlockNumber page)
 {
 	Buffer		buffer;
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..34db3e6 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesample_method.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index fc9dd44..63feb07 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1146,7 +1146,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * sampler_random_fract());
+						int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index a951c55..20cc7a1 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -732,6 +732,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -957,6 +958,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			pname = sname = "Sample Scan";
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1074,6 +1078,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1326,6 +1331,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2220,6 +2226,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 6ebad2f..4948a26 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index 1c8be25..5cfe549 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 9892499..03c2feb 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..34ea4ab
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,500 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "catalog/pg_tablesample_method.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "pgstat.h"
+#include "storage/bufmgr.h"
+#include "storage/predicate.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate,
+							 int eflags, TableSampleClause *tablesample);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+static HeapTuple samplenexttup(SampleScanState *node, HeapScanDesc scan);
+
+
+/*
+ * Initialize the sampling method - loads function info and
+ * calls the tsminit function.
+ *
+ * We need special handling for this because the tsminit function
+ * is allowed to take optional additional arguments.
+ */
+static void
+InitSamplingMethod(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(scanstate->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(scanstate->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(scanstate->tsmnexttuple));
+	if (OidIsValid(tablesample->tsmexaminetuple))
+		fmgr_info(tablesample->tsmexaminetuple, &(scanstate->tsmexaminetuple));
+	else
+		scanstate->tsmexaminetuple.fn_oid = InvalidOid;
+	fmgr_info(tablesample->tsmend, &(scanstate->tsmend));
+	fmgr_info(tablesample->tsmreset, &(scanstate->tsmreset));
+
+	InitFunctionCallInfoData(fcinfo, &scanstate->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	/* First arg is always SampleScanState */
+	fcinfo.arg[0] = PointerGetDatum(scanstate);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause cannot be NULL")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+}
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	TupleTableSlot *slot;
+	HeapScanDesc	scan;
+	HeapTuple		tuple;
+
+	/*
+	 * get information from the scan state
+	 */
+	slot = node->ss.ss_ScanTupleSlot;
+	scan = node->ss.ss_currentScanDesc;
+
+	tuple = samplenexttup(node, scan);
+
+	if (tuple)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   scan->rs_cbuf,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+static HeapTuple
+samplenexttup(SampleScanState *node, HeapScanDesc scan)
+{
+	HeapTuple		tuple = &(scan->rs_ctup);
+	Snapshot		snapshot = scan->rs_snapshot;
+	BlockNumber		blockno;
+	Page			page;
+	ItemId			itemid;
+	OffsetNumber	tupoffset,
+					maxoffset;
+
+	if (!scan->rs_inited)
+	{
+		/*
+		 * return null immediately if relation is empty
+		 */
+		if (scan->rs_nblocks == 0)
+		{
+			Assert(!BufferIsValid(scan->rs_cbuf));
+			tuple->t_data = NULL;
+			return NULL;
+		}
+		blockno = DatumGetInt32(FunctionCall1(&node->tsmnextblock,
+											  PointerGetDatum(node)));
+		if (!BlockNumberIsValid(blockno))
+		{
+			tuple->t_data = NULL;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+		scan->rs_inited = true;
+	}
+	else
+	{
+		/* continue from previously returned page/tuple */
+		blockno = scan->rs_cblock;		/* current page */
+	}
+
+	LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+	page = (Page) BufferGetPage(scan->rs_cbuf);
+	maxoffset = PageGetMaxOffsetNumber(page);
+
+	for (;;)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		tupoffset = DatumGetUInt16(FunctionCall3(&node->tsmnexttuple,
+												 PointerGetDatum(node),
+												 UInt32GetDatum(blockno),
+												 UInt16GetDatum(maxoffset)));
+
+		if (OffsetNumberIsValid(tupoffset))
+		{
+			bool	visible;
+			bool	found;
+
+			/* Skip invalid tuple pointers. */
+			itemid = PageGetItemId(page, tupoffset);
+			if (!ItemIdIsNormal(itemid))
+				continue;
+
+			tuple->t_data = (HeapTupleHeader) PageGetItem((Page) page, itemid);
+			tuple->t_len = ItemIdGetLength(itemid);
+			ItemPointerSet(&(tuple->t_self), blockno, tupoffset);
+
+			visible = HeapTupleSatisfiesVisibility(tuple, snapshot, scan->rs_cbuf);
+
+			CheckForSerializableConflictOut(visible, scan->rs_rd, tuple,
+											scan->rs_cbuf, snapshot);
+
+			/*
+			 * Let the sampling method examine the actual tuple and decide if we
+			 * should return it.
+			 *
+			 * Note that we let it examine even invisible tuples for
+			 * statistical purposes, but not return them since user should
+			 * never see invisible tuples.
+			 */
+			if (OidIsValid(node->tsmexaminetuple.fn_oid))
+			{
+				found = DatumGetBool(FunctionCall4(&node->tsmexaminetuple,
+												   PointerGetDatum(node),
+												   UInt32GetDatum(blockno),
+												   PointerGetDatum(tuple),
+												   BoolGetDatum(visible)));
+				/* Should not happen if sampling method is well written. */
+				if (found && !visible)
+					elog(ERROR, "Sampling method wanted to return invisible tuple");
+			}
+			else
+				found = visible;
+
+			/* Found visible tuple, return it. */
+			if (found)
+			{
+				LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+				break;
+			}
+			else
+			{
+				/* Try next tuple from same page. */
+				continue;
+			}
+		}
+
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+		blockno = DatumGetInt32(FunctionCall1(&node->tsmnextblock,
+											  PointerGetDatum(node)));
+
+		/*
+		 * Report our new scan position for synchronization purposes. We
+		 * don't do that when moving backwards, however. That would just
+		 * mess up any other forward-moving scanners.
+		 *
+		 * Note: we do this before checking for end of scan so that the
+		 * final state of the position hint is back at the start of the
+		 * rel.  That's not strictly necessary, but otherwise when you run
+		 * the same query multiple times the starting position would shift
+		 * a little bit backwards on every invocation, which is confusing.
+		 * We don't guarantee any specific ordering in general, though.
+		 */
+		if (scan->rs_syncscan)
+			ss_report_location(scan->rs_rd, BlockNumberIsValid(blockno) ?
+							   blockno : scan->rs_startblock);
+
+		/*
+		 * Reached end of scan.
+		 */
+		if (!BlockNumberIsValid(blockno))
+		{
+			if (BufferIsValid(scan->rs_cbuf))
+				ReleaseBuffer(scan->rs_cbuf);
+			scan->rs_cbuf = InvalidBuffer;
+			scan->rs_cblock = InvalidBlockNumber;
+			tuple->t_data = NULL;
+			scan->rs_inited = false;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+		page = (Page) BufferGetPage(scan->rs_cbuf);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	pgstat_count_heap_getnext(scan->rs_rd);
+
+	return &(scan->rs_ctup);
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags,
+				 TableSampleClause *tablesample)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+
+	/*
+	 * Even though we aren't going to do a conventional seqscan, it is useful
+	 * to create a HeapScanDesc --- many of the fields in it are usable.
+	 */
+	node->ss.ss_currentScanDesc =
+		heap_beginscan_strat(currentRelation,
+							 estate->es_snapshot,
+							 0, NULL, false,
+							 tablesample->tsmseqscan);
+
+	/*
+	 * Page at a time mode is useless for us as we need to check visibility
+	 * of tuples individually because tuple offsets returned by sampling
+	 * methods map to rs_vistuples values and not to its indexes.
+	 */
+	node->ss.ss_currentScanDesc->rs_pageatatime = false;
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags, rte->tablesample);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	InitSamplingMethod(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished thes can.
+	 */
+	FunctionCall1(&node->tsmend, PointerGetDatum(node));
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close heap scan
+	 */
+	heap_endscan(node->ss.ss_currentScanDesc);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *node)
+{
+	heap_rescan(node->ss.ss_currentScanDesc, NULL);
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	FunctionCall1(&node->tsmreset, PointerGetDatum(node));
+
+	ExecScanReScan(&node->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index e5b0dce..d47b6ca 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -629,6 +629,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2007,6 +2023,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2139,6 +2156,39 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsmseqscan);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmexaminetuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4076,6 +4126,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4724,6 +4777,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_PrivGrantee:
 			retval = _copyPrivGrantee(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 6e8b308..165c4e5 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2323,6 +2323,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2442,6 +2443,35 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsmseqscan);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmexaminetuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3150,6 +3180,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_PrivGrantee:
 			retval = _equalPrivGrantee(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 21dfda7..bd9ce09 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3209,6 +3209,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 8486448..a4f92ad 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -579,6 +579,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -2392,6 +2400,35 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_BOOL_FIELD(tsmseqscan);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmexaminetuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2421,6 +2458,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2888,6 +2926,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3229,6 +3270,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index ae24d05..076c958 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,45 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_BOOL_FIELD(tsmseqscan);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmexaminetuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1216,6 +1255,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1311,6 +1351,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 58d78e6..5f12477 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,10 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
+				   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -265,6 +269,11 @@ set_rel_size(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_size(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Sampled relation */
+					set_tablesample_rel_size(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -332,6 +341,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +432,41 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_size
+ *	  Set size estimates for a sampled relation.
+ */
+static void
+set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	/* Mark rel with estimated output rows, width, etc */
+	set_baserel_size_estimates(root, rel);
+}
+
+/*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids	required_outer;
+	Path   *path;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	path = create_samplescan_path(root, rel, required_outer);
+	rel->pathlist = list_make1(path);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 78ef229..d8523de 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -90,6 +90,7 @@
 #include "utils/lsyscache.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
+#include "utils/tablesample.h"
 #include "utils/tuplesort.h"
 
 
@@ -219,6 +220,73 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we dont't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	RangeTblEntry		   *rte = planner_rt_fetch(baserel->relid, root);
+	TableSampleClause	   *tablesample = rte->tablesample;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Mark the path with the correct row estimate */
+	if (path->param_info)
+		path->rows = path->param_info->ppi_rows;
+	else
+		path->rows = baserel->rows;
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(tablesample->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(tablesample->args),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples));
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = tablesample->tsmseqscan ? spc_seq_page_cost :
+					spc_random_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->startup_cost = startup_cost;
+	path->total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 76ba1bf..2aaa2b1 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3318,6 +3369,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index ec828cd..82771dc 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -445,6 +445,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 5a1d539..84b305f 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2163,6 +2163,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 1395a21..014d670 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,26 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+Path *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	Path		   *pathnode = makeNode(Path);
+
+	pathnode->pathtype = T_SampleScan;
+	pathnode->parent = rel;
+	pathnode->param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->pathkeys = NIL;	/* samplescan has unordered result */
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1921,6 +1941,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 36dac29..ac5e095 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -447,6 +447,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -611,8 +612,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10227,6 +10228,12 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample opt_alias_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10522,7 +10529,6 @@ relation_expr_list:
 			| relation_expr_list ',' relation_expr	{ $$ = lappend($1, $3); }
 		;
 
-
 /*
  * Given "UPDATE foo set set ...", we have to decide without looking any
  * further ahead whether the first "set" is an alias or the UPDATE's SET
@@ -10552,6 +10558,31 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $2;
+					n->relation = $1;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' func_arg_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' AexprConst ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/						{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13334,7 +13365,6 @@ unreserved_keyword:
 			| RELATIVE_P
 			| RELEASE
 			| RENAME
-			| REPEATABLE
 			| REPLACE
 			| REPLICA
 			| RESET
@@ -13509,6 +13539,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
@@ -13577,6 +13608,7 @@ reserved_keyword:
 			| PLACING
 			| PRIMARY
 			| REFERENCES
+			| REPEATABLE
 			| RETURNING
 			| SELECT
 			| SESSION_USER
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 654dce6..e3554b3 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -413,6 +416,28 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *r)
+{
+	RangeTblEntry  *rte;
+	TableSampleClause *tablesample = NULL;
+
+	rte = transformTableEntry(pstate, r->relation);
+
+	if (rte->relkind != RELKIND_RELATION &&
+		rte->relkind != RELKIND_MATVIEW)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("TABLESAMPLE clause can only be used on tables and materialized views"),
+				 parser_errposition(pstate,
+									 exprLocation((Node *) r))));
+
+	tablesample = ParseTableSample(pstate, r->method, r->repeatable, r->args);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -421,7 +446,7 @@ transformTableEntry(ParseState *pstate, RangeVar *r)
 {
 	RangeTblEntry *rte;
 
-	/* We need only build a range table entry */
+	/* We first need to build a range table entry */
 	rte = addRangeTableEntry(pstate, r, r->alias,
 							 interpretInhOption(r->inhOpt), true);
 
@@ -1121,6 +1146,27 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index a200804..541f415 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -760,6 +762,134 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+extern TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				actual_arg_types[FUNC_MAX_ARGS];
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						samplemethod)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsmseqscan = tsm->tsmseqscan;
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmexaminetuple = tsm->tsmexaminetuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Transform the rest of arguments ... */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *arg = transformExpr(pstate, (Node *) lfirst(larg), EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		fargs = lappend(fargs, arg);
+
+		actual_arg_types[nargs++] = argtype;
+	}
+
+	/*
+	 * Check if parameters are correct.
+	 *
+	 * XXX: can we do better at hinting here?
+	 */
+	if (initnargs != nargs ||
+			!can_coerce_type(initnargs, actual_arg_types, init_arg_types,
+						COERCION_IMPLICIT))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("wrong parameters for tablesample method \"%s\"",
+						samplemethod)));
+
+	/* perform the necessary typecasting of arguments */
+	make_fn_arguments(pstate, fargs, actual_arg_types, init_arg_types);
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/utils/Makefile b/src/backend/utils/Makefile
index 8374533..9daa2ae 100644
--- a/src/backend/utils/Makefile
+++ b/src/backend/utils/Makefile
@@ -9,7 +9,8 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS        = fmgrtab.o
-SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time
+SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time \
+			  tablesample
 
 # location of Catalog.pm
 catalogdir  = $(top_srcdir)/src/backend/catalog
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index c1d860c..8198fc7 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -31,6 +31,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -343,6 +344,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4184,6 +4187,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for tablesample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8411,6 +8458,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index bd27168..3a8f01e 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
index 1eeabaf..f213c46 100644
--- a/src/backend/utils/misc/sampling.c
+++ b/src/backend/utils/misc/sampling.c
@@ -46,6 +46,8 @@ BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
 	bs->n = samplesize;
 	bs->t = 0;					/* blocks scanned so far */
 	bs->m = 0;					/* blocks selected so far */
+
+	sampler_random_init_state(randseed, bs->randstate);
 }
 
 bool
@@ -92,7 +94,7 @@ BlockSampler_Next(BlockSampler bs)
 	 * less than k, which means that we cannot fail to select enough blocks.
 	 *----------
 	 */
-	V = sampler_random_fract();
+	V = sampler_random_fract(bs->randstate);
 	p = 1.0 - (double) k / (double) K;
 	while (V < p)
 	{
@@ -126,8 +128,14 @@ BlockSampler_Next(BlockSampler bs)
 void
 reservoir_init_selection_state(ReservoirState rs, int n)
 {
+	/*
+	 * Reservoir sampling is not used anywhere where it would need to return
+	 * repeatable results so we can initialize it randomly.
+	 */
+	sampler_random_init_state(random(), rs->randstate);
+
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	*rs = exp(-log(sampler_random_fract()) / n);
+	rs->W = exp(-log(sampler_random_fract(rs->randstate)) / n);
 }
 
 double
@@ -142,7 +150,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 		double		V,
 					quot;
 
-		V = sampler_random_fract(); /* Generate V */
+		V = sampler_random_fract(rs->randstate); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -158,7 +166,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 	else
 	{
 		/* Now apply Algorithm Z */
-		double		W = *rs;
+		double		W = rs->W;
 		double		term = t - (double) n + 1;
 
 		for (;;)
@@ -174,7 +182,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 						tmp;
 
 			/* Generate U and X */
-			U = sampler_random_fract();
+			U = sampler_random_fract(rs->randstate);
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -203,11 +211,11 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract(rs->randstate)) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
-		*rs = W;
+		rs->W = W;
 	}
 	return S;
 }
@@ -217,10 +225,17 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
  * Random number generator used by sampling
  *----------
  */
+void
+sampler_random_init_state(long seed, SamplerRandomState randstate)
+{
+	randstate[0] = 0x330e;
+	randstate[1] = (unsigned short) seed;
+	randstate[2] = (unsigned short) (seed >> 16);
+}
 
 /* Select a random value R uniformly distributed in (0 - 1) */
 double
-sampler_random_fract()
+sampler_random_fract(SamplerRandomState randstate)
 {
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+	return pg_erand48(randstate);
 }
diff --git a/src/backend/utils/tablesample/Makefile b/src/backend/utils/tablesample/Makefile
new file mode 100644
index 0000000..df92939
--- /dev/null
+++ b/src/backend/utils/tablesample/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for utils/tablesample
+#
+# IDENTIFICATION
+#    src/backend/utils/tablesample/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/utils/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = system.o bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/tablesample/bernoulli.c b/src/backend/utils/tablesample/bernoulli.c
new file mode 100644
index 0000000..f7e9688
--- /dev/null
+++ b/src/backend/utils/tablesample/bernoulli.c
@@ -0,0 +1,224 @@
+/*-------------------------------------------------------------------------
+ *
+ * bernoulli.c
+ *	  interface routines for BERNOULLI tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/relscan.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/* State */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* number of blocks */
+	BlockNumber blockno;		/* current block */
+	float4 probability;			/* probabilty that tuple will be returned (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	HeapScanDesc	scan = scanstate->ss.ss_currentScanDesc;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->startblock = scan->rs_startblock;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->blockno = InvalidBlockNumber;
+	sampler->probability = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	/*
+	 * Bernoulli sampling scans all blocks on the table and supports
+	 * syncscan so loop from startblock to startblock instead of
+	 * from 0 to nblocks.
+	 */
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = sampler->startblock;
+	else
+	{
+		sampler->blockno++;
+
+		if (sampler->blockno >= sampler->nblocks)
+			sampler->blockno = 0;
+
+		if (sampler->blockno == sampler->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+	float4			probability = sampler->probability;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/*
+	 * Loop over tuple offsets until the random generator returns value that
+	 * is within the probability of returning the tuple or until we reach
+	 * end of the block.
+	 *
+	 * (This is our implementation of bernoulli trial)
+	 */
+	while (sampler_random_fract(sampler->randstate) > probability)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1;
+	}
+
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/utils/tablesample/system.c b/src/backend/utils/tablesample/system.c
new file mode 100644
index 0000000..0c4da28
--- /dev/null
+++ b/src/backend/utils/tablesample/system.c
@@ -0,0 +1,185 @@
+/*-------------------------------------------------------------------------
+ *
+ * system.c
+ *	  interface routines for system tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	SystemSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks =
+		RelationGetNumberOfBlocks(scanstate->ss.ss_currentRelation);
+	sampler->samplesize = 1 + (int) (sampler->tblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as VACUUM for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	BlockNumber		blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1;
+	}
+
+	*pages = baserel->pages * samplesize;
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 939d93d..9dabcb0 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -115,6 +115,7 @@ extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key);
 extern void heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk,
 		   BlockNumber endBlk);
+extern void heapgetpage(HeapScanDesc scan, BlockNumber page);
 extern void heap_rescan(HeapScanDesc scan, ScanKey key);
 extern void heap_endscan(HeapScanDesc scan);
 extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 9bb6362..e2b2b4f 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -29,6 +29,7 @@ typedef struct HeapScanDescData
 	int			rs_nkeys;		/* number of scan keys */
 	ScanKey		rs_key;			/* array of scan key descriptors */
 	bool		rs_bitmapscan;	/* true if this is really a bitmap scan */
+	bool		rs_samplescan;	/* true if this is really a sample scan */
 	bool		rs_pageatatime; /* verify visibility page-at-a-time? */
 	bool		rs_allow_strat; /* allow or disallow use of access strategy */
 	bool		rs_allow_sync;	/* allow or disallow use of syncscan */
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index a680229..c711cca 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3281, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3281
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3282, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3282
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 4268b99..756911c 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5145,6 +5145,31 @@ DESCR("rank of hypothetical row without gaps");
 DATA(insert OID = 3993 ( dense_rank_final	PGNSP PGUID 12 1 0 2276 0 f f f f f f i 2 0 20 "2281 2276" "{2281,2276}" "{i,v}" _null_ _null_	hypothetical_dense_rank_final _null_ _null_ _null_ ));
 DESCR("aggregate final function");
 
+DATA(insert OID = 3285 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3286 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3287 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3288 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3289 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3290 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3291 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3292 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3293 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3294 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3296 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3297 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 0000000..fd76f77
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,75 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3280
+
+CATALOG(pg_tablesample_method,3280)
+{
+	NameData	tsmname;		/* tablesample method name */
+	bool		tsmseqscan;		/* does this method scan whole table sequentially? */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmexaminetuple;	/* optional function which can examine tuple contents and
+								   decide if tuple should be returned or not */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method					9
+#define Anum_pg_tablesample_method_tsmname			1
+#define Anum_pg_tablesample_method_tsmseqscan		2
+#define Anum_pg_tablesample_method_tsminit			3
+#define Anum_pg_tablesample_method_tsmnextblock		4
+#define Anum_pg_tablesample_method_tsmnexttuple		5
+#define Anum_pg_tablesample_method_tsmexaminetuple	6
+#define Anum_pg_tablesample_method_tsmend			7
+#define Anum_pg_tablesample_method_tsmreset			8
+#define Anum_pg_tablesample_method_tsmcost			9
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3283 ( system false tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3284 ( bernoulli true tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 41288ed..e913924 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1212,6 +1212,24 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState		ss;
+
+	/* Sampling method functions. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmexaminetuple;
+	FmgrInfo		tsmend;
+	FmgrInfo		tsmreset;
+
+	void		   *tsmdata;		/* for use by table scan method */
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 97ef0fc..3276be8 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -413,6 +415,8 @@ typedef enum NodeTag
 	T_XmlSerialize,
 	T_WithClause,
 	T_CommonTableExpr,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index b1dfa85..2f4df1d 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -307,6 +307,25 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	bool		tsmseqscan;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmexaminetuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -507,6 +526,21 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * We are more generic than SQL Standard so we pass generic function
+ * arguments to the sampling method.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -751,6 +785,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index f6683f0..5289c43 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -279,6 +279,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 9c2000b..24003ae 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 9923f0e..89c8ded 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern Path *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+									Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 7c243ec..6ff7b44 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -312,7 +312,7 @@ PG_KEYWORD("reindex", REINDEX, UNRESERVED_KEYWORD)
 PG_KEYWORD("relative", RELATIVE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("release", RELEASE, UNRESERVED_KEYWORD)
 PG_KEYWORD("rename", RENAME, UNRESERVED_KEYWORD)
-PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
+PG_KEYWORD("repeatable", REPEATABLE, RESERVED_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 3264691..6727e55 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,10 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 6bd786d..185bd81 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
index e3e7f9c..4ac208d 100644
--- a/src/include/utils/sampling.h
+++ b/src/include/utils/sampling.h
@@ -15,7 +15,12 @@
 
 #include "storage/bufmgr.h"
 
-extern double sampler_random_fract(void);
+/* Random generator for sampling code */
+typedef unsigned short SamplerRandomState[3];
+
+extern void sampler_random_init_state(long seed,
+									  SamplerRandomState randstate);
+extern double sampler_random_fract(SamplerRandomState randstate);
 
 /* Block sampling methods */
 /* Data structure for Algorithm S from Knuth 3.4.2 */
@@ -25,6 +30,7 @@ typedef struct
 	int			n;				/* desired sample size */
 	BlockNumber t;				/* current block number */
 	int			m;				/* blocks selected so far */
+	SamplerRandomState randstate; /* random generator state */
 } BlockSamplerData;
 
 typedef BlockSamplerData *BlockSampler;
@@ -35,7 +41,12 @@ extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
 /* Reservoid sampling methods */
-typedef double ReservoirStateData;
+typedef struct
+{
+	double	W;
+	SamplerRandomState randstate; /* random generator state */
+} ReservoirStateData;
+
 typedef ReservoirStateData *ReservoirState;
 
 extern void reservoir_init_selection_state(ReservoirState rs, int n);
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index ba0b090..6b628f6 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/include/utils/tablesample.h b/src/include/utils/tablesample.h
new file mode 100644
index 0000000..1a24cb6
--- /dev/null
+++ b/src/include/utils/tablesample.h
@@ -0,0 +1,27 @@
+/*--------------------------------------------------------------------------
+ * tablesample.h
+ *	  Header file for builtin table sampling methods.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/utils/tablesample.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TABLESAMPLE_H
+#define TABLESAMPLE_H
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TABLESAMPLE_H */
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..5946edf 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..ce9abf7
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,168 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+CLOSE tablesample_cur;
+END;
+-- should fail
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+ERROR:  TABLESAMPLE clause can only be used on tables and materialized views
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index e0ae2f2..e0240ac 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 7f762bd..9a7611b 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -152,3 +152,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..0d8ce39
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,42 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+CLOSE tablesample_cur;
+END;
+
+-- should fail
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+
+DROP TABLE test_tablesample CASCADE;
-- 
1.9.1

>From 01ad447b67cb860fd1ded19b736c8955a80ce5a8 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:51:44 +0100
Subject: [PATCH 3/3] tablesample-ddl v4

---
 doc/src/sgml/ref/allfiles.sgml                     |   2 +
 doc/src/sgml/ref/create_tablesamplemethod.sgml     | 173 +++++++++
 doc/src/sgml/ref/drop_tablesamplemethod.sgml       |  87 +++++
 doc/src/sgml/reference.sgml                        |   2 +
 src/backend/catalog/dependency.c                   |  15 +-
 src/backend/catalog/objectaddress.c                |  65 +++-
 src/backend/commands/Makefile                      |   6 +-
 src/backend/commands/dropcmds.c                    |   4 +
 src/backend/commands/event_trigger.c               |   3 +
 src/backend/commands/tablecmds.c                   |   1 +
 src/backend/commands/tablesample.c                 | 422 +++++++++++++++++++++
 src/backend/parser/gram.y                          |  14 +-
 src/backend/tcop/utility.c                         |  12 +
 src/bin/pg_dump/common.c                           |   5 +
 src/bin/pg_dump/pg_dump.c                          | 171 +++++++++
 src/bin/pg_dump/pg_dump.h                          |  10 +-
 src/bin/pg_dump/pg_dump_sort.c                     |  11 +-
 src/include/catalog/dependency.h                   |   1 +
 src/include/catalog/pg_tablesample_method.h        |  11 +
 src/include/nodes/parsenodes.h                     |   1 +
 src/include/parser/kwlist.h                        |   1 +
 src/test/modules/Makefile                          |   3 +-
 src/test/modules/tablesample/.gitignore            |   4 +
 src/test/modules/tablesample/Makefile              |  21 +
 .../modules/tablesample/expected/tablesample.out   |  38 ++
 src/test/modules/tablesample/sql/tablesample.sql   |  14 +
 src/test/modules/tablesample/tsm_test--1.0.sql     |  51 +++
 src/test/modules/tablesample/tsm_test.c            | 228 +++++++++++
 src/test/modules/tablesample/tsm_test.control      |   5 +
 29 files changed, 1370 insertions(+), 11 deletions(-)
 create mode 100644 doc/src/sgml/ref/create_tablesamplemethod.sgml
 create mode 100644 doc/src/sgml/ref/drop_tablesamplemethod.sgml
 create mode 100644 src/backend/commands/tablesample.c
 create mode 100644 src/test/modules/tablesample/.gitignore
 create mode 100644 src/test/modules/tablesample/Makefile
 create mode 100644 src/test/modules/tablesample/expected/tablesample.out
 create mode 100644 src/test/modules/tablesample/sql/tablesample.sql
 create mode 100644 src/test/modules/tablesample/tsm_test--1.0.sql
 create mode 100644 src/test/modules/tablesample/tsm_test.c
 create mode 100644 src/test/modules/tablesample/tsm_test.control

diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index 7aa3128..2fad084 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -78,6 +78,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY createServer       SYSTEM "create_server.sgml">
 <!ENTITY createTable        SYSTEM "create_table.sgml">
 <!ENTITY createTableAs      SYSTEM "create_table_as.sgml">
+<!ENTITY createTablesampleMethod SYSTEM "create_tablesamplemethod.sgml">
 <!ENTITY createTableSpace   SYSTEM "create_tablespace.sgml">
 <!ENTITY createTrigger      SYSTEM "create_trigger.sgml">
 <!ENTITY createTSConfig     SYSTEM "create_tsconfig.sgml">
@@ -119,6 +120,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY dropSequence       SYSTEM "drop_sequence.sgml">
 <!ENTITY dropServer         SYSTEM "drop_server.sgml">
 <!ENTITY dropTable          SYSTEM "drop_table.sgml">
+<!ENTITY dropTablesampleMethod SYSTEM "drop_tablesamplemethod.sgml">
 <!ENTITY dropTableSpace     SYSTEM "drop_tablespace.sgml">
 <!ENTITY dropTrigger        SYSTEM "drop_trigger.sgml">
 <!ENTITY dropTSConfig       SYSTEM "drop_tsconfig.sgml">
diff --git a/doc/src/sgml/ref/create_tablesamplemethod.sgml b/doc/src/sgml/ref/create_tablesamplemethod.sgml
new file mode 100644
index 0000000..62a8ce4
--- /dev/null
+++ b/doc/src/sgml/ref/create_tablesamplemethod.sgml
@@ -0,0 +1,173 @@
+<!--
+doc/src/sgml/ref/create_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-CREATETABLESAMPLEMETHOD">
+ <indexterm zone="sql-createtablesamplemethod">
+  <primary>CREATE TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE TABLESAMPLE METHOD</refname>
+  <refpurpose>define custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE TABLESAMPLE METHOD <replaceable class="parameter">name</replaceable> (
+    INIT = <replaceable class="parameter">init_function</replaceable> ,
+    NEXTBLOCK = <replaceable class="parameter">nextblock_function</replaceable> ,
+    NEXTTUPLE = <replaceable class="parameter">nexttuple_function</replaceable> ,
+    END = <replaceable class="parameter">end_function</replaceable> ,
+    RESET = <replaceable class="parameter">reset_function</replaceable> ,
+    COST = <replaceable class="parameter">cost_function</replaceable>
+    [ , EXAMINETUPLE = <replaceable class="parameter">examinetuple_function</replaceable> ]
+    [ , SEQSCAN = <replaceable class="parameter">seqscan</replaceable> ]
+)
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE TABLESAMPLE METHOD</command> creates a tablesample method.
+   A tablesample method provides alrorithm for reading sample part of a table
+   when used in <command>TABLESAMPLE</> clause of a <command>SELECT</>
+   statement.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the tablesample method to be created. This name must be
+      unique within the database.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">init_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the init function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nextblock_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-block function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nexttuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-tuple function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">end_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the end function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">reset_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the reset function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">cost_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the costing function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">examinetuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the function for inspecting the tuple contents in order
+      to make decision if it should be returned or not. This parameter
+      is optional.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">seqscan</replaceable></term>
+    <listitem>
+     <para>
+      True if the sampling method will do sequential scan of the whole table.
+      Used for cost estimation and syncscan. The default value if not specified
+      is False.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+  <para>
+   The function names can be schema-qualified if necessary.  Argument types
+   are not given, since the argument list for each type of function is
+   predetermined.  All functions are required.
+  </para>
+
+  <para>
+   The arguments can appear in any order, not only the one shown above.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>CREATE TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-droptablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/ref/drop_tablesamplemethod.sgml b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
new file mode 100644
index 0000000..dffd2ec
--- /dev/null
+++ b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
@@ -0,0 +1,87 @@
+<!--
+doc/src/sgml/ref/drop_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-DROPTABLESAMPLEMETHOD">
+ <indexterm zone="sql-droptablesamplemethod">
+  <primary>DROP TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DROP TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP TABLESAMPLE METHOD</refname>
+  <refpurpose>remove a custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP TABLESAMPLE METHOD [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>DROP TABLESAMPLE METHOD</command> drop an existing tablesample
+   method.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the tablesample method does not exist.
+      A notice is issued in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of an existing tablesample method to be removed.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>DROP TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createtablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index 10c9a6d..2c09a3c 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -106,6 +106,7 @@
    &createServer;
    &createTable;
    &createTableAs;
+   &createTablesampleMethod;
    &createTableSpace;
    &createTSConfig;
    &createTSDictionary;
@@ -147,6 +148,7 @@
    &dropSequence;
    &dropServer;
    &dropTable;
+   &dropTablesampleMethod;
    &dropTableSpace;
    &dropTSConfig;
    &dropTSDictionary;
diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index bacb242..6acb5b3 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -46,6 +46,7 @@
 #include "catalog/pg_policy.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -157,7 +158,8 @@ static const Oid object_classes[MAX_OCLASS] = {
 	DefaultAclRelationId,		/* OCLASS_DEFACL */
 	ExtensionRelationId,		/* OCLASS_EXTENSION */
 	EventTriggerRelationId,		/* OCLASS_EVENT_TRIGGER */
-	PolicyRelationId			/* OCLASS_POLICY */
+	PolicyRelationId,			/* OCLASS_POLICY */
+	TableSampleMethodRelationId			/* OCLASS_TABLESAMPLEMETHOD */
 };
 
 
@@ -1265,6 +1267,10 @@ doDeletion(const ObjectAddress *object, int flags)
 			RemovePolicyById(object->objectId);
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			RemoveTablesampleMethodById(object->objectId);
+			break;
+
 		default:
 			elog(ERROR, "unrecognized object class: %u",
 				 object->classId);
@@ -1794,6 +1800,10 @@ find_expr_references_walker(Node *node,
 				case RTE_RELATION:
 					add_object_address(OCLASS_CLASS, rte->relid, 0,
 									   context->addrs);
+					if (rte->tablesample)
+						add_object_address(OCLASS_TABLESAMPLEMETHOD,
+										   rte->tablesample->tsmid, 0,
+										   context->addrs);
 					break;
 				default:
 					break;
@@ -2373,6 +2383,9 @@ getObjectClass(const ObjectAddress *object)
 
 		case PolicyRelationId:
 			return OCLASS_POLICY;
+
+		case TableSampleMethodRelationId:
+			return OCLASS_TABLESAMPLEMETHOD;
 	}
 
 	/* shouldn't get here */
diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index d899dd7..6d8d129 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -44,6 +44,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_policy.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -429,7 +430,19 @@ static const ObjectPropertyType ObjectProperty[] =
 		Anum_pg_type_typacl,
 		ACL_KIND_TYPE,
 		true
-	}
+	},
+	{
+		TableSampleMethodRelationId,
+		TableSampleMethodOidIndexId,
+		TABLESAMPLEMETHODOID,
+		TABLESAMPLEMETHODNAME,
+		Anum_pg_tablesample_method_tsmname,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		-1,
+		true
+	},
 };
 
 /*
@@ -528,7 +541,9 @@ ObjectTypeMap[] =
 	/* OCLASS_EVENT_TRIGGER */
 	{ "event trigger", OBJECT_EVENT_TRIGGER },
 	/* OCLASS_POLICY */
-	{ "policy", OBJECT_POLICY }
+	{ "policy", OBJECT_POLICY },
+	/* OCLASS_TABLESAMPLEMETHOD */
+	{ "tablesample method", OBJECT_TABLESAMPLEMETHOD }
 };
 
 
@@ -670,6 +685,7 @@ get_object_address(ObjectType objtype, List *objname, List *objargs,
 			case OBJECT_FDW:
 			case OBJECT_FOREIGN_SERVER:
 			case OBJECT_EVENT_TRIGGER:
+			case OBJECT_TABLESAMPLEMETHOD:
 				address = get_object_address_unqualified(objtype,
 														 objname, missing_ok);
 				break;
@@ -896,6 +912,9 @@ get_object_address_unqualified(ObjectType objtype,
 			case OBJECT_EVENT_TRIGGER:
 				msg = gettext_noop("event trigger name cannot be qualified");
 				break;
+			case OBJECT_TABLESAMPLEMETHOD:
+				msg = gettext_noop("tablesample method name cannot be qualified");
+				break;
 			default:
 				elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 				msg = NULL;		/* placate compiler */
@@ -956,6 +975,11 @@ get_object_address_unqualified(ObjectType objtype,
 			address.objectId = get_event_trigger_oid(name, missing_ok);
 			address.objectSubId = 0;
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			address.classId = TableSampleMethodRelationId;
+			address.objectId = get_tablesample_method_oid(name, missing_ok);
+			address.objectSubId = 0;
+			break;
 		default:
 			elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 			/* placate compiler, which doesn't know elog won't return */
@@ -1720,6 +1744,7 @@ check_object_ownership(Oid roleid, ObjectType objtype, ObjectAddress address,
 			break;
 		case OBJECT_TSPARSER:
 		case OBJECT_TSTEMPLATE:
+		case OBJECT_TABLESAMPLEMETHOD:
 			/* We treat these object types as being owned by superusers */
 			if (!superuser_arg(roleid))
 				ereport(ERROR,
@@ -2654,6 +2679,21 @@ getObjectDescription(const ObjectAddress *object)
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				appendStringInfo(&buffer, _("tablesample method %s"),
+					 NameStr(((Form_pg_tablesample_method) GETSTRUCT(tup))->tsmname));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
@@ -3131,6 +3171,10 @@ getObjectTypeDescription(const ObjectAddress *object)
 			appendStringInfoString(&buffer, "policy");
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			appendStringInfoString(&buffer, "tablesample method");
+			break;
+
 		default:
 			appendStringInfo(&buffer, "unrecognized %u", object->classId);
 			break;
@@ -4029,6 +4073,23 @@ getObjectIdentityParts(const ObjectAddress *object,
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+				Form_pg_tablesample_method tsmForm;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				tsmForm = (Form_pg_tablesample_method) GETSTRUCT(tup);
+				appendStringInfoString(&buffer,
+							   quote_identifier(NameStr(tsmForm->tsmname)));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index b1ac704..04fcd8c 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -18,8 +18,8 @@ OBJS = aggregatecmds.o alter.o analyze.o async.o cluster.o comment.o  \
 	event_trigger.o explain.o extension.o foreigncmds.o functioncmds.o \
 	indexcmds.o lockcmds.o matview.o operatorcmds.o opclasscmds.o \
 	policy.o portalcmds.o prepare.o proclang.o \
-	schemacmds.o seclabel.o sequence.o tablecmds.o tablespace.o trigger.o \
-	tsearchcmds.o typecmds.o user.o vacuum.o vacuumlazy.o \
-	variable.o view.o
+	schemacmds.o seclabel.o sequence.o tablecmds.o tablesample.o \
+	tablespace.o trigger.o tsearchcmds.o typecmds.o user.o vacuum.o \
+	vacuumlazy.o variable.o view.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/commands/dropcmds.c b/src/backend/commands/dropcmds.c
index e5185ba..04d29a2 100644
--- a/src/backend/commands/dropcmds.c
+++ b/src/backend/commands/dropcmds.c
@@ -421,6 +421,10 @@ does_not_exist_skipping(ObjectType objtype, List *objname, List *objargs)
 				args = strVal(linitial(objargs));
 			}
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			msg = gettext_noop("tablesample method \"%s\" does not exist, skipping");
+			name = NameListToString(objname);
+			break;
 		default:
 			elog(ERROR, "unexpected object type (%d)", (int) objtype);
 			break;
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index a33a5ad..f20e9f7 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -97,6 +97,7 @@ static event_trigger_support_data event_trigger_support[] = {
 	{"SEQUENCE", true},
 	{"SERVER", true},
 	{"TABLE", true},
+	{"TABLESAMPLE METHOD", true},
 	{"TABLESPACE", false},
 	{"TRIGGER", true},
 	{"TEXT SEARCH CONFIGURATION", true},
@@ -1078,6 +1079,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_SEQUENCE:
 		case OBJECT_TABCONSTRAINT:
 		case OBJECT_TABLE:
+		case OBJECT_TABLESAMPLEMETHOD:
 		case OBJECT_TRIGGER:
 		case OBJECT_TSCONFIGURATION:
 		case OBJECT_TSDICTIONARY:
@@ -1134,6 +1136,7 @@ EventTriggerSupportsObjectClass(ObjectClass objclass)
 		case OCLASS_DEFACL:
 		case OCLASS_EXTENSION:
 		case OCLASS_POLICY:
+		case OCLASS_TABLESAMPLEMETHOD:
 			return true;
 
 		case MAX_OCLASS:
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index b2993b8..1e408bc 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8062,6 +8062,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 			case OCLASS_USER_MAPPING:
 			case OCLASS_DEFACL:
 			case OCLASS_EXTENSION:
+			case OCLASS_TABLESAMPLEMETHOD:
 
 				/*
 				 * We don't expect any of these sorts of objects to depend on
diff --git a/src/backend/commands/tablesample.c b/src/backend/commands/tablesample.c
new file mode 100644
index 0000000..ed8102d
--- /dev/null
+++ b/src/backend/commands/tablesample.c
@@ -0,0 +1,422 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *	  Commands to manipulate tablesample methods
+ *
+ * Table sampling methods provide algorithms for doing sample scan over
+ * the table.
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/tablesample.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "access/heapam.h"
+#include "access/htup_details.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/objectaccess.h"
+#include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
+#include "catalog/pg_type.h"
+#include "commands/defrem.h"
+#include "miscadmin.h"
+#include "parser/parse_func.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+
+static Datum
+get_tablesample_method_func(DefElem *defel, int attnum)
+{
+	List	   *funcName = defGetQualifiedName(defel);
+	/* Big enough size for our needs. */
+	Oid		   *typeId = palloc0(7 * sizeof(Oid));
+	Oid			retTypeId;
+	int			nargs;
+	Oid			procOid = InvalidOid;
+	FuncCandidateList clist;
+
+	switch (attnum)
+	{
+		case Anum_pg_tablesample_method_tsminit:
+			/*
+			 * tsminit needs special handling because it is defined as function
+			 * with 3 or more arguments and only first two arguments must have
+			 * specific type, the rest is up to the tablesample method creator.
+			 */
+			{
+				nargs = 2;
+				typeId[0] = INTERNALOID;
+				typeId[1] = INT4OID;
+				retTypeId = VOIDOID;
+
+				clist = FuncnameGetCandidates(funcName, -1, NIL, false, false, false);
+
+				while (clist)
+				{
+					if (clist->nargs >= 3 &&
+						memcmp(typeId, clist->args, nargs * sizeof(Oid)) == 0)
+					{
+						procOid = clist->oid;
+						/* Save real function signature for future errors. */
+						nargs = clist->nargs;
+						pfree(typeId);
+						typeId = clist->args;
+						break;
+					}
+					clist = clist->next;
+				}
+
+				if (!OidIsValid(procOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_UNDEFINED_FUNCTION),
+							 errmsg("function \"%s\" does not exist or does not have valid signature",
+									NameListToString(funcName)),
+							 errhint("The tamplesample method init function "
+									 "must have at least 3 input parameters "
+									 "with first one of type INTERNAL and second of type INTEGER.")));
+			}
+			break;
+
+		case Anum_pg_tablesample_method_tsmnextblock:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = INT4OID;
+			break;
+		case Anum_pg_tablesample_method_tsmnexttuple:
+			nargs = 3;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INT2OID;
+			retTypeId = INT2OID;
+			break;
+		case Anum_pg_tablesample_method_tsmexaminetuple:
+			nargs = 4;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = BOOLOID;
+			retTypeId = BOOLOID;
+			break;
+		case Anum_pg_tablesample_method_tsmend:
+		case Anum_pg_tablesample_method_tsmreset:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		case Anum_pg_tablesample_method_tsmcost:
+			nargs = 7;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INTERNALOID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = INTERNALOID;
+			typeId[4] = INTERNALOID;
+			typeId[5] = INTERNALOID;
+			typeId[6] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		default:
+			/* should not be here */
+			elog(ERROR, "unrecognized attribute for tablesample method: %d",
+				 attnum);
+			nargs = 0;			/* keep compiler quiet */
+	}
+
+	if (!OidIsValid(procOid))
+		procOid = LookupFuncName(funcName, nargs, typeId, false);
+	if (get_func_rettype(procOid) != retTypeId)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("function %s should return type %s",
+						func_signature_string(funcName, nargs, NIL, typeId),
+						format_type_be(retTypeId))));
+
+	return ObjectIdGetDatum(procOid);
+}
+
+/*
+ * make pg_depend entries for a new pg_tablesample_method entry
+ */
+static void
+makeTablesampleMethodDeps(HeapTuple tuple)
+{
+	Form_pg_tablesample_method tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	ObjectAddress	myself,
+					referenced;
+
+	myself.classId = TableSampleMethodRelationId;
+	myself.objectId = HeapTupleGetOid(tuple);
+	myself.objectSubId = 0;
+
+	/* dependency on extension */
+	recordDependencyOnCurrentExtension(&myself, false);
+
+	/* dependencies on functions */
+	referenced.classId = ProcedureRelationId;
+	referenced.objectSubId = 0;
+
+	referenced.objectId = tsm->tsminit;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnextblock;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnexttuple;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	if (OidIsValid(tsm->tsmexaminetuple))
+	{
+		referenced.objectId = tsm->tsmexaminetuple;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
+
+	referenced.objectId = tsm->tsmend;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmreset;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmcost;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+}
+
+/*
+ * Create a table sampling method
+ *
+ * Only superusers can create a table sampling methods.
+ */
+Oid
+DefineTablesampleMethod(List *names, List *parameters)
+{
+	char	   *tsmname = strVal(linitial(names));
+	Oid			tsmoid;
+	ListCell   *pl;
+	Relation	rel;
+	Datum		values[Natts_pg_tablesample_method];
+	bool		nulls[Natts_pg_tablesample_method];
+	HeapTuple	tuple;
+
+	/* Must be super user. */
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied to create tablesample method \"%s\"",
+						tsmname),
+				 errhint("Must be superuser to create a tablesample method.")));
+
+	/* Must not already exist. */
+	tsmoid = get_tablesample_method_oid(tsmname, true);
+	if (OidIsValid(tsmoid))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" already exists",
+						tsmname)));
+
+	/* Initialize the values. */
+	memset(values, 0, sizeof(values));
+	memset(nulls, false, sizeof(nulls));
+
+	values[Anum_pg_tablesample_method_tsmname - 1] =
+		DirectFunctionCall1(namein, CStringGetDatum(tsmname));
+
+	/*
+	 * loop over the definition list and extract the information we need.
+	 */
+	foreach(pl, parameters)
+	{
+		DefElem    *defel = (DefElem *) lfirst(pl);
+
+		if (pg_strcasecmp(defel->defname, "seqscan") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmseqscan - 1] =
+				BoolGetDatum(defGetBoolean(defel));
+		}
+		else if (pg_strcasecmp(defel->defname, "init") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsminit - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsminit);
+		}
+		else if (pg_strcasecmp(defel->defname, "nextblock") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnextblock - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnextblock);
+		}
+		else if (pg_strcasecmp(defel->defname, "nexttuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnexttuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnexttuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "examinetuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmexaminetuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmexaminetuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "end") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmend - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmend);
+		}
+		else if (pg_strcasecmp(defel->defname, "reset") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmreset - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmreset);
+		}
+		else if (pg_strcasecmp(defel->defname, "cost") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmcost - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmcost);
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("tablesample method parameter \"%s\" not recognized",
+						defel->defname)));
+	}
+
+	/*
+	 * Validation.
+	 */
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsminit - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method init function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnextblock - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nextblock function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnexttuple - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nexttuple function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmend - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method end function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmreset - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method reset function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmcost - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method cost function is required")));
+
+	/*
+	 * Insert tuple into pg_tablesample_method.
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = heap_form_tuple(rel->rd_att, values, nulls);
+
+	tsmoid = simple_heap_insert(rel, tuple);
+
+	CatalogUpdateIndexes(rel, tuple);
+
+	makeTablesampleMethodDeps(tuple);
+
+	heap_freetuple(tuple);
+
+	/* Post creation hook for new tablesample method */
+	InvokeObjectPostCreateHook(TableSampleMethodRelationId, tsmoid, 0);
+
+	heap_close(rel, RowExclusiveLock);
+
+	return tsmoid;
+}
+
+/*
+ * Drop a tablesample method.
+ */
+void
+RemoveTablesampleMethodById(Oid tsmoid)
+{
+	Relation	rel;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+
+	/*
+	 * Find the target tuple
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmoid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for tablesample method %u",
+			 tsmoid);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	/* Can't drop builtin tablesample methods. */
+	if (tsmoid == TABLESAMPLE_METHOD_SYSTEM_OID ||
+		tsmoid == TABLESAMPLE_METHOD_BERNOULLI_OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied for tablesample method %s",
+						NameStr(tsm->tsmname))));
+
+	/*
+	 * Remove the pg_tablespace tuple (this will roll back if we fail below)
+	 */
+	simple_heap_delete(rel, &tuple->t_self);
+
+	ReleaseSysCache(tuple);
+
+	heap_close(rel, RowExclusiveLock);
+}
+
+/*
+ * get_tablesample_method_oid - given a tablesample method name,
+ * look up the OID
+ *
+ * If missing_ok is false, throw an error if tablesample method name not found.
+ * If true, just return InvalidOid.
+ */
+Oid
+get_tablesample_method_oid(const char *tsmname, bool missing_ok)
+{
+	Oid			result;
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(tsmname));
+	if (HeapTupleIsValid(tuple))
+	{
+		result = HeapTupleGetOid(tuple);
+		ReleaseSysCache(tuple);
+	}
+	else
+		result = InvalidOid;
+
+	if (!OidIsValid(result) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						tsmname)));
+
+	return result;
+}
+
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index ac5e095..4578b5e 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -586,7 +586,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATERIALIZED MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
+	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P
+	MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEXT NO NONE
 	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
@@ -5094,6 +5095,15 @@ DefineStmt:
 					n->definition = list_make1(makeDefElem("from", (Node *) $5));
 					$$ = (Node *)n;
 				}
+			| CREATE TABLESAMPLE METHOD name definition
+				{
+					DefineStmt *n = makeNode(DefineStmt);
+					n->kind = OBJECT_TABLESAMPLEMETHOD;
+					n->args = NIL;
+					n->defnames = list_make1(makeString($4));
+					n->definition = $5;
+					$$ = (Node *)n;
+				}
 		;
 
 definition: '(' def_list ')'						{ $$ = $2; }
@@ -5552,6 +5562,7 @@ drop_type:	TABLE									{ $$ = OBJECT_TABLE; }
 			| TEXT_P SEARCH DICTIONARY				{ $$ = OBJECT_TSDICTIONARY; }
 			| TEXT_P SEARCH TEMPLATE				{ $$ = OBJECT_TSTEMPLATE; }
 			| TEXT_P SEARCH CONFIGURATION			{ $$ = OBJECT_TSCONFIGURATION; }
+			| TABLESAMPLE METHOD					{ $$ = OBJECT_TABLESAMPLEMETHOD; }
 		;
 
 any_name_list:
@@ -13313,6 +13324,7 @@ unreserved_keyword:
 			| MATCH
 			| MATERIALIZED
 			| MAXVALUE
+			| METHOD
 			| MINUTE_P
 			| MINVALUE
 			| MODE
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 3533cfa..532256d 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -23,6 +23,7 @@
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/toasting.h"
 #include "commands/alter.h"
 #include "commands/async.h"
@@ -1106,6 +1107,11 @@ ProcessUtilitySlow(Node *parsetree,
 							Assert(stmt->args == NIL);
 							DefineCollation(stmt->defnames, stmt->definition);
 							break;
+						case OBJECT_TABLESAMPLEMETHOD:
+							Assert(stmt->args == NIL);
+							Assert(list_length(stmt->defnames) == 1);
+							DefineTablesampleMethod(stmt->defnames, stmt->definition);
+							break;
 						default:
 							elog(ERROR, "unrecognized define stmt type: %d",
 								 (int) stmt->kind);
@@ -1960,6 +1966,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_POLICY:
 					tag = "DROP POLICY";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "DROP TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
@@ -2056,6 +2065,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_COLLATION:
 					tag = "CREATE COLLATION";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "CREATE TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
diff --git a/src/bin/pg_dump/common.c b/src/bin/pg_dump/common.c
index 1a0a587..8a64e4b 100644
--- a/src/bin/pg_dump/common.c
+++ b/src/bin/pg_dump/common.c
@@ -103,6 +103,7 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 	int			numForeignServers;
 	int			numDefaultACLs;
 	int			numEventTriggers;
+	int			numTSMs;
 
 	if (g_verbose)
 		write_msg(NULL, "reading schemas\n");
@@ -251,6 +252,10 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 		write_msg(NULL, "reading policies\n");
 	getPolicies(fout, tblinfo, numTables);
 
+	if (g_verbose)
+		write_msg(NULL, "reading tablesample methods\n");
+	getTableSampleMethods(fout, &numTSMs);
+
 	*numTablesPtr = numTables;
 	return tblinfo;
 }
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 2b53c72..0af75f4 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -182,6 +182,7 @@ static void dumpSequenceData(Archive *fout, TableDataInfo *tdinfo);
 static void dumpIndex(Archive *fout, DumpOptions *dopt, IndxInfo *indxinfo);
 static void dumpConstraint(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
 static void dumpTableConstraintComment(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
+static void dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tbinfo);
 static void dumpTSParser(Archive *fout, DumpOptions *dopt, TSParserInfo *prsinfo);
 static void dumpTSDictionary(Archive *fout, DumpOptions *dopt, TSDictInfo *dictinfo);
 static void dumpTSTemplate(Archive *fout, DumpOptions *dopt, TSTemplateInfo *tmplinfo);
@@ -7177,6 +7178,75 @@ getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tblinfo, int numTable
 }
 
 /*
+ * getTableSampleMethods:
+ *	  read all tablesample methods in the system catalogs and return them
+ *	  in the TSMInfo* structure
+ *
+ *	numTSMs is set to the number of tablesample methods read in
+ */
+TSMInfo *
+getTableSampleMethods(Archive *fout, int *numTSMs)
+{
+	PGresult   *res;
+	int			ntups;
+	int			i;
+	PQExpBuffer query;
+	TSMInfo	   *tsminfo;
+	int			i_tableoid,
+				i_oid,
+				i_tsmname,
+				i_tsmseqscan;
+
+	/* Before 9.5, there were no tablesample methods */
+	if (fout->remoteVersion < 90500)
+	{
+		*numTSMs = 0;
+		return NULL;
+	}
+
+	query = createPQExpBuffer();
+
+	appendPQExpBuffer(query,
+					  "SELECT tableoid, oid, tsmname, tsmseqscan "
+					  "FROM pg_catalog.pg_tablesample_method "
+					  "WHERE oid >= '%u'::pg_catalog.oid",
+					  FirstNormalObjectId);
+
+	res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
+
+	ntups = PQntuples(res);
+	*numTSMs = ntups;
+
+	tsminfo = (TSMInfo *) pg_malloc(ntups * sizeof(TSMInfo));
+
+	i_tableoid = PQfnumber(res, "tableoid");
+	i_oid = PQfnumber(res, "oid");
+	i_tsmname = PQfnumber(res, "tsmname");
+	i_tsmseqscan = PQfnumber(res, "tsmseqscan");
+
+	for (i = 0; i < ntups; i++)
+	{
+		tsminfo[i].dobj.objType = DO_TABLESAMPLE_METHOD;
+		tsminfo[i].dobj.catId.tableoid = atooid(PQgetvalue(res, i, i_tableoid));
+		tsminfo[i].dobj.catId.oid = atooid(PQgetvalue(res, i, i_oid));
+		AssignDumpId(&tsminfo[i].dobj);
+		tsminfo[i].dobj.name = pg_strdup(PQgetvalue(res, i, i_tsmname));
+		tsminfo[i].dobj.namespace = NULL;
+		tsminfo[i].tsmseqscan = PQgetvalue(res, i, i_tsmseqscan)[0] == 't';
+
+		/* Decide whether we want to dump it */
+		selectDumpableObject(&(tsminfo[i].dobj));
+	}
+
+	PQclear(res);
+
+	destroyPQExpBuffer(query);
+
+	return tsminfo;
+}
+
+
+/*
  * Test whether a column should be printed as part of table's CREATE TABLE.
  * Column number is zero-based.
  *
@@ -8269,6 +8339,9 @@ dumpDumpableObject(Archive *fout, DumpOptions *dopt, DumpableObject *dobj)
 		case DO_POLICY:
 			dumpPolicy(fout, dopt, (PolicyInfo *) dobj);
 			break;
+		case DO_TABLESAMPLE_METHOD:
+			dumpTableSampleMethod(fout, dopt, (TSMInfo *) dobj);
+			break;
 		case DO_PRE_DATA_BOUNDARY:
 		case DO_POST_DATA_BOUNDARY:
 			/* never dumped, nothing to do */
@@ -12269,6 +12342,103 @@ dumpAgg(Archive *fout, DumpOptions *dopt, AggInfo *agginfo)
 }
 
 /*
+ * dumpTableSampleMethod
+ *	  write the declaration of one user-defined tablesample method
+ */
+static void
+dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tsminfo)
+{
+	PGresult   *res;
+	PQExpBuffer q;
+	PQExpBuffer delq;
+	PQExpBuffer labelq;
+	PQExpBuffer query;
+	char	   *tsminit;
+	char	   *tsmnextblock;
+	char	   *tsmnexttuple;
+	char	   *tsmexaminetuple;
+	char	   *tsmend;
+	char	   *tsmreset;
+	char	   *tsmcost;
+
+	/* Skip if not to be dumped */
+	if (!tsminfo->dobj.dump || dopt->dataOnly)
+		return;
+
+	q = createPQExpBuffer();
+	delq = createPQExpBuffer();
+	labelq = createPQExpBuffer();
+	query = createPQExpBuffer();
+
+	/* Make sure we are in proper schema */
+	selectSourceSchema(fout, "pg_catalog");
+
+	appendPQExpBuffer(query, "SELECT tsminit, tsmnextblock, "
+							 "tsmnexttuple, tsmexaminetuple, "
+							 "tsmend, tsmreset, tsmcost "
+							 "FROM pg_catalog.pg_tablesample_method "
+							 "WHERE oid = '%u'::pg_catalog.oid",
+							 tsminfo->dobj.catId.oid);
+
+	res = ExecuteSqlQueryForSingleRow(fout, query->data);
+
+	tsminit = PQgetvalue(res, 0, PQfnumber(res, "tsminit"));
+	tsmnexttuple = PQgetvalue(res, 0, PQfnumber(res, "tsmnexttuple"));
+	tsmnextblock = PQgetvalue(res, 0, PQfnumber(res, "tsmnextblock"));
+	tsmexaminetuple = PQgetvalue(res, 0, PQfnumber(res, "tsmexaminetuple"));
+	tsmend = PQgetvalue(res, 0, PQfnumber(res, "tsmend"));
+	tsmreset = PQgetvalue(res, 0, PQfnumber(res, "tsmreset"));
+	 tsmcost = PQgetvalue(res, 0, PQfnumber(res, "tsmcost"));
+
+	appendPQExpBuffer(q, "CREATE TABLESAMPLE METHOD %s (\n",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(q, "    INIT = %s,\n", tsminit);
+	appendPQExpBuffer(q, "    NEXTTUPLE = %s,\n", tsmnexttuple);
+	appendPQExpBuffer(q, "    NEXTBLOCK = %s,\n", tsmnextblock);
+	appendPQExpBuffer(q, "    END = %s,\n", tsmend);
+	appendPQExpBuffer(q, "    RESET = %s,\n", tsmreset);
+	appendPQExpBuffer(q, "    COST = %s", tsmcost);
+
+	if (strcmp(tsmexaminetuple, "-") != 0)
+		appendPQExpBuffer(q, ",\n    EXAMINETUPLE = %s", tsmexaminetuple);
+
+	if (tsminfo->tsmseqscan)
+		appendPQExpBufferStr(q, ",\n    SEQSCAN = true");
+
+	appendPQExpBufferStr(q, "\n);");
+
+	appendPQExpBuffer(delq, "DROP TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(labelq, "TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	if (dopt->binary_upgrade)
+		binary_upgrade_extension_member(q, &tsminfo->dobj, labelq->data);
+
+	ArchiveEntry(fout, tsminfo->dobj.catId, tsminfo->dobj.dumpId,
+				 tsminfo->dobj.name,
+				 NULL,
+				 NULL,
+				 "",
+				 false, "TABLESAMPLE METHOD", SECTION_PRE_DATA,
+				 q->data, delq->data, NULL,
+				 NULL, 0,
+				 NULL, NULL);
+
+	/* Dump Parser Comments */
+	dumpComment(fout, dopt, labelq->data,
+				NULL, "",
+				tsminfo->dobj.catId, 0, tsminfo->dobj.dumpId);
+
+	PQclear(res);
+	destroyPQExpBuffer(q);
+	destroyPQExpBuffer(delq);
+	destroyPQExpBuffer(labelq);
+}
+
+/*
  * dumpTSParser
  *	  write out a single text search parser
  */
@@ -15622,6 +15792,7 @@ addBoundaryDependencies(DumpableObject **dobjs, int numObjs,
 			case DO_FDW:
 			case DO_FOREIGN_SERVER:
 			case DO_BLOB:
+			case DO_TABLESAMPLE_METHOD:
 				/* Pre-data objects: must come before the pre-data boundary */
 				addObjectDependency(preDataBound, dobj->dumpId);
 				break;
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index f42c42d..645c07c 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -76,7 +76,8 @@ typedef enum
 	DO_POST_DATA_BOUNDARY,
 	DO_EVENT_TRIGGER,
 	DO_REFRESH_MATVIEW,
-	DO_POLICY
+	DO_POLICY,
+	DO_TABLESAMPLE_METHOD
 } DumpableObjectType;
 
 typedef struct _dumpableObject
@@ -384,6 +385,12 @@ typedef struct _inhInfo
 	Oid			inhparent;		/* OID of its parent */
 } InhInfo;
 
+typedef struct _tsmInfo
+{
+	DumpableObject dobj;
+	bool		tsmseqscan;
+} TSMInfo;
+
 typedef struct _prsInfo
 {
 	DumpableObject dobj;
@@ -537,6 +544,7 @@ extern ProcLangInfo *getProcLangs(Archive *fout, int *numProcLangs);
 extern CastInfo *getCasts(Archive *fout, DumpOptions *dopt, int *numCasts);
 extern void getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tbinfo, int numTables);
 extern bool shouldPrintColumn(DumpOptions *dopt, TableInfo *tbinfo, int colno);
+extern TSMInfo *getTableSampleMethods(Archive *fout, int *numTSMs);
 extern TSParserInfo *getTSParsers(Archive *fout, int *numTSParsers);
 extern TSDictInfo *getTSDictionaries(Archive *fout, int *numTSDicts);
 extern TSTemplateInfo *getTSTemplates(Archive *fout, int *numTSTemplates);
diff --git a/src/bin/pg_dump/pg_dump_sort.c b/src/bin/pg_dump/pg_dump_sort.c
index 4b9bba0..cb009ce 100644
--- a/src/bin/pg_dump/pg_dump_sort.c
+++ b/src/bin/pg_dump/pg_dump_sort.c
@@ -73,7 +73,8 @@ static const int oldObjectTypePriority[] =
 	13,							/* DO_POST_DATA_BOUNDARY */
 	20,							/* DO_EVENT_TRIGGER */
 	15,							/* DO_REFRESH_MATVIEW */
-	21							/* DO_POLICY */
+	21,							/* DO_POLICY */
+	5							/* DO_TABLESAMPLE_METHOD */
 };
 
 /*
@@ -122,7 +123,8 @@ static const int newObjectTypePriority[] =
 	25,							/* DO_POST_DATA_BOUNDARY */
 	32,							/* DO_EVENT_TRIGGER */
 	33,							/* DO_REFRESH_MATVIEW */
-	34							/* DO_POLICY */
+	34,							/* DO_POLICY */
+	17							/* DO_TABLESAMPLE_METHOD */
 };
 
 static DumpId preDataBoundId;
@@ -1443,6 +1445,11 @@ describeDumpableObject(DumpableObject *obj, char *buf, int bufsize)
 					 "POLICY (ID %d OID %u)",
 					 obj->dumpId, obj->catId.oid);
 			return;
+		case DO_TABLESAMPLE_METHOD:
+			snprintf(buf, bufsize,
+					 "TABLESAMPLE METHOD %s  (ID %d OID %u)",
+					 obj->name, obj->dumpId, obj->catId.oid);
+			return;
 		case DO_PRE_DATA_BOUNDARY:
 			snprintf(buf, bufsize,
 					 "PRE-DATA BOUNDARY  (ID %d)",
diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 6481ac8..30653f8 100644
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -148,6 +148,7 @@ typedef enum ObjectClass
 	OCLASS_EXTENSION,			/* pg_extension */
 	OCLASS_EVENT_TRIGGER,		/* pg_event_trigger */
 	OCLASS_POLICY,				/* pg_policy */
+	OCLASS_TABLESAMPLEMETHOD,	/* pg_tablesample_method */
 	MAX_OCLASS					/* MUST BE LAST */
 } ObjectClass;
 
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
index fd76f77..6a55669 100644
--- a/src/include/catalog/pg_tablesample_method.h
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -69,7 +69,18 @@ typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
 
 DATA(insert OID = 3283 ( system false tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
 DESCR("SYSTEM table sampling method");
+#define TABLESAMPLE_METHOD_SYSTEM_OID 3283
 DATA(insert OID = 3284 ( bernoulli true tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
 DESCR("BERNOULLI table sampling method");
+#define TABLESAMPLE_METHOD_BERNOULLI_OID 3284
+
+/* ----------------
+ *		functions for manipulation of pg_tablesample_method
+ * ----------------
+ */
+
+extern Oid DefineTablesampleMethod(List *names, List *parameters);
+extern void RemoveTablesampleMethodById(Oid tsmoid);
+extern Oid get_tablesample_method_oid(const char *tsmname, bool missing_ok);
 
 #endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 2f4df1d..bc1fef2 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1269,6 +1269,7 @@ typedef enum ObjectType
 	OBJECT_SEQUENCE,
 	OBJECT_TABCONSTRAINT,
 	OBJECT_TABLE,
+	OBJECT_TABLESAMPLEMETHOD,
 	OBJECT_TABLESPACE,
 	OBJECT_TRIGGER,
 	OBJECT_TSCONFIGURATION,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 6ff7b44..c3269c0 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -236,6 +236,7 @@ PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("mode", MODE, UNRESERVED_KEYWORD)
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 93d93af..37ea524 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -9,7 +9,8 @@ SUBDIRS = \
 		  worker_spi \
 		  dummy_seclabel \
 		  test_shm_mq \
-		  test_parser
+		  test_parser \
+		  tablesample
 
 all: submake-errcodes
 
diff --git a/src/test/modules/tablesample/.gitignore b/src/test/modules/tablesample/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/src/test/modules/tablesample/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/src/test/modules/tablesample/Makefile b/src/test/modules/tablesample/Makefile
new file mode 100644
index 0000000..469b004
--- /dev/null
+++ b/src/test/modules/tablesample/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/tsm_test/Makefile
+
+MODULE_big = tsm_test
+OBJS = tsm_test.o $(WIN32RES)
+PGFILEDESC = "tsm_test - example of a custom tablesample method"
+
+EXTENSION = tsm_test
+DATA = tsm_test--1.0.sql
+
+REGRESS = tablesample
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/tablesample/expected/tablesample.out b/src/test/modules/tablesample/expected/tablesample.out
new file mode 100644
index 0000000..3cb3848
--- /dev/null
+++ b/src/test/modules/tablesample/expected/tablesample.out
@@ -0,0 +1,38 @@
+CREATE EXTENSION tsm_test;
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ c81e728d9d4c2f636f067f89cc14862c | 0.5
+ a87ff679a2f3e71d9181a67b7542122c | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ d3d9446802a44259755d38e6d163e820 | 0.5
+(6 rows)
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ e4da3b7fbbce2345d7772b0674a318d5 | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ c9f0f895fb98ab9159f51fd0297e236d | 0.5
+(5 rows)
+
+DROP TABLESAMPLE METHOD tsm_test;
+ERROR:  cannot drop tablesample method tsm_test because extension tsm_test requires it
+HINT:  You can drop extension tsm_test instead.
+DROP EXTENSION tsm_test;
+ERROR:  cannot drop extension tsm_test because other objects depend on it
+DETAIL:  view test_tsm_v depends on tablesample method tsm_test
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+DROP EXTENSION tsm_test CASCADE;
+NOTICE:  drop cascades to view test_tsm_v
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
+ tsmname | tsmseqscan | tsminit | tsmnextblock | tsmnexttuple | tsmexaminetuple | tsmend | tsmreset | tsmcost 
+---------+------------+---------+--------------+--------------+-----------------+--------+----------+---------
+(0 rows)
+
diff --git a/src/test/modules/tablesample/sql/tablesample.sql b/src/test/modules/tablesample/sql/tablesample.sql
new file mode 100644
index 0000000..b1104d6
--- /dev/null
+++ b/src/test/modules/tablesample/sql/tablesample.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_test;
+
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+
+DROP TABLESAMPLE METHOD tsm_test;
+DROP EXTENSION tsm_test;
+DROP EXTENSION tsm_test CASCADE;
+
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
diff --git a/src/test/modules/tablesample/tsm_test--1.0.sql b/src/test/modules/tablesample/tsm_test--1.0.sql
new file mode 100644
index 0000000..2280ab0
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test--1.0.sql
@@ -0,0 +1,51 @@
+/* src/test/modules/tablesample/tsm_test--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_test" to load this file. \quit
+
+CREATE FUNCTION tsm_test_init(internal, int4, text)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nextblock(internal)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nexttuple(internal, int4, int2)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_examinetuple(internal, int4, internal, bool)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_cost(internal, internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+
+CREATE TABLESAMPLE METHOD tsm_test (
+	SEQSCAN		= true,
+	INIT		= tsm_test_init,
+	NEXTBLOCK	= tsm_test_nextblock,
+	NEXTTUPLE	= tsm_test_nexttuple,
+	EXAMINETUPLE	= tsm_test_examinetuple,
+	END			= tsm_test_end,
+	RESET		= tsm_test_reset,
+	COST		= tsm_test_cost
+);
diff --git a/src/test/modules/tablesample/tsm_test.c b/src/test/modules/tablesample/tsm_test.c
new file mode 100644
index 0000000..be4dcb9
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.c
@@ -0,0 +1,228 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_test.c
+ *	  Simple example of a custom tablesample method
+ *
+ * Copyright (c) 2007-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/test/modules/tablesample/tsm_test.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/htup_details.h"
+#include "access/relscan.h"
+#include "access/tupdesc.h"
+#include "catalog/pg_type.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/builtins.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+PG_MODULE_MAGIC;
+
+/* State */
+typedef struct
+{
+	uint32		seed;			/* random seed */
+	AttrNumber	attnum;			/* column to check */
+	TupleDesc	tupDesc;		/* tuple descriptor of table */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} tsm_test_state;
+
+
+PG_FUNCTION_INFO_V1(tsm_test_init);
+PG_FUNCTION_INFO_V1(tsm_test_nextblock);
+PG_FUNCTION_INFO_V1(tsm_test_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_test_examinetuple);
+PG_FUNCTION_INFO_V1(tsm_test_end);
+PG_FUNCTION_INFO_V1(tsm_test_reset);
+PG_FUNCTION_INFO_V1(tsm_test_cost);
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_test_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	char		   *attname;
+	AttrNumber		attnum;
+	Oid				atttype;
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	HeapScanDesc	scan = scanstate->ss.ss_currentScanDesc;
+	tsm_test_state *state;
+	TupleDesc		tupDesc = RelationGetDescr(rel);
+
+	if (PG_ARGISNULL(2))
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("attnum cannot be NULL.")));
+
+	attname = text_to_cstring(PG_GETARG_TEXT_P(2));
+
+	attnum = get_attnum(rel->rd_id, attname);
+	if (!AttrNumberIsForUserDefinedAttr(attnum))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s does not exist", attname)));
+
+	atttype = get_atttype(rel->rd_id, attnum);
+	if (atttype != FLOAT8OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s is not of type float.", attname)));
+
+	state = palloc0(sizeof(tsm_test_state));
+
+	/* Remember initial values for reinit */
+	state->seed = seed;
+	state->attnum = attnum;
+	state->tupDesc = tupDesc;
+	state->startblock = scan->rs_startblock;
+	state->nblocks = scan->rs_nblocks;
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+	sampler_random_init_state(state->seed, state->randstate);
+
+	scanstate->tsmdata = (void *) state;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_test_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	/* Cycle from startblock to startblock to support syncscan. */
+	if (state->blockno == InvalidBlockNumber)
+		state->blockno = state->startblock;
+	else
+	{
+		state->blockno++;
+
+		if (state->blockno >= state->nblocks)
+			state->blockno = 0;
+
+		if (state->blockno == state->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(state->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ */
+Datum
+tsm_test_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (state->lt == InvalidOffsetNumber)
+		state->lt = FirstOffsetNumber;
+	else if (++state->lt > maxoffset)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	PG_RETURN_UINT16(state->lt);
+}
+
+/*
+ * Examine tuple and decide if it should be returned.
+ */
+Datum
+tsm_test_examinetuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	HeapTuple		tuple = (HeapTuple) PG_GETARG_POINTER(2);
+	bool			visible = PG_GETARG_BOOL(3);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+	bool			isnull;
+	float8			val, rand;
+
+	if (!visible)
+		PG_RETURN_BOOL(false);
+
+	val = DatumGetFloat8(heap_getattr(tuple, state->attnum, state->tupDesc, &isnull));
+	rand = sampler_random_fract(state->randstate);
+	if (isnull || val < rand)
+		PG_RETURN_BOOL(false);
+	else
+		PG_RETURN_BOOL(true);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_test_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_test_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+
+	sampler_random_init_state(state->seed, state->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_test_cost(PG_FUNCTION_ARGS)
+{
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+
+	*pages = baserel->pages;
+
+	/* This is very bad estimation */
+	*tuples = path->rows = path->rows/2;
+
+	PG_RETURN_VOID();
+}
+
diff --git a/src/test/modules/tablesample/tsm_test.control b/src/test/modules/tablesample/tsm_test.control
new file mode 100644
index 0000000..a7b2741
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.control
@@ -0,0 +1,5 @@
+# tsm_test extension
+comment = 'test module for custom tablesample method'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_test'
+relocatable = true
-- 
1.9.1

>From 70cd678bdfe87bde171eeeab6345ba684c58c8bb Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:51:44 +0100
Subject: [PATCH 3/3] tablesample-ddl v5

---
 doc/src/sgml/ref/allfiles.sgml                     |   2 +
 doc/src/sgml/ref/create_tablesamplemethod.sgml     | 184 +++++++++
 doc/src/sgml/ref/drop_tablesamplemethod.sgml       |  87 +++++
 doc/src/sgml/reference.sgml                        |   2 +
 src/backend/catalog/dependency.c                   |  15 +-
 src/backend/catalog/objectaddress.c                |  65 +++-
 src/backend/commands/Makefile                      |   6 +-
 src/backend/commands/dropcmds.c                    |   4 +
 src/backend/commands/event_trigger.c               |   3 +
 src/backend/commands/tablecmds.c                   |   1 +
 src/backend/commands/tablesample.c                 | 427 +++++++++++++++++++++
 src/backend/parser/gram.y                          |  14 +-
 src/backend/tcop/utility.c                         |  12 +
 src/bin/pg_dump/common.c                           |   5 +
 src/bin/pg_dump/pg_dump.c                          | 177 +++++++++
 src/bin/pg_dump/pg_dump.h                          |  11 +-
 src/bin/pg_dump/pg_dump_sort.c                     |  11 +-
 src/include/catalog/dependency.h                   |   1 +
 src/include/catalog/pg_tablesample_method.h        |  11 +
 src/include/nodes/parsenodes.h                     |   1 +
 src/include/parser/kwlist.h                        |   1 +
 src/test/modules/Makefile                          |   3 +-
 src/test/modules/tablesample/.gitignore            |   4 +
 src/test/modules/tablesample/Makefile              |  21 +
 .../modules/tablesample/expected/tablesample.out   |  38 ++
 src/test/modules/tablesample/sql/tablesample.sql   |  14 +
 src/test/modules/tablesample/tsm_test--1.0.sql     |  52 +++
 src/test/modules/tablesample/tsm_test.c            | 228 +++++++++++
 src/test/modules/tablesample/tsm_test.control      |   5 +
 29 files changed, 1394 insertions(+), 11 deletions(-)
 create mode 100644 doc/src/sgml/ref/create_tablesamplemethod.sgml
 create mode 100644 doc/src/sgml/ref/drop_tablesamplemethod.sgml
 create mode 100644 src/backend/commands/tablesample.c
 create mode 100644 src/test/modules/tablesample/.gitignore
 create mode 100644 src/test/modules/tablesample/Makefile
 create mode 100644 src/test/modules/tablesample/expected/tablesample.out
 create mode 100644 src/test/modules/tablesample/sql/tablesample.sql
 create mode 100644 src/test/modules/tablesample/tsm_test--1.0.sql
 create mode 100644 src/test/modules/tablesample/tsm_test.c
 create mode 100644 src/test/modules/tablesample/tsm_test.control

diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index 7aa3128..2fad084 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -78,6 +78,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY createServer       SYSTEM "create_server.sgml">
 <!ENTITY createTable        SYSTEM "create_table.sgml">
 <!ENTITY createTableAs      SYSTEM "create_table_as.sgml">
+<!ENTITY createTablesampleMethod SYSTEM "create_tablesamplemethod.sgml">
 <!ENTITY createTableSpace   SYSTEM "create_tablespace.sgml">
 <!ENTITY createTrigger      SYSTEM "create_trigger.sgml">
 <!ENTITY createTSConfig     SYSTEM "create_tsconfig.sgml">
@@ -119,6 +120,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY dropSequence       SYSTEM "drop_sequence.sgml">
 <!ENTITY dropServer         SYSTEM "drop_server.sgml">
 <!ENTITY dropTable          SYSTEM "drop_table.sgml">
+<!ENTITY dropTablesampleMethod SYSTEM "drop_tablesamplemethod.sgml">
 <!ENTITY dropTableSpace     SYSTEM "drop_tablespace.sgml">
 <!ENTITY dropTrigger        SYSTEM "drop_trigger.sgml">
 <!ENTITY dropTSConfig       SYSTEM "drop_tsconfig.sgml">
diff --git a/doc/src/sgml/ref/create_tablesamplemethod.sgml b/doc/src/sgml/ref/create_tablesamplemethod.sgml
new file mode 100644
index 0000000..ff105d2
--- /dev/null
+++ b/doc/src/sgml/ref/create_tablesamplemethod.sgml
@@ -0,0 +1,184 @@
+<!--
+doc/src/sgml/ref/create_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-CREATETABLESAMPLEMETHOD">
+ <indexterm zone="sql-createtablesamplemethod">
+  <primary>CREATE TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE TABLESAMPLE METHOD</refname>
+  <refpurpose>define custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE TABLESAMPLE METHOD <replaceable class="parameter">name</replaceable> (
+    INIT = <replaceable class="parameter">init_function</replaceable> ,
+    NEXTBLOCK = <replaceable class="parameter">nextblock_function</replaceable> ,
+    NEXTTUPLE = <replaceable class="parameter">nexttuple_function</replaceable> ,
+    END = <replaceable class="parameter">end_function</replaceable> ,
+    RESET = <replaceable class="parameter">reset_function</replaceable> ,
+    COST = <replaceable class="parameter">cost_function</replaceable>
+    [ , EXAMINETUPLE = <replaceable class="parameter">examinetuple_function</replaceable> ]
+    [ , SEQSCAN = <replaceable class="parameter">seqscan</replaceable> ]
+    [ , PAGEMODE = <replaceable class="parameter">pagemode</replaceable> ]
+)
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE TABLESAMPLE METHOD</command> creates a tablesample method.
+   A tablesample method provides alrorithm for reading sample part of a table
+   when used in <command>TABLESAMPLE</> clause of a <command>SELECT</>
+   statement.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the tablesample method to be created. This name must be
+      unique within the database.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">init_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the init function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nextblock_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-block function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nexttuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-tuple function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">end_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the end function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">reset_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the reset function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">cost_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the costing function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">examinetuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the function for inspecting the tuple contents in order
+      to make decision if it should be returned or not. This parameter
+      is optional.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">seqscan</replaceable></term>
+    <listitem>
+     <para>
+      True if the sampling method will do sequential scan of the whole table.
+      Used for cost estimation and syncscan. The default value if not specified
+      is False.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">pagemode</replaceable></term>
+    <listitem>
+     <para>
+      True if the sampling method will read whole page at a time. The default
+      value if not specified is False.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+  <para>
+   The function names can be schema-qualified if necessary.  Argument types
+   are not given, since the argument list for each type of function is
+   predetermined.  All functions are required.
+  </para>
+
+  <para>
+   The arguments can appear in any order, not only the one shown above.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>CREATE TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-droptablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/ref/drop_tablesamplemethod.sgml b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
new file mode 100644
index 0000000..dffd2ec
--- /dev/null
+++ b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
@@ -0,0 +1,87 @@
+<!--
+doc/src/sgml/ref/drop_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-DROPTABLESAMPLEMETHOD">
+ <indexterm zone="sql-droptablesamplemethod">
+  <primary>DROP TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DROP TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP TABLESAMPLE METHOD</refname>
+  <refpurpose>remove a custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP TABLESAMPLE METHOD [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>DROP TABLESAMPLE METHOD</command> drop an existing tablesample
+   method.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the tablesample method does not exist.
+      A notice is issued in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of an existing tablesample method to be removed.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>DROP TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createtablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index 10c9a6d..2c09a3c 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -106,6 +106,7 @@
    &createServer;
    &createTable;
    &createTableAs;
+   &createTablesampleMethod;
    &createTableSpace;
    &createTSConfig;
    &createTSDictionary;
@@ -147,6 +148,7 @@
    &dropSequence;
    &dropServer;
    &dropTable;
+   &dropTablesampleMethod;
    &dropTableSpace;
    &dropTSConfig;
    &dropTSDictionary;
diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index bacb242..6acb5b3 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -46,6 +46,7 @@
 #include "catalog/pg_policy.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -157,7 +158,8 @@ static const Oid object_classes[MAX_OCLASS] = {
 	DefaultAclRelationId,		/* OCLASS_DEFACL */
 	ExtensionRelationId,		/* OCLASS_EXTENSION */
 	EventTriggerRelationId,		/* OCLASS_EVENT_TRIGGER */
-	PolicyRelationId			/* OCLASS_POLICY */
+	PolicyRelationId,			/* OCLASS_POLICY */
+	TableSampleMethodRelationId			/* OCLASS_TABLESAMPLEMETHOD */
 };
 
 
@@ -1265,6 +1267,10 @@ doDeletion(const ObjectAddress *object, int flags)
 			RemovePolicyById(object->objectId);
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			RemoveTablesampleMethodById(object->objectId);
+			break;
+
 		default:
 			elog(ERROR, "unrecognized object class: %u",
 				 object->classId);
@@ -1794,6 +1800,10 @@ find_expr_references_walker(Node *node,
 				case RTE_RELATION:
 					add_object_address(OCLASS_CLASS, rte->relid, 0,
 									   context->addrs);
+					if (rte->tablesample)
+						add_object_address(OCLASS_TABLESAMPLEMETHOD,
+										   rte->tablesample->tsmid, 0,
+										   context->addrs);
 					break;
 				default:
 					break;
@@ -2373,6 +2383,9 @@ getObjectClass(const ObjectAddress *object)
 
 		case PolicyRelationId:
 			return OCLASS_POLICY;
+
+		case TableSampleMethodRelationId:
+			return OCLASS_TABLESAMPLEMETHOD;
 	}
 
 	/* shouldn't get here */
diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index 142bc68..b50925f 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -44,6 +44,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_policy.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -429,7 +430,19 @@ static const ObjectPropertyType ObjectProperty[] =
 		Anum_pg_type_typacl,
 		ACL_KIND_TYPE,
 		true
-	}
+	},
+	{
+		TableSampleMethodRelationId,
+		TableSampleMethodOidIndexId,
+		TABLESAMPLEMETHODOID,
+		TABLESAMPLEMETHODNAME,
+		Anum_pg_tablesample_method_tsmname,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		-1,
+		true
+	},
 };
 
 /*
@@ -528,7 +541,9 @@ ObjectTypeMap[] =
 	/* OCLASS_EVENT_TRIGGER */
 	{ "event trigger", OBJECT_EVENT_TRIGGER },
 	/* OCLASS_POLICY */
-	{ "policy", OBJECT_POLICY }
+	{ "policy", OBJECT_POLICY },
+	/* OCLASS_TABLESAMPLEMETHOD */
+	{ "tablesample method", OBJECT_TABLESAMPLEMETHOD }
 };
 
 const ObjectAddress InvalidObjectAddress =
@@ -680,6 +695,7 @@ get_object_address(ObjectType objtype, List *objname, List *objargs,
 			case OBJECT_FDW:
 			case OBJECT_FOREIGN_SERVER:
 			case OBJECT_EVENT_TRIGGER:
+			case OBJECT_TABLESAMPLEMETHOD:
 				address = get_object_address_unqualified(objtype,
 														 objname, missing_ok);
 				break;
@@ -914,6 +930,9 @@ get_object_address_unqualified(ObjectType objtype,
 			case OBJECT_EVENT_TRIGGER:
 				msg = gettext_noop("event trigger name cannot be qualified");
 				break;
+			case OBJECT_TABLESAMPLEMETHOD:
+				msg = gettext_noop("tablesample method name cannot be qualified");
+				break;
 			default:
 				elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 				msg = NULL;		/* placate compiler */
@@ -974,6 +993,11 @@ get_object_address_unqualified(ObjectType objtype,
 			address.objectId = get_event_trigger_oid(name, missing_ok);
 			address.objectSubId = 0;
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			address.classId = TableSampleMethodRelationId;
+			address.objectId = get_tablesample_method_oid(name, missing_ok);
+			address.objectSubId = 0;
+			break;
 		default:
 			elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 			/* placate compiler, which doesn't know elog won't return */
@@ -1916,6 +1940,7 @@ check_object_ownership(Oid roleid, ObjectType objtype, ObjectAddress address,
 			break;
 		case OBJECT_TSPARSER:
 		case OBJECT_TSTEMPLATE:
+		case OBJECT_TABLESAMPLEMETHOD:
 			/* We treat these object types as being owned by superusers */
 			if (!superuser_arg(roleid))
 				ereport(ERROR,
@@ -2854,6 +2879,21 @@ getObjectDescription(const ObjectAddress *object)
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				appendStringInfo(&buffer, _("tablesample method %s"),
+					 NameStr(((Form_pg_tablesample_method) GETSTRUCT(tup))->tsmname));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
@@ -3331,6 +3371,10 @@ getObjectTypeDescription(const ObjectAddress *object)
 			appendStringInfoString(&buffer, "policy");
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			appendStringInfoString(&buffer, "tablesample method");
+			break;
+
 		default:
 			appendStringInfo(&buffer, "unrecognized %u", object->classId);
 			break;
@@ -4242,6 +4286,23 @@ getObjectIdentityParts(const ObjectAddress *object,
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+				Form_pg_tablesample_method tsmForm;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				tsmForm = (Form_pg_tablesample_method) GETSTRUCT(tup);
+				appendStringInfoString(&buffer,
+							   quote_identifier(NameStr(tsmForm->tsmname)));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index b1ac704..04fcd8c 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -18,8 +18,8 @@ OBJS = aggregatecmds.o alter.o analyze.o async.o cluster.o comment.o  \
 	event_trigger.o explain.o extension.o foreigncmds.o functioncmds.o \
 	indexcmds.o lockcmds.o matview.o operatorcmds.o opclasscmds.o \
 	policy.o portalcmds.o prepare.o proclang.o \
-	schemacmds.o seclabel.o sequence.o tablecmds.o tablespace.o trigger.o \
-	tsearchcmds.o typecmds.o user.o vacuum.o vacuumlazy.o \
-	variable.o view.o
+	schemacmds.o seclabel.o sequence.o tablecmds.o tablesample.o \
+	tablespace.o trigger.o tsearchcmds.o typecmds.o user.o vacuum.o \
+	vacuumlazy.o variable.o view.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/commands/dropcmds.c b/src/backend/commands/dropcmds.c
index e5185ba..04d29a2 100644
--- a/src/backend/commands/dropcmds.c
+++ b/src/backend/commands/dropcmds.c
@@ -421,6 +421,10 @@ does_not_exist_skipping(ObjectType objtype, List *objname, List *objargs)
 				args = strVal(linitial(objargs));
 			}
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			msg = gettext_noop("tablesample method \"%s\" does not exist, skipping");
+			name = NameListToString(objname);
+			break;
 		default:
 			elog(ERROR, "unexpected object type (%d)", (int) objtype);
 			break;
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 3fec57e..f774975 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -97,6 +97,7 @@ static event_trigger_support_data event_trigger_support[] = {
 	{"SEQUENCE", true},
 	{"SERVER", true},
 	{"TABLE", true},
+	{"TABLESAMPLE METHOD", true},
 	{"TABLESPACE", false},
 	{"TRIGGER", true},
 	{"TEXT SEARCH CONFIGURATION", true},
@@ -1087,6 +1088,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_SEQUENCE:
 		case OBJECT_TABCONSTRAINT:
 		case OBJECT_TABLE:
+		case OBJECT_TABLESAMPLEMETHOD:
 		case OBJECT_TRIGGER:
 		case OBJECT_TSCONFIGURATION:
 		case OBJECT_TSDICTIONARY:
@@ -1144,6 +1146,7 @@ EventTriggerSupportsObjectClass(ObjectClass objclass)
 		case OCLASS_DEFACL:
 		case OCLASS_EXTENSION:
 		case OCLASS_POLICY:
+		case OCLASS_TABLESAMPLEMETHOD:
 			return true;
 
 		case MAX_OCLASS:
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 623e6bf..aad7a58 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8086,6 +8086,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 			case OCLASS_USER_MAPPING:
 			case OCLASS_DEFACL:
 			case OCLASS_EXTENSION:
+			case OCLASS_TABLESAMPLEMETHOD:
 
 				/*
 				 * We don't expect any of these sorts of objects to depend on
diff --git a/src/backend/commands/tablesample.c b/src/backend/commands/tablesample.c
new file mode 100644
index 0000000..f40820b
--- /dev/null
+++ b/src/backend/commands/tablesample.c
@@ -0,0 +1,427 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *	  Commands to manipulate tablesample methods
+ *
+ * Table sampling methods provide algorithms for doing sample scan over
+ * the table.
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/tablesample.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "access/heapam.h"
+#include "access/htup_details.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/objectaccess.h"
+#include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
+#include "catalog/pg_type.h"
+#include "commands/defrem.h"
+#include "miscadmin.h"
+#include "parser/parse_func.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+
+static Datum
+get_tablesample_method_func(DefElem *defel, int attnum)
+{
+	List	   *funcName = defGetQualifiedName(defel);
+	/* Big enough size for our needs. */
+	Oid		   *typeId = palloc0(7 * sizeof(Oid));
+	Oid			retTypeId;
+	int			nargs;
+	Oid			procOid = InvalidOid;
+	FuncCandidateList clist;
+
+	switch (attnum)
+	{
+		case Anum_pg_tablesample_method_tsminit:
+			/*
+			 * tsminit needs special handling because it is defined as function
+			 * with 3 or more arguments and only first two arguments must have
+			 * specific type, the rest is up to the tablesample method creator.
+			 */
+			{
+				nargs = 2;
+				typeId[0] = INTERNALOID;
+				typeId[1] = INT4OID;
+				retTypeId = VOIDOID;
+
+				clist = FuncnameGetCandidates(funcName, -1, NIL, false, false, false);
+
+				while (clist)
+				{
+					if (clist->nargs >= 3 &&
+						memcmp(typeId, clist->args, nargs * sizeof(Oid)) == 0)
+					{
+						procOid = clist->oid;
+						/* Save real function signature for future errors. */
+						nargs = clist->nargs;
+						pfree(typeId);
+						typeId = clist->args;
+						break;
+					}
+					clist = clist->next;
+				}
+
+				if (!OidIsValid(procOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_UNDEFINED_FUNCTION),
+							 errmsg("function \"%s\" does not exist or does not have valid signature",
+									NameListToString(funcName)),
+							 errhint("The tamplesample method init function "
+									 "must have at least 3 input parameters "
+									 "with first one of type INTERNAL and second of type INTEGER.")));
+			}
+			break;
+
+		case Anum_pg_tablesample_method_tsmnextblock:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = INT4OID;
+			break;
+		case Anum_pg_tablesample_method_tsmnexttuple:
+			nargs = 3;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INT2OID;
+			retTypeId = INT2OID;
+			break;
+		case Anum_pg_tablesample_method_tsmexaminetuple:
+			nargs = 4;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = BOOLOID;
+			retTypeId = BOOLOID;
+			break;
+		case Anum_pg_tablesample_method_tsmend:
+		case Anum_pg_tablesample_method_tsmreset:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		case Anum_pg_tablesample_method_tsmcost:
+			nargs = 7;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INTERNALOID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = INTERNALOID;
+			typeId[4] = INTERNALOID;
+			typeId[5] = INTERNALOID;
+			typeId[6] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		default:
+			/* should not be here */
+			elog(ERROR, "unrecognized attribute for tablesample method: %d",
+				 attnum);
+			nargs = 0;			/* keep compiler quiet */
+	}
+
+	if (!OidIsValid(procOid))
+		procOid = LookupFuncName(funcName, nargs, typeId, false);
+	if (get_func_rettype(procOid) != retTypeId)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("function %s should return type %s",
+						func_signature_string(funcName, nargs, NIL, typeId),
+						format_type_be(retTypeId))));
+
+	return ObjectIdGetDatum(procOid);
+}
+
+/*
+ * make pg_depend entries for a new pg_tablesample_method entry
+ */
+static void
+makeTablesampleMethodDeps(HeapTuple tuple)
+{
+	Form_pg_tablesample_method tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	ObjectAddress	myself,
+					referenced;
+
+	myself.classId = TableSampleMethodRelationId;
+	myself.objectId = HeapTupleGetOid(tuple);
+	myself.objectSubId = 0;
+
+	/* dependency on extension */
+	recordDependencyOnCurrentExtension(&myself, false);
+
+	/* dependencies on functions */
+	referenced.classId = ProcedureRelationId;
+	referenced.objectSubId = 0;
+
+	referenced.objectId = tsm->tsminit;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnextblock;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnexttuple;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	if (OidIsValid(tsm->tsmexaminetuple))
+	{
+		referenced.objectId = tsm->tsmexaminetuple;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
+
+	referenced.objectId = tsm->tsmend;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmreset;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmcost;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+}
+
+/*
+ * Create a table sampling method
+ *
+ * Only superusers can create a table sampling methods.
+ */
+Oid
+DefineTablesampleMethod(List *names, List *parameters)
+{
+	char	   *tsmname = strVal(linitial(names));
+	Oid			tsmoid;
+	ListCell   *pl;
+	Relation	rel;
+	Datum		values[Natts_pg_tablesample_method];
+	bool		nulls[Natts_pg_tablesample_method];
+	HeapTuple	tuple;
+
+	/* Must be super user. */
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied to create tablesample method \"%s\"",
+						tsmname),
+				 errhint("Must be superuser to create a tablesample method.")));
+
+	/* Must not already exist. */
+	tsmoid = get_tablesample_method_oid(tsmname, true);
+	if (OidIsValid(tsmoid))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" already exists",
+						tsmname)));
+
+	/* Initialize the values. */
+	memset(values, 0, sizeof(values));
+	memset(nulls, false, sizeof(nulls));
+
+	values[Anum_pg_tablesample_method_tsmname - 1] =
+		DirectFunctionCall1(namein, CStringGetDatum(tsmname));
+
+	/*
+	 * loop over the definition list and extract the information we need.
+	 */
+	foreach(pl, parameters)
+	{
+		DefElem    *defel = (DefElem *) lfirst(pl);
+
+		if (pg_strcasecmp(defel->defname, "seqscan") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmseqscan - 1] =
+				BoolGetDatum(defGetBoolean(defel));
+		}
+		else if (pg_strcasecmp(defel->defname, "pagemode") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmpagemode - 1] =
+				BoolGetDatum(defGetBoolean(defel));
+		}
+		else if (pg_strcasecmp(defel->defname, "init") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsminit - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsminit);
+		}
+		else if (pg_strcasecmp(defel->defname, "nextblock") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnextblock - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnextblock);
+		}
+		else if (pg_strcasecmp(defel->defname, "nexttuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnexttuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnexttuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "examinetuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmexaminetuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmexaminetuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "end") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmend - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmend);
+		}
+		else if (pg_strcasecmp(defel->defname, "reset") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmreset - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmreset);
+		}
+		else if (pg_strcasecmp(defel->defname, "cost") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmcost - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmcost);
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("tablesample method parameter \"%s\" not recognized",
+						defel->defname)));
+	}
+
+	/*
+	 * Validation.
+	 */
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsminit - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method init function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnextblock - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nextblock function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnexttuple - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nexttuple function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmend - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method end function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmreset - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method reset function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmcost - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method cost function is required")));
+
+	/*
+	 * Insert tuple into pg_tablesample_method.
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = heap_form_tuple(rel->rd_att, values, nulls);
+
+	tsmoid = simple_heap_insert(rel, tuple);
+
+	CatalogUpdateIndexes(rel, tuple);
+
+	makeTablesampleMethodDeps(tuple);
+
+	heap_freetuple(tuple);
+
+	/* Post creation hook for new tablesample method */
+	InvokeObjectPostCreateHook(TableSampleMethodRelationId, tsmoid, 0);
+
+	heap_close(rel, RowExclusiveLock);
+
+	return tsmoid;
+}
+
+/*
+ * Drop a tablesample method.
+ */
+void
+RemoveTablesampleMethodById(Oid tsmoid)
+{
+	Relation	rel;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+
+	/*
+	 * Find the target tuple
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmoid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for tablesample method %u",
+			 tsmoid);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	/* Can't drop builtin tablesample methods. */
+	if (tsmoid == TABLESAMPLE_METHOD_SYSTEM_OID ||
+		tsmoid == TABLESAMPLE_METHOD_BERNOULLI_OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied for tablesample method %s",
+						NameStr(tsm->tsmname))));
+
+	/*
+	 * Remove the pg_tablespace tuple (this will roll back if we fail below)
+	 */
+	simple_heap_delete(rel, &tuple->t_self);
+
+	ReleaseSysCache(tuple);
+
+	heap_close(rel, RowExclusiveLock);
+}
+
+/*
+ * get_tablesample_method_oid - given a tablesample method name,
+ * look up the OID
+ *
+ * If missing_ok is false, throw an error if tablesample method name not found.
+ * If true, just return InvalidOid.
+ */
+Oid
+get_tablesample_method_oid(const char *tsmname, bool missing_ok)
+{
+	Oid			result;
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(tsmname));
+	if (HeapTupleIsValid(tuple))
+	{
+		result = HeapTupleGetOid(tuple);
+		ReleaseSysCache(tuple);
+	}
+	else
+		result = InvalidOid;
+
+	if (!OidIsValid(result) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						tsmname)));
+
+	return result;
+}
+
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 41f71d6..9f02d31 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -590,7 +590,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATERIALIZED MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
+	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P
+	MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEXT NO NONE
 	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
@@ -5091,6 +5092,15 @@ DefineStmt:
 					n->definition = list_make1(makeDefElem("from", (Node *) $5));
 					$$ = (Node *)n;
 				}
+			| CREATE TABLESAMPLE METHOD name definition
+				{
+					DefineStmt *n = makeNode(DefineStmt);
+					n->kind = OBJECT_TABLESAMPLEMETHOD;
+					n->args = NIL;
+					n->defnames = list_make1(makeString($4));
+					n->definition = $5;
+					$$ = (Node *)n;
+				}
 		;
 
 definition: '(' def_list ')'						{ $$ = $2; }
@@ -5549,6 +5559,7 @@ drop_type:	TABLE									{ $$ = OBJECT_TABLE; }
 			| TEXT_P SEARCH DICTIONARY				{ $$ = OBJECT_TSDICTIONARY; }
 			| TEXT_P SEARCH TEMPLATE				{ $$ = OBJECT_TSTEMPLATE; }
 			| TEXT_P SEARCH CONFIGURATION			{ $$ = OBJECT_TSCONFIGURATION; }
+			| TABLESAMPLE METHOD					{ $$ = OBJECT_TABLESAMPLEMETHOD; }
 		;
 
 any_name_list:
@@ -13443,6 +13454,7 @@ unreserved_keyword:
 			| MATCH
 			| MATERIALIZED
 			| MAXVALUE
+			| METHOD
 			| MINUTE_P
 			| MINVALUE
 			| MODE
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 126e38d..862113b 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -23,6 +23,7 @@
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/toasting.h"
 #include "commands/alter.h"
 #include "commands/async.h"
@@ -1135,6 +1136,11 @@ ProcessUtilitySlow(Node *parsetree,
 							Assert(stmt->args == NIL);
 							DefineCollation(stmt->defnames, stmt->definition);
 							break;
+						case OBJECT_TABLESAMPLEMETHOD:
+							Assert(stmt->args == NIL);
+							Assert(list_length(stmt->defnames) == 1);
+							DefineTablesampleMethod(stmt->defnames, stmt->definition);
+							break;
 						default:
 							elog(ERROR, "unrecognized define stmt type: %d",
 								 (int) stmt->kind);
@@ -2003,6 +2009,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_POLICY:
 					tag = "DROP POLICY";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "DROP TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
@@ -2099,6 +2108,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_COLLATION:
 					tag = "CREATE COLLATION";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "CREATE TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
diff --git a/src/bin/pg_dump/common.c b/src/bin/pg_dump/common.c
index 1a0a587..8a64e4b 100644
--- a/src/bin/pg_dump/common.c
+++ b/src/bin/pg_dump/common.c
@@ -103,6 +103,7 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 	int			numForeignServers;
 	int			numDefaultACLs;
 	int			numEventTriggers;
+	int			numTSMs;
 
 	if (g_verbose)
 		write_msg(NULL, "reading schemas\n");
@@ -251,6 +252,10 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 		write_msg(NULL, "reading policies\n");
 	getPolicies(fout, tblinfo, numTables);
 
+	if (g_verbose)
+		write_msg(NULL, "reading tablesample methods\n");
+	getTableSampleMethods(fout, &numTSMs);
+
 	*numTablesPtr = numTables;
 	return tblinfo;
 }
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index fdfb431..20630cf 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -182,6 +182,7 @@ static void dumpSequenceData(Archive *fout, TableDataInfo *tdinfo);
 static void dumpIndex(Archive *fout, DumpOptions *dopt, IndxInfo *indxinfo);
 static void dumpConstraint(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
 static void dumpTableConstraintComment(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
+static void dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tbinfo);
 static void dumpTSParser(Archive *fout, DumpOptions *dopt, TSParserInfo *prsinfo);
 static void dumpTSDictionary(Archive *fout, DumpOptions *dopt, TSDictInfo *dictinfo);
 static void dumpTSTemplate(Archive *fout, DumpOptions *dopt, TSTemplateInfo *tmplinfo);
@@ -7134,6 +7135,78 @@ getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tblinfo, int numTable
 }
 
 /*
+ * getTableSampleMethods:
+ *	  read all tablesample methods in the system catalogs and return them
+ *	  in the TSMInfo* structure
+ *
+ *	numTSMs is set to the number of tablesample methods read in
+ */
+TSMInfo *
+getTableSampleMethods(Archive *fout, int *numTSMs)
+{
+	PGresult   *res;
+	int			ntups;
+	int			i;
+	PQExpBuffer query;
+	TSMInfo	   *tsminfo;
+	int			i_tableoid,
+				i_oid,
+				i_tsmname,
+				i_tsmseqscan,
+				i_tsmpagemode;
+
+	/* Before 9.5, there were no tablesample methods */
+	if (fout->remoteVersion < 90500)
+	{
+		*numTSMs = 0;
+		return NULL;
+	}
+
+	query = createPQExpBuffer();
+
+	appendPQExpBuffer(query,
+					  "SELECT tableoid, oid, tsmname, tsmseqscan, tsmpagemode "
+					  "FROM pg_catalog.pg_tablesample_method "
+					  "WHERE oid >= '%u'::pg_catalog.oid",
+					  FirstNormalObjectId);
+
+	res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
+
+	ntups = PQntuples(res);
+	*numTSMs = ntups;
+
+	tsminfo = (TSMInfo *) pg_malloc(ntups * sizeof(TSMInfo));
+
+	i_tableoid = PQfnumber(res, "tableoid");
+	i_oid = PQfnumber(res, "oid");
+	i_tsmname = PQfnumber(res, "tsmname");
+	i_tsmseqscan = PQfnumber(res, "tsmseqscan");
+	i_tsmpagemode = PQfnumber(res, "tsmpagemode");
+
+	for (i = 0; i < ntups; i++)
+	{
+		tsminfo[i].dobj.objType = DO_TABLESAMPLE_METHOD;
+		tsminfo[i].dobj.catId.tableoid = atooid(PQgetvalue(res, i, i_tableoid));
+		tsminfo[i].dobj.catId.oid = atooid(PQgetvalue(res, i, i_oid));
+		AssignDumpId(&tsminfo[i].dobj);
+		tsminfo[i].dobj.name = pg_strdup(PQgetvalue(res, i, i_tsmname));
+		tsminfo[i].dobj.namespace = NULL;
+		tsminfo[i].tsmseqscan = PQgetvalue(res, i, i_tsmseqscan)[0] == 't';
+		tsminfo[i].tsmpagemode = PQgetvalue(res, i, i_tsmpagemode)[0] == 't';
+
+		/* Decide whether we want to dump it */
+		selectDumpableObject(&(tsminfo[i].dobj));
+	}
+
+	PQclear(res);
+
+	destroyPQExpBuffer(query);
+
+	return tsminfo;
+}
+
+
+/*
  * Test whether a column should be printed as part of table's CREATE TABLE.
  * Column number is zero-based.
  *
@@ -8226,6 +8299,9 @@ dumpDumpableObject(Archive *fout, DumpOptions *dopt, DumpableObject *dobj)
 		case DO_POLICY:
 			dumpPolicy(fout, dopt, (PolicyInfo *) dobj);
 			break;
+		case DO_TABLESAMPLE_METHOD:
+			dumpTableSampleMethod(fout, dopt, (TSMInfo *) dobj);
+			break;
 		case DO_PRE_DATA_BOUNDARY:
 		case DO_POST_DATA_BOUNDARY:
 			/* never dumped, nothing to do */
@@ -12226,6 +12302,106 @@ dumpAgg(Archive *fout, DumpOptions *dopt, AggInfo *agginfo)
 }
 
 /*
+ * dumpTableSampleMethod
+ *	  write the declaration of one user-defined tablesample method
+ */
+static void
+dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tsminfo)
+{
+	PGresult   *res;
+	PQExpBuffer q;
+	PQExpBuffer delq;
+	PQExpBuffer labelq;
+	PQExpBuffer query;
+	char	   *tsminit;
+	char	   *tsmnextblock;
+	char	   *tsmnexttuple;
+	char	   *tsmexaminetuple;
+	char	   *tsmend;
+	char	   *tsmreset;
+	char	   *tsmcost;
+
+	/* Skip if not to be dumped */
+	if (!tsminfo->dobj.dump || dopt->dataOnly)
+		return;
+
+	q = createPQExpBuffer();
+	delq = createPQExpBuffer();
+	labelq = createPQExpBuffer();
+	query = createPQExpBuffer();
+
+	/* Make sure we are in proper schema */
+	selectSourceSchema(fout, "pg_catalog");
+
+	appendPQExpBuffer(query, "SELECT tsminit, tsmnextblock, "
+							 "tsmnexttuple, tsmexaminetuple, "
+							 "tsmend, tsmreset, tsmcost "
+							 "FROM pg_catalog.pg_tablesample_method "
+							 "WHERE oid = '%u'::pg_catalog.oid",
+							 tsminfo->dobj.catId.oid);
+
+	res = ExecuteSqlQueryForSingleRow(fout, query->data);
+
+	tsminit = PQgetvalue(res, 0, PQfnumber(res, "tsminit"));
+	tsmnexttuple = PQgetvalue(res, 0, PQfnumber(res, "tsmnexttuple"));
+	tsmnextblock = PQgetvalue(res, 0, PQfnumber(res, "tsmnextblock"));
+	tsmexaminetuple = PQgetvalue(res, 0, PQfnumber(res, "tsmexaminetuple"));
+	tsmend = PQgetvalue(res, 0, PQfnumber(res, "tsmend"));
+	tsmreset = PQgetvalue(res, 0, PQfnumber(res, "tsmreset"));
+	 tsmcost = PQgetvalue(res, 0, PQfnumber(res, "tsmcost"));
+
+	appendPQExpBuffer(q, "CREATE TABLESAMPLE METHOD %s (\n",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(q, "    INIT = %s,\n", tsminit);
+	appendPQExpBuffer(q, "    NEXTTUPLE = %s,\n", tsmnexttuple);
+	appendPQExpBuffer(q, "    NEXTBLOCK = %s,\n", tsmnextblock);
+	appendPQExpBuffer(q, "    END = %s,\n", tsmend);
+	appendPQExpBuffer(q, "    RESET = %s,\n", tsmreset);
+	appendPQExpBuffer(q, "    COST = %s", tsmcost);
+
+	if (strcmp(tsmexaminetuple, "-") != 0)
+		appendPQExpBuffer(q, ",\n    EXAMINETUPLE = %s", tsmexaminetuple);
+
+	if (tsminfo->tsmseqscan)
+		appendPQExpBufferStr(q, ",\n    SEQSCAN = true");
+
+	if (tsminfo->tsmpagemode)
+		appendPQExpBufferStr(q, ",\n    PAGEMODE = true");
+
+	appendPQExpBufferStr(q, "\n);");
+
+	appendPQExpBuffer(delq, "DROP TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(labelq, "TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	if (dopt->binary_upgrade)
+		binary_upgrade_extension_member(q, &tsminfo->dobj, labelq->data);
+
+	ArchiveEntry(fout, tsminfo->dobj.catId, tsminfo->dobj.dumpId,
+				 tsminfo->dobj.name,
+				 NULL,
+				 NULL,
+				 "",
+				 false, "TABLESAMPLE METHOD", SECTION_PRE_DATA,
+				 q->data, delq->data, NULL,
+				 NULL, 0,
+				 NULL, NULL);
+
+	/* Dump Parser Comments */
+	dumpComment(fout, dopt, labelq->data,
+				NULL, "",
+				tsminfo->dobj.catId, 0, tsminfo->dobj.dumpId);
+
+	PQclear(res);
+	destroyPQExpBuffer(q);
+	destroyPQExpBuffer(delq);
+	destroyPQExpBuffer(labelq);
+}
+
+/*
  * dumpTSParser
  *	  write out a single text search parser
  */
@@ -15655,6 +15831,7 @@ addBoundaryDependencies(DumpableObject **dobjs, int numObjs,
 			case DO_FDW:
 			case DO_FOREIGN_SERVER:
 			case DO_BLOB:
+			case DO_TABLESAMPLE_METHOD:
 				/* Pre-data objects: must come before the pre-data boundary */
 				addObjectDependency(preDataBound, dobj->dumpId);
 				break;
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index a9d3c10..87bef24 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -76,7 +76,8 @@ typedef enum
 	DO_POST_DATA_BOUNDARY,
 	DO_EVENT_TRIGGER,
 	DO_REFRESH_MATVIEW,
-	DO_POLICY
+	DO_POLICY,
+	DO_TABLESAMPLE_METHOD
 } DumpableObjectType;
 
 typedef struct _dumpableObject
@@ -383,6 +384,13 @@ typedef struct _inhInfo
 	Oid			inhparent;		/* OID of its parent */
 } InhInfo;
 
+typedef struct _tsmInfo
+{
+	DumpableObject dobj;
+	bool		tsmseqscan;
+	bool		tsmpagemode;
+} TSMInfo;
+
 typedef struct _prsInfo
 {
 	DumpableObject dobj;
@@ -536,6 +544,7 @@ extern ProcLangInfo *getProcLangs(Archive *fout, int *numProcLangs);
 extern CastInfo *getCasts(Archive *fout, DumpOptions *dopt, int *numCasts);
 extern void getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tbinfo, int numTables);
 extern bool shouldPrintColumn(DumpOptions *dopt, TableInfo *tbinfo, int colno);
+extern TSMInfo *getTableSampleMethods(Archive *fout, int *numTSMs);
 extern TSParserInfo *getTSParsers(Archive *fout, int *numTSParsers);
 extern TSDictInfo *getTSDictionaries(Archive *fout, int *numTSDicts);
 extern TSTemplateInfo *getTSTemplates(Archive *fout, int *numTSTemplates);
diff --git a/src/bin/pg_dump/pg_dump_sort.c b/src/bin/pg_dump/pg_dump_sort.c
index c5ed593..9567cf6 100644
--- a/src/bin/pg_dump/pg_dump_sort.c
+++ b/src/bin/pg_dump/pg_dump_sort.c
@@ -73,7 +73,8 @@ static const int oldObjectTypePriority[] =
 	13,							/* DO_POST_DATA_BOUNDARY */
 	20,							/* DO_EVENT_TRIGGER */
 	15,							/* DO_REFRESH_MATVIEW */
-	21							/* DO_POLICY */
+	21,							/* DO_POLICY */
+	5							/* DO_TABLESAMPLE_METHOD */
 };
 
 /*
@@ -122,7 +123,8 @@ static const int newObjectTypePriority[] =
 	25,							/* DO_POST_DATA_BOUNDARY */
 	32,							/* DO_EVENT_TRIGGER */
 	33,							/* DO_REFRESH_MATVIEW */
-	34							/* DO_POLICY */
+	34,							/* DO_POLICY */
+	17							/* DO_TABLESAMPLE_METHOD */
 };
 
 static DumpId preDataBoundId;
@@ -1460,6 +1462,11 @@ describeDumpableObject(DumpableObject *obj, char *buf, int bufsize)
 					 "POLICY (ID %d OID %u)",
 					 obj->dumpId, obj->catId.oid);
 			return;
+		case DO_TABLESAMPLE_METHOD:
+			snprintf(buf, bufsize,
+					 "TABLESAMPLE METHOD %s  (ID %d OID %u)",
+					 obj->name, obj->dumpId, obj->catId.oid);
+			return;
 		case DO_PRE_DATA_BOUNDARY:
 			snprintf(buf, bufsize,
 					 "PRE-DATA BOUNDARY  (ID %d)",
diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 6481ac8..30653f8 100644
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -148,6 +148,7 @@ typedef enum ObjectClass
 	OCLASS_EXTENSION,			/* pg_extension */
 	OCLASS_EVENT_TRIGGER,		/* pg_event_trigger */
 	OCLASS_POLICY,				/* pg_policy */
+	OCLASS_TABLESAMPLEMETHOD,	/* pg_tablesample_method */
 	MAX_OCLASS					/* MUST BE LAST */
 } ObjectClass;
 
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
index 98df9cb..217e3e0 100644
--- a/src/include/catalog/pg_tablesample_method.h
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -71,7 +71,18 @@ typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
 
 DATA(insert OID = 3283 ( system false true tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
 DESCR("SYSTEM table sampling method");
+#define TABLESAMPLE_METHOD_SYSTEM_OID 3283
 DATA(insert OID = 3284 ( bernoulli true false tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
 DESCR("BERNOULLI table sampling method");
+#define TABLESAMPLE_METHOD_BERNOULLI_OID 3284
+
+/* ----------------
+ *		functions for manipulation of pg_tablesample_method
+ * ----------------
+ */
+
+extern Oid DefineTablesampleMethod(List *names, List *parameters);
+extern void RemoveTablesampleMethodById(Oid tsmoid);
+extern Oid get_tablesample_method_oid(const char *tsmname, bool missing_ok);
 
 #endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 3672e37..d4a7b69 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1298,6 +1298,7 @@ typedef enum ObjectType
 	OBJECT_SEQUENCE,
 	OBJECT_TABCONSTRAINT,
 	OBJECT_TABLE,
+	OBJECT_TABLESAMPLEMETHOD,
 	OBJECT_TABLESPACE,
 	OBJECT_TRIGGER,
 	OBJECT_TSCONFIGURATION,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 0a7b650..515304c 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -236,6 +236,7 @@ PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("mode", MODE, UNRESERVED_KEYWORD)
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 93d93af..37ea524 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -9,7 +9,8 @@ SUBDIRS = \
 		  worker_spi \
 		  dummy_seclabel \
 		  test_shm_mq \
-		  test_parser
+		  test_parser \
+		  tablesample
 
 all: submake-errcodes
 
diff --git a/src/test/modules/tablesample/.gitignore b/src/test/modules/tablesample/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/src/test/modules/tablesample/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/src/test/modules/tablesample/Makefile b/src/test/modules/tablesample/Makefile
new file mode 100644
index 0000000..469b004
--- /dev/null
+++ b/src/test/modules/tablesample/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/tsm_test/Makefile
+
+MODULE_big = tsm_test
+OBJS = tsm_test.o $(WIN32RES)
+PGFILEDESC = "tsm_test - example of a custom tablesample method"
+
+EXTENSION = tsm_test
+DATA = tsm_test--1.0.sql
+
+REGRESS = tablesample
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/tablesample/expected/tablesample.out b/src/test/modules/tablesample/expected/tablesample.out
new file mode 100644
index 0000000..ad62e32
--- /dev/null
+++ b/src/test/modules/tablesample/expected/tablesample.out
@@ -0,0 +1,38 @@
+CREATE EXTENSION tsm_test;
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ c81e728d9d4c2f636f067f89cc14862c | 0.5
+ a87ff679a2f3e71d9181a67b7542122c | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ d3d9446802a44259755d38e6d163e820 | 0.5
+(6 rows)
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ e4da3b7fbbce2345d7772b0674a318d5 | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ c9f0f895fb98ab9159f51fd0297e236d | 0.5
+(5 rows)
+
+DROP TABLESAMPLE METHOD tsm_test;
+ERROR:  cannot drop tablesample method tsm_test because extension tsm_test requires it
+HINT:  You can drop extension tsm_test instead.
+DROP EXTENSION tsm_test;
+ERROR:  cannot drop extension tsm_test because other objects depend on it
+DETAIL:  view test_tsm_v depends on tablesample method tsm_test
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+DROP EXTENSION tsm_test CASCADE;
+NOTICE:  drop cascades to view test_tsm_v
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
+ tsmname | tsmseqscan | tsmpagemode | tsminit | tsmnextblock | tsmnexttuple | tsmexaminetuple | tsmend | tsmreset | tsmcost 
+---------+------------+-------------+---------+--------------+--------------+-----------------+--------+----------+---------
+(0 rows)
+
diff --git a/src/test/modules/tablesample/sql/tablesample.sql b/src/test/modules/tablesample/sql/tablesample.sql
new file mode 100644
index 0000000..b1104d6
--- /dev/null
+++ b/src/test/modules/tablesample/sql/tablesample.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_test;
+
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+
+DROP TABLESAMPLE METHOD tsm_test;
+DROP EXTENSION tsm_test;
+DROP EXTENSION tsm_test CASCADE;
+
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
diff --git a/src/test/modules/tablesample/tsm_test--1.0.sql b/src/test/modules/tablesample/tsm_test--1.0.sql
new file mode 100644
index 0000000..e5a9ae8
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test--1.0.sql
@@ -0,0 +1,52 @@
+/* src/test/modules/tablesample/tsm_test--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_test" to load this file. \quit
+
+CREATE FUNCTION tsm_test_init(internal, int4, text)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nextblock(internal)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nexttuple(internal, int4, int2)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_examinetuple(internal, int4, internal, bool)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_cost(internal, internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+
+CREATE TABLESAMPLE METHOD tsm_test (
+	SEQSCAN		= true,
+	PAGEMODE	= true,
+	INIT		= tsm_test_init,
+	NEXTBLOCK	= tsm_test_nextblock,
+	NEXTTUPLE	= tsm_test_nexttuple,
+	EXAMINETUPLE	= tsm_test_examinetuple,
+	END			= tsm_test_end,
+	RESET		= tsm_test_reset,
+	COST		= tsm_test_cost
+);
diff --git a/src/test/modules/tablesample/tsm_test.c b/src/test/modules/tablesample/tsm_test.c
new file mode 100644
index 0000000..be4dcb9
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.c
@@ -0,0 +1,228 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_test.c
+ *	  Simple example of a custom tablesample method
+ *
+ * Copyright (c) 2007-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/test/modules/tablesample/tsm_test.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/htup_details.h"
+#include "access/relscan.h"
+#include "access/tupdesc.h"
+#include "catalog/pg_type.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/builtins.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+PG_MODULE_MAGIC;
+
+/* State */
+typedef struct
+{
+	uint32		seed;			/* random seed */
+	AttrNumber	attnum;			/* column to check */
+	TupleDesc	tupDesc;		/* tuple descriptor of table */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} tsm_test_state;
+
+
+PG_FUNCTION_INFO_V1(tsm_test_init);
+PG_FUNCTION_INFO_V1(tsm_test_nextblock);
+PG_FUNCTION_INFO_V1(tsm_test_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_test_examinetuple);
+PG_FUNCTION_INFO_V1(tsm_test_end);
+PG_FUNCTION_INFO_V1(tsm_test_reset);
+PG_FUNCTION_INFO_V1(tsm_test_cost);
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_test_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	char		   *attname;
+	AttrNumber		attnum;
+	Oid				atttype;
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	HeapScanDesc	scan = scanstate->ss.ss_currentScanDesc;
+	tsm_test_state *state;
+	TupleDesc		tupDesc = RelationGetDescr(rel);
+
+	if (PG_ARGISNULL(2))
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("attnum cannot be NULL.")));
+
+	attname = text_to_cstring(PG_GETARG_TEXT_P(2));
+
+	attnum = get_attnum(rel->rd_id, attname);
+	if (!AttrNumberIsForUserDefinedAttr(attnum))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s does not exist", attname)));
+
+	atttype = get_atttype(rel->rd_id, attnum);
+	if (atttype != FLOAT8OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s is not of type float.", attname)));
+
+	state = palloc0(sizeof(tsm_test_state));
+
+	/* Remember initial values for reinit */
+	state->seed = seed;
+	state->attnum = attnum;
+	state->tupDesc = tupDesc;
+	state->startblock = scan->rs_startblock;
+	state->nblocks = scan->rs_nblocks;
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+	sampler_random_init_state(state->seed, state->randstate);
+
+	scanstate->tsmdata = (void *) state;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_test_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	/* Cycle from startblock to startblock to support syncscan. */
+	if (state->blockno == InvalidBlockNumber)
+		state->blockno = state->startblock;
+	else
+	{
+		state->blockno++;
+
+		if (state->blockno >= state->nblocks)
+			state->blockno = 0;
+
+		if (state->blockno == state->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(state->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ */
+Datum
+tsm_test_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (state->lt == InvalidOffsetNumber)
+		state->lt = FirstOffsetNumber;
+	else if (++state->lt > maxoffset)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	PG_RETURN_UINT16(state->lt);
+}
+
+/*
+ * Examine tuple and decide if it should be returned.
+ */
+Datum
+tsm_test_examinetuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	HeapTuple		tuple = (HeapTuple) PG_GETARG_POINTER(2);
+	bool			visible = PG_GETARG_BOOL(3);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+	bool			isnull;
+	float8			val, rand;
+
+	if (!visible)
+		PG_RETURN_BOOL(false);
+
+	val = DatumGetFloat8(heap_getattr(tuple, state->attnum, state->tupDesc, &isnull));
+	rand = sampler_random_fract(state->randstate);
+	if (isnull || val < rand)
+		PG_RETURN_BOOL(false);
+	else
+		PG_RETURN_BOOL(true);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_test_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_test_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+
+	sampler_random_init_state(state->seed, state->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_test_cost(PG_FUNCTION_ARGS)
+{
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+
+	*pages = baserel->pages;
+
+	/* This is very bad estimation */
+	*tuples = path->rows = path->rows/2;
+
+	PG_RETURN_VOID();
+}
+
diff --git a/src/test/modules/tablesample/tsm_test.control b/src/test/modules/tablesample/tsm_test.control
new file mode 100644
index 0000000..a7b2741
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.control
@@ -0,0 +1,5 @@
+# tsm_test extension
+comment = 'test module for custom tablesample method'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_test'
+relocatable = true
-- 
1.9.1

>From 170685a1c3d6b8d8c74d1cc0f1af455f655438cb Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:37:55 +0100
Subject: [PATCH 2/3] tablesample v10

---
 contrib/file_fdw/file_fdw.c                 |   2 +-
 contrib/postgres_fdw/postgres_fdw.c         |   2 +-
 doc/src/sgml/catalogs.sgml                  | 112 ++++++
 doc/src/sgml/ref/select.sgml                |  38 +-
 src/backend/access/Makefile                 |   3 +-
 src/backend/access/heap/heapam.c            |  43 ++-
 src/backend/catalog/Makefile                |   2 +-
 src/backend/commands/analyze.c              |   2 +-
 src/backend/commands/explain.c              |   7 +
 src/backend/executor/Makefile               |   2 +-
 src/backend/executor/execAmi.c              |   8 +
 src/backend/executor/execCurrent.c          |   1 +
 src/backend/executor/execProcnode.c         |  14 +
 src/backend/executor/nodeSamplescan.c       | 556 ++++++++++++++++++++++++++++
 src/backend/nodes/copyfuncs.c               |  60 +++
 src/backend/nodes/equalfuncs.c              |  37 ++
 src/backend/nodes/nodeFuncs.c               |  12 +
 src/backend/nodes/outfuncs.c                |  48 +++
 src/backend/nodes/readfuncs.c               |  45 +++
 src/backend/optimizer/path/allpaths.c       |  49 +++
 src/backend/optimizer/path/costsize.c       |  68 ++++
 src/backend/optimizer/plan/createplan.c     |  69 ++++
 src/backend/optimizer/plan/setrefs.c        |  11 +
 src/backend/optimizer/plan/subselect.c      |   1 +
 src/backend/optimizer/util/pathnode.c       |  22 ++
 src/backend/parser/gram.y                   |  39 +-
 src/backend/parser/parse_clause.c           |  48 ++-
 src/backend/parser/parse_func.c             | 131 +++++++
 src/backend/utils/Makefile                  |   3 +-
 src/backend/utils/adt/ruleutils.c           |  50 +++
 src/backend/utils/cache/syscache.c          |  23 ++
 src/backend/utils/misc/sampling.c           |  33 +-
 src/backend/utils/tablesample/Makefile      |  17 +
 src/backend/utils/tablesample/bernoulli.c   | 224 +++++++++++
 src/backend/utils/tablesample/system.c      | 185 +++++++++
 src/include/access/heapam.h                 |   4 +
 src/include/access/relscan.h                |   1 +
 src/include/catalog/indexing.h              |   5 +
 src/include/catalog/pg_proc.h               |  25 ++
 src/include/catalog/pg_tablesample_method.h |  77 ++++
 src/include/executor/nodeSamplescan.h       |  24 ++
 src/include/nodes/execnodes.h               |  18 +
 src/include/nodes/nodes.h                   |   4 +
 src/include/nodes/parsenodes.h              |  36 ++
 src/include/nodes/plannodes.h               |   6 +
 src/include/optimizer/cost.h                |   1 +
 src/include/optimizer/pathnode.h            |   2 +
 src/include/parser/kwlist.h                 |   3 +-
 src/include/parser/parse_func.h             |   4 +
 src/include/utils/rel.h                     |   1 -
 src/include/utils/sampling.h                |  15 +-
 src/include/utils/syscache.h                |   2 +
 src/include/utils/tablesample.h             |  27 ++
 src/test/regress/expected/sanity_check.out  |   1 +
 src/test/regress/expected/tablesample.out   | 168 +++++++++
 src/test/regress/parallel_schedule          |   2 +-
 src/test/regress/serial_schedule            |   1 +
 src/test/regress/sql/tablesample.sql        |  42 +++
 58 files changed, 2397 insertions(+), 39 deletions(-)
 create mode 100644 src/backend/executor/nodeSamplescan.c
 create mode 100644 src/backend/utils/tablesample/Makefile
 create mode 100644 src/backend/utils/tablesample/bernoulli.c
 create mode 100644 src/backend/utils/tablesample/system.c
 create mode 100644 src/include/catalog/pg_tablesample_method.h
 create mode 100644 src/include/executor/nodeSamplescan.h
 create mode 100644 src/include/utils/tablesample.h
 create mode 100644 src/test/regress/expected/tablesample.out
 create mode 100644 src/test/regress/sql/tablesample.sql

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 249d541..6a813a3 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -1096,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * sampler_random_fract());
+				int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 59aaff7..5b2335f 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -2539,7 +2539,7 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * sampler_random_fract());
+			pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 2325962..0335abc 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -269,6 +269,11 @@
      </row>
 
      <row>
+      <entry><link linkend="catalog-pg-tablesample-method"><structname>pg_tablesample_method</structname></link></entry>
+      <entry>table sampling methods</entry>
+     </row>
+
+     <row>
       <entry><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link></entry>
       <entry>tablespaces within this database cluster</entry>
      </row>
@@ -5980,6 +5985,113 @@
  </sect1>
 
 
+ <sect1 id="catalog-pg-tablesample-method">
+  <title><structname>pg_tabesample_method</structname></title>
+
+  <indexterm zone="catalog-pg-tablesample-method">
+   <primary>pg_am</primary>
+  </indexterm>
+
+  <para>
+   The catalog <structname>pg_tablesample_method</structname> stores
+   information about table sampling methods which can be used in
+   <command>TABLESAMPLE</command> clause of a <command>SELECT</command>
+   statement.
+  </para>
+
+  <table>
+   <title><structname>pg_tablesample_method</> Columns</title>
+
+   <tgroup cols="4">
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Type</entry>
+      <entry>References</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+    <tbody>
+
+     <row>
+      <entry><structfield>oid</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry></entry>
+      <entry>Row identifier (hidden attribute; must be explicitly selected)</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmname</structfield></entry>
+      <entry><type>name</type></entry>
+      <entry></entry>
+      <entry>Name of the sampling method</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmseqscan</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry></entry>
+      <entry>Does the sampling method scan the whole table sequentially?
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsminit</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Initialize the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnextblock</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next block number</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnexttuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next tuple offset</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmexaminetuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Function which examines the tuple contents and decides if to
+        return in, or zero if none</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmend</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>End the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmreset</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Restart the state of sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmcost</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Costing function</entry>
+     </row>
+
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect1>
+
+
  <sect1 id="catalog-pg-tablespace">
   <title><structname>pg_tablespace</structname></title>
 
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 01d24a5..407bf9d 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,42 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        one of:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of those sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability.
+        The optional numeric parameter <literal>REPEATABLE</literal> is used
+        as random seed for sampling. Note that subsequent commands may return
+        different results even if same <literal>REPEATABLE</literal> clause
+        was specified. This happens because <acronym>DML</acronym> statements
+        and maintenance operations such as <command>VACUUM</> affect physical
+        distribution of data.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..238057a 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  transam
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index cb6f8a3..76c2d3a 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -79,8 +79,9 @@ bool		synchronize_seqscans = true;
 static HeapScanDesc heap_beginscan_internal(Relation relation,
 						Snapshot snapshot,
 						int nkeys, ScanKey key,
-						bool allow_strat, bool allow_sync,
-						bool is_bitmapscan, bool temp_snap);
+						bool allow_strat, bool allow_sync, bool allow_pagemode,
+						bool is_bitmapscan, bool is_samplescan,
+						bool temp_snap);
 static HeapTuple heap_prepare_insert(Relation relation, HeapTuple tup,
 					TransactionId xid, CommandId cid, int options);
 static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf,
@@ -293,9 +294,10 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
 
 	/*
 	 * Currently, we don't have a stats counter for bitmap heap scans (but the
-	 * underlying bitmap index scans will be counted).
+	 * underlying bitmap index scans will be counted) or sample scans (we only
+	 * update stats for tuple fetches there)
 	 */
-	if (!scan->rs_bitmapscan)
+	if (!scan->rs_bitmapscan && !scan->rs_samplescan)
 		pgstat_count_heap_scan(scan->rs_rd);
 }
 
@@ -314,7 +316,7 @@ heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk, BlockNumber numBlks)
  * In page-at-a-time mode it performs additional work, namely determining
  * which tuples on the page are visible.
  */
-static void
+void
 heapgetpage(HeapScanDesc scan, BlockNumber page)
 {
 	Buffer		buffer;
@@ -1289,7 +1291,7 @@ heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
  *		heap_beginscan	- begin relation scan
  *
  * heap_beginscan_strat offers an extended API that lets the caller control
- * whether a nondefault buffer access strategy can be used, and whether
+ * whether a nondefault buffer access strategy can be used and whether
  * syncscan can be chosen (possibly resulting in the scan not starting from
  * block zero).  Both of these default to TRUE with plain heap_beginscan.
  *
@@ -1297,6 +1299,9 @@ heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
  * HeapScanDesc for a bitmap heap scan.  Although that scan technology is
  * really quite unlike a standard seqscan, there is just enough commonality
  * to make it worth using the same data structure.
+ *
+ * heap_beginscan_ss is alternate entry point for setting up a
+ * HeapScanDesc for a TABLESAMPLE scan.
  * ----------------
  */
 HeapScanDesc
@@ -1304,7 +1309,7 @@ heap_beginscan(Relation relation, Snapshot snapshot,
 			   int nkeys, ScanKey key)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   true, true, false, false);
+								   true, true, true, false, false, false);
 }
 
 HeapScanDesc
@@ -1314,7 +1319,7 @@ heap_beginscan_catalog(Relation relation, int nkeys, ScanKey key)
 	Snapshot	snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
 
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   true, true, false, true);
+								   true, true, true, false, false, true);
 }
 
 HeapScanDesc
@@ -1323,7 +1328,8 @@ heap_beginscan_strat(Relation relation, Snapshot snapshot,
 					 bool allow_strat, bool allow_sync)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   allow_strat, allow_sync, false, false);
+								   allow_strat, allow_sync, true,
+								   false, false, false);
 }
 
 HeapScanDesc
@@ -1331,14 +1337,24 @@ heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   false, false, true, false);
+								   false, false, true, true, false, false);
+}
+
+HeapScanDesc
+heap_beginscan_ss(Relation relation, Snapshot snapshot,
+				  int nkeys, ScanKey key,
+				  bool allow_strat, bool allow_pagemode)
+{
+	return heap_beginscan_internal(relation, snapshot, nkeys, key,
+								   allow_strat, false, allow_pagemode,
+								   false, true, false);
 }
 
 static HeapScanDesc
 heap_beginscan_internal(Relation relation, Snapshot snapshot,
 						int nkeys, ScanKey key,
-						bool allow_strat, bool allow_sync,
-						bool is_bitmapscan, bool temp_snap)
+						bool allow_strat, bool allow_sync, bool allow_pagemode,
+						bool is_bitmapscan, bool is_samplescan, bool temp_snap)
 {
 	HeapScanDesc scan;
 
@@ -1360,6 +1376,7 @@ heap_beginscan_internal(Relation relation, Snapshot snapshot,
 	scan->rs_snapshot = snapshot;
 	scan->rs_nkeys = nkeys;
 	scan->rs_bitmapscan = is_bitmapscan;
+	scan->rs_samplescan = is_samplescan;
 	scan->rs_strategy = NULL;	/* set in initscan */
 	scan->rs_allow_strat = allow_strat;
 	scan->rs_allow_sync = allow_sync;
@@ -1368,7 +1385,7 @@ heap_beginscan_internal(Relation relation, Snapshot snapshot,
 	/*
 	 * we can use page-at-a-time mode if it's an MVCC-safe snapshot
 	 */
-	scan->rs_pageatatime = IsMVCCSnapshot(snapshot);
+	scan->rs_pageatatime = allow_pagemode && IsMVCCSnapshot(snapshot);
 
 	/*
 	 * For a seqscan in a serializable transaction, acquire a predicate lock
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..34db3e6 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesample_method.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index fc9dd44..63feb07 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1146,7 +1146,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * sampler_random_fract());
+						int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index a951c55..20cc7a1 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -732,6 +732,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -957,6 +958,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			pname = sname = "Sample Scan";
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1074,6 +1078,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1326,6 +1331,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2220,6 +2226,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 6ebad2f..4948a26 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index 1c8be25..5cfe549 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 9892499..03c2feb 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..c7951d1
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,556 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "catalog/pg_tablesample_method.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "pgstat.h"
+#include "storage/bufmgr.h"
+#include "storage/predicate.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate,
+							 int eflags, TableSampleClause *tablesample);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+static HeapTuple samplenexttup(SampleScanState *node, HeapScanDesc scan);
+
+
+/*
+ * Initialize the sampling method - loads function info and
+ * calls the tsminit function.
+ *
+ * We need special handling for this because the tsminit function
+ * is allowed to take optional additional arguments.
+ */
+static void
+InitSamplingMethod(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(scanstate->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(scanstate->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(scanstate->tsmnexttuple));
+	if (OidIsValid(tablesample->tsmexaminetuple))
+		fmgr_info(tablesample->tsmexaminetuple, &(scanstate->tsmexaminetuple));
+	else
+		scanstate->tsmexaminetuple.fn_oid = InvalidOid;
+	fmgr_info(tablesample->tsmend, &(scanstate->tsmend));
+	fmgr_info(tablesample->tsmreset, &(scanstate->tsmreset));
+
+	InitFunctionCallInfoData(fcinfo, &scanstate->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	/* First arg is always SampleScanState */
+	fcinfo.arg[0] = PointerGetDatum(scanstate);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause cannot be NULL")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+}
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	TupleTableSlot *slot;
+	HeapScanDesc	scan;
+	HeapTuple		tuple;
+
+	/*
+	 * get information from the scan state
+	 */
+	slot = node->ss.ss_ScanTupleSlot;
+	scan = node->ss.ss_currentScanDesc;
+
+	tuple = samplenexttup(node, scan);
+
+	if (tuple)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   scan->rs_cbuf,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+/*
+ * Check visibility of the tuple.
+ */
+static bool
+SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan)
+{
+	/*
+	 * If this scan is reading whole pages at a time, there is already
+	 * visibilty info present in rs_vistuples so we can just search it
+	 * for the tupoffset.
+	 */
+	if (scan->rs_pageatatime)
+	{
+		int start = 0,
+			end = scan->rs_ntuples - 1;
+
+		/*
+		 * Do the binary search over rs_vistuples, it's already sorted by
+		 * OffsetNumber so we don't need to do any sorting ourselves here.
+		 *
+		 * We could use bsearch() here but it's slower for integers because
+		 * of the function call overhead and because it needs boiler plate code
+		 * it would not save us anything code-wise anyway.
+		 */
+		while (start <= end)
+		{
+			int mid = start + (end - start) / 2;
+			OffsetNumber curoffset = scan->rs_vistuples[mid];
+
+			if (curoffset == tupoffset)
+				return true;
+			else if (curoffset > tupoffset)
+				end = mid - 1;
+			else
+				start = mid + 1;
+		}
+
+		return false;
+	}
+	else
+	{
+		/* No pagemode, we have to check the tuple itself. */
+		Snapshot	snapshot = scan->rs_snapshot;
+		Buffer		buffer = scan->rs_cbuf;
+
+		bool visible = HeapTupleSatisfiesVisibility(tuple, snapshot, buffer);
+
+		CheckForSerializableConflictOut(visible, scan->rs_rd, tuple, buffer,
+										snapshot);
+
+		return visible;
+	}
+}
+
+/*
+ * Read next tuple using the correct sampling method.
+ */
+static HeapTuple
+samplenexttup(SampleScanState *node, HeapScanDesc scan)
+{
+	HeapTuple		tuple = &(scan->rs_ctup);
+	bool			pagemode = scan->rs_pageatatime;
+	BlockNumber		blockno;
+	Page			page;
+	ItemId			itemid;
+	OffsetNumber	tupoffset,
+					maxoffset;
+
+	if (!scan->rs_inited)
+	{
+		/*
+		 * return null immediately if relation is empty
+		 */
+		if (scan->rs_nblocks == 0)
+		{
+			Assert(!BufferIsValid(scan->rs_cbuf));
+			tuple->t_data = NULL;
+			return NULL;
+		}
+		blockno = DatumGetInt32(FunctionCall1(&node->tsmnextblock,
+											  PointerGetDatum(node)));
+		if (!BlockNumberIsValid(blockno))
+		{
+			tuple->t_data = NULL;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+		scan->rs_inited = true;
+	}
+	else
+	{
+		/* continue from previously returned page/tuple */
+		blockno = scan->rs_cblock;		/* current page */
+	}
+
+	/*
+	 * When pagemode is disabled, the scan will do visibility checks for each
+	 * tuple it finds so the buffer needs to be locked.
+	 */
+	if (!pagemode)
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+	page = (Page) BufferGetPage(scan->rs_cbuf);
+	maxoffset = PageGetMaxOffsetNumber(page);
+
+	for (;;)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		tupoffset = DatumGetUInt16(FunctionCall3(&node->tsmnexttuple,
+												 PointerGetDatum(node),
+												 UInt32GetDatum(blockno),
+												 UInt16GetDatum(maxoffset)));
+
+		if (OffsetNumberIsValid(tupoffset))
+		{
+			bool	visible;
+			bool	found;
+
+			/* Skip invalid tuple pointers. */
+			itemid = PageGetItemId(page, tupoffset);
+			if (!ItemIdIsNormal(itemid))
+				continue;
+
+			tuple->t_data = (HeapTupleHeader) PageGetItem((Page) page, itemid);
+			tuple->t_len = ItemIdGetLength(itemid);
+			ItemPointerSet(&(tuple->t_self), blockno, tupoffset);
+
+			visible = SampleTupleVisible(tuple, tupoffset, scan);
+
+			/*
+			 * Let the sampling method examine the actual tuple and decide if we
+			 * should return it.
+			 *
+			 * Note that we let it examine even invisible tuples for
+			 * statistical purposes, but not return them since user should
+			 * never see invisible tuples.
+			 */
+			if (OidIsValid(node->tsmexaminetuple.fn_oid))
+			{
+				found = DatumGetBool(FunctionCall4(&node->tsmexaminetuple,
+												   PointerGetDatum(node),
+												   UInt32GetDatum(blockno),
+												   PointerGetDatum(tuple),
+												   BoolGetDatum(visible)));
+				/* Should not happen if sampling method is well written. */
+				if (found && !visible)
+					elog(ERROR, "Sampling method wanted to return invisible tuple");
+			}
+			else
+				found = visible;
+
+			/* Found visible tuple, return it. */
+			if (found)
+			{
+				if (!pagemode)
+					LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+				break;
+			}
+			else
+			{
+				/* Try next tuple from same page. */
+				continue;
+			}
+		}
+
+
+		if (!pagemode)
+			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+
+		blockno = DatumGetInt32(FunctionCall1(&node->tsmnextblock,
+											  PointerGetDatum(node)));
+
+		/*
+		 * Report our new scan position for synchronization purposes. We
+		 * don't do that when moving backwards, however. That would just
+		 * mess up any other forward-moving scanners.
+		 *
+		 * Note: we do this before checking for end of scan so that the
+		 * final state of the position hint is back at the start of the
+		 * rel.  That's not strictly necessary, but otherwise when you run
+		 * the same query multiple times the starting position would shift
+		 * a little bit backwards on every invocation, which is confusing.
+		 * We don't guarantee any specific ordering in general, though.
+		 */
+		if (scan->rs_syncscan)
+			ss_report_location(scan->rs_rd, BlockNumberIsValid(blockno) ?
+							   blockno : scan->rs_startblock);
+
+		/*
+		 * Reached end of scan.
+		 */
+		if (!BlockNumberIsValid(blockno))
+		{
+			if (BufferIsValid(scan->rs_cbuf))
+				ReleaseBuffer(scan->rs_cbuf);
+			scan->rs_cbuf = InvalidBuffer;
+			scan->rs_cblock = InvalidBlockNumber;
+			tuple->t_data = NULL;
+			scan->rs_inited = false;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+
+		if (!pagemode)
+			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+		page = (Page) BufferGetPage(scan->rs_cbuf);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	pgstat_count_heap_getnext(scan->rs_rd);
+
+	return &(scan->rs_ctup);
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags,
+				 TableSampleClause *tablesample)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+
+	/*
+	 * Even though we aren't going to do a conventional seqscan, it is useful
+	 * to create a HeapScanDesc --- many of the fields in it are usable.
+	 */
+	node->ss.ss_currentScanDesc =
+		heap_beginscan_ss(currentRelation, estate->es_snapshot, 0, NULL,
+						  tablesample->tsmseqscan, tablesample->tsmpagemode);
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags, rte->tablesample);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	InitSamplingMethod(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished thes can.
+	 */
+	FunctionCall1(&node->tsmend, PointerGetDatum(node));
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close heap scan
+	 */
+	heap_endscan(node->ss.ss_currentScanDesc);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *node)
+{
+	heap_rescan(node->ss.ss_currentScanDesc, NULL);
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	FunctionCall1(&node->tsmreset, PointerGetDatum(node));
+
+	ExecScanReScan(&node->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 291e6a7..24be3ad 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -630,6 +630,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2013,6 +2029,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2145,6 +2162,40 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsmseqscan);
+	COPY_SCALAR_FIELD(tsmpagemode);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmexaminetuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4086,6 +4137,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4734,6 +4788,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_FuncWithArgs:
 			retval = _copyFuncWithArgs(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index fcd58ad..8ab3b0b 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2322,6 +2322,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2441,6 +2442,36 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsmseqscan);
+	COMPARE_SCALAR_FIELD(tsmpagemode);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmexaminetuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3159,6 +3190,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_FuncWithArgs:
 			retval = _equalFuncWithArgs(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index d6f1f5b..7742189 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3219,6 +3219,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index fc418fc..c087495 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -580,6 +580,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -2402,6 +2410,36 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_BOOL_FIELD(tsmseqscan);
+	WRITE_BOOL_FIELD(tsmpagemode);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmexaminetuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2431,6 +2469,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2929,6 +2968,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3270,6 +3312,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 563209c..05ed9a8 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,46 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_BOOL_FIELD(tsmseqscan);
+	READ_BOOL_FIELD(tsmpagemode);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmexaminetuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1218,6 +1258,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1313,6 +1354,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 58d78e6..5f12477 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,10 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
+				   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -265,6 +269,11 @@ set_rel_size(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_size(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Sampled relation */
+					set_tablesample_rel_size(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -332,6 +341,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +432,41 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_size
+ *	  Set size estimates for a sampled relation.
+ */
+static void
+set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	/* Mark rel with estimated output rows, width, etc */
+	set_baserel_size_estimates(root, rel);
+}
+
+/*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids	required_outer;
+	Path   *path;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	path = create_samplescan_path(root, rel, required_outer);
+	rel->pathlist = list_make1(path);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 1a0d358..51583a1 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -90,6 +90,7 @@
 #include "utils/lsyscache.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
+#include "utils/tablesample.h"
 #include "utils/tuplesort.h"
 
 
@@ -220,6 +221,73 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we dont't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	RangeTblEntry		   *rte = planner_rt_fetch(baserel->relid, root);
+	TableSampleClause	   *tablesample = rte->tablesample;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Mark the path with the correct row estimate */
+	if (path->param_info)
+		path->rows = path->param_info->ppi_rows;
+	else
+		path->rows = baserel->rows;
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(tablesample->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(tablesample->args),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples));
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = tablesample->tsmseqscan ? spc_seq_page_cost :
+					spc_random_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->startup_cost = startup_cost;
+	path->total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index cb69c03..3fc84e2 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3321,6 +3372,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index ec828cd..82771dc 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -445,6 +445,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index acfd0bc..9971b54 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2167,6 +2167,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index faca30b..ea7a47b 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,26 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+Path *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	Path		   *pathnode = makeNode(Path);
+
+	pathnode->pathtype = T_SampleScan;
+	pathnode->parent = rel;
+	pathnode->param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->pathkeys = NIL;	/* samplescan has unordered result */
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1778,6 +1798,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index cf0d317..41f71d6 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -448,6 +448,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -615,8 +616,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10223,6 +10224,12 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample opt_alias_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10548,6 +10555,31 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $2;
+					n->relation = $1;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' func_arg_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' a_expr ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/					{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13463,7 +13495,6 @@ unreserved_keyword:
 			| RELATIVE_P
 			| RELEASE
 			| RENAME
-			| REPEATABLE
 			| REPLACE
 			| REPLICA
 			| RESET
@@ -13589,6 +13620,7 @@ col_name_keyword:
 			| SETOF
 			| SMALLINT
 			| SUBSTRING
+			| TABLESAMPLE
 			| TIME
 			| TIMESTAMP
 			| TREAT
@@ -13636,6 +13668,7 @@ type_func_name_keyword:
 			| NOTNULL
 			| OUTER_P
 			| OVERLAPS
+			| REPEATABLE
 			| RIGHT
 			| SIMILAR
 			| VERBOSE
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 8d90b50..63c6f9a 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -414,6 +417,28 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *r)
+{
+	RangeTblEntry  *rte;
+	TableSampleClause *tablesample = NULL;
+
+	rte = transformTableEntry(pstate, r->relation);
+
+	if (rte->relkind != RELKIND_RELATION &&
+		rte->relkind != RELKIND_MATVIEW)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("TABLESAMPLE clause can only be used on tables and materialized views"),
+				 parser_errposition(pstate,
+									 exprLocation((Node *) r))));
+
+	tablesample = ParseTableSample(pstate, r->method, r->repeatable, r->args);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -422,7 +447,7 @@ transformTableEntry(ParseState *pstate, RangeVar *r)
 {
 	RangeTblEntry *rte;
 
-	/* We need only build a range table entry */
+	/* We first need to build a range table entry */
 	rte = addRangeTableEntry(pstate, r, r->alias,
 							 interpretInhOption(r->inhOpt), true);
 
@@ -1122,6 +1147,27 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 53bbaec..090f2a6 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -760,6 +762,135 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+extern TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				actual_arg_types[FUNC_MAX_ARGS];
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						samplemethod)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsmseqscan = tsm->tsmseqscan;
+	tablesample->tsmpagemode = tsm->tsmpagemode;
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmexaminetuple = tsm->tsmexaminetuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Transform the rest of arguments ... */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *arg = transformExpr(pstate, (Node *) lfirst(larg), EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		fargs = lappend(fargs, arg);
+
+		actual_arg_types[nargs++] = argtype;
+	}
+
+	/*
+	 * Check if parameters are correct.
+	 *
+	 * XXX: can we do better at hinting here?
+	 */
+	if (initnargs != nargs ||
+			!can_coerce_type(initnargs, actual_arg_types, init_arg_types,
+						COERCION_IMPLICIT))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("wrong parameters for tablesample method \"%s\"",
+						samplemethod)));
+
+	/* perform the necessary typecasting of arguments */
+	make_fn_arguments(pstate, fargs, actual_arg_types, init_arg_types);
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/utils/Makefile b/src/backend/utils/Makefile
index 8374533..9daa2ae 100644
--- a/src/backend/utils/Makefile
+++ b/src/backend/utils/Makefile
@@ -9,7 +9,8 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS        = fmgrtab.o
-SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time
+SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time \
+			  tablesample
 
 # location of Catalog.pm
 catalogdir  = $(top_srcdir)/src/backend/catalog
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 2fa30be..49e7a84 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -31,6 +31,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -343,6 +344,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4184,6 +4187,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for tablesample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8435,6 +8482,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index bd27168..3a8f01e 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
index 1eeabaf..f213c46 100644
--- a/src/backend/utils/misc/sampling.c
+++ b/src/backend/utils/misc/sampling.c
@@ -46,6 +46,8 @@ BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
 	bs->n = samplesize;
 	bs->t = 0;					/* blocks scanned so far */
 	bs->m = 0;					/* blocks selected so far */
+
+	sampler_random_init_state(randseed, bs->randstate);
 }
 
 bool
@@ -92,7 +94,7 @@ BlockSampler_Next(BlockSampler bs)
 	 * less than k, which means that we cannot fail to select enough blocks.
 	 *----------
 	 */
-	V = sampler_random_fract();
+	V = sampler_random_fract(bs->randstate);
 	p = 1.0 - (double) k / (double) K;
 	while (V < p)
 	{
@@ -126,8 +128,14 @@ BlockSampler_Next(BlockSampler bs)
 void
 reservoir_init_selection_state(ReservoirState rs, int n)
 {
+	/*
+	 * Reservoir sampling is not used anywhere where it would need to return
+	 * repeatable results so we can initialize it randomly.
+	 */
+	sampler_random_init_state(random(), rs->randstate);
+
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	*rs = exp(-log(sampler_random_fract()) / n);
+	rs->W = exp(-log(sampler_random_fract(rs->randstate)) / n);
 }
 
 double
@@ -142,7 +150,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 		double		V,
 					quot;
 
-		V = sampler_random_fract(); /* Generate V */
+		V = sampler_random_fract(rs->randstate); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -158,7 +166,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 	else
 	{
 		/* Now apply Algorithm Z */
-		double		W = *rs;
+		double		W = rs->W;
 		double		term = t - (double) n + 1;
 
 		for (;;)
@@ -174,7 +182,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 						tmp;
 
 			/* Generate U and X */
-			U = sampler_random_fract();
+			U = sampler_random_fract(rs->randstate);
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -203,11 +211,11 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract(rs->randstate)) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
-		*rs = W;
+		rs->W = W;
 	}
 	return S;
 }
@@ -217,10 +225,17 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
  * Random number generator used by sampling
  *----------
  */
+void
+sampler_random_init_state(long seed, SamplerRandomState randstate)
+{
+	randstate[0] = 0x330e;
+	randstate[1] = (unsigned short) seed;
+	randstate[2] = (unsigned short) (seed >> 16);
+}
 
 /* Select a random value R uniformly distributed in (0 - 1) */
 double
-sampler_random_fract()
+sampler_random_fract(SamplerRandomState randstate)
 {
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+	return pg_erand48(randstate);
 }
diff --git a/src/backend/utils/tablesample/Makefile b/src/backend/utils/tablesample/Makefile
new file mode 100644
index 0000000..df92939
--- /dev/null
+++ b/src/backend/utils/tablesample/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for utils/tablesample
+#
+# IDENTIFICATION
+#    src/backend/utils/tablesample/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/utils/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = system.o bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/tablesample/bernoulli.c b/src/backend/utils/tablesample/bernoulli.c
new file mode 100644
index 0000000..36f4bcb
--- /dev/null
+++ b/src/backend/utils/tablesample/bernoulli.c
@@ -0,0 +1,224 @@
+/*-------------------------------------------------------------------------
+ *
+ * bernoulli.c
+ *	  interface routines for BERNOULLI tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/relscan.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/* State */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* number of blocks */
+	BlockNumber blockno;		/* current block */
+	float4 probability;			/* probabilty that tuple will be returned (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	HeapScanDesc	scan = scanstate->ss.ss_currentScanDesc;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->startblock = scan->rs_startblock;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->blockno = InvalidBlockNumber;
+	sampler->probability = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	/*
+	 * Bernoulli sampling scans all blocks on the table and supports
+	 * syncscan so loop from startblock to startblock instead of
+	 * from 0 to nblocks.
+	 */
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = sampler->startblock;
+	else
+	{
+		sampler->blockno++;
+
+		if (sampler->blockno >= sampler->nblocks)
+			sampler->blockno = 0;
+
+		if (sampler->blockno == sampler->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+	float4			probability = sampler->probability;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/*
+	 * Loop over tuple offsets until the random generator returns value that
+	 * is within the probability of returning the tuple or until we reach
+	 * end of the block.
+	 *
+	 * (This is our implementation of bernoulli trial)
+	 */
+	while (sampler_random_fract(sampler->randstate) > probability)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1f;
+	}
+
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/utils/tablesample/system.c b/src/backend/utils/tablesample/system.c
new file mode 100644
index 0000000..07d1f3a
--- /dev/null
+++ b/src/backend/utils/tablesample/system.c
@@ -0,0 +1,185 @@
+/*-------------------------------------------------------------------------
+ *
+ * system.c
+ *	  interface routines for system tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	SystemSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks =
+		RelationGetNumberOfBlocks(scanstate->ss.ss_currentRelation);
+	sampler->samplesize = 1 + (int) (sampler->tblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as VACUUM for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	BlockNumber		blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1f;
+	}
+
+	*pages = baserel->pages * samplesize;
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 939d93d..94458aa 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -113,8 +113,12 @@ extern HeapScanDesc heap_beginscan_strat(Relation relation, Snapshot snapshot,
 					 bool allow_strat, bool allow_sync);
 extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key);
+extern HeapScanDesc heap_beginscan_ss(Relation relation, Snapshot snapshot,
+				  int nkeys, ScanKey key,
+				  bool allow_strat, bool allow_pagemode);
 extern void heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk,
 		   BlockNumber endBlk);
+extern void heapgetpage(HeapScanDesc scan, BlockNumber page);
 extern void heap_rescan(HeapScanDesc scan, ScanKey key);
 extern void heap_endscan(HeapScanDesc scan);
 extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 9bb6362..e2b2b4f 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -29,6 +29,7 @@ typedef struct HeapScanDescData
 	int			rs_nkeys;		/* number of scan keys */
 	ScanKey		rs_key;			/* array of scan key descriptors */
 	bool		rs_bitmapscan;	/* true if this is really a bitmap scan */
+	bool		rs_samplescan;	/* true if this is really a sample scan */
 	bool		rs_pageatatime; /* verify visibility page-at-a-time? */
 	bool		rs_allow_strat; /* allow or disallow use of access strategy */
 	bool		rs_allow_sync;	/* allow or disallow use of syncscan */
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index a680229..c711cca 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3281, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3281
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3282, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3282
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index b8a3660..a1a6f16 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5149,6 +5149,31 @@ DESCR("rank of hypothetical row without gaps");
 DATA(insert OID = 3993 ( dense_rank_final	PGNSP PGUID 12 1 0 2276 0 f f f f f f i 2 0 20 "2281 2276" "{2281,2276}" "{i,v}" _null_ _null_	hypothetical_dense_rank_final _null_ _null_ _null_ ));
 DESCR("aggregate final function");
 
+DATA(insert OID = 3285 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3286 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3287 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3288 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3289 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3290 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3291 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3292 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3293 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3294 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3296 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3297 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 0000000..98df9cb
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,77 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3280
+
+CATALOG(pg_tablesample_method,3280)
+{
+	NameData	tsmname;		/* tablesample method name */
+	bool		tsmseqscan;		/* does this method scan whole table sequentially? */
+	bool		tsmpagemode;	/* does this method scan page at a time? */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmexaminetuple;	/* optional function which can examine tuple contents and
+								   decide if tuple should be returned or not */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method					10
+#define Anum_pg_tablesample_method_tsmname			1
+#define Anum_pg_tablesample_method_tsmseqscan		2
+#define Anum_pg_tablesample_method_tsmpagemode		3
+#define Anum_pg_tablesample_method_tsminit			4
+#define Anum_pg_tablesample_method_tsmnextblock		5
+#define Anum_pg_tablesample_method_tsmnexttuple		6
+#define Anum_pg_tablesample_method_tsmexaminetuple	7
+#define Anum_pg_tablesample_method_tsmend			8
+#define Anum_pg_tablesample_method_tsmreset			9
+#define Anum_pg_tablesample_method_tsmcost			10
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3283 ( system false true tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3284 ( bernoulli true false tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 59b17f3..0a7f4da 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1213,6 +1213,24 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState		ss;
+
+	/* Sampling method functions. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmexaminetuple;
+	FmgrInfo		tsmend;
+	FmgrInfo		tsmreset;
+
+	void		   *tsmdata;		/* for use by table scan method */
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 38469ef..caaedbf 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -414,6 +416,8 @@ typedef enum NodeTag
 	T_WithClause,
 	T_CommonTableExpr,
 	T_RoleSpec,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 38ed661..3672e37 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -334,6 +334,26 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	bool		tsmseqscan;
+	bool		tsmpagemode;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmexaminetuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -534,6 +554,21 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * We are more generic than SQL Standard so we pass generic function
+ * arguments to the sampling method.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -778,6 +813,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index f6683f0..5289c43 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -279,6 +279,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 9c2000b..24003ae 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 9923f0e..89c8ded 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern Path *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+									Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 7c243ec..0a7b650 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -312,7 +312,7 @@ PG_KEYWORD("reindex", REINDEX, UNRESERVED_KEYWORD)
 PG_KEYWORD("relative", RELATIVE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("release", RELEASE, UNRESERVED_KEYWORD)
 PG_KEYWORD("rename", RENAME, UNRESERVED_KEYWORD)
-PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
+PG_KEYWORD("repeatable", REPEATABLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, COL_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 3264691..6727e55 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,10 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 6bd786d..185bd81 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
index e3e7f9c..4ac208d 100644
--- a/src/include/utils/sampling.h
+++ b/src/include/utils/sampling.h
@@ -15,7 +15,12 @@
 
 #include "storage/bufmgr.h"
 
-extern double sampler_random_fract(void);
+/* Random generator for sampling code */
+typedef unsigned short SamplerRandomState[3];
+
+extern void sampler_random_init_state(long seed,
+									  SamplerRandomState randstate);
+extern double sampler_random_fract(SamplerRandomState randstate);
 
 /* Block sampling methods */
 /* Data structure for Algorithm S from Knuth 3.4.2 */
@@ -25,6 +30,7 @@ typedef struct
 	int			n;				/* desired sample size */
 	BlockNumber t;				/* current block number */
 	int			m;				/* blocks selected so far */
+	SamplerRandomState randstate; /* random generator state */
 } BlockSamplerData;
 
 typedef BlockSamplerData *BlockSampler;
@@ -35,7 +41,12 @@ extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
 /* Reservoid sampling methods */
-typedef double ReservoirStateData;
+typedef struct
+{
+	double	W;
+	SamplerRandomState randstate; /* random generator state */
+} ReservoirStateData;
+
 typedef ReservoirStateData *ReservoirState;
 
 extern void reservoir_init_selection_state(ReservoirState rs, int n);
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index ba0b090..6b628f6 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/include/utils/tablesample.h b/src/include/utils/tablesample.h
new file mode 100644
index 0000000..1a24cb6
--- /dev/null
+++ b/src/include/utils/tablesample.h
@@ -0,0 +1,27 @@
+/*--------------------------------------------------------------------------
+ * tablesample.h
+ *	  Header file for builtin table sampling methods.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/utils/tablesample.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TABLESAMPLE_H
+#define TABLESAMPLE_H
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TABLESAMPLE_H */
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..5946edf 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..ce9abf7
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,168 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+CLOSE tablesample_cur;
+END;
+-- should fail
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+ERROR:  TABLESAMPLE clause can only be used on tables and materialized views
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index 6d3b865..300e1fb 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 8326894..d815496 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -153,3 +153,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..0d8ce39
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,42 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+CLOSE tablesample_cur;
+END;
+
+-- should fail
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+
+DROP TABLE test_tablesample CASCADE;
-- 
1.9.1

>From 23a512b5a8417d0ef656381482d30b147b872cd8 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:36:56 +0100
Subject: [PATCH 1/3] separate block sampling functions v2

---
 contrib/file_fdw/file_fdw.c         |   9 +-
 contrib/postgres_fdw/postgres_fdw.c |  10 +-
 src/backend/commands/analyze.c      | 225 +----------------------------------
 src/backend/utils/misc/Makefile     |   2 +-
 src/backend/utils/misc/sampling.c   | 226 ++++++++++++++++++++++++++++++++++++
 src/include/commands/vacuum.h       |   3 -
 src/include/utils/sampling.h        |  44 +++++++
 7 files changed, 287 insertions(+), 232 deletions(-)
 create mode 100644 src/backend/utils/misc/sampling.c
 create mode 100644 src/include/utils/sampling.h

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 4368897..249d541 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -34,6 +34,7 @@
 #include "optimizer/var.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -1005,7 +1006,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 {
 	int			numrows = 0;
 	double		rowstoskip = -1;	/* -1 means not set yet */
-	double		rstate;
+	ReservoirStateData rstate;
 	TupleDesc	tupDesc;
 	Datum	   *values;
 	bool	   *nulls;
@@ -1043,7 +1044,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 									   ALLOCSET_DEFAULT_MAXSIZE);
 
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Set up callback to identify error line number. */
 	errcallback.callback = CopyFromErrorCallback;
@@ -1087,7 +1088,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 			 * not-yet-incremented value of totalrows as t.
 			 */
 			if (rowstoskip < 0)
-				rowstoskip = anl_get_next_S(*totalrows, targrows, &rstate);
+				rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
 
 			if (rowstoskip <= 0)
 			{
@@ -1095,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * anl_random_fract());
+				int			k = (int) (targrows * sampler_random_fract());
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 63f0577..59aaff7 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -37,6 +37,7 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -202,7 +203,7 @@ typedef struct PgFdwAnalyzeState
 	/* for random sampling */
 	double		samplerows;		/* # of rows fetched */
 	double		rowstoskip;		/* # of rows to skip before next sample */
-	double		rstate;			/* random state */
+	ReservoirStateData rstate;		/* state for reservoir sampling*/
 
 	/* working memory contexts */
 	MemoryContext anl_cxt;		/* context for per-analyze lifespan data */
@@ -2393,7 +2394,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 	astate.numrows = 0;
 	astate.samplerows = 0;
 	astate.rowstoskip = -1;		/* -1 means not set yet */
-	astate.rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&astate.rstate, targrows);
 
 	/* Remember ANALYZE context, and create a per-tuple temp context */
 	astate.anl_cxt = CurrentMemoryContext;
@@ -2533,13 +2534,12 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		 * analyze.c; see Jeff Vitter's paper.
 		 */
 		if (astate->rowstoskip < 0)
-			astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
-												&astate->rstate);
+			astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
 
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * anl_random_fract());
+			pos = (int) (targrows * sampler_random_fract());
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index d2856a3..fc9dd44 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -88,10 +78,6 @@ static BufferAccessStrategy vac_strategy;
 static void do_analyze_rel(Relation onerel, VacuumStmt *vacstmt,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -947,94 +933,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1080,7 +978,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	BlockNumber totalblocks;
 	TransactionId OldestXmin;
 	BlockSamplerData bs;
-	double		rstate;
+	ReservoirStateData rstate;
 
 	Assert(targrows > 0);
 
@@ -1090,9 +988,9 @@ acquire_sample_rows(Relation onerel, int elevel,
 	OldestXmin = GetOldestXmin(onerel, true);
 
 	/* Prepare for sampling block numbers */
-	BlockSampler_Init(&bs, totalblocks, targrows);
+	BlockSampler_Init(&bs, totalblocks, targrows, random());
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Outer loop over blocks to sample */
 	while (BlockSampler_HasMore(&bs))
@@ -1240,8 +1138,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 					 * t.
 					 */
 					if (rowstoskip < 0)
-						rowstoskip = anl_get_next_S(samplerows, targrows,
-													&rstate);
+						rowstoskip = reservoir_get_next_S(&rstate, samplerows, targrows);
 
 					if (rowstoskip <= 0)
 					{
@@ -1249,7 +1146,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1308,116 +1205,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
-/*
- * These two routines embody Algorithm Z from "Random sampling with a
- * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
- * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
- * of the count S of records to skip before processing another record.
- * It is computed primarily based on t, the number of records already read.
- * The only extra state needed between calls is W, a random state variable.
- *
- * anl_init_selection_state computes the initial W value.
- *
- * Given that we've already read t records (t >= n), anl_get_next_S
- * determines the number of records to skip before the next record is
- * processed.
- */
-double
-anl_init_selection_state(int n)
-{
-	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
-}
-
-double
-anl_get_next_S(double t, int n, double *stateptr)
-{
-	double		S;
-
-	/* The magic constant here is T from Vitter's paper */
-	if (t <= (22.0 * n))
-	{
-		/* Process records using Algorithm X until t is large enough */
-		double		V,
-					quot;
-
-		V = anl_random_fract(); /* Generate V */
-		S = 0;
-		t += 1;
-		/* Note: "num" in Vitter's code is always equal to t - n */
-		quot = (t - (double) n) / t;
-		/* Find min S satisfying (4.1) */
-		while (quot > V)
-		{
-			S += 1;
-			t += 1;
-			quot *= (t - (double) n) / t;
-		}
-	}
-	else
-	{
-		/* Now apply Algorithm Z */
-		double		W = *stateptr;
-		double		term = t - (double) n + 1;
-
-		for (;;)
-		{
-			double		numer,
-						numer_lim,
-						denom;
-			double		U,
-						X,
-						lhs,
-						rhs,
-						y,
-						tmp;
-
-			/* Generate U and X */
-			U = anl_random_fract();
-			X = t * (W - 1.0);
-			S = floor(X);		/* S is tentatively set to floor(X) */
-			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
-			tmp = (t + 1) / term;
-			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
-			rhs = (((t + X) / (term + S)) * term) / t;
-			if (lhs <= rhs)
-			{
-				W = rhs / lhs;
-				break;
-			}
-			/* Test if U <= f(S)/cg(X) */
-			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
-			if ((double) n < S)
-			{
-				denom = t;
-				numer_lim = term + S;
-			}
-			else
-			{
-				denom = t - (double) n + S;
-				numer_lim = t + 1;
-			}
-			for (numer = t + S; numer >= numer_lim; numer -= 1)
-			{
-				y *= numer / denom;
-				denom -= 1;
-			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
-			if (exp(log(y) / n) <= (t + X) / t)
-				break;
-		}
-		*stateptr = W;
-	}
-	return S;
-}
-
 /*
  * qsort comparator for sorting rows[] array
  */
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index 378b77e..7889101 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o rls.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..1eeabaf
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,226 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Relation block sampling routines.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler provides algorithm for block level sampling of a relation
+ * as discussed on pgsql-hackers 2004-04-02 (subject "Large DB")
+ * It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table. If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
+				  long randseed)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+/*
+ * These two routines embody Algorithm Z from "Random sampling with a
+ * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
+ * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
+ * of the count S of records to skip before processing another record.
+ * It is computed primarily based on t, the number of records already read.
+ * The only extra state needed between calls is W, a random state variable.
+ *
+ * reservoir_init_selection_state computes the initial W value.
+ *
+ * Given that we've already read t records (t >= n), reservoir_get_next_S
+ * determines the number of records to skip before the next record is
+ * processed.
+ */
+void
+reservoir_init_selection_state(ReservoirState rs, int n)
+{
+	/* Initial value of W (for use when Algorithm Z is first applied) */
+	*rs = exp(-log(sampler_random_fract()) / n);
+}
+
+double
+reservoir_get_next_S(ReservoirState rs, double t, int n)
+{
+	double		S;
+
+	/* The magic constant here is T from Vitter's paper */
+	if (t <= (22.0 * n))
+	{
+		/* Process records using Algorithm X until t is large enough */
+		double		V,
+					quot;
+
+		V = sampler_random_fract(); /* Generate V */
+		S = 0;
+		t += 1;
+		/* Note: "num" in Vitter's code is always equal to t - n */
+		quot = (t - (double) n) / t;
+		/* Find min S satisfying (4.1) */
+		while (quot > V)
+		{
+			S += 1;
+			t += 1;
+			quot *= (t - (double) n) / t;
+		}
+	}
+	else
+	{
+		/* Now apply Algorithm Z */
+		double		W = *rs;
+		double		term = t - (double) n + 1;
+
+		for (;;)
+		{
+			double		numer,
+						numer_lim,
+						denom;
+			double		U,
+						X,
+						lhs,
+						rhs,
+						y,
+						tmp;
+
+			/* Generate U and X */
+			U = sampler_random_fract();
+			X = t * (W - 1.0);
+			S = floor(X);		/* S is tentatively set to floor(X) */
+			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
+			tmp = (t + 1) / term;
+			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
+			rhs = (((t + X) / (term + S)) * term) / t;
+			if (lhs <= rhs)
+			{
+				W = rhs / lhs;
+				break;
+			}
+			/* Test if U <= f(S)/cg(X) */
+			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
+			if ((double) n < S)
+			{
+				denom = t;
+				numer_lim = term + S;
+			}
+			else
+			{
+				denom = t - (double) n + S;
+				numer_lim = t + 1;
+			}
+			for (numer = t + S; numer >= numer_lim; numer -= 1)
+			{
+				y *= numer / denom;
+				denom -= 1;
+			}
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			if (exp(log(y) / n) <= (t + X) / t)
+				break;
+		}
+		*rs = W;
+	}
+	return S;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract()
+{
+	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+}
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 4275484..d38fead 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -178,8 +178,5 @@ extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt,
 extern void analyze_rel(Oid relid, VacuumStmt *vacstmt,
 			bool in_outer_xact, BufferAccessStrategy bstrategy);
 extern bool std_typanalyze(VacAttrStats *stats);
-extern double anl_random_fract(void);
-extern double anl_init_selection_state(int n);
-extern double anl_get_next_S(double t, int n, double *stateptr);
 
 #endif   /* VACUUM_H */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..e3e7f9c
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,44 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+extern double sampler_random_fract(void);
+
+/* Block sampling methods */
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize, long randseed);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Reservoid sampling methods */
+typedef double ReservoirStateData;
+typedef ReservoirStateData *ReservoirState;
+
+extern void reservoir_init_selection_state(ReservoirState rs, int n);
+extern double reservoir_get_next_S(ReservoirState rs, double t, int n);
+
+#endif /* SAMPLING_H */
-- 
1.9.1

>From 813e641c9ae202b8bfb4be4b978bb2c22a60eea4 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Sun, 15 Mar 2015 17:39:22 +0100
Subject: [PATCH 4/4] tablesample api doc v1

---
 doc/src/sgml/filelist.sgml           |   1 +
 doc/src/sgml/postgres.sgml           |   1 +
 doc/src/sgml/tablesample-method.sgml | 169 +++++++++++++++++++++++++++++++++++
 3 files changed, 171 insertions(+)
 create mode 100644 doc/src/sgml/tablesample-method.sgml

diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index 89fff77..23d932d 100644
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@@ -98,6 +98,7 @@
 <!ENTITY protocol   SYSTEM "protocol.sgml">
 <!ENTITY sources    SYSTEM "sources.sgml">
 <!ENTITY storage    SYSTEM "storage.sgml">
+<!ENTITY tablesample-method SYSTEM "tablesample-method.sgml">
 
 <!-- contrib information -->
 <!ENTITY contrib         SYSTEM "contrib.sgml">
diff --git a/doc/src/sgml/postgres.sgml b/doc/src/sgml/postgres.sgml
index e378d69..dc1f020 100644
--- a/doc/src/sgml/postgres.sgml
+++ b/doc/src/sgml/postgres.sgml
@@ -250,6 +250,7 @@
   &gin;
   &brin;
   &storage;
+  &tablesample-method;
   &bki;
   &planstats;
 
diff --git a/doc/src/sgml/tablesample-method.sgml b/doc/src/sgml/tablesample-method.sgml
new file mode 100644
index 0000000..2d6d323
--- /dev/null
+++ b/doc/src/sgml/tablesample-method.sgml
@@ -0,0 +1,169 @@
+<!-- doc/src/sgml/tablesample-method.sgml -->
+
+<chapter id="tablesample-method">
+ <title>Writing A TABLESAMPLE Sampling Method</title>
+
+ <indexterm zone="tablesample-method">
+  <primary>tablesample method</primary>
+ </indexterm>
+
+ <para>
+  The <command>TABLESAMPLE</command> clause implementation in
+  <productname>PostgreSQL</> supports creating a custom sampling methods.
+  These methods control what sample of the table will be returned when the
+  <command>TABLESAMPLE</command> clause is used.
+ </para>
+
+ <sect1 id="tablesample-method-functions">
+  <title>Tablesample Method Functions</title>
+
+  <para>
+   The tablesample method must provide following set of functions:
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_init (SampleScanState *scanstate,
+         uint32 seed, ...);
+</programlisting>
+   Initialize the tablesample scan. The function is called at the beginning
+   of each relation scan.
+  </para>
+  <para>
+   Note that the first two parameters are required but you can specify
+   additional parameters which then will be used by the <command>TABLESAMPLE</>
+   clause to determine the required user input in the query itself.
+   This means that if your function will specify additional float4 parameter
+   named percent, the user will have to call the tablesample method with
+   expression which evaluates (or can be coerced) to float4.
+   For example this definition:
+<programlisting>
+tsm_init (SampleScanState *scanstate,
+          uint32 seed, float4 pct);
+</programlisting>
+Will lead to SQL call like this:
+<programlisting>
+... TABLESAMPLE yourmethod(0.5) ...
+</programlisting>
+  </para>
+
+  <para>
+<programlisting>
+BlockNumber
+tsm_nextblock (SampleScanState *scanstate);
+</programlisting>
+   Returns the block number of next page to be scanned. InvalidBlockNumber
+   should be returned if the sampling has reached end of the relation.
+  </para>
+
+  <para>
+<programlisting>
+OffsetNumber
+tsm_nexttuple (SampleScanState *scanstate, BlockNumber blockno,
+               OffsetNumber maxoffset);
+</programlisting>
+   Return next tuple offset for the current page. InvalidOffsetNumber should
+   be returned if the sampling has reached end of the page.
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_end (SampleScanState *scanstate);
+</programlisting>
+   The scan has finished, cleanup any left over state.
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_reset (SampleScanState *scanstate);
+</programlisting>
+   The scan needs to rescan the relation again, reset any tablesample method
+   state.
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_cost (PlannerInfo *root, Path *path, RelOptInfo *baserel,
+          List *args, BlockNumber *pages, double *tuples);
+</programlisting>
+   This function is used by optimizer to decide best plan and is also used
+   for output of <command>EXPLAIN</>.
+  </para>
+
+  <para>
+   There is function that tablesampling method can implement in order to gain
+   more fine grained control over sampling. This function is optional:
+  </para>
+
+  <para>
+<programlisting>
+bool
+tsm_examinetuple (SampleScanState *scanstate, BlockNumber blockno,
+                  HeapTuple tuple, bool visible);
+</programlisting>
+   Function that enables the sampling method to examine contents of the tuple
+   (for example to collect some internal statistics). The return value of this
+   function is used to determine if the tuple should be returned to client.
+   Note that this function will receive even invisible tuples but it is not
+   allowed to return true for such tuple (if it does,
+   <productname>PostgreSQL</> will raise an error).
+  </para>
+
+  <para>
+  As you can see most of the tablesample method interfaces get the
+  <structname>SampleScanState</> as a first parameter. This structure holds
+  state of the current scan and also provides storage for the tablesample
+  method's state. It is defined as following:
+<programlisting>
+typedef struct SampleScanState
+{
+    ScanState   ss;
+    FmgrInfo    tsminit;
+    FmgrInfo    tsmnextblock;
+    FmgrInfo    tsmnexttuple;
+    FmgrInfo    tsmexaminetuple;
+    FmgrInfo    tsmend;
+    FmgrInfo    tsmreset;
+    void       *tsmdata;
+} SampleScanState;
+</programlisting>
+  Where <structfield>ss</> is the <structname>ScanState</> itself. From it, you
+  can get <structfield>ss_currentRelation</> (currently scanned relation) and
+  <structfield>ss_currentScanDesc</> (information about the scan).
+  Those are usually useful for the <function>tsm_init</> function.
+  The <structfield>tsminit</>, <structfield>tsmnextblock</>,
+  <structfield>tsmnexttuple</>, <structfield>tsmend</> and
+  <structfield>tsmreset</> are pointers to the tablesample method functions for
+  use by the sample scan itself and the tablesample method does not need to be
+  concerned about these values. The <structfield>tsmdata</> can be used by
+  tablesample method to store any state info it might need during the scan.
+  </para>
+ </sect1>
+
+ <sect1 id="tablesample-method-sql">
+  <title>Tablesample Method Installation</title>
+
+  <para>
+   Once you have written and built the custom tablesample method, you can
+   install it using the SQL statement
+   <xref linkend="sql-createtablesamplemethod"> and removed again using
+   <xref linkend="sql-droptablesamplemethod">.
+  </para>
+
+ </sect1>
+
+ <sect1 id="tablesample-method-example">
+  <title>Tablesample Method Example</title>
+
+  <para>
+   Example of how to implement custom tablesample method can be found in the
+   <productname>PostgreSQL</>'s sources under
+   <filename>src/test/modules/tablesample</> directory.
+  </para>
+ </sect1>
+
+</chapter>
-- 
1.9.1

>From 01040f72fffe090e9fcd409bfd43c5ed4da26897 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:51:44 +0100
Subject: [PATCH 3/4] tablesample-ddl v6

---
 doc/src/sgml/ref/allfiles.sgml                     |   2 +
 doc/src/sgml/ref/create_tablesamplemethod.sgml     | 184 +++++++++
 doc/src/sgml/ref/drop_tablesamplemethod.sgml       |  87 +++++
 doc/src/sgml/reference.sgml                        |   2 +
 src/backend/catalog/dependency.c                   |  15 +-
 src/backend/catalog/objectaddress.c                |  65 +++-
 src/backend/commands/Makefile                      |   6 +-
 src/backend/commands/dropcmds.c                    |   4 +
 src/backend/commands/event_trigger.c               |   3 +
 src/backend/commands/tablecmds.c                   |   1 +
 src/backend/commands/tablesample.c                 | 427 +++++++++++++++++++++
 src/backend/parser/gram.y                          |  14 +-
 src/backend/tcop/utility.c                         |  12 +
 src/bin/pg_dump/common.c                           |   5 +
 src/bin/pg_dump/pg_dump.c                          | 177 +++++++++
 src/bin/pg_dump/pg_dump.h                          |  11 +-
 src/bin/pg_dump/pg_dump_sort.c                     |  11 +-
 src/include/catalog/dependency.h                   |   1 +
 src/include/catalog/pg_tablesample_method.h        |  11 +
 src/include/nodes/parsenodes.h                     |   1 +
 src/include/parser/kwlist.h                        |   1 +
 src/test/modules/Makefile                          |   3 +-
 src/test/modules/tablesample/.gitignore            |   4 +
 src/test/modules/tablesample/Makefile              |  21 +
 .../modules/tablesample/expected/tablesample.out   |  38 ++
 src/test/modules/tablesample/sql/tablesample.sql   |  14 +
 src/test/modules/tablesample/tsm_test--1.0.sql     |  52 +++
 src/test/modules/tablesample/tsm_test.c            | 228 +++++++++++
 src/test/modules/tablesample/tsm_test.control      |   5 +
 29 files changed, 1394 insertions(+), 11 deletions(-)
 create mode 100644 doc/src/sgml/ref/create_tablesamplemethod.sgml
 create mode 100644 doc/src/sgml/ref/drop_tablesamplemethod.sgml
 create mode 100644 src/backend/commands/tablesample.c
 create mode 100644 src/test/modules/tablesample/.gitignore
 create mode 100644 src/test/modules/tablesample/Makefile
 create mode 100644 src/test/modules/tablesample/expected/tablesample.out
 create mode 100644 src/test/modules/tablesample/sql/tablesample.sql
 create mode 100644 src/test/modules/tablesample/tsm_test--1.0.sql
 create mode 100644 src/test/modules/tablesample/tsm_test.c
 create mode 100644 src/test/modules/tablesample/tsm_test.control

diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index 5b4692f..d31a2db 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -78,6 +78,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY createServer       SYSTEM "create_server.sgml">
 <!ENTITY createTable        SYSTEM "create_table.sgml">
 <!ENTITY createTableAs      SYSTEM "create_table_as.sgml">
+<!ENTITY createTablesampleMethod SYSTEM "create_tablesamplemethod.sgml">
 <!ENTITY createTableSpace   SYSTEM "create_tablespace.sgml">
 <!ENTITY createTrigger      SYSTEM "create_trigger.sgml">
 <!ENTITY createTSConfig     SYSTEM "create_tsconfig.sgml">
@@ -119,6 +120,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY dropSequence       SYSTEM "drop_sequence.sgml">
 <!ENTITY dropServer         SYSTEM "drop_server.sgml">
 <!ENTITY dropTable          SYSTEM "drop_table.sgml">
+<!ENTITY dropTablesampleMethod SYSTEM "drop_tablesamplemethod.sgml">
 <!ENTITY dropTableSpace     SYSTEM "drop_tablespace.sgml">
 <!ENTITY dropTrigger        SYSTEM "drop_trigger.sgml">
 <!ENTITY dropTSConfig       SYSTEM "drop_tsconfig.sgml">
diff --git a/doc/src/sgml/ref/create_tablesamplemethod.sgml b/doc/src/sgml/ref/create_tablesamplemethod.sgml
new file mode 100644
index 0000000..ff105d2
--- /dev/null
+++ b/doc/src/sgml/ref/create_tablesamplemethod.sgml
@@ -0,0 +1,184 @@
+<!--
+doc/src/sgml/ref/create_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-CREATETABLESAMPLEMETHOD">
+ <indexterm zone="sql-createtablesamplemethod">
+  <primary>CREATE TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE TABLESAMPLE METHOD</refname>
+  <refpurpose>define custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE TABLESAMPLE METHOD <replaceable class="parameter">name</replaceable> (
+    INIT = <replaceable class="parameter">init_function</replaceable> ,
+    NEXTBLOCK = <replaceable class="parameter">nextblock_function</replaceable> ,
+    NEXTTUPLE = <replaceable class="parameter">nexttuple_function</replaceable> ,
+    END = <replaceable class="parameter">end_function</replaceable> ,
+    RESET = <replaceable class="parameter">reset_function</replaceable> ,
+    COST = <replaceable class="parameter">cost_function</replaceable>
+    [ , EXAMINETUPLE = <replaceable class="parameter">examinetuple_function</replaceable> ]
+    [ , SEQSCAN = <replaceable class="parameter">seqscan</replaceable> ]
+    [ , PAGEMODE = <replaceable class="parameter">pagemode</replaceable> ]
+)
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE TABLESAMPLE METHOD</command> creates a tablesample method.
+   A tablesample method provides alrorithm for reading sample part of a table
+   when used in <command>TABLESAMPLE</> clause of a <command>SELECT</>
+   statement.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the tablesample method to be created. This name must be
+      unique within the database.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">init_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the init function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nextblock_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-block function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nexttuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-tuple function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">end_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the end function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">reset_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the reset function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">cost_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the costing function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">examinetuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the function for inspecting the tuple contents in order
+      to make decision if it should be returned or not. This parameter
+      is optional.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">seqscan</replaceable></term>
+    <listitem>
+     <para>
+      True if the sampling method will do sequential scan of the whole table.
+      Used for cost estimation and syncscan. The default value if not specified
+      is False.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">pagemode</replaceable></term>
+    <listitem>
+     <para>
+      True if the sampling method will read whole page at a time. The default
+      value if not specified is False.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+  <para>
+   The function names can be schema-qualified if necessary.  Argument types
+   are not given, since the argument list for each type of function is
+   predetermined.  All functions are required.
+  </para>
+
+  <para>
+   The arguments can appear in any order, not only the one shown above.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>CREATE TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-droptablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/ref/drop_tablesamplemethod.sgml b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
new file mode 100644
index 0000000..dffd2ec
--- /dev/null
+++ b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
@@ -0,0 +1,87 @@
+<!--
+doc/src/sgml/ref/drop_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-DROPTABLESAMPLEMETHOD">
+ <indexterm zone="sql-droptablesamplemethod">
+  <primary>DROP TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DROP TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP TABLESAMPLE METHOD</refname>
+  <refpurpose>remove a custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP TABLESAMPLE METHOD [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>DROP TABLESAMPLE METHOD</command> drop an existing tablesample
+   method.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the tablesample method does not exist.
+      A notice is issued in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of an existing tablesample method to be removed.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>DROP TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createtablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index 65ad795..4f55893 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -106,6 +106,7 @@
    &createServer;
    &createTable;
    &createTableAs;
+   &createTablesampleMethod;
    &createTableSpace;
    &createTSConfig;
    &createTSDictionary;
@@ -147,6 +148,7 @@
    &dropSequence;
    &dropServer;
    &dropTable;
+   &dropTablesampleMethod;
    &dropTableSpace;
    &dropTSConfig;
    &dropTSDictionary;
diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index bacb242..6acb5b3 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -46,6 +46,7 @@
 #include "catalog/pg_policy.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -157,7 +158,8 @@ static const Oid object_classes[MAX_OCLASS] = {
 	DefaultAclRelationId,		/* OCLASS_DEFACL */
 	ExtensionRelationId,		/* OCLASS_EXTENSION */
 	EventTriggerRelationId,		/* OCLASS_EVENT_TRIGGER */
-	PolicyRelationId			/* OCLASS_POLICY */
+	PolicyRelationId,			/* OCLASS_POLICY */
+	TableSampleMethodRelationId			/* OCLASS_TABLESAMPLEMETHOD */
 };
 
 
@@ -1265,6 +1267,10 @@ doDeletion(const ObjectAddress *object, int flags)
 			RemovePolicyById(object->objectId);
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			RemoveTablesampleMethodById(object->objectId);
+			break;
+
 		default:
 			elog(ERROR, "unrecognized object class: %u",
 				 object->classId);
@@ -1794,6 +1800,10 @@ find_expr_references_walker(Node *node,
 				case RTE_RELATION:
 					add_object_address(OCLASS_CLASS, rte->relid, 0,
 									   context->addrs);
+					if (rte->tablesample)
+						add_object_address(OCLASS_TABLESAMPLEMETHOD,
+										   rte->tablesample->tsmid, 0,
+										   context->addrs);
 					break;
 				default:
 					break;
@@ -2373,6 +2383,9 @@ getObjectClass(const ObjectAddress *object)
 
 		case PolicyRelationId:
 			return OCLASS_POLICY;
+
+		case TableSampleMethodRelationId:
+			return OCLASS_TABLESAMPLEMETHOD;
 	}
 
 	/* shouldn't get here */
diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index e82a448..3f47076 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -44,6 +44,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_policy.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -429,7 +430,19 @@ static const ObjectPropertyType ObjectProperty[] =
 		Anum_pg_type_typacl,
 		ACL_KIND_TYPE,
 		true
-	}
+	},
+	{
+		TableSampleMethodRelationId,
+		TableSampleMethodOidIndexId,
+		TABLESAMPLEMETHODOID,
+		TABLESAMPLEMETHODNAME,
+		Anum_pg_tablesample_method_tsmname,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		-1,
+		true
+	},
 };
 
 /*
@@ -528,7 +541,9 @@ ObjectTypeMap[] =
 	/* OCLASS_EVENT_TRIGGER */
 	{ "event trigger", OBJECT_EVENT_TRIGGER },
 	/* OCLASS_POLICY */
-	{ "policy", OBJECT_POLICY }
+	{ "policy", OBJECT_POLICY },
+	/* OCLASS_TABLESAMPLEMETHOD */
+	{ "tablesample method", OBJECT_TABLESAMPLEMETHOD }
 };
 
 const ObjectAddress InvalidObjectAddress =
@@ -683,6 +698,7 @@ get_object_address(ObjectType objtype, List *objname, List *objargs,
 			case OBJECT_FDW:
 			case OBJECT_FOREIGN_SERVER:
 			case OBJECT_EVENT_TRIGGER:
+			case OBJECT_TABLESAMPLEMETHOD:
 				address = get_object_address_unqualified(objtype,
 														 objname, missing_ok);
 				break;
@@ -921,6 +937,9 @@ get_object_address_unqualified(ObjectType objtype,
 			case OBJECT_EVENT_TRIGGER:
 				msg = gettext_noop("event trigger name cannot be qualified");
 				break;
+			case OBJECT_TABLESAMPLEMETHOD:
+				msg = gettext_noop("tablesample method name cannot be qualified");
+				break;
 			default:
 				elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 				msg = NULL;		/* placate compiler */
@@ -981,6 +1000,11 @@ get_object_address_unqualified(ObjectType objtype,
 			address.objectId = get_event_trigger_oid(name, missing_ok);
 			address.objectSubId = 0;
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			address.classId = TableSampleMethodRelationId;
+			address.objectId = get_tablesample_method_oid(name, missing_ok);
+			address.objectSubId = 0;
+			break;
 		default:
 			elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 			/* placate compiler, which doesn't know elog won't return */
@@ -2044,6 +2068,7 @@ check_object_ownership(Oid roleid, ObjectType objtype, ObjectAddress address,
 			break;
 		case OBJECT_TSPARSER:
 		case OBJECT_TSTEMPLATE:
+		case OBJECT_TABLESAMPLEMETHOD:
 			/* We treat these object types as being owned by superusers */
 			if (!superuser_arg(roleid))
 				ereport(ERROR,
@@ -2982,6 +3007,21 @@ getObjectDescription(const ObjectAddress *object)
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				appendStringInfo(&buffer, _("tablesample method %s"),
+					 NameStr(((Form_pg_tablesample_method) GETSTRUCT(tup))->tsmname));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
@@ -3459,6 +3499,10 @@ getObjectTypeDescription(const ObjectAddress *object)
 			appendStringInfoString(&buffer, "policy");
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			appendStringInfoString(&buffer, "tablesample method");
+			break;
+
 		default:
 			appendStringInfo(&buffer, "unrecognized %u", object->classId);
 			break;
@@ -4381,6 +4425,23 @@ getObjectIdentityParts(const ObjectAddress *object,
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+				Form_pg_tablesample_method tsmForm;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				tsmForm = (Form_pg_tablesample_method) GETSTRUCT(tup);
+				appendStringInfoString(&buffer,
+							   quote_identifier(NameStr(tsmForm->tsmname)));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index b1ac704..04fcd8c 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -18,8 +18,8 @@ OBJS = aggregatecmds.o alter.o analyze.o async.o cluster.o comment.o  \
 	event_trigger.o explain.o extension.o foreigncmds.o functioncmds.o \
 	indexcmds.o lockcmds.o matview.o operatorcmds.o opclasscmds.o \
 	policy.o portalcmds.o prepare.o proclang.o \
-	schemacmds.o seclabel.o sequence.o tablecmds.o tablespace.o trigger.o \
-	tsearchcmds.o typecmds.o user.o vacuum.o vacuumlazy.o \
-	variable.o view.o
+	schemacmds.o seclabel.o sequence.o tablecmds.o tablesample.o \
+	tablespace.o trigger.o tsearchcmds.o typecmds.o user.o vacuum.o \
+	vacuumlazy.o variable.o view.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/commands/dropcmds.c b/src/backend/commands/dropcmds.c
index a1b0d4d..c307dcf 100644
--- a/src/backend/commands/dropcmds.c
+++ b/src/backend/commands/dropcmds.c
@@ -429,6 +429,10 @@ does_not_exist_skipping(ObjectType objtype, List *objname, List *objargs)
 				}
 			}
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			msg = gettext_noop("tablesample method \"%s\" does not exist, skipping");
+			name = NameListToString(objname);
+			break;
 		default:
 			elog(ERROR, "unexpected object type (%d)", (int) objtype);
 			break;
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 4bcc327..9e9ef38 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -97,6 +97,7 @@ static event_trigger_support_data event_trigger_support[] = {
 	{"SEQUENCE", true},
 	{"SERVER", true},
 	{"TABLE", true},
+	{"TABLESAMPLE METHOD", true},
 	{"TABLESPACE", false},
 	{"TRIGGER", true},
 	{"TEXT SEARCH CONFIGURATION", true},
@@ -1089,6 +1090,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_SEQUENCE:
 		case OBJECT_TABCONSTRAINT:
 		case OBJECT_TABLE:
+		case OBJECT_TABLESAMPLEMETHOD:
 		case OBJECT_TRIGGER:
 		case OBJECT_TSCONFIGURATION:
 		case OBJECT_TSDICTIONARY:
@@ -1146,6 +1148,7 @@ EventTriggerSupportsObjectClass(ObjectClass objclass)
 		case OCLASS_DEFACL:
 		case OCLASS_EXTENSION:
 		case OCLASS_POLICY:
+		case OCLASS_TABLESAMPLEMETHOD:
 			return true;
 
 		case MAX_OCLASS:
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 002319e..7790afc 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8256,6 +8256,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 			case OCLASS_USER_MAPPING:
 			case OCLASS_DEFACL:
 			case OCLASS_EXTENSION:
+			case OCLASS_TABLESAMPLEMETHOD:
 
 				/*
 				 * We don't expect any of these sorts of objects to depend on
diff --git a/src/backend/commands/tablesample.c b/src/backend/commands/tablesample.c
new file mode 100644
index 0000000..f40820b
--- /dev/null
+++ b/src/backend/commands/tablesample.c
@@ -0,0 +1,427 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *	  Commands to manipulate tablesample methods
+ *
+ * Table sampling methods provide algorithms for doing sample scan over
+ * the table.
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/tablesample.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "access/heapam.h"
+#include "access/htup_details.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/objectaccess.h"
+#include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
+#include "catalog/pg_type.h"
+#include "commands/defrem.h"
+#include "miscadmin.h"
+#include "parser/parse_func.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+
+static Datum
+get_tablesample_method_func(DefElem *defel, int attnum)
+{
+	List	   *funcName = defGetQualifiedName(defel);
+	/* Big enough size for our needs. */
+	Oid		   *typeId = palloc0(7 * sizeof(Oid));
+	Oid			retTypeId;
+	int			nargs;
+	Oid			procOid = InvalidOid;
+	FuncCandidateList clist;
+
+	switch (attnum)
+	{
+		case Anum_pg_tablesample_method_tsminit:
+			/*
+			 * tsminit needs special handling because it is defined as function
+			 * with 3 or more arguments and only first two arguments must have
+			 * specific type, the rest is up to the tablesample method creator.
+			 */
+			{
+				nargs = 2;
+				typeId[0] = INTERNALOID;
+				typeId[1] = INT4OID;
+				retTypeId = VOIDOID;
+
+				clist = FuncnameGetCandidates(funcName, -1, NIL, false, false, false);
+
+				while (clist)
+				{
+					if (clist->nargs >= 3 &&
+						memcmp(typeId, clist->args, nargs * sizeof(Oid)) == 0)
+					{
+						procOid = clist->oid;
+						/* Save real function signature for future errors. */
+						nargs = clist->nargs;
+						pfree(typeId);
+						typeId = clist->args;
+						break;
+					}
+					clist = clist->next;
+				}
+
+				if (!OidIsValid(procOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_UNDEFINED_FUNCTION),
+							 errmsg("function \"%s\" does not exist or does not have valid signature",
+									NameListToString(funcName)),
+							 errhint("The tamplesample method init function "
+									 "must have at least 3 input parameters "
+									 "with first one of type INTERNAL and second of type INTEGER.")));
+			}
+			break;
+
+		case Anum_pg_tablesample_method_tsmnextblock:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = INT4OID;
+			break;
+		case Anum_pg_tablesample_method_tsmnexttuple:
+			nargs = 3;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INT2OID;
+			retTypeId = INT2OID;
+			break;
+		case Anum_pg_tablesample_method_tsmexaminetuple:
+			nargs = 4;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = BOOLOID;
+			retTypeId = BOOLOID;
+			break;
+		case Anum_pg_tablesample_method_tsmend:
+		case Anum_pg_tablesample_method_tsmreset:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		case Anum_pg_tablesample_method_tsmcost:
+			nargs = 7;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INTERNALOID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = INTERNALOID;
+			typeId[4] = INTERNALOID;
+			typeId[5] = INTERNALOID;
+			typeId[6] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		default:
+			/* should not be here */
+			elog(ERROR, "unrecognized attribute for tablesample method: %d",
+				 attnum);
+			nargs = 0;			/* keep compiler quiet */
+	}
+
+	if (!OidIsValid(procOid))
+		procOid = LookupFuncName(funcName, nargs, typeId, false);
+	if (get_func_rettype(procOid) != retTypeId)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("function %s should return type %s",
+						func_signature_string(funcName, nargs, NIL, typeId),
+						format_type_be(retTypeId))));
+
+	return ObjectIdGetDatum(procOid);
+}
+
+/*
+ * make pg_depend entries for a new pg_tablesample_method entry
+ */
+static void
+makeTablesampleMethodDeps(HeapTuple tuple)
+{
+	Form_pg_tablesample_method tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	ObjectAddress	myself,
+					referenced;
+
+	myself.classId = TableSampleMethodRelationId;
+	myself.objectId = HeapTupleGetOid(tuple);
+	myself.objectSubId = 0;
+
+	/* dependency on extension */
+	recordDependencyOnCurrentExtension(&myself, false);
+
+	/* dependencies on functions */
+	referenced.classId = ProcedureRelationId;
+	referenced.objectSubId = 0;
+
+	referenced.objectId = tsm->tsminit;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnextblock;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnexttuple;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	if (OidIsValid(tsm->tsmexaminetuple))
+	{
+		referenced.objectId = tsm->tsmexaminetuple;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
+
+	referenced.objectId = tsm->tsmend;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmreset;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmcost;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+}
+
+/*
+ * Create a table sampling method
+ *
+ * Only superusers can create a table sampling methods.
+ */
+Oid
+DefineTablesampleMethod(List *names, List *parameters)
+{
+	char	   *tsmname = strVal(linitial(names));
+	Oid			tsmoid;
+	ListCell   *pl;
+	Relation	rel;
+	Datum		values[Natts_pg_tablesample_method];
+	bool		nulls[Natts_pg_tablesample_method];
+	HeapTuple	tuple;
+
+	/* Must be super user. */
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied to create tablesample method \"%s\"",
+						tsmname),
+				 errhint("Must be superuser to create a tablesample method.")));
+
+	/* Must not already exist. */
+	tsmoid = get_tablesample_method_oid(tsmname, true);
+	if (OidIsValid(tsmoid))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" already exists",
+						tsmname)));
+
+	/* Initialize the values. */
+	memset(values, 0, sizeof(values));
+	memset(nulls, false, sizeof(nulls));
+
+	values[Anum_pg_tablesample_method_tsmname - 1] =
+		DirectFunctionCall1(namein, CStringGetDatum(tsmname));
+
+	/*
+	 * loop over the definition list and extract the information we need.
+	 */
+	foreach(pl, parameters)
+	{
+		DefElem    *defel = (DefElem *) lfirst(pl);
+
+		if (pg_strcasecmp(defel->defname, "seqscan") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmseqscan - 1] =
+				BoolGetDatum(defGetBoolean(defel));
+		}
+		else if (pg_strcasecmp(defel->defname, "pagemode") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmpagemode - 1] =
+				BoolGetDatum(defGetBoolean(defel));
+		}
+		else if (pg_strcasecmp(defel->defname, "init") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsminit - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsminit);
+		}
+		else if (pg_strcasecmp(defel->defname, "nextblock") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnextblock - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnextblock);
+		}
+		else if (pg_strcasecmp(defel->defname, "nexttuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnexttuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnexttuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "examinetuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmexaminetuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmexaminetuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "end") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmend - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmend);
+		}
+		else if (pg_strcasecmp(defel->defname, "reset") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmreset - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmreset);
+		}
+		else if (pg_strcasecmp(defel->defname, "cost") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmcost - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmcost);
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("tablesample method parameter \"%s\" not recognized",
+						defel->defname)));
+	}
+
+	/*
+	 * Validation.
+	 */
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsminit - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method init function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnextblock - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nextblock function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnexttuple - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nexttuple function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmend - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method end function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmreset - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method reset function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmcost - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method cost function is required")));
+
+	/*
+	 * Insert tuple into pg_tablesample_method.
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = heap_form_tuple(rel->rd_att, values, nulls);
+
+	tsmoid = simple_heap_insert(rel, tuple);
+
+	CatalogUpdateIndexes(rel, tuple);
+
+	makeTablesampleMethodDeps(tuple);
+
+	heap_freetuple(tuple);
+
+	/* Post creation hook for new tablesample method */
+	InvokeObjectPostCreateHook(TableSampleMethodRelationId, tsmoid, 0);
+
+	heap_close(rel, RowExclusiveLock);
+
+	return tsmoid;
+}
+
+/*
+ * Drop a tablesample method.
+ */
+void
+RemoveTablesampleMethodById(Oid tsmoid)
+{
+	Relation	rel;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+
+	/*
+	 * Find the target tuple
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmoid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for tablesample method %u",
+			 tsmoid);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	/* Can't drop builtin tablesample methods. */
+	if (tsmoid == TABLESAMPLE_METHOD_SYSTEM_OID ||
+		tsmoid == TABLESAMPLE_METHOD_BERNOULLI_OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied for tablesample method %s",
+						NameStr(tsm->tsmname))));
+
+	/*
+	 * Remove the pg_tablespace tuple (this will roll back if we fail below)
+	 */
+	simple_heap_delete(rel, &tuple->t_self);
+
+	ReleaseSysCache(tuple);
+
+	heap_close(rel, RowExclusiveLock);
+}
+
+/*
+ * get_tablesample_method_oid - given a tablesample method name,
+ * look up the OID
+ *
+ * If missing_ok is false, throw an error if tablesample method name not found.
+ * If true, just return InvalidOid.
+ */
+Oid
+get_tablesample_method_oid(const char *tsmname, bool missing_ok)
+{
+	Oid			result;
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(tsmname));
+	if (HeapTupleIsValid(tuple))
+	{
+		result = HeapTupleGetOid(tuple);
+		ReleaseSysCache(tuple);
+	}
+	else
+		result = InvalidOid;
+
+	if (!OidIsValid(result) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						tsmname)));
+
+	return result;
+}
+
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 711cdd5..d3f1273 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -590,7 +590,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATERIALIZED MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
+	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P
+	MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEXT NO NONE
 	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
@@ -5103,6 +5104,15 @@ DefineStmt:
 					n->definition = list_make1(makeDefElem("from", (Node *) $5));
 					$$ = (Node *)n;
 				}
+			| CREATE TABLESAMPLE METHOD name definition
+				{
+					DefineStmt *n = makeNode(DefineStmt);
+					n->kind = OBJECT_TABLESAMPLEMETHOD;
+					n->args = NIL;
+					n->defnames = list_make1(makeString($4));
+					n->definition = $5;
+					$$ = (Node *)n;
+				}
 		;
 
 definition: '(' def_list ')'						{ $$ = $2; }
@@ -5557,6 +5567,7 @@ drop_type:	TABLE									{ $$ = OBJECT_TABLE; }
 			| TEXT_P SEARCH DICTIONARY				{ $$ = OBJECT_TSDICTIONARY; }
 			| TEXT_P SEARCH TEMPLATE				{ $$ = OBJECT_TSTEMPLATE; }
 			| TEXT_P SEARCH CONFIGURATION			{ $$ = OBJECT_TSCONFIGURATION; }
+			| TABLESAMPLE METHOD					{ $$ = OBJECT_TABLESAMPLEMETHOD; }
 		;
 
 any_name_list:
@@ -13417,6 +13428,7 @@ unreserved_keyword:
 			| MATCH
 			| MATERIALIZED
 			| MAXVALUE
+			| METHOD
 			| MINUTE_P
 			| MINVALUE
 			| MODE
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index fd09d3a..cadf6b4 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -23,6 +23,7 @@
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/toasting.h"
 #include "commands/alter.h"
 #include "commands/async.h"
@@ -1136,6 +1137,11 @@ ProcessUtilitySlow(Node *parsetree,
 							Assert(stmt->args == NIL);
 							DefineCollation(stmt->defnames, stmt->definition);
 							break;
+						case OBJECT_TABLESAMPLEMETHOD:
+							Assert(stmt->args == NIL);
+							Assert(list_length(stmt->defnames) == 1);
+							DefineTablesampleMethod(stmt->defnames, stmt->definition);
+							break;
 						default:
 							elog(ERROR, "unrecognized define stmt type: %d",
 								 (int) stmt->kind);
@@ -2004,6 +2010,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_POLICY:
 					tag = "DROP POLICY";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "DROP TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
@@ -2100,6 +2109,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_COLLATION:
 					tag = "CREATE COLLATION";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "CREATE TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
diff --git a/src/bin/pg_dump/common.c b/src/bin/pg_dump/common.c
index 1a0a587..8a64e4b 100644
--- a/src/bin/pg_dump/common.c
+++ b/src/bin/pg_dump/common.c
@@ -103,6 +103,7 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 	int			numForeignServers;
 	int			numDefaultACLs;
 	int			numEventTriggers;
+	int			numTSMs;
 
 	if (g_verbose)
 		write_msg(NULL, "reading schemas\n");
@@ -251,6 +252,10 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 		write_msg(NULL, "reading policies\n");
 	getPolicies(fout, tblinfo, numTables);
 
+	if (g_verbose)
+		write_msg(NULL, "reading tablesample methods\n");
+	getTableSampleMethods(fout, &numTSMs);
+
 	*numTablesPtr = numTables;
 	return tblinfo;
 }
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 7da5c41..324ca4e 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -182,6 +182,7 @@ static void dumpSequenceData(Archive *fout, TableDataInfo *tdinfo);
 static void dumpIndex(Archive *fout, DumpOptions *dopt, IndxInfo *indxinfo);
 static void dumpConstraint(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
 static void dumpTableConstraintComment(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
+static void dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tbinfo);
 static void dumpTSParser(Archive *fout, DumpOptions *dopt, TSParserInfo *prsinfo);
 static void dumpTSDictionary(Archive *fout, DumpOptions *dopt, TSDictInfo *dictinfo);
 static void dumpTSTemplate(Archive *fout, DumpOptions *dopt, TSTemplateInfo *tmplinfo);
@@ -7134,6 +7135,78 @@ getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tblinfo, int numTable
 }
 
 /*
+ * getTableSampleMethods:
+ *	  read all tablesample methods in the system catalogs and return them
+ *	  in the TSMInfo* structure
+ *
+ *	numTSMs is set to the number of tablesample methods read in
+ */
+TSMInfo *
+getTableSampleMethods(Archive *fout, int *numTSMs)
+{
+	PGresult   *res;
+	int			ntups;
+	int			i;
+	PQExpBuffer query;
+	TSMInfo	   *tsminfo;
+	int			i_tableoid,
+				i_oid,
+				i_tsmname,
+				i_tsmseqscan,
+				i_tsmpagemode;
+
+	/* Before 9.5, there were no tablesample methods */
+	if (fout->remoteVersion < 90500)
+	{
+		*numTSMs = 0;
+		return NULL;
+	}
+
+	query = createPQExpBuffer();
+
+	appendPQExpBuffer(query,
+					  "SELECT tableoid, oid, tsmname, tsmseqscan, tsmpagemode "
+					  "FROM pg_catalog.pg_tablesample_method "
+					  "WHERE oid >= '%u'::pg_catalog.oid",
+					  FirstNormalObjectId);
+
+	res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
+
+	ntups = PQntuples(res);
+	*numTSMs = ntups;
+
+	tsminfo = (TSMInfo *) pg_malloc(ntups * sizeof(TSMInfo));
+
+	i_tableoid = PQfnumber(res, "tableoid");
+	i_oid = PQfnumber(res, "oid");
+	i_tsmname = PQfnumber(res, "tsmname");
+	i_tsmseqscan = PQfnumber(res, "tsmseqscan");
+	i_tsmpagemode = PQfnumber(res, "tsmpagemode");
+
+	for (i = 0; i < ntups; i++)
+	{
+		tsminfo[i].dobj.objType = DO_TABLESAMPLE_METHOD;
+		tsminfo[i].dobj.catId.tableoid = atooid(PQgetvalue(res, i, i_tableoid));
+		tsminfo[i].dobj.catId.oid = atooid(PQgetvalue(res, i, i_oid));
+		AssignDumpId(&tsminfo[i].dobj);
+		tsminfo[i].dobj.name = pg_strdup(PQgetvalue(res, i, i_tsmname));
+		tsminfo[i].dobj.namespace = NULL;
+		tsminfo[i].tsmseqscan = PQgetvalue(res, i, i_tsmseqscan)[0] == 't';
+		tsminfo[i].tsmpagemode = PQgetvalue(res, i, i_tsmpagemode)[0] == 't';
+
+		/* Decide whether we want to dump it */
+		selectDumpableObject(&(tsminfo[i].dobj));
+	}
+
+	PQclear(res);
+
+	destroyPQExpBuffer(query);
+
+	return tsminfo;
+}
+
+
+/*
  * Test whether a column should be printed as part of table's CREATE TABLE.
  * Column number is zero-based.
  *
@@ -8226,6 +8299,9 @@ dumpDumpableObject(Archive *fout, DumpOptions *dopt, DumpableObject *dobj)
 		case DO_POLICY:
 			dumpPolicy(fout, dopt, (PolicyInfo *) dobj);
 			break;
+		case DO_TABLESAMPLE_METHOD:
+			dumpTableSampleMethod(fout, dopt, (TSMInfo *) dobj);
+			break;
 		case DO_PRE_DATA_BOUNDARY:
 		case DO_POST_DATA_BOUNDARY:
 			/* never dumped, nothing to do */
@@ -12226,6 +12302,106 @@ dumpAgg(Archive *fout, DumpOptions *dopt, AggInfo *agginfo)
 }
 
 /*
+ * dumpTableSampleMethod
+ *	  write the declaration of one user-defined tablesample method
+ */
+static void
+dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tsminfo)
+{
+	PGresult   *res;
+	PQExpBuffer q;
+	PQExpBuffer delq;
+	PQExpBuffer labelq;
+	PQExpBuffer query;
+	char	   *tsminit;
+	char	   *tsmnextblock;
+	char	   *tsmnexttuple;
+	char	   *tsmexaminetuple;
+	char	   *tsmend;
+	char	   *tsmreset;
+	char	   *tsmcost;
+
+	/* Skip if not to be dumped */
+	if (!tsminfo->dobj.dump || dopt->dataOnly)
+		return;
+
+	q = createPQExpBuffer();
+	delq = createPQExpBuffer();
+	labelq = createPQExpBuffer();
+	query = createPQExpBuffer();
+
+	/* Make sure we are in proper schema */
+	selectSourceSchema(fout, "pg_catalog");
+
+	appendPQExpBuffer(query, "SELECT tsminit, tsmnextblock, "
+							 "tsmnexttuple, tsmexaminetuple, "
+							 "tsmend, tsmreset, tsmcost "
+							 "FROM pg_catalog.pg_tablesample_method "
+							 "WHERE oid = '%u'::pg_catalog.oid",
+							 tsminfo->dobj.catId.oid);
+
+	res = ExecuteSqlQueryForSingleRow(fout, query->data);
+
+	tsminit = PQgetvalue(res, 0, PQfnumber(res, "tsminit"));
+	tsmnexttuple = PQgetvalue(res, 0, PQfnumber(res, "tsmnexttuple"));
+	tsmnextblock = PQgetvalue(res, 0, PQfnumber(res, "tsmnextblock"));
+	tsmexaminetuple = PQgetvalue(res, 0, PQfnumber(res, "tsmexaminetuple"));
+	tsmend = PQgetvalue(res, 0, PQfnumber(res, "tsmend"));
+	tsmreset = PQgetvalue(res, 0, PQfnumber(res, "tsmreset"));
+	 tsmcost = PQgetvalue(res, 0, PQfnumber(res, "tsmcost"));
+
+	appendPQExpBuffer(q, "CREATE TABLESAMPLE METHOD %s (\n",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(q, "    INIT = %s,\n", tsminit);
+	appendPQExpBuffer(q, "    NEXTTUPLE = %s,\n", tsmnexttuple);
+	appendPQExpBuffer(q, "    NEXTBLOCK = %s,\n", tsmnextblock);
+	appendPQExpBuffer(q, "    END = %s,\n", tsmend);
+	appendPQExpBuffer(q, "    RESET = %s,\n", tsmreset);
+	appendPQExpBuffer(q, "    COST = %s", tsmcost);
+
+	if (strcmp(tsmexaminetuple, "-") != 0)
+		appendPQExpBuffer(q, ",\n    EXAMINETUPLE = %s", tsmexaminetuple);
+
+	if (tsminfo->tsmseqscan)
+		appendPQExpBufferStr(q, ",\n    SEQSCAN = true");
+
+	if (tsminfo->tsmpagemode)
+		appendPQExpBufferStr(q, ",\n    PAGEMODE = true");
+
+	appendPQExpBufferStr(q, "\n);");
+
+	appendPQExpBuffer(delq, "DROP TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(labelq, "TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	if (dopt->binary_upgrade)
+		binary_upgrade_extension_member(q, &tsminfo->dobj, labelq->data);
+
+	ArchiveEntry(fout, tsminfo->dobj.catId, tsminfo->dobj.dumpId,
+				 tsminfo->dobj.name,
+				 NULL,
+				 NULL,
+				 "",
+				 false, "TABLESAMPLE METHOD", SECTION_PRE_DATA,
+				 q->data, delq->data, NULL,
+				 NULL, 0,
+				 NULL, NULL);
+
+	/* Dump Parser Comments */
+	dumpComment(fout, dopt, labelq->data,
+				NULL, "",
+				tsminfo->dobj.catId, 0, tsminfo->dobj.dumpId);
+
+	PQclear(res);
+	destroyPQExpBuffer(q);
+	destroyPQExpBuffer(delq);
+	destroyPQExpBuffer(labelq);
+}
+
+/*
  * dumpTSParser
  *	  write out a single text search parser
  */
@@ -15659,6 +15835,7 @@ addBoundaryDependencies(DumpableObject **dobjs, int numObjs,
 			case DO_FDW:
 			case DO_FOREIGN_SERVER:
 			case DO_BLOB:
+			case DO_TABLESAMPLE_METHOD:
 				/* Pre-data objects: must come before the pre-data boundary */
 				addObjectDependency(preDataBound, dobj->dumpId);
 				break;
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index a9d3c10..87bef24 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -76,7 +76,8 @@ typedef enum
 	DO_POST_DATA_BOUNDARY,
 	DO_EVENT_TRIGGER,
 	DO_REFRESH_MATVIEW,
-	DO_POLICY
+	DO_POLICY,
+	DO_TABLESAMPLE_METHOD
 } DumpableObjectType;
 
 typedef struct _dumpableObject
@@ -383,6 +384,13 @@ typedef struct _inhInfo
 	Oid			inhparent;		/* OID of its parent */
 } InhInfo;
 
+typedef struct _tsmInfo
+{
+	DumpableObject dobj;
+	bool		tsmseqscan;
+	bool		tsmpagemode;
+} TSMInfo;
+
 typedef struct _prsInfo
 {
 	DumpableObject dobj;
@@ -536,6 +544,7 @@ extern ProcLangInfo *getProcLangs(Archive *fout, int *numProcLangs);
 extern CastInfo *getCasts(Archive *fout, DumpOptions *dopt, int *numCasts);
 extern void getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tbinfo, int numTables);
 extern bool shouldPrintColumn(DumpOptions *dopt, TableInfo *tbinfo, int colno);
+extern TSMInfo *getTableSampleMethods(Archive *fout, int *numTSMs);
 extern TSParserInfo *getTSParsers(Archive *fout, int *numTSParsers);
 extern TSDictInfo *getTSDictionaries(Archive *fout, int *numTSDicts);
 extern TSTemplateInfo *getTSTemplates(Archive *fout, int *numTSTemplates);
diff --git a/src/bin/pg_dump/pg_dump_sort.c b/src/bin/pg_dump/pg_dump_sort.c
index c5ed593..9567cf6 100644
--- a/src/bin/pg_dump/pg_dump_sort.c
+++ b/src/bin/pg_dump/pg_dump_sort.c
@@ -73,7 +73,8 @@ static const int oldObjectTypePriority[] =
 	13,							/* DO_POST_DATA_BOUNDARY */
 	20,							/* DO_EVENT_TRIGGER */
 	15,							/* DO_REFRESH_MATVIEW */
-	21							/* DO_POLICY */
+	21,							/* DO_POLICY */
+	5							/* DO_TABLESAMPLE_METHOD */
 };
 
 /*
@@ -122,7 +123,8 @@ static const int newObjectTypePriority[] =
 	25,							/* DO_POST_DATA_BOUNDARY */
 	32,							/* DO_EVENT_TRIGGER */
 	33,							/* DO_REFRESH_MATVIEW */
-	34							/* DO_POLICY */
+	34,							/* DO_POLICY */
+	17							/* DO_TABLESAMPLE_METHOD */
 };
 
 static DumpId preDataBoundId;
@@ -1460,6 +1462,11 @@ describeDumpableObject(DumpableObject *obj, char *buf, int bufsize)
 					 "POLICY (ID %d OID %u)",
 					 obj->dumpId, obj->catId.oid);
 			return;
+		case DO_TABLESAMPLE_METHOD:
+			snprintf(buf, bufsize,
+					 "TABLESAMPLE METHOD %s  (ID %d OID %u)",
+					 obj->name, obj->dumpId, obj->catId.oid);
+			return;
 		case DO_PRE_DATA_BOUNDARY:
 			snprintf(buf, bufsize,
 					 "PRE-DATA BOUNDARY  (ID %d)",
diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 6481ac8..30653f8 100644
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -148,6 +148,7 @@ typedef enum ObjectClass
 	OCLASS_EXTENSION,			/* pg_extension */
 	OCLASS_EVENT_TRIGGER,		/* pg_event_trigger */
 	OCLASS_POLICY,				/* pg_policy */
+	OCLASS_TABLESAMPLEMETHOD,	/* pg_tablesample_method */
 	MAX_OCLASS					/* MUST BE LAST */
 } ObjectClass;
 
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
index ec826e3..bc22edd 100644
--- a/src/include/catalog/pg_tablesample_method.h
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -71,7 +71,18 @@ typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
 
 DATA(insert OID = 3293 ( system false true tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
 DESCR("SYSTEM table sampling method");
+#define TABLESAMPLE_METHOD_SYSTEM_OID 3293
 DATA(insert OID = 3294 ( bernoulli true false tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
 DESCR("BERNOULLI table sampling method");
+#define TABLESAMPLE_METHOD_BERNOULLI_OID 3294
+
+/* ----------------
+ *		functions for manipulation of pg_tablesample_method
+ * ----------------
+ */
+
+extern Oid DefineTablesampleMethod(List *names, List *parameters);
+extern void RemoveTablesampleMethodById(Oid tsmoid);
+extern Oid get_tablesample_method_oid(const char *tsmname, bool missing_ok);
 
 #endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index a4288d1..359119a 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1291,6 +1291,7 @@ typedef enum ObjectType
 	OBJECT_SEQUENCE,
 	OBJECT_TABCONSTRAINT,
 	OBJECT_TABLE,
+	OBJECT_TABLESAMPLEMETHOD,
 	OBJECT_TABLESPACE,
 	OBJECT_TRIGGER,
 	OBJECT_TSCONFIGURATION,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index ae90df8..902c189 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -236,6 +236,7 @@ PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("mode", MODE, UNRESERVED_KEYWORD)
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 93d93af..37ea524 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -9,7 +9,8 @@ SUBDIRS = \
 		  worker_spi \
 		  dummy_seclabel \
 		  test_shm_mq \
-		  test_parser
+		  test_parser \
+		  tablesample
 
 all: submake-errcodes
 
diff --git a/src/test/modules/tablesample/.gitignore b/src/test/modules/tablesample/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/src/test/modules/tablesample/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/src/test/modules/tablesample/Makefile b/src/test/modules/tablesample/Makefile
new file mode 100644
index 0000000..469b004
--- /dev/null
+++ b/src/test/modules/tablesample/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/tsm_test/Makefile
+
+MODULE_big = tsm_test
+OBJS = tsm_test.o $(WIN32RES)
+PGFILEDESC = "tsm_test - example of a custom tablesample method"
+
+EXTENSION = tsm_test
+DATA = tsm_test--1.0.sql
+
+REGRESS = tablesample
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/tablesample/expected/tablesample.out b/src/test/modules/tablesample/expected/tablesample.out
new file mode 100644
index 0000000..ad62e32
--- /dev/null
+++ b/src/test/modules/tablesample/expected/tablesample.out
@@ -0,0 +1,38 @@
+CREATE EXTENSION tsm_test;
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ c81e728d9d4c2f636f067f89cc14862c | 0.5
+ a87ff679a2f3e71d9181a67b7542122c | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ d3d9446802a44259755d38e6d163e820 | 0.5
+(6 rows)
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ e4da3b7fbbce2345d7772b0674a318d5 | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ c9f0f895fb98ab9159f51fd0297e236d | 0.5
+(5 rows)
+
+DROP TABLESAMPLE METHOD tsm_test;
+ERROR:  cannot drop tablesample method tsm_test because extension tsm_test requires it
+HINT:  You can drop extension tsm_test instead.
+DROP EXTENSION tsm_test;
+ERROR:  cannot drop extension tsm_test because other objects depend on it
+DETAIL:  view test_tsm_v depends on tablesample method tsm_test
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+DROP EXTENSION tsm_test CASCADE;
+NOTICE:  drop cascades to view test_tsm_v
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
+ tsmname | tsmseqscan | tsmpagemode | tsminit | tsmnextblock | tsmnexttuple | tsmexaminetuple | tsmend | tsmreset | tsmcost 
+---------+------------+-------------+---------+--------------+--------------+-----------------+--------+----------+---------
+(0 rows)
+
diff --git a/src/test/modules/tablesample/sql/tablesample.sql b/src/test/modules/tablesample/sql/tablesample.sql
new file mode 100644
index 0000000..b1104d6
--- /dev/null
+++ b/src/test/modules/tablesample/sql/tablesample.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_test;
+
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+
+DROP TABLESAMPLE METHOD tsm_test;
+DROP EXTENSION tsm_test;
+DROP EXTENSION tsm_test CASCADE;
+
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
diff --git a/src/test/modules/tablesample/tsm_test--1.0.sql b/src/test/modules/tablesample/tsm_test--1.0.sql
new file mode 100644
index 0000000..e5a9ae8
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test--1.0.sql
@@ -0,0 +1,52 @@
+/* src/test/modules/tablesample/tsm_test--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_test" to load this file. \quit
+
+CREATE FUNCTION tsm_test_init(internal, int4, text)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nextblock(internal)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nexttuple(internal, int4, int2)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_examinetuple(internal, int4, internal, bool)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_cost(internal, internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+
+CREATE TABLESAMPLE METHOD tsm_test (
+	SEQSCAN		= true,
+	PAGEMODE	= true,
+	INIT		= tsm_test_init,
+	NEXTBLOCK	= tsm_test_nextblock,
+	NEXTTUPLE	= tsm_test_nexttuple,
+	EXAMINETUPLE	= tsm_test_examinetuple,
+	END			= tsm_test_end,
+	RESET		= tsm_test_reset,
+	COST		= tsm_test_cost
+);
diff --git a/src/test/modules/tablesample/tsm_test.c b/src/test/modules/tablesample/tsm_test.c
new file mode 100644
index 0000000..be4dcb9
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.c
@@ -0,0 +1,228 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_test.c
+ *	  Simple example of a custom tablesample method
+ *
+ * Copyright (c) 2007-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/test/modules/tablesample/tsm_test.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/htup_details.h"
+#include "access/relscan.h"
+#include "access/tupdesc.h"
+#include "catalog/pg_type.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/builtins.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+PG_MODULE_MAGIC;
+
+/* State */
+typedef struct
+{
+	uint32		seed;			/* random seed */
+	AttrNumber	attnum;			/* column to check */
+	TupleDesc	tupDesc;		/* tuple descriptor of table */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} tsm_test_state;
+
+
+PG_FUNCTION_INFO_V1(tsm_test_init);
+PG_FUNCTION_INFO_V1(tsm_test_nextblock);
+PG_FUNCTION_INFO_V1(tsm_test_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_test_examinetuple);
+PG_FUNCTION_INFO_V1(tsm_test_end);
+PG_FUNCTION_INFO_V1(tsm_test_reset);
+PG_FUNCTION_INFO_V1(tsm_test_cost);
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_test_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	char		   *attname;
+	AttrNumber		attnum;
+	Oid				atttype;
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	HeapScanDesc	scan = scanstate->ss.ss_currentScanDesc;
+	tsm_test_state *state;
+	TupleDesc		tupDesc = RelationGetDescr(rel);
+
+	if (PG_ARGISNULL(2))
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("attnum cannot be NULL.")));
+
+	attname = text_to_cstring(PG_GETARG_TEXT_P(2));
+
+	attnum = get_attnum(rel->rd_id, attname);
+	if (!AttrNumberIsForUserDefinedAttr(attnum))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s does not exist", attname)));
+
+	atttype = get_atttype(rel->rd_id, attnum);
+	if (atttype != FLOAT8OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s is not of type float.", attname)));
+
+	state = palloc0(sizeof(tsm_test_state));
+
+	/* Remember initial values for reinit */
+	state->seed = seed;
+	state->attnum = attnum;
+	state->tupDesc = tupDesc;
+	state->startblock = scan->rs_startblock;
+	state->nblocks = scan->rs_nblocks;
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+	sampler_random_init_state(state->seed, state->randstate);
+
+	scanstate->tsmdata = (void *) state;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_test_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	/* Cycle from startblock to startblock to support syncscan. */
+	if (state->blockno == InvalidBlockNumber)
+		state->blockno = state->startblock;
+	else
+	{
+		state->blockno++;
+
+		if (state->blockno >= state->nblocks)
+			state->blockno = 0;
+
+		if (state->blockno == state->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(state->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ */
+Datum
+tsm_test_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (state->lt == InvalidOffsetNumber)
+		state->lt = FirstOffsetNumber;
+	else if (++state->lt > maxoffset)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	PG_RETURN_UINT16(state->lt);
+}
+
+/*
+ * Examine tuple and decide if it should be returned.
+ */
+Datum
+tsm_test_examinetuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	HeapTuple		tuple = (HeapTuple) PG_GETARG_POINTER(2);
+	bool			visible = PG_GETARG_BOOL(3);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+	bool			isnull;
+	float8			val, rand;
+
+	if (!visible)
+		PG_RETURN_BOOL(false);
+
+	val = DatumGetFloat8(heap_getattr(tuple, state->attnum, state->tupDesc, &isnull));
+	rand = sampler_random_fract(state->randstate);
+	if (isnull || val < rand)
+		PG_RETURN_BOOL(false);
+	else
+		PG_RETURN_BOOL(true);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_test_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_test_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+
+	sampler_random_init_state(state->seed, state->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_test_cost(PG_FUNCTION_ARGS)
+{
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+
+	*pages = baserel->pages;
+
+	/* This is very bad estimation */
+	*tuples = path->rows = path->rows/2;
+
+	PG_RETURN_VOID();
+}
+
diff --git a/src/test/modules/tablesample/tsm_test.control b/src/test/modules/tablesample/tsm_test.control
new file mode 100644
index 0000000..a7b2741
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.control
@@ -0,0 +1,5 @@
+# tsm_test extension
+comment = 'test module for custom tablesample method'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_test'
+relocatable = true
-- 
1.9.1

>From f39a165a2273417bd8f36ce9af611d511ca39eed Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:37:55 +0100
Subject: [PATCH 2/4] tablesample v11

---
 contrib/file_fdw/file_fdw.c                 |   2 +-
 contrib/postgres_fdw/postgres_fdw.c         |   2 +-
 doc/src/sgml/catalogs.sgml                  | 120 ++++++
 doc/src/sgml/ref/select.sgml                |  38 +-
 src/backend/access/Makefile                 |   3 +-
 src/backend/access/heap/heapam.c            |  43 ++-
 src/backend/catalog/Makefile                |   2 +-
 src/backend/commands/analyze.c              |   2 +-
 src/backend/commands/explain.c              |   7 +
 src/backend/executor/Makefile               |   2 +-
 src/backend/executor/execAmi.c              |   8 +
 src/backend/executor/execCurrent.c          |   1 +
 src/backend/executor/execProcnode.c         |  14 +
 src/backend/executor/nodeSamplescan.c       | 556 ++++++++++++++++++++++++++++
 src/backend/nodes/copyfuncs.c               |  60 +++
 src/backend/nodes/equalfuncs.c              |  37 ++
 src/backend/nodes/nodeFuncs.c               |  12 +
 src/backend/nodes/outfuncs.c                |  48 +++
 src/backend/nodes/readfuncs.c               |  45 +++
 src/backend/optimizer/path/allpaths.c       |  49 +++
 src/backend/optimizer/path/costsize.c       |  68 ++++
 src/backend/optimizer/plan/createplan.c     |  69 ++++
 src/backend/optimizer/plan/setrefs.c        |  11 +
 src/backend/optimizer/plan/subselect.c      |   1 +
 src/backend/optimizer/util/pathnode.c       |  22 ++
 src/backend/parser/gram.y                   |  37 +-
 src/backend/parser/parse_clause.c           |  47 +++
 src/backend/parser/parse_func.c             | 131 +++++++
 src/backend/utils/Makefile                  |   3 +-
 src/backend/utils/adt/ruleutils.c           |  50 +++
 src/backend/utils/cache/syscache.c          |  23 ++
 src/backend/utils/misc/sampling.c           |  33 +-
 src/backend/utils/tablesample/Makefile      |  17 +
 src/backend/utils/tablesample/bernoulli.c   | 224 +++++++++++
 src/backend/utils/tablesample/system.c      | 185 +++++++++
 src/include/access/heapam.h                 |   4 +
 src/include/access/relscan.h                |   1 +
 src/include/catalog/indexing.h              |   5 +
 src/include/catalog/pg_proc.h               |  25 ++
 src/include/catalog/pg_tablesample_method.h |  77 ++++
 src/include/executor/nodeSamplescan.h       |  24 ++
 src/include/nodes/execnodes.h               |  18 +
 src/include/nodes/nodes.h                   |   4 +
 src/include/nodes/parsenodes.h              |  36 ++
 src/include/nodes/plannodes.h               |   6 +
 src/include/optimizer/cost.h                |   1 +
 src/include/optimizer/pathnode.h            |   2 +
 src/include/parser/kwlist.h                 |   1 +
 src/include/parser/parse_func.h             |   4 +
 src/include/utils/rel.h                     |   1 -
 src/include/utils/sampling.h                |  15 +-
 src/include/utils/syscache.h                |   2 +
 src/include/utils/tablesample.h             |  27 ++
 src/test/regress/expected/sanity_check.out  |   1 +
 src/test/regress/expected/tablesample.out   | 168 +++++++++
 src/test/regress/parallel_schedule          |   2 +-
 src/test/regress/serial_schedule            |   1 +
 src/test/regress/sql/tablesample.sql        |  42 +++
 58 files changed, 2403 insertions(+), 36 deletions(-)
 create mode 100644 src/backend/executor/nodeSamplescan.c
 create mode 100644 src/backend/utils/tablesample/Makefile
 create mode 100644 src/backend/utils/tablesample/bernoulli.c
 create mode 100644 src/backend/utils/tablesample/system.c
 create mode 100644 src/include/catalog/pg_tablesample_method.h
 create mode 100644 src/include/executor/nodeSamplescan.h
 create mode 100644 src/include/utils/tablesample.h
 create mode 100644 src/test/regress/expected/tablesample.out
 create mode 100644 src/test/regress/sql/tablesample.sql

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 249d541..6a813a3 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -1096,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * sampler_random_fract());
+				int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 74ef792..5903384 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -2543,7 +2543,7 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * sampler_random_fract());
+			pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index d0b78f2..af808a0 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -269,6 +269,11 @@
      </row>
 
      <row>
+      <entry><link linkend="catalog-pg-tablesample-method"><structname>pg_tablesample_method</structname></link></entry>
+      <entry>table sampling methods</entry>
+     </row>
+
+     <row>
       <entry><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link></entry>
       <entry>tablespaces within this database cluster</entry>
      </row>
@@ -5980,6 +5985,121 @@
  </sect1>
 
 
+ <sect1 id="catalog-pg-tablesample-method">
+  <title><structname>pg_tabesample_method</structname></title>
+
+  <indexterm zone="catalog-pg-tablesample-method">
+   <primary>pg_am</primary>
+  </indexterm>
+
+  <para>
+   The catalog <structname>pg_tablesample_method</structname> stores
+   information about table sampling methods which can be used in
+   <command>TABLESAMPLE</command> clause of a <command>SELECT</command>
+   statement.
+  </para>
+
+  <table>
+   <title><structname>pg_tablesample_method</> Columns</title>
+
+   <tgroup cols="4">
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Type</entry>
+      <entry>References</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+    <tbody>
+
+     <row>
+      <entry><structfield>oid</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry></entry>
+      <entry>Row identifier (hidden attribute; must be explicitly selected)</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmname</structfield></entry>
+      <entry><type>name</type></entry>
+      <entry></entry>
+      <entry>Name of the sampling method</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmseqscan</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry></entry>
+      <entry>Does the sampling method scan the whole table sequentially?
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmpagemode</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry></entry>
+      <entry>Does the sampling method always read whole pages?
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsminit</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Initialize the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnextblock</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next block number</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnexttuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next tuple offset</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmexaminetuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Function which examines the tuple contents and decides if to
+        return in, or zero if none</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmend</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>End the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmreset</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Restart the state of sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmcost</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Costing function</entry>
+     </row>
+
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect1>
+
+
  <sect1 id="catalog-pg-tablespace">
   <title><structname>pg_tablespace</structname></title>
 
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 2295f63..c16285e 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,42 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        one of:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of those sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability.
+        The optional numeric parameter <literal>REPEATABLE</literal> is used
+        as random seed for sampling. Note that subsequent commands may return
+        different results even if same <literal>REPEATABLE</literal> clause
+        was specified. This happens because <acronym>DML</acronym> statements
+        and maintenance operations such as <command>VACUUM</> affect physical
+        distribution of data.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..238057a 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  transam
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index cb6f8a3..76c2d3a 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -79,8 +79,9 @@ bool		synchronize_seqscans = true;
 static HeapScanDesc heap_beginscan_internal(Relation relation,
 						Snapshot snapshot,
 						int nkeys, ScanKey key,
-						bool allow_strat, bool allow_sync,
-						bool is_bitmapscan, bool temp_snap);
+						bool allow_strat, bool allow_sync, bool allow_pagemode,
+						bool is_bitmapscan, bool is_samplescan,
+						bool temp_snap);
 static HeapTuple heap_prepare_insert(Relation relation, HeapTuple tup,
 					TransactionId xid, CommandId cid, int options);
 static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf,
@@ -293,9 +294,10 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
 
 	/*
 	 * Currently, we don't have a stats counter for bitmap heap scans (but the
-	 * underlying bitmap index scans will be counted).
+	 * underlying bitmap index scans will be counted) or sample scans (we only
+	 * update stats for tuple fetches there)
 	 */
-	if (!scan->rs_bitmapscan)
+	if (!scan->rs_bitmapscan && !scan->rs_samplescan)
 		pgstat_count_heap_scan(scan->rs_rd);
 }
 
@@ -314,7 +316,7 @@ heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk, BlockNumber numBlks)
  * In page-at-a-time mode it performs additional work, namely determining
  * which tuples on the page are visible.
  */
-static void
+void
 heapgetpage(HeapScanDesc scan, BlockNumber page)
 {
 	Buffer		buffer;
@@ -1289,7 +1291,7 @@ heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
  *		heap_beginscan	- begin relation scan
  *
  * heap_beginscan_strat offers an extended API that lets the caller control
- * whether a nondefault buffer access strategy can be used, and whether
+ * whether a nondefault buffer access strategy can be used and whether
  * syncscan can be chosen (possibly resulting in the scan not starting from
  * block zero).  Both of these default to TRUE with plain heap_beginscan.
  *
@@ -1297,6 +1299,9 @@ heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
  * HeapScanDesc for a bitmap heap scan.  Although that scan technology is
  * really quite unlike a standard seqscan, there is just enough commonality
  * to make it worth using the same data structure.
+ *
+ * heap_beginscan_ss is alternate entry point for setting up a
+ * HeapScanDesc for a TABLESAMPLE scan.
  * ----------------
  */
 HeapScanDesc
@@ -1304,7 +1309,7 @@ heap_beginscan(Relation relation, Snapshot snapshot,
 			   int nkeys, ScanKey key)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   true, true, false, false);
+								   true, true, true, false, false, false);
 }
 
 HeapScanDesc
@@ -1314,7 +1319,7 @@ heap_beginscan_catalog(Relation relation, int nkeys, ScanKey key)
 	Snapshot	snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
 
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   true, true, false, true);
+								   true, true, true, false, false, true);
 }
 
 HeapScanDesc
@@ -1323,7 +1328,8 @@ heap_beginscan_strat(Relation relation, Snapshot snapshot,
 					 bool allow_strat, bool allow_sync)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   allow_strat, allow_sync, false, false);
+								   allow_strat, allow_sync, true,
+								   false, false, false);
 }
 
 HeapScanDesc
@@ -1331,14 +1337,24 @@ heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   false, false, true, false);
+								   false, false, true, true, false, false);
+}
+
+HeapScanDesc
+heap_beginscan_ss(Relation relation, Snapshot snapshot,
+				  int nkeys, ScanKey key,
+				  bool allow_strat, bool allow_pagemode)
+{
+	return heap_beginscan_internal(relation, snapshot, nkeys, key,
+								   allow_strat, false, allow_pagemode,
+								   false, true, false);
 }
 
 static HeapScanDesc
 heap_beginscan_internal(Relation relation, Snapshot snapshot,
 						int nkeys, ScanKey key,
-						bool allow_strat, bool allow_sync,
-						bool is_bitmapscan, bool temp_snap)
+						bool allow_strat, bool allow_sync, bool allow_pagemode,
+						bool is_bitmapscan, bool is_samplescan, bool temp_snap)
 {
 	HeapScanDesc scan;
 
@@ -1360,6 +1376,7 @@ heap_beginscan_internal(Relation relation, Snapshot snapshot,
 	scan->rs_snapshot = snapshot;
 	scan->rs_nkeys = nkeys;
 	scan->rs_bitmapscan = is_bitmapscan;
+	scan->rs_samplescan = is_samplescan;
 	scan->rs_strategy = NULL;	/* set in initscan */
 	scan->rs_allow_strat = allow_strat;
 	scan->rs_allow_sync = allow_sync;
@@ -1368,7 +1385,7 @@ heap_beginscan_internal(Relation relation, Snapshot snapshot,
 	/*
 	 * we can use page-at-a-time mode if it's an MVCC-safe snapshot
 	 */
-	scan->rs_pageatatime = IsMVCCSnapshot(snapshot);
+	scan->rs_pageatatime = allow_pagemode && IsMVCCSnapshot(snapshot);
 
 	/*
 	 * For a seqscan in a serializable transaction, acquire a predicate lock
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..34db3e6 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesample_method.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 5730f26..eb0da5b 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1147,7 +1147,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * sampler_random_fract());
+						int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 315a528..90190cd 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -732,6 +732,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -957,6 +958,9 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			pname = sname = "Sample Scan";
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1074,6 +1078,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1326,6 +1331,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2224,6 +2230,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 6ebad2f..4948a26 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index d87be96..bcd287f 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 9892499..03c2feb 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..c7951d1
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,556 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "catalog/pg_tablesample_method.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "pgstat.h"
+#include "storage/bufmgr.h"
+#include "storage/predicate.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate,
+							 int eflags, TableSampleClause *tablesample);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+static HeapTuple samplenexttup(SampleScanState *node, HeapScanDesc scan);
+
+
+/*
+ * Initialize the sampling method - loads function info and
+ * calls the tsminit function.
+ *
+ * We need special handling for this because the tsminit function
+ * is allowed to take optional additional arguments.
+ */
+static void
+InitSamplingMethod(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(scanstate->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(scanstate->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(scanstate->tsmnexttuple));
+	if (OidIsValid(tablesample->tsmexaminetuple))
+		fmgr_info(tablesample->tsmexaminetuple, &(scanstate->tsmexaminetuple));
+	else
+		scanstate->tsmexaminetuple.fn_oid = InvalidOid;
+	fmgr_info(tablesample->tsmend, &(scanstate->tsmend));
+	fmgr_info(tablesample->tsmreset, &(scanstate->tsmreset));
+
+	InitFunctionCallInfoData(fcinfo, &scanstate->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	/* First arg is always SampleScanState */
+	fcinfo.arg[0] = PointerGetDatum(scanstate);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause cannot be NULL")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+}
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	TupleTableSlot *slot;
+	HeapScanDesc	scan;
+	HeapTuple		tuple;
+
+	/*
+	 * get information from the scan state
+	 */
+	slot = node->ss.ss_ScanTupleSlot;
+	scan = node->ss.ss_currentScanDesc;
+
+	tuple = samplenexttup(node, scan);
+
+	if (tuple)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   scan->rs_cbuf,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+/*
+ * Check visibility of the tuple.
+ */
+static bool
+SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan)
+{
+	/*
+	 * If this scan is reading whole pages at a time, there is already
+	 * visibilty info present in rs_vistuples so we can just search it
+	 * for the tupoffset.
+	 */
+	if (scan->rs_pageatatime)
+	{
+		int start = 0,
+			end = scan->rs_ntuples - 1;
+
+		/*
+		 * Do the binary search over rs_vistuples, it's already sorted by
+		 * OffsetNumber so we don't need to do any sorting ourselves here.
+		 *
+		 * We could use bsearch() here but it's slower for integers because
+		 * of the function call overhead and because it needs boiler plate code
+		 * it would not save us anything code-wise anyway.
+		 */
+		while (start <= end)
+		{
+			int mid = start + (end - start) / 2;
+			OffsetNumber curoffset = scan->rs_vistuples[mid];
+
+			if (curoffset == tupoffset)
+				return true;
+			else if (curoffset > tupoffset)
+				end = mid - 1;
+			else
+				start = mid + 1;
+		}
+
+		return false;
+	}
+	else
+	{
+		/* No pagemode, we have to check the tuple itself. */
+		Snapshot	snapshot = scan->rs_snapshot;
+		Buffer		buffer = scan->rs_cbuf;
+
+		bool visible = HeapTupleSatisfiesVisibility(tuple, snapshot, buffer);
+
+		CheckForSerializableConflictOut(visible, scan->rs_rd, tuple, buffer,
+										snapshot);
+
+		return visible;
+	}
+}
+
+/*
+ * Read next tuple using the correct sampling method.
+ */
+static HeapTuple
+samplenexttup(SampleScanState *node, HeapScanDesc scan)
+{
+	HeapTuple		tuple = &(scan->rs_ctup);
+	bool			pagemode = scan->rs_pageatatime;
+	BlockNumber		blockno;
+	Page			page;
+	ItemId			itemid;
+	OffsetNumber	tupoffset,
+					maxoffset;
+
+	if (!scan->rs_inited)
+	{
+		/*
+		 * return null immediately if relation is empty
+		 */
+		if (scan->rs_nblocks == 0)
+		{
+			Assert(!BufferIsValid(scan->rs_cbuf));
+			tuple->t_data = NULL;
+			return NULL;
+		}
+		blockno = DatumGetInt32(FunctionCall1(&node->tsmnextblock,
+											  PointerGetDatum(node)));
+		if (!BlockNumberIsValid(blockno))
+		{
+			tuple->t_data = NULL;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+		scan->rs_inited = true;
+	}
+	else
+	{
+		/* continue from previously returned page/tuple */
+		blockno = scan->rs_cblock;		/* current page */
+	}
+
+	/*
+	 * When pagemode is disabled, the scan will do visibility checks for each
+	 * tuple it finds so the buffer needs to be locked.
+	 */
+	if (!pagemode)
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+	page = (Page) BufferGetPage(scan->rs_cbuf);
+	maxoffset = PageGetMaxOffsetNumber(page);
+
+	for (;;)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		tupoffset = DatumGetUInt16(FunctionCall3(&node->tsmnexttuple,
+												 PointerGetDatum(node),
+												 UInt32GetDatum(blockno),
+												 UInt16GetDatum(maxoffset)));
+
+		if (OffsetNumberIsValid(tupoffset))
+		{
+			bool	visible;
+			bool	found;
+
+			/* Skip invalid tuple pointers. */
+			itemid = PageGetItemId(page, tupoffset);
+			if (!ItemIdIsNormal(itemid))
+				continue;
+
+			tuple->t_data = (HeapTupleHeader) PageGetItem((Page) page, itemid);
+			tuple->t_len = ItemIdGetLength(itemid);
+			ItemPointerSet(&(tuple->t_self), blockno, tupoffset);
+
+			visible = SampleTupleVisible(tuple, tupoffset, scan);
+
+			/*
+			 * Let the sampling method examine the actual tuple and decide if we
+			 * should return it.
+			 *
+			 * Note that we let it examine even invisible tuples for
+			 * statistical purposes, but not return them since user should
+			 * never see invisible tuples.
+			 */
+			if (OidIsValid(node->tsmexaminetuple.fn_oid))
+			{
+				found = DatumGetBool(FunctionCall4(&node->tsmexaminetuple,
+												   PointerGetDatum(node),
+												   UInt32GetDatum(blockno),
+												   PointerGetDatum(tuple),
+												   BoolGetDatum(visible)));
+				/* Should not happen if sampling method is well written. */
+				if (found && !visible)
+					elog(ERROR, "Sampling method wanted to return invisible tuple");
+			}
+			else
+				found = visible;
+
+			/* Found visible tuple, return it. */
+			if (found)
+			{
+				if (!pagemode)
+					LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+				break;
+			}
+			else
+			{
+				/* Try next tuple from same page. */
+				continue;
+			}
+		}
+
+
+		if (!pagemode)
+			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+
+		blockno = DatumGetInt32(FunctionCall1(&node->tsmnextblock,
+											  PointerGetDatum(node)));
+
+		/*
+		 * Report our new scan position for synchronization purposes. We
+		 * don't do that when moving backwards, however. That would just
+		 * mess up any other forward-moving scanners.
+		 *
+		 * Note: we do this before checking for end of scan so that the
+		 * final state of the position hint is back at the start of the
+		 * rel.  That's not strictly necessary, but otherwise when you run
+		 * the same query multiple times the starting position would shift
+		 * a little bit backwards on every invocation, which is confusing.
+		 * We don't guarantee any specific ordering in general, though.
+		 */
+		if (scan->rs_syncscan)
+			ss_report_location(scan->rs_rd, BlockNumberIsValid(blockno) ?
+							   blockno : scan->rs_startblock);
+
+		/*
+		 * Reached end of scan.
+		 */
+		if (!BlockNumberIsValid(blockno))
+		{
+			if (BufferIsValid(scan->rs_cbuf))
+				ReleaseBuffer(scan->rs_cbuf);
+			scan->rs_cbuf = InvalidBuffer;
+			scan->rs_cblock = InvalidBlockNumber;
+			tuple->t_data = NULL;
+			scan->rs_inited = false;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+
+		if (!pagemode)
+			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+		page = (Page) BufferGetPage(scan->rs_cbuf);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	pgstat_count_heap_getnext(scan->rs_rd);
+
+	return &(scan->rs_ctup);
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags,
+				 TableSampleClause *tablesample)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+
+	/*
+	 * Even though we aren't going to do a conventional seqscan, it is useful
+	 * to create a HeapScanDesc --- many of the fields in it are usable.
+	 */
+	node->ss.ss_currentScanDesc =
+		heap_beginscan_ss(currentRelation, estate->es_snapshot, 0, NULL,
+						  tablesample->tsmseqscan, tablesample->tsmpagemode);
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags, rte->tablesample);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	InitSamplingMethod(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished thes can.
+	 */
+	FunctionCall1(&node->tsmend, PointerGetDatum(node));
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close heap scan
+	 */
+	heap_endscan(node->ss.ss_currentScanDesc);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *node)
+{
+	heap_rescan(node->ss.ss_currentScanDesc, NULL);
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	FunctionCall1(&node->tsmreset, PointerGetDatum(node));
+
+	ExecScanReScan(&node->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 029761e..1a4c85b 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -630,6 +630,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2015,6 +2031,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2147,6 +2164,40 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsmseqscan);
+	COPY_SCALAR_FIELD(tsmpagemode);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmexaminetuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4084,6 +4135,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4732,6 +4786,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_FuncWithArgs:
 			retval = _copyFuncWithArgs(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 190e50a..27626b5 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2318,6 +2318,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2437,6 +2438,36 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsmseqscan);
+	COMPARE_SCALAR_FIELD(tsmpagemode);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmexaminetuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3155,6 +3186,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_FuncWithArgs:
 			retval = _equalFuncWithArgs(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index d6f1f5b..7742189 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3219,6 +3219,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 385b289..e26dbf0 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -580,6 +580,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -2404,6 +2412,36 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_BOOL_FIELD(tsmseqscan);
+	WRITE_BOOL_FIELD(tsmpagemode);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmexaminetuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2433,6 +2471,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2931,6 +2970,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3272,6 +3314,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 563209c..05ed9a8 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,46 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_BOOL_FIELD(tsmseqscan);
+	READ_BOOL_FIELD(tsmpagemode);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmexaminetuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1218,6 +1258,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1313,6 +1354,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 58d78e6..5f12477 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,10 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
+				   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -265,6 +269,11 @@ set_rel_size(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_size(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Sampled relation */
+					set_tablesample_rel_size(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -332,6 +341,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +432,41 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_size
+ *	  Set size estimates for a sampled relation.
+ */
+static void
+set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	/* Mark rel with estimated output rows, width, etc */
+	set_baserel_size_estimates(root, rel);
+}
+
+/*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids	required_outer;
+	Path   *path;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	path = create_samplescan_path(root, rel, required_outer);
+	rel->pathlist = list_make1(path);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 1a0d358..51583a1 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -90,6 +90,7 @@
 #include "utils/lsyscache.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
+#include "utils/tablesample.h"
 #include "utils/tuplesort.h"
 
 
@@ -220,6 +221,73 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we dont't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	RangeTblEntry		   *rte = planner_rt_fetch(baserel->relid, root);
+	TableSampleClause	   *tablesample = rte->tablesample;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Mark the path with the correct row estimate */
+	if (path->param_info)
+		path->rows = path->param_info->ppi_rows;
+	else
+		path->rows = baserel->rows;
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(tablesample->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(tablesample->args),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples));
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = tablesample->tsmseqscan ? spc_seq_page_cost :
+					spc_random_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->startup_cost = startup_cost;
+	path->total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index cb69c03..3fc84e2 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3321,6 +3372,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index ec828cd..82771dc 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -445,6 +445,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index acfd0bc..9971b54 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2167,6 +2167,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index faca30b..ea7a47b 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,26 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+Path *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	Path		   *pathnode = makeNode(Path);
+
+	pathnode->pathtype = T_SampleScan;
+	pathnode->parent = rel;
+	pathnode->param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->pathkeys = NIL;	/* samplescan has unordered result */
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1778,6 +1798,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 88ec83c..711cdd5 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -448,6 +448,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -615,8 +616,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10197,6 +10198,11 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample
+				{
+					RangeTableSample *n = (RangeTableSample *) $1;
+					$$ = (Node *) n;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10522,6 +10528,32 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr opt_alias_clause tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $3;
+					n->relation = $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' func_arg_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' a_expr ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/					{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13612,6 +13644,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 8d90b50..8318948 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -414,6 +417,29 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *r)
+{
+	RangeTblEntry  *rte;
+	TableSampleClause *tablesample = NULL;
+
+	/* We first need to build a range table entry */
+	rte = transformTableEntry(pstate, r->relation);
+
+	if (rte->relkind != RELKIND_RELATION &&
+		rte->relkind != RELKIND_MATVIEW)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("TABLESAMPLE clause can only be used on tables and materialized views"),
+				 parser_errposition(pstate,
+									 exprLocation((Node *) r))));
+
+	tablesample = ParseTableSample(pstate, r->method, r->repeatable, r->args);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -1122,6 +1148,27 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 1385776..0610873 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -767,6 +769,135 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+extern TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				actual_arg_types[FUNC_MAX_ARGS];
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						samplemethod)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsmseqscan = tsm->tsmseqscan;
+	tablesample->tsmpagemode = tsm->tsmpagemode;
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmexaminetuple = tsm->tsmexaminetuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Transform the rest of arguments ... */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *arg = transformExpr(pstate, (Node *) lfirst(larg), EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		fargs = lappend(fargs, arg);
+
+		actual_arg_types[nargs++] = argtype;
+	}
+
+	/*
+	 * Check if parameters are correct.
+	 *
+	 * XXX: can we do better at hinting here?
+	 */
+	if (initnargs != nargs ||
+			!can_coerce_type(initnargs, actual_arg_types, init_arg_types,
+						COERCION_IMPLICIT))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("wrong parameters for tablesample method \"%s\"",
+						samplemethod)));
+
+	/* perform the necessary typecasting of arguments */
+	make_fn_arguments(pstate, fargs, actual_arg_types, init_arg_types);
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/utils/Makefile b/src/backend/utils/Makefile
index 8374533..9daa2ae 100644
--- a/src/backend/utils/Makefile
+++ b/src/backend/utils/Makefile
@@ -9,7 +9,8 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS        = fmgrtab.o
-SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time
+SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time \
+			  tablesample
 
 # location of Catalog.pm
 catalogdir  = $(top_srcdir)/src/backend/catalog
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 29b5b1b..a6bd34c 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -32,6 +32,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -344,6 +345,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4185,6 +4188,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for tablesample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8453,6 +8500,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index bd27168..3a8f01e 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
index 1eeabaf..f213c46 100644
--- a/src/backend/utils/misc/sampling.c
+++ b/src/backend/utils/misc/sampling.c
@@ -46,6 +46,8 @@ BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
 	bs->n = samplesize;
 	bs->t = 0;					/* blocks scanned so far */
 	bs->m = 0;					/* blocks selected so far */
+
+	sampler_random_init_state(randseed, bs->randstate);
 }
 
 bool
@@ -92,7 +94,7 @@ BlockSampler_Next(BlockSampler bs)
 	 * less than k, which means that we cannot fail to select enough blocks.
 	 *----------
 	 */
-	V = sampler_random_fract();
+	V = sampler_random_fract(bs->randstate);
 	p = 1.0 - (double) k / (double) K;
 	while (V < p)
 	{
@@ -126,8 +128,14 @@ BlockSampler_Next(BlockSampler bs)
 void
 reservoir_init_selection_state(ReservoirState rs, int n)
 {
+	/*
+	 * Reservoir sampling is not used anywhere where it would need to return
+	 * repeatable results so we can initialize it randomly.
+	 */
+	sampler_random_init_state(random(), rs->randstate);
+
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	*rs = exp(-log(sampler_random_fract()) / n);
+	rs->W = exp(-log(sampler_random_fract(rs->randstate)) / n);
 }
 
 double
@@ -142,7 +150,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 		double		V,
 					quot;
 
-		V = sampler_random_fract(); /* Generate V */
+		V = sampler_random_fract(rs->randstate); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -158,7 +166,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 	else
 	{
 		/* Now apply Algorithm Z */
-		double		W = *rs;
+		double		W = rs->W;
 		double		term = t - (double) n + 1;
 
 		for (;;)
@@ -174,7 +182,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 						tmp;
 
 			/* Generate U and X */
-			U = sampler_random_fract();
+			U = sampler_random_fract(rs->randstate);
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -203,11 +211,11 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract(rs->randstate)) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
-		*rs = W;
+		rs->W = W;
 	}
 	return S;
 }
@@ -217,10 +225,17 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
  * Random number generator used by sampling
  *----------
  */
+void
+sampler_random_init_state(long seed, SamplerRandomState randstate)
+{
+	randstate[0] = 0x330e;
+	randstate[1] = (unsigned short) seed;
+	randstate[2] = (unsigned short) (seed >> 16);
+}
 
 /* Select a random value R uniformly distributed in (0 - 1) */
 double
-sampler_random_fract()
+sampler_random_fract(SamplerRandomState randstate)
 {
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+	return pg_erand48(randstate);
 }
diff --git a/src/backend/utils/tablesample/Makefile b/src/backend/utils/tablesample/Makefile
new file mode 100644
index 0000000..df92939
--- /dev/null
+++ b/src/backend/utils/tablesample/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for utils/tablesample
+#
+# IDENTIFICATION
+#    src/backend/utils/tablesample/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/utils/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = system.o bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/tablesample/bernoulli.c b/src/backend/utils/tablesample/bernoulli.c
new file mode 100644
index 0000000..36f4bcb
--- /dev/null
+++ b/src/backend/utils/tablesample/bernoulli.c
@@ -0,0 +1,224 @@
+/*-------------------------------------------------------------------------
+ *
+ * bernoulli.c
+ *	  interface routines for BERNOULLI tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/relscan.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/* State */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* number of blocks */
+	BlockNumber blockno;		/* current block */
+	float4 probability;			/* probabilty that tuple will be returned (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	HeapScanDesc	scan = scanstate->ss.ss_currentScanDesc;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->startblock = scan->rs_startblock;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->blockno = InvalidBlockNumber;
+	sampler->probability = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	/*
+	 * Bernoulli sampling scans all blocks on the table and supports
+	 * syncscan so loop from startblock to startblock instead of
+	 * from 0 to nblocks.
+	 */
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = sampler->startblock;
+	else
+	{
+		sampler->blockno++;
+
+		if (sampler->blockno >= sampler->nblocks)
+			sampler->blockno = 0;
+
+		if (sampler->blockno == sampler->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+	float4			probability = sampler->probability;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/*
+	 * Loop over tuple offsets until the random generator returns value that
+	 * is within the probability of returning the tuple or until we reach
+	 * end of the block.
+	 *
+	 * (This is our implementation of bernoulli trial)
+	 */
+	while (sampler_random_fract(sampler->randstate) > probability)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1f;
+	}
+
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/utils/tablesample/system.c b/src/backend/utils/tablesample/system.c
new file mode 100644
index 0000000..07d1f3a
--- /dev/null
+++ b/src/backend/utils/tablesample/system.c
@@ -0,0 +1,185 @@
+/*-------------------------------------------------------------------------
+ *
+ * system.c
+ *	  interface routines for system tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	SystemSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks =
+		RelationGetNumberOfBlocks(scanstate->ss.ss_currentRelation);
+	sampler->samplesize = 1 + (int) (sampler->tblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as VACUUM for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	BlockNumber		blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1f;
+	}
+
+	*pages = baserel->pages * samplesize;
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 888cce7..69cc702 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -113,8 +113,12 @@ extern HeapScanDesc heap_beginscan_strat(Relation relation, Snapshot snapshot,
 					 bool allow_strat, bool allow_sync);
 extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key);
+extern HeapScanDesc heap_beginscan_ss(Relation relation, Snapshot snapshot,
+				  int nkeys, ScanKey key,
+				  bool allow_strat, bool allow_pagemode);
 extern void heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk,
 		   BlockNumber endBlk);
+extern void heapgetpage(HeapScanDesc scan, BlockNumber page);
 extern void heap_rescan(HeapScanDesc scan, ScanKey key);
 extern void heap_endscan(HeapScanDesc scan);
 extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 9bb6362..e2b2b4f 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -29,6 +29,7 @@ typedef struct HeapScanDescData
 	int			rs_nkeys;		/* number of scan keys */
 	ScanKey		rs_key;			/* array of scan key descriptors */
 	bool		rs_bitmapscan;	/* true if this is really a bitmap scan */
+	bool		rs_samplescan;	/* true if this is really a sample scan */
 	bool		rs_pageatatime; /* verify visibility page-at-a-time? */
 	bool		rs_allow_strat; /* allow or disallow use of access strategy */
 	bool		rs_allow_sync;	/* allow or disallow use of syncscan */
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index a680229..e01bd0c 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3291, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3291
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3292, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3292
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index d90ecc5..91aab0d 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5182,6 +5182,31 @@ DESCR("rank of hypothetical row without gaps");
 DATA(insert OID = 3993 ( dense_rank_final	PGNSP PGUID 12 1 0 2276 0 f f f f f f i 2 0 20 "2281 2276" "{2281,2276}" "{i,v}" _null_ _null_	hypothetical_dense_rank_final _null_ _null_ _null_ ));
 DESCR("aggregate final function");
 
+DATA(insert OID = 3295 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3296 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3297 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3298 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3299 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3300 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3301 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3302 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3303 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3304 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3306 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3307 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 0000000..ec826e3
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,77 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3290
+
+CATALOG(pg_tablesample_method,3290)
+{
+	NameData	tsmname;		/* tablesample method name */
+	bool		tsmseqscan;		/* does this method scan whole table sequentially? */
+	bool		tsmpagemode;	/* does this method scan page at a time? */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmexaminetuple;	/* optional function which can examine tuple contents and
+								   decide if tuple should be returned or not */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method					10
+#define Anum_pg_tablesample_method_tsmname			1
+#define Anum_pg_tablesample_method_tsmseqscan		2
+#define Anum_pg_tablesample_method_tsmpagemode		3
+#define Anum_pg_tablesample_method_tsminit			4
+#define Anum_pg_tablesample_method_tsmnextblock		5
+#define Anum_pg_tablesample_method_tsmnexttuple		6
+#define Anum_pg_tablesample_method_tsmexaminetuple	7
+#define Anum_pg_tablesample_method_tsmend			8
+#define Anum_pg_tablesample_method_tsmreset			9
+#define Anum_pg_tablesample_method_tsmcost			10
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3293 ( system false true tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3294 ( bernoulli true false tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index ac75f86..20edee4 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1216,6 +1216,24 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState		ss;
+
+	/* Sampling method functions. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmexaminetuple;
+	FmgrInfo		tsmend;
+	FmgrInfo		tsmreset;
+
+	void		   *tsmdata;		/* for use by table scan method */
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 38469ef..caaedbf 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -414,6 +416,8 @@ typedef enum NodeTag
 	T_WithClause,
 	T_CommonTableExpr,
 	T_RoleSpec,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 0e257ac..a4288d1 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -334,6 +334,26 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	bool		tsmseqscan;
+	bool		tsmpagemode;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmexaminetuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -534,6 +554,21 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * We are more generic than SQL Standard so we pass generic function
+ * arguments to the sampling method.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -769,6 +804,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 21cbfa8..ddc3708 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -279,6 +279,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 9c2000b..24003ae 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 9923f0e..89c8ded 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern Path *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+									Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 7c243ec..ae90df8 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 3264691..6727e55 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,10 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 6bd786d..185bd81 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
index e3e7f9c..4ac208d 100644
--- a/src/include/utils/sampling.h
+++ b/src/include/utils/sampling.h
@@ -15,7 +15,12 @@
 
 #include "storage/bufmgr.h"
 
-extern double sampler_random_fract(void);
+/* Random generator for sampling code */
+typedef unsigned short SamplerRandomState[3];
+
+extern void sampler_random_init_state(long seed,
+									  SamplerRandomState randstate);
+extern double sampler_random_fract(SamplerRandomState randstate);
 
 /* Block sampling methods */
 /* Data structure for Algorithm S from Knuth 3.4.2 */
@@ -25,6 +30,7 @@ typedef struct
 	int			n;				/* desired sample size */
 	BlockNumber t;				/* current block number */
 	int			m;				/* blocks selected so far */
+	SamplerRandomState randstate; /* random generator state */
 } BlockSamplerData;
 
 typedef BlockSamplerData *BlockSampler;
@@ -35,7 +41,12 @@ extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
 /* Reservoid sampling methods */
-typedef double ReservoirStateData;
+typedef struct
+{
+	double	W;
+	SamplerRandomState randstate; /* random generator state */
+} ReservoirStateData;
+
 typedef ReservoirStateData *ReservoirState;
 
 extern void reservoir_init_selection_state(ReservoirState rs, int n);
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index ba0b090..6b628f6 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/include/utils/tablesample.h b/src/include/utils/tablesample.h
new file mode 100644
index 0000000..1a24cb6
--- /dev/null
+++ b/src/include/utils/tablesample.h
@@ -0,0 +1,27 @@
+/*--------------------------------------------------------------------------
+ * tablesample.h
+ *	  Header file for builtin table sampling methods.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/utils/tablesample.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TABLESAMPLE_H
+#define TABLESAMPLE_H
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TABLESAMPLE_H */
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..5946edf 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..5ba23c3
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,168 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+CLOSE tablesample_cur;
+END;
+-- should fail
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+ERROR:  TABLESAMPLE clause can only be used on tables and materialized views
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index 6d3b865..300e1fb 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 8326894..d815496 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -153,3 +153,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..d0c069c
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,42 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+CLOSE tablesample_cur;
+END;
+
+-- should fail
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+
+DROP TABLE test_tablesample CASCADE;
-- 
1.9.1

>From b3262d29606aaf6df97d48267658f6b2469791ac Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:36:56 +0100
Subject: [PATCH 1/4] separate block sampling functions v2

---
 contrib/file_fdw/file_fdw.c         |   9 +-
 contrib/postgres_fdw/postgres_fdw.c |  10 +-
 src/backend/commands/analyze.c      | 225 +----------------------------------
 src/backend/utils/misc/Makefile     |   2 +-
 src/backend/utils/misc/sampling.c   | 226 ++++++++++++++++++++++++++++++++++++
 src/include/commands/vacuum.h       |   3 -
 src/include/utils/sampling.h        |  44 +++++++
 7 files changed, 287 insertions(+), 232 deletions(-)
 create mode 100644 src/backend/utils/misc/sampling.c
 create mode 100644 src/include/utils/sampling.h

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 4368897..249d541 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -34,6 +34,7 @@
 #include "optimizer/var.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -1005,7 +1006,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 {
 	int			numrows = 0;
 	double		rowstoskip = -1;	/* -1 means not set yet */
-	double		rstate;
+	ReservoirStateData rstate;
 	TupleDesc	tupDesc;
 	Datum	   *values;
 	bool	   *nulls;
@@ -1043,7 +1044,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 									   ALLOCSET_DEFAULT_MAXSIZE);
 
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Set up callback to identify error line number. */
 	errcallback.callback = CopyFromErrorCallback;
@@ -1087,7 +1088,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 			 * not-yet-incremented value of totalrows as t.
 			 */
 			if (rowstoskip < 0)
-				rowstoskip = anl_get_next_S(*totalrows, targrows, &rstate);
+				rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
 
 			if (rowstoskip <= 0)
 			{
@@ -1095,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * anl_random_fract());
+				int			k = (int) (targrows * sampler_random_fract());
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 478e124..74ef792 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -37,6 +37,7 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -202,7 +203,7 @@ typedef struct PgFdwAnalyzeState
 	/* for random sampling */
 	double		samplerows;		/* # of rows fetched */
 	double		rowstoskip;		/* # of rows to skip before next sample */
-	double		rstate;			/* random state */
+	ReservoirStateData rstate;		/* state for reservoir sampling*/
 
 	/* working memory contexts */
 	MemoryContext anl_cxt;		/* context for per-analyze lifespan data */
@@ -2397,7 +2398,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 	astate.numrows = 0;
 	astate.samplerows = 0;
 	astate.rowstoskip = -1;		/* -1 means not set yet */
-	astate.rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&astate.rstate, targrows);
 
 	/* Remember ANALYZE context, and create a per-tuple temp context */
 	astate.anl_cxt = CurrentMemoryContext;
@@ -2537,13 +2538,12 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		 * analyze.c; see Jeff Vitter's paper.
 		 */
 		if (astate->rowstoskip < 0)
-			astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
-												&astate->rstate);
+			astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
 
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * anl_random_fract());
+			pos = (int) (targrows * sampler_random_fract());
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index d4d1914..5730f26 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -88,10 +78,6 @@ static BufferAccessStrategy vac_strategy;
 static void do_analyze_rel(Relation onerel, int options, List *va_cols,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -948,94 +934,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1081,7 +979,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	BlockNumber totalblocks;
 	TransactionId OldestXmin;
 	BlockSamplerData bs;
-	double		rstate;
+	ReservoirStateData rstate;
 
 	Assert(targrows > 0);
 
@@ -1091,9 +989,9 @@ acquire_sample_rows(Relation onerel, int elevel,
 	OldestXmin = GetOldestXmin(onerel, true);
 
 	/* Prepare for sampling block numbers */
-	BlockSampler_Init(&bs, totalblocks, targrows);
+	BlockSampler_Init(&bs, totalblocks, targrows, random());
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Outer loop over blocks to sample */
 	while (BlockSampler_HasMore(&bs))
@@ -1241,8 +1139,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 					 * t.
 					 */
 					if (rowstoskip < 0)
-						rowstoskip = anl_get_next_S(samplerows, targrows,
-													&rstate);
+						rowstoskip = reservoir_get_next_S(&rstate, samplerows, targrows);
 
 					if (rowstoskip <= 0)
 					{
@@ -1250,7 +1147,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1309,116 +1206,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
-/*
- * These two routines embody Algorithm Z from "Random sampling with a
- * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
- * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
- * of the count S of records to skip before processing another record.
- * It is computed primarily based on t, the number of records already read.
- * The only extra state needed between calls is W, a random state variable.
- *
- * anl_init_selection_state computes the initial W value.
- *
- * Given that we've already read t records (t >= n), anl_get_next_S
- * determines the number of records to skip before the next record is
- * processed.
- */
-double
-anl_init_selection_state(int n)
-{
-	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
-}
-
-double
-anl_get_next_S(double t, int n, double *stateptr)
-{
-	double		S;
-
-	/* The magic constant here is T from Vitter's paper */
-	if (t <= (22.0 * n))
-	{
-		/* Process records using Algorithm X until t is large enough */
-		double		V,
-					quot;
-
-		V = anl_random_fract(); /* Generate V */
-		S = 0;
-		t += 1;
-		/* Note: "num" in Vitter's code is always equal to t - n */
-		quot = (t - (double) n) / t;
-		/* Find min S satisfying (4.1) */
-		while (quot > V)
-		{
-			S += 1;
-			t += 1;
-			quot *= (t - (double) n) / t;
-		}
-	}
-	else
-	{
-		/* Now apply Algorithm Z */
-		double		W = *stateptr;
-		double		term = t - (double) n + 1;
-
-		for (;;)
-		{
-			double		numer,
-						numer_lim,
-						denom;
-			double		U,
-						X,
-						lhs,
-						rhs,
-						y,
-						tmp;
-
-			/* Generate U and X */
-			U = anl_random_fract();
-			X = t * (W - 1.0);
-			S = floor(X);		/* S is tentatively set to floor(X) */
-			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
-			tmp = (t + 1) / term;
-			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
-			rhs = (((t + X) / (term + S)) * term) / t;
-			if (lhs <= rhs)
-			{
-				W = rhs / lhs;
-				break;
-			}
-			/* Test if U <= f(S)/cg(X) */
-			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
-			if ((double) n < S)
-			{
-				denom = t;
-				numer_lim = term + S;
-			}
-			else
-			{
-				denom = t - (double) n + S;
-				numer_lim = t + 1;
-			}
-			for (numer = t + S; numer >= numer_lim; numer -= 1)
-			{
-				y *= numer / denom;
-				denom -= 1;
-			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
-			if (exp(log(y) / n) <= (t + X) / t)
-				break;
-		}
-		*stateptr = W;
-	}
-	return S;
-}
-
 /*
  * qsort comparator for sorting rows[] array
  */
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index 378b77e..7889101 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o rls.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..1eeabaf
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,226 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Relation block sampling routines.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler provides algorithm for block level sampling of a relation
+ * as discussed on pgsql-hackers 2004-04-02 (subject "Large DB")
+ * It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table. If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
+				  long randseed)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+/*
+ * These two routines embody Algorithm Z from "Random sampling with a
+ * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
+ * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
+ * of the count S of records to skip before processing another record.
+ * It is computed primarily based on t, the number of records already read.
+ * The only extra state needed between calls is W, a random state variable.
+ *
+ * reservoir_init_selection_state computes the initial W value.
+ *
+ * Given that we've already read t records (t >= n), reservoir_get_next_S
+ * determines the number of records to skip before the next record is
+ * processed.
+ */
+void
+reservoir_init_selection_state(ReservoirState rs, int n)
+{
+	/* Initial value of W (for use when Algorithm Z is first applied) */
+	*rs = exp(-log(sampler_random_fract()) / n);
+}
+
+double
+reservoir_get_next_S(ReservoirState rs, double t, int n)
+{
+	double		S;
+
+	/* The magic constant here is T from Vitter's paper */
+	if (t <= (22.0 * n))
+	{
+		/* Process records using Algorithm X until t is large enough */
+		double		V,
+					quot;
+
+		V = sampler_random_fract(); /* Generate V */
+		S = 0;
+		t += 1;
+		/* Note: "num" in Vitter's code is always equal to t - n */
+		quot = (t - (double) n) / t;
+		/* Find min S satisfying (4.1) */
+		while (quot > V)
+		{
+			S += 1;
+			t += 1;
+			quot *= (t - (double) n) / t;
+		}
+	}
+	else
+	{
+		/* Now apply Algorithm Z */
+		double		W = *rs;
+		double		term = t - (double) n + 1;
+
+		for (;;)
+		{
+			double		numer,
+						numer_lim,
+						denom;
+			double		U,
+						X,
+						lhs,
+						rhs,
+						y,
+						tmp;
+
+			/* Generate U and X */
+			U = sampler_random_fract();
+			X = t * (W - 1.0);
+			S = floor(X);		/* S is tentatively set to floor(X) */
+			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
+			tmp = (t + 1) / term;
+			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
+			rhs = (((t + X) / (term + S)) * term) / t;
+			if (lhs <= rhs)
+			{
+				W = rhs / lhs;
+				break;
+			}
+			/* Test if U <= f(S)/cg(X) */
+			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
+			if ((double) n < S)
+			{
+				denom = t;
+				numer_lim = term + S;
+			}
+			else
+			{
+				denom = t - (double) n + S;
+				numer_lim = t + 1;
+			}
+			for (numer = t + S; numer >= numer_lim; numer -= 1)
+			{
+				y *= numer / denom;
+				denom -= 1;
+			}
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			if (exp(log(y) / n) <= (t + X) / t)
+				break;
+		}
+		*rs = W;
+	}
+	return S;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract()
+{
+	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+}
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 9fd2516..27f5195 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -194,8 +194,5 @@ extern void analyze_rel(Oid relid, RangeVar *relation, int options,
 			List *va_cols, bool in_outer_xact,
 			BufferAccessStrategy bstrategy);
 extern bool std_typanalyze(VacAttrStats *stats);
-extern double anl_random_fract(void);
-extern double anl_init_selection_state(int n);
-extern double anl_get_next_S(double t, int n, double *stateptr);
 
 #endif   /* VACUUM_H */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..e3e7f9c
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,44 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+extern double sampler_random_fract(void);
+
+/* Block sampling methods */
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize, long randseed);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Reservoid sampling methods */
+typedef double ReservoirStateData;
+typedef ReservoirStateData *ReservoirState;
+
+extern void reservoir_init_selection_state(ReservoirState rs, int n);
+extern double reservoir_get_next_S(ReservoirState rs, double t, int n);
+
+#endif /* SAMPLING_H */
-- 
1.9.1

>From 788bb84c35b0ece6a7e287b67cb924b8af32723c Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:36:56 +0100
Subject: [PATCH 1/4] separate block sampling functions v2

---
 contrib/file_fdw/file_fdw.c         |   9 +-
 contrib/postgres_fdw/postgres_fdw.c |  10 +-
 src/backend/commands/analyze.c      | 225 +----------------------------------
 src/backend/utils/misc/Makefile     |   2 +-
 src/backend/utils/misc/sampling.c   | 226 ++++++++++++++++++++++++++++++++++++
 src/include/commands/vacuum.h       |   3 -
 src/include/utils/sampling.h        |  44 +++++++
 7 files changed, 287 insertions(+), 232 deletions(-)
 create mode 100644 src/backend/utils/misc/sampling.c
 create mode 100644 src/include/utils/sampling.h

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 4368897..249d541 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -34,6 +34,7 @@
 #include "optimizer/var.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -1005,7 +1006,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 {
 	int			numrows = 0;
 	double		rowstoskip = -1;	/* -1 means not set yet */
-	double		rstate;
+	ReservoirStateData rstate;
 	TupleDesc	tupDesc;
 	Datum	   *values;
 	bool	   *nulls;
@@ -1043,7 +1044,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 									   ALLOCSET_DEFAULT_MAXSIZE);
 
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Set up callback to identify error line number. */
 	errcallback.callback = CopyFromErrorCallback;
@@ -1087,7 +1088,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 			 * not-yet-incremented value of totalrows as t.
 			 */
 			if (rowstoskip < 0)
-				rowstoskip = anl_get_next_S(*totalrows, targrows, &rstate);
+				rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
 
 			if (rowstoskip <= 0)
 			{
@@ -1095,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * anl_random_fract());
+				int			k = (int) (targrows * sampler_random_fract());
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 478e124..74ef792 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -37,6 +37,7 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -202,7 +203,7 @@ typedef struct PgFdwAnalyzeState
 	/* for random sampling */
 	double		samplerows;		/* # of rows fetched */
 	double		rowstoskip;		/* # of rows to skip before next sample */
-	double		rstate;			/* random state */
+	ReservoirStateData rstate;		/* state for reservoir sampling*/
 
 	/* working memory contexts */
 	MemoryContext anl_cxt;		/* context for per-analyze lifespan data */
@@ -2397,7 +2398,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 	astate.numrows = 0;
 	astate.samplerows = 0;
 	astate.rowstoskip = -1;		/* -1 means not set yet */
-	astate.rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&astate.rstate, targrows);
 
 	/* Remember ANALYZE context, and create a per-tuple temp context */
 	astate.anl_cxt = CurrentMemoryContext;
@@ -2537,13 +2538,12 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		 * analyze.c; see Jeff Vitter's paper.
 		 */
 		if (astate->rowstoskip < 0)
-			astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
-												&astate->rstate);
+			astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
 
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * anl_random_fract());
+			pos = (int) (targrows * sampler_random_fract());
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 15ec0ad..952cf20 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -89,10 +79,6 @@ static void do_analyze_rel(Relation onerel, int options,
 			   VacuumParams *params, List *va_cols,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -951,94 +937,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1084,7 +982,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	BlockNumber totalblocks;
 	TransactionId OldestXmin;
 	BlockSamplerData bs;
-	double		rstate;
+	ReservoirStateData rstate;
 
 	Assert(targrows > 0);
 
@@ -1094,9 +992,9 @@ acquire_sample_rows(Relation onerel, int elevel,
 	OldestXmin = GetOldestXmin(onerel, true);
 
 	/* Prepare for sampling block numbers */
-	BlockSampler_Init(&bs, totalblocks, targrows);
+	BlockSampler_Init(&bs, totalblocks, targrows, random());
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Outer loop over blocks to sample */
 	while (BlockSampler_HasMore(&bs))
@@ -1244,8 +1142,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 					 * t.
 					 */
 					if (rowstoskip < 0)
-						rowstoskip = anl_get_next_S(samplerows, targrows,
-													&rstate);
+						rowstoskip = reservoir_get_next_S(&rstate, samplerows, targrows);
 
 					if (rowstoskip <= 0)
 					{
@@ -1253,7 +1150,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1312,116 +1209,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
-/*
- * These two routines embody Algorithm Z from "Random sampling with a
- * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
- * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
- * of the count S of records to skip before processing another record.
- * It is computed primarily based on t, the number of records already read.
- * The only extra state needed between calls is W, a random state variable.
- *
- * anl_init_selection_state computes the initial W value.
- *
- * Given that we've already read t records (t >= n), anl_get_next_S
- * determines the number of records to skip before the next record is
- * processed.
- */
-double
-anl_init_selection_state(int n)
-{
-	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
-}
-
-double
-anl_get_next_S(double t, int n, double *stateptr)
-{
-	double		S;
-
-	/* The magic constant here is T from Vitter's paper */
-	if (t <= (22.0 * n))
-	{
-		/* Process records using Algorithm X until t is large enough */
-		double		V,
-					quot;
-
-		V = anl_random_fract(); /* Generate V */
-		S = 0;
-		t += 1;
-		/* Note: "num" in Vitter's code is always equal to t - n */
-		quot = (t - (double) n) / t;
-		/* Find min S satisfying (4.1) */
-		while (quot > V)
-		{
-			S += 1;
-			t += 1;
-			quot *= (t - (double) n) / t;
-		}
-	}
-	else
-	{
-		/* Now apply Algorithm Z */
-		double		W = *stateptr;
-		double		term = t - (double) n + 1;
-
-		for (;;)
-		{
-			double		numer,
-						numer_lim,
-						denom;
-			double		U,
-						X,
-						lhs,
-						rhs,
-						y,
-						tmp;
-
-			/* Generate U and X */
-			U = anl_random_fract();
-			X = t * (W - 1.0);
-			S = floor(X);		/* S is tentatively set to floor(X) */
-			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
-			tmp = (t + 1) / term;
-			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
-			rhs = (((t + X) / (term + S)) * term) / t;
-			if (lhs <= rhs)
-			{
-				W = rhs / lhs;
-				break;
-			}
-			/* Test if U <= f(S)/cg(X) */
-			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
-			if ((double) n < S)
-			{
-				denom = t;
-				numer_lim = term + S;
-			}
-			else
-			{
-				denom = t - (double) n + S;
-				numer_lim = t + 1;
-			}
-			for (numer = t + S; numer >= numer_lim; numer -= 1)
-			{
-				y *= numer / denom;
-				denom -= 1;
-			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
-			if (exp(log(y) / n) <= (t + X) / t)
-				break;
-		}
-		*stateptr = W;
-	}
-	return S;
-}
-
 /*
  * qsort comparator for sorting rows[] array
  */
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index 378b77e..7889101 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o rls.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..1eeabaf
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,226 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Relation block sampling routines.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler provides algorithm for block level sampling of a relation
+ * as discussed on pgsql-hackers 2004-04-02 (subject "Large DB")
+ * It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table. If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
+				  long randseed)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+/*
+ * These two routines embody Algorithm Z from "Random sampling with a
+ * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
+ * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
+ * of the count S of records to skip before processing another record.
+ * It is computed primarily based on t, the number of records already read.
+ * The only extra state needed between calls is W, a random state variable.
+ *
+ * reservoir_init_selection_state computes the initial W value.
+ *
+ * Given that we've already read t records (t >= n), reservoir_get_next_S
+ * determines the number of records to skip before the next record is
+ * processed.
+ */
+void
+reservoir_init_selection_state(ReservoirState rs, int n)
+{
+	/* Initial value of W (for use when Algorithm Z is first applied) */
+	*rs = exp(-log(sampler_random_fract()) / n);
+}
+
+double
+reservoir_get_next_S(ReservoirState rs, double t, int n)
+{
+	double		S;
+
+	/* The magic constant here is T from Vitter's paper */
+	if (t <= (22.0 * n))
+	{
+		/* Process records using Algorithm X until t is large enough */
+		double		V,
+					quot;
+
+		V = sampler_random_fract(); /* Generate V */
+		S = 0;
+		t += 1;
+		/* Note: "num" in Vitter's code is always equal to t - n */
+		quot = (t - (double) n) / t;
+		/* Find min S satisfying (4.1) */
+		while (quot > V)
+		{
+			S += 1;
+			t += 1;
+			quot *= (t - (double) n) / t;
+		}
+	}
+	else
+	{
+		/* Now apply Algorithm Z */
+		double		W = *rs;
+		double		term = t - (double) n + 1;
+
+		for (;;)
+		{
+			double		numer,
+						numer_lim,
+						denom;
+			double		U,
+						X,
+						lhs,
+						rhs,
+						y,
+						tmp;
+
+			/* Generate U and X */
+			U = sampler_random_fract();
+			X = t * (W - 1.0);
+			S = floor(X);		/* S is tentatively set to floor(X) */
+			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
+			tmp = (t + 1) / term;
+			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
+			rhs = (((t + X) / (term + S)) * term) / t;
+			if (lhs <= rhs)
+			{
+				W = rhs / lhs;
+				break;
+			}
+			/* Test if U <= f(S)/cg(X) */
+			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
+			if ((double) n < S)
+			{
+				denom = t;
+				numer_lim = term + S;
+			}
+			else
+			{
+				denom = t - (double) n + S;
+				numer_lim = t + 1;
+			}
+			for (numer = t + S; numer >= numer_lim; numer -= 1)
+			{
+				y *= numer / denom;
+				denom -= 1;
+			}
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			if (exp(log(y) / n) <= (t + X) / t)
+				break;
+		}
+		*rs = W;
+	}
+	return S;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract()
+{
+	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+}
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 71f0165..ce7b28d 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -197,8 +197,5 @@ extern void analyze_rel(Oid relid, RangeVar *relation, int options,
 			VacuumParams *params, List *va_cols, bool in_outer_xact,
 			BufferAccessStrategy bstrategy);
 extern bool std_typanalyze(VacAttrStats *stats);
-extern double anl_random_fract(void);
-extern double anl_init_selection_state(int n);
-extern double anl_get_next_S(double t, int n, double *stateptr);
 
 #endif   /* VACUUM_H */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..e3e7f9c
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,44 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+extern double sampler_random_fract(void);
+
+/* Block sampling methods */
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize, long randseed);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Reservoid sampling methods */
+typedef double ReservoirStateData;
+typedef ReservoirStateData *ReservoirState;
+
+extern void reservoir_init_selection_state(ReservoirState rs, int n);
+extern double reservoir_get_next_S(ReservoirState rs, double t, int n);
+
+#endif /* SAMPLING_H */
-- 
1.9.1

>From c17558e5da82b2b94460f6889510d54cdae16b16 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:37:55 +0100
Subject: [PATCH 2/4] tablesample v12

---
 contrib/file_fdw/file_fdw.c                 |   2 +-
 contrib/postgres_fdw/postgres_fdw.c         |   2 +-
 doc/src/sgml/catalogs.sgml                  | 120 ++++++
 doc/src/sgml/ref/select.sgml                |  44 ++-
 src/backend/access/Makefile                 |   3 +-
 src/backend/access/heap/heapam.c            |  43 ++-
 src/backend/catalog/Makefile                |   2 +-
 src/backend/commands/analyze.c              |   2 +-
 src/backend/commands/explain.c              |  13 +
 src/backend/executor/Makefile               |   2 +-
 src/backend/executor/execAmi.c              |   8 +
 src/backend/executor/execCurrent.c          |   1 +
 src/backend/executor/execProcnode.c         |  14 +
 src/backend/executor/nodeSamplescan.c       | 562 ++++++++++++++++++++++++++++
 src/backend/nodes/copyfuncs.c               |  60 +++
 src/backend/nodes/equalfuncs.c              |  37 ++
 src/backend/nodes/nodeFuncs.c               |  12 +
 src/backend/nodes/outfuncs.c                |  48 +++
 src/backend/nodes/readfuncs.c               |  45 +++
 src/backend/optimizer/path/allpaths.c       |  49 +++
 src/backend/optimizer/path/costsize.c       |  68 ++++
 src/backend/optimizer/plan/createplan.c     |  69 ++++
 src/backend/optimizer/plan/setrefs.c        |  11 +
 src/backend/optimizer/plan/subselect.c      |   1 +
 src/backend/optimizer/util/pathnode.c       |  22 ++
 src/backend/parser/gram.y                   |  36 +-
 src/backend/parser/parse_clause.c           |  47 +++
 src/backend/parser/parse_func.c             | 143 +++++++
 src/backend/rewrite/rewriteHandler.c        |   3 +
 src/backend/utils/Makefile                  |   3 +-
 src/backend/utils/adt/ruleutils.c           |  50 +++
 src/backend/utils/cache/lsyscache.c         |  27 ++
 src/backend/utils/cache/syscache.c          |  23 ++
 src/backend/utils/misc/sampling.c           |  33 +-
 src/backend/utils/tablesample/Makefile      |  17 +
 src/backend/utils/tablesample/bernoulli.c   | 224 +++++++++++
 src/backend/utils/tablesample/system.c      | 185 +++++++++
 src/include/access/heapam.h                 |   4 +
 src/include/access/relscan.h                |   1 +
 src/include/catalog/indexing.h              |   5 +
 src/include/catalog/pg_proc.h               |  25 ++
 src/include/catalog/pg_tablesample_method.h |  78 ++++
 src/include/executor/nodeSamplescan.h       |  24 ++
 src/include/nodes/execnodes.h               |  18 +
 src/include/nodes/nodes.h                   |   4 +
 src/include/nodes/parsenodes.h              |  36 ++
 src/include/nodes/plannodes.h               |   6 +
 src/include/optimizer/cost.h                |   1 +
 src/include/optimizer/pathnode.h            |   2 +
 src/include/parser/kwlist.h                 |   1 +
 src/include/parser/parse_func.h             |   5 +
 src/include/utils/lsyscache.h               |   1 +
 src/include/utils/rel.h                     |   1 -
 src/include/utils/sampling.h                |  15 +-
 src/include/utils/syscache.h                |   2 +
 src/include/utils/tablesample.h             |  27 ++
 src/test/regress/expected/sanity_check.out  |   1 +
 src/test/regress/expected/tablesample.out   | 170 +++++++++
 src/test/regress/parallel_schedule          |   2 +-
 src/test/regress/serial_schedule            |   1 +
 src/test/regress/sql/tablesample.sql        |  42 +++
 61 files changed, 2467 insertions(+), 36 deletions(-)
 create mode 100644 src/backend/executor/nodeSamplescan.c
 create mode 100644 src/backend/utils/tablesample/Makefile
 create mode 100644 src/backend/utils/tablesample/bernoulli.c
 create mode 100644 src/backend/utils/tablesample/system.c
 create mode 100644 src/include/catalog/pg_tablesample_method.h
 create mode 100644 src/include/executor/nodeSamplescan.h
 create mode 100644 src/include/utils/tablesample.h
 create mode 100644 src/test/regress/expected/tablesample.out
 create mode 100644 src/test/regress/sql/tablesample.sql

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 249d541..6a813a3 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -1096,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * sampler_random_fract());
+				int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 74ef792..5903384 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -2543,7 +2543,7 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * sampler_random_fract());
+			pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index d0b78f2..af808a0 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -269,6 +269,11 @@
      </row>
 
      <row>
+      <entry><link linkend="catalog-pg-tablesample-method"><structname>pg_tablesample_method</structname></link></entry>
+      <entry>table sampling methods</entry>
+     </row>
+
+     <row>
       <entry><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link></entry>
       <entry>tablespaces within this database cluster</entry>
      </row>
@@ -5980,6 +5985,121 @@
  </sect1>
 
 
+ <sect1 id="catalog-pg-tablesample-method">
+  <title><structname>pg_tabesample_method</structname></title>
+
+  <indexterm zone="catalog-pg-tablesample-method">
+   <primary>pg_am</primary>
+  </indexterm>
+
+  <para>
+   The catalog <structname>pg_tablesample_method</structname> stores
+   information about table sampling methods which can be used in
+   <command>TABLESAMPLE</command> clause of a <command>SELECT</command>
+   statement.
+  </para>
+
+  <table>
+   <title><structname>pg_tablesample_method</> Columns</title>
+
+   <tgroup cols="4">
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Type</entry>
+      <entry>References</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+    <tbody>
+
+     <row>
+      <entry><structfield>oid</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry></entry>
+      <entry>Row identifier (hidden attribute; must be explicitly selected)</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmname</structfield></entry>
+      <entry><type>name</type></entry>
+      <entry></entry>
+      <entry>Name of the sampling method</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmseqscan</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry></entry>
+      <entry>Does the sampling method scan the whole table sequentially?
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmpagemode</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry></entry>
+      <entry>Does the sampling method always read whole pages?
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsminit</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Initialize the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnextblock</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next block number</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnexttuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next tuple offset</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmexaminetuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Function which examines the tuple contents and decides if to
+        return in, or zero if none</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmend</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>End the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmreset</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Restart the state of sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmcost</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Costing function</entry>
+     </row>
+
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect1>
+
+
  <sect1 id="catalog-pg-tablespace">
   <title><structname>pg_tablespace</structname></title>
 
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 2295f63..f70d8c4 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,48 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        any sampling method installed in the database. There are currently two
+        sampling methods available in the standard
+        <productname>PostgreSQL</productname> distrribution:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of those sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability. Additional sampling methods
+        may be installed in the database via extensions.
+       </para>
+       <para>
+        The optional parameter <literal>REPEATABLE</literal> acceps any number
+        or expression producing a number and is used as random seed for
+        sampling. Note that subsequent commands may return different results
+        even if same <literal>REPEATABLE</literal> clause was specified. This
+        happens because <acronym>DML</acronym> statements and maintenance
+        operations such as <command>VACUUM</> may affect physical distribution
+        of data.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..238057a 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  transam
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index cb6f8a3..76c2d3a 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -79,8 +79,9 @@ bool		synchronize_seqscans = true;
 static HeapScanDesc heap_beginscan_internal(Relation relation,
 						Snapshot snapshot,
 						int nkeys, ScanKey key,
-						bool allow_strat, bool allow_sync,
-						bool is_bitmapscan, bool temp_snap);
+						bool allow_strat, bool allow_sync, bool allow_pagemode,
+						bool is_bitmapscan, bool is_samplescan,
+						bool temp_snap);
 static HeapTuple heap_prepare_insert(Relation relation, HeapTuple tup,
 					TransactionId xid, CommandId cid, int options);
 static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf,
@@ -293,9 +294,10 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
 
 	/*
 	 * Currently, we don't have a stats counter for bitmap heap scans (but the
-	 * underlying bitmap index scans will be counted).
+	 * underlying bitmap index scans will be counted) or sample scans (we only
+	 * update stats for tuple fetches there)
 	 */
-	if (!scan->rs_bitmapscan)
+	if (!scan->rs_bitmapscan && !scan->rs_samplescan)
 		pgstat_count_heap_scan(scan->rs_rd);
 }
 
@@ -314,7 +316,7 @@ heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk, BlockNumber numBlks)
  * In page-at-a-time mode it performs additional work, namely determining
  * which tuples on the page are visible.
  */
-static void
+void
 heapgetpage(HeapScanDesc scan, BlockNumber page)
 {
 	Buffer		buffer;
@@ -1289,7 +1291,7 @@ heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
  *		heap_beginscan	- begin relation scan
  *
  * heap_beginscan_strat offers an extended API that lets the caller control
- * whether a nondefault buffer access strategy can be used, and whether
+ * whether a nondefault buffer access strategy can be used and whether
  * syncscan can be chosen (possibly resulting in the scan not starting from
  * block zero).  Both of these default to TRUE with plain heap_beginscan.
  *
@@ -1297,6 +1299,9 @@ heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
  * HeapScanDesc for a bitmap heap scan.  Although that scan technology is
  * really quite unlike a standard seqscan, there is just enough commonality
  * to make it worth using the same data structure.
+ *
+ * heap_beginscan_ss is alternate entry point for setting up a
+ * HeapScanDesc for a TABLESAMPLE scan.
  * ----------------
  */
 HeapScanDesc
@@ -1304,7 +1309,7 @@ heap_beginscan(Relation relation, Snapshot snapshot,
 			   int nkeys, ScanKey key)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   true, true, false, false);
+								   true, true, true, false, false, false);
 }
 
 HeapScanDesc
@@ -1314,7 +1319,7 @@ heap_beginscan_catalog(Relation relation, int nkeys, ScanKey key)
 	Snapshot	snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
 
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   true, true, false, true);
+								   true, true, true, false, false, true);
 }
 
 HeapScanDesc
@@ -1323,7 +1328,8 @@ heap_beginscan_strat(Relation relation, Snapshot snapshot,
 					 bool allow_strat, bool allow_sync)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   allow_strat, allow_sync, false, false);
+								   allow_strat, allow_sync, true,
+								   false, false, false);
 }
 
 HeapScanDesc
@@ -1331,14 +1337,24 @@ heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   false, false, true, false);
+								   false, false, true, true, false, false);
+}
+
+HeapScanDesc
+heap_beginscan_ss(Relation relation, Snapshot snapshot,
+				  int nkeys, ScanKey key,
+				  bool allow_strat, bool allow_pagemode)
+{
+	return heap_beginscan_internal(relation, snapshot, nkeys, key,
+								   allow_strat, false, allow_pagemode,
+								   false, true, false);
 }
 
 static HeapScanDesc
 heap_beginscan_internal(Relation relation, Snapshot snapshot,
 						int nkeys, ScanKey key,
-						bool allow_strat, bool allow_sync,
-						bool is_bitmapscan, bool temp_snap)
+						bool allow_strat, bool allow_sync, bool allow_pagemode,
+						bool is_bitmapscan, bool is_samplescan, bool temp_snap)
 {
 	HeapScanDesc scan;
 
@@ -1360,6 +1376,7 @@ heap_beginscan_internal(Relation relation, Snapshot snapshot,
 	scan->rs_snapshot = snapshot;
 	scan->rs_nkeys = nkeys;
 	scan->rs_bitmapscan = is_bitmapscan;
+	scan->rs_samplescan = is_samplescan;
 	scan->rs_strategy = NULL;	/* set in initscan */
 	scan->rs_allow_strat = allow_strat;
 	scan->rs_allow_sync = allow_sync;
@@ -1368,7 +1385,7 @@ heap_beginscan_internal(Relation relation, Snapshot snapshot,
 	/*
 	 * we can use page-at-a-time mode if it's an MVCC-safe snapshot
 	 */
-	scan->rs_pageatatime = IsMVCCSnapshot(snapshot);
+	scan->rs_pageatatime = allow_pagemode && IsMVCCSnapshot(snapshot);
 
 	/*
 	 * For a seqscan in a serializable transaction, acquire a predicate lock
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..34db3e6 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesample_method.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 952cf20..65e329e 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1150,7 +1150,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * sampler_random_fract());
+						int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 315a528..aee3c4f 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -732,6 +732,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -957,6 +958,15 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			{
+				/* Fetch the tablesample method info from RTE */
+				RangeTblEntry *rte;
+				rte = rt_fetch(((SampleScan *) plan)->scanrelid, es->rtable);
+				custom_name = get_tablesample_method_name(rte->tablesample->tsmid);
+				pname = psprintf("Sample Scan (%s)", custom_name);
+			}
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1074,6 +1084,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1326,6 +1337,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2224,6 +2236,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 6ebad2f..4948a26 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index d87be96..bcd287f 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 9892499..03c2feb 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..065f9f5
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,562 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "catalog/pg_tablesample_method.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "pgstat.h"
+#include "storage/bufmgr.h"
+#include "storage/predicate.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate,
+							 int eflags, TableSampleClause *tablesample);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+static HeapTuple samplenexttup(SampleScanState *node, HeapScanDesc scan);
+
+
+/*
+ * Initialize the sampling method - loads function info and
+ * calls the tsminit function.
+ *
+ * We need special handling for this because the tsminit function
+ * is allowed to take optional additional arguments.
+ */
+static void
+InitSamplingMethod(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(scanstate->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(scanstate->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(scanstate->tsmnexttuple));
+	if (OidIsValid(tablesample->tsmexaminetuple))
+		fmgr_info(tablesample->tsmexaminetuple, &(scanstate->tsmexaminetuple));
+	else
+		scanstate->tsmexaminetuple.fn_oid = InvalidOid;
+	fmgr_info(tablesample->tsmend, &(scanstate->tsmend));
+	fmgr_info(tablesample->tsmreset, &(scanstate->tsmreset));
+
+	InitFunctionCallInfoData(fcinfo, &scanstate->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	/* First arg is always SampleScanState */
+	fcinfo.arg[0] = PointerGetDatum(scanstate);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause must be NOT NULL numeric value")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+}
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	TupleTableSlot *slot;
+	HeapScanDesc	scan;
+	HeapTuple		tuple;
+
+	/*
+	 * get information from the scan state
+	 */
+	slot = node->ss.ss_ScanTupleSlot;
+	scan = node->ss.ss_currentScanDesc;
+
+	tuple = samplenexttup(node, scan);
+
+	if (tuple)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   scan->rs_cbuf,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+/*
+ * Check visibility of the tuple.
+ */
+static bool
+SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan)
+{
+	/*
+	 * If this scan is reading whole pages at a time, there is already
+	 * visibilty info present in rs_vistuples so we can just search it
+	 * for the tupoffset.
+	 */
+	if (scan->rs_pageatatime)
+	{
+		int start = 0,
+			end = scan->rs_ntuples - 1;
+
+		/*
+		 * Do the binary search over rs_vistuples, it's already sorted by
+		 * OffsetNumber so we don't need to do any sorting ourselves here.
+		 *
+		 * We could use bsearch() here but it's slower for integers because
+		 * of the function call overhead and because it needs boiler plate code
+		 * it would not save us anything code-wise anyway.
+		 */
+		while (start <= end)
+		{
+			int mid = start + (end - start) / 2;
+			OffsetNumber curoffset = scan->rs_vistuples[mid];
+
+			if (curoffset == tupoffset)
+				return true;
+			else if (curoffset > tupoffset)
+				end = mid - 1;
+			else
+				start = mid + 1;
+		}
+
+		return false;
+	}
+	else
+	{
+		/* No pagemode, we have to check the tuple itself. */
+		Snapshot	snapshot = scan->rs_snapshot;
+		Buffer		buffer = scan->rs_cbuf;
+
+		bool visible = HeapTupleSatisfiesVisibility(tuple, snapshot, buffer);
+
+		CheckForSerializableConflictOut(visible, scan->rs_rd, tuple, buffer,
+										snapshot);
+
+		return visible;
+	}
+}
+
+/*
+ * Read next tuple using the correct sampling method.
+ */
+static HeapTuple
+samplenexttup(SampleScanState *node, HeapScanDesc scan)
+{
+	HeapTuple		tuple = &(scan->rs_ctup);
+	bool			pagemode = scan->rs_pageatatime;
+	BlockNumber		blockno;
+	Page			page;
+	bool			page_all_visible;
+	ItemId			itemid;
+	OffsetNumber	tupoffset,
+					maxoffset;
+
+	if (!scan->rs_inited)
+	{
+		/*
+		 * return null immediately if relation is empty
+		 */
+		if (scan->rs_nblocks == 0)
+		{
+			Assert(!BufferIsValid(scan->rs_cbuf));
+			tuple->t_data = NULL;
+			return NULL;
+		}
+		blockno = DatumGetInt32(FunctionCall1(&node->tsmnextblock,
+											  PointerGetDatum(node)));
+		if (!BlockNumberIsValid(blockno))
+		{
+			tuple->t_data = NULL;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+		scan->rs_inited = true;
+	}
+	else
+	{
+		/* continue from previously returned page/tuple */
+		blockno = scan->rs_cblock;		/* current page */
+	}
+
+	/*
+	 * When pagemode is disabled, the scan will do visibility checks for each
+	 * tuple it finds so the buffer needs to be locked.
+	 */
+	if (!pagemode)
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+	page = (Page) BufferGetPage(scan->rs_cbuf);
+	page_all_visible = PageIsAllVisible(page);
+	maxoffset = PageGetMaxOffsetNumber(page);
+
+	for (;;)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		tupoffset = DatumGetUInt16(FunctionCall3(&node->tsmnexttuple,
+												 PointerGetDatum(node),
+												 UInt32GetDatum(blockno),
+												 UInt16GetDatum(maxoffset)));
+
+		if (OffsetNumberIsValid(tupoffset))
+		{
+			bool	visible;
+			bool	found;
+
+			/* Skip invalid tuple pointers. */
+			itemid = PageGetItemId(page, tupoffset);
+			if (!ItemIdIsNormal(itemid))
+				continue;
+
+			tuple->t_data = (HeapTupleHeader) PageGetItem((Page) page, itemid);
+			tuple->t_len = ItemIdGetLength(itemid);
+			ItemPointerSet(&(tuple->t_self), blockno, tupoffset);
+
+			if (page_all_visible)
+				visible = true;
+			else
+				visible = SampleTupleVisible(tuple, tupoffset, scan);
+
+			/*
+			 * Let the sampling method examine the actual tuple and decide if we
+			 * should return it.
+			 *
+			 * Note that we let it examine even invisible tuples for
+			 * statistical purposes, but not return them since user should
+			 * never see invisible tuples.
+			 */
+			if (OidIsValid(node->tsmexaminetuple.fn_oid))
+			{
+				found = DatumGetBool(FunctionCall4(&node->tsmexaminetuple,
+												   PointerGetDatum(node),
+												   UInt32GetDatum(blockno),
+												   PointerGetDatum(tuple),
+												   BoolGetDatum(visible)));
+				/* Should not happen if sampling method is well written. */
+				if (found && !visible)
+					elog(ERROR, "Sampling method wanted to return invisible tuple");
+			}
+			else
+				found = visible;
+
+			/* Found visible tuple, return it. */
+			if (found)
+			{
+				if (!pagemode)
+					LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+				break;
+			}
+			else
+			{
+				/* Try next tuple from same page. */
+				continue;
+			}
+		}
+
+
+		if (!pagemode)
+			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+
+		blockno = DatumGetInt32(FunctionCall1(&node->tsmnextblock,
+											  PointerGetDatum(node)));
+
+		/*
+		 * Report our new scan position for synchronization purposes. We
+		 * don't do that when moving backwards, however. That would just
+		 * mess up any other forward-moving scanners.
+		 *
+		 * Note: we do this before checking for end of scan so that the
+		 * final state of the position hint is back at the start of the
+		 * rel.  That's not strictly necessary, but otherwise when you run
+		 * the same query multiple times the starting position would shift
+		 * a little bit backwards on every invocation, which is confusing.
+		 * We don't guarantee any specific ordering in general, though.
+		 */
+		if (scan->rs_syncscan)
+			ss_report_location(scan->rs_rd, BlockNumberIsValid(blockno) ?
+							   blockno : scan->rs_startblock);
+
+		/*
+		 * Reached end of scan.
+		 */
+		if (!BlockNumberIsValid(blockno))
+		{
+			if (BufferIsValid(scan->rs_cbuf))
+				ReleaseBuffer(scan->rs_cbuf);
+			scan->rs_cbuf = InvalidBuffer;
+			scan->rs_cblock = InvalidBlockNumber;
+			tuple->t_data = NULL;
+			scan->rs_inited = false;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+
+		if (!pagemode)
+			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+		page = (Page) BufferGetPage(scan->rs_cbuf);
+		page_all_visible = PageIsAllVisible(page);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	pgstat_count_heap_getnext(scan->rs_rd);
+
+	return &(scan->rs_ctup);
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags,
+				 TableSampleClause *tablesample)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+
+	/*
+	 * Even though we aren't going to do a conventional seqscan, it is useful
+	 * to create a HeapScanDesc --- many of the fields in it are usable.
+	 */
+	node->ss.ss_currentScanDesc =
+		heap_beginscan_ss(currentRelation, estate->es_snapshot, 0, NULL,
+						  tablesample->tsmseqscan, tablesample->tsmpagemode);
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags, rte->tablesample);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	InitSamplingMethod(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished thes can.
+	 */
+	FunctionCall1(&node->tsmend, PointerGetDatum(node));
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close heap scan
+	 */
+	heap_endscan(node->ss.ss_currentScanDesc);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *node)
+{
+	heap_rescan(node->ss.ss_currentScanDesc, NULL);
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	FunctionCall1(&node->tsmreset, PointerGetDatum(node));
+
+	ExecScanReScan(&node->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 029761e..1a4c85b 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -630,6 +630,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2015,6 +2031,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2147,6 +2164,40 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsmseqscan);
+	COPY_SCALAR_FIELD(tsmpagemode);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmexaminetuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4084,6 +4135,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4732,6 +4786,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_FuncWithArgs:
 			retval = _copyFuncWithArgs(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 190e50a..27626b5 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2318,6 +2318,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2437,6 +2438,36 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsmseqscan);
+	COMPARE_SCALAR_FIELD(tsmpagemode);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmexaminetuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3155,6 +3186,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_FuncWithArgs:
 			retval = _equalFuncWithArgs(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index d6f1f5b..7742189 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3219,6 +3219,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 385b289..e26dbf0 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -580,6 +580,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -2404,6 +2412,36 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_BOOL_FIELD(tsmseqscan);
+	WRITE_BOOL_FIELD(tsmpagemode);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmexaminetuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2433,6 +2471,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2931,6 +2970,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3272,6 +3314,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 563209c..05ed9a8 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,46 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_BOOL_FIELD(tsmseqscan);
+	READ_BOOL_FIELD(tsmpagemode);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmexaminetuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1218,6 +1258,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1313,6 +1354,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 58d78e6..5f12477 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,10 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
+				   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -265,6 +269,11 @@ set_rel_size(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_size(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Sampled relation */
+					set_tablesample_rel_size(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -332,6 +341,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +432,41 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_size
+ *	  Set size estimates for a sampled relation.
+ */
+static void
+set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	/* Mark rel with estimated output rows, width, etc */
+	set_baserel_size_estimates(root, rel);
+}
+
+/*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids	required_outer;
+	Path   *path;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	path = create_samplescan_path(root, rel, required_outer);
+	rel->pathlist = list_make1(path);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 1a0d358..51583a1 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -90,6 +90,7 @@
 #include "utils/lsyscache.h"
 #include "utils/selfuncs.h"
 #include "utils/spccache.h"
+#include "utils/tablesample.h"
 #include "utils/tuplesort.h"
 
 
@@ -220,6 +221,73 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we dont't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	RangeTblEntry		   *rte = planner_rt_fetch(baserel->relid, root);
+	TableSampleClause	   *tablesample = rte->tablesample;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Mark the path with the correct row estimate */
+	if (path->param_info)
+		path->rows = path->param_info->ppi_rows;
+	else
+		path->rows = baserel->rows;
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(tablesample->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(tablesample->args),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples));
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = tablesample->tsmseqscan ? spc_seq_page_cost :
+					spc_random_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->startup_cost = startup_cost;
+	path->total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index cb69c03..3fc84e2 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3321,6 +3372,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 94b12ab..a2ae940 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -445,6 +445,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index acfd0bc..9971b54 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2167,6 +2167,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index faca30b..ea7a47b 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,26 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+Path *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	Path		   *pathnode = makeNode(Path);
+
+	pathnode->pathtype = T_SampleScan;
+	pathnode->parent = rel;
+	pathnode->param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->pathkeys = NIL;	/* samplescan has unordered result */
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1778,6 +1798,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 88ec83c..8ee6b40 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -448,6 +448,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -615,8 +616,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10197,6 +10198,10 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample
+				{
+					$$ = (Node *) $1;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10522,6 +10527,32 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr opt_alias_clause tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $3;
+					n->relation = $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' expr_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' a_expr ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/					{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13612,6 +13643,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 8d90b50..44a3021 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -414,6 +417,29 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *r)
+{
+	RangeTblEntry  *rte;
+	TableSampleClause *tablesample = NULL;
+
+	/* We first need to build a range table entry */
+	rte = transformTableEntry(pstate, r->relation);
+
+	if (rte->relkind != RELKIND_RELATION &&
+		rte->relkind != RELKIND_MATVIEW)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("TABLESAMPLE clause can only be used on tables and materialized views"),
+				 parser_errposition(pstate, r->relation->location)));
+
+	tablesample = ParseTableSample(pstate, r->method, r->repeatable, r->args,
+								   r->relation->location);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -1122,6 +1148,27 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 1385776..ab87635 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -767,6 +769,147 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs, int location)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						samplemethod),
+				 parser_errposition(pstate, location)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsmseqscan = tsm->tsmseqscan;
+	tablesample->tsmpagemode = tsm->tsmpagemode;
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmexaminetuple = tsm->tsmexaminetuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Check user provided expected number of arguments. */
+	if (list_length(sampleargs) != initnargs)
+		ereport(ERROR,
+				(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
+		 errmsg_plural("tablesample method \"%s\" expects %d argument got %d",
+					   "tablesample method \"%s\" expects %d arguments got %d",
+					   initnargs,
+					   samplemethod,
+					   initnargs, list_length(sampleargs)),
+		 parser_errposition(pstate, location)));
+
+	/* Transform the arguments, typecasting them as needed. */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *inarg = (Node *) lfirst(larg);
+		Node   *arg = transformExpr(pstate, inarg, EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		if (argtype != init_arg_types[nargs])
+		{
+			if (!can_coerce_type(1, &argtype, &init_arg_types[nargs],
+								 COERCION_IMPLICIT))
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("wrong parameter %d for tablesample method \"%s\"",
+							nargs + 1, samplemethod),
+					 errdetail("Expected type %s got %s.",
+							   format_type_be(init_arg_types[nargs]),
+							   format_type_be(argtype)),
+					 parser_errposition(pstate, exprLocation(inarg))));
+
+			arg = coerce_type(pstate, arg, argtype, init_arg_types[nargs], -1,
+							  COERCION_IMPLICIT, COERCE_IMPLICIT_CAST, -1);
+		}
+
+		fargs = lappend(fargs, arg);
+		nargs++;
+	}
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index 9d2c280..385ae9c 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -2160,6 +2160,9 @@ view_query_is_auto_updatable(Query *viewquery, bool check_cols)
 		 base_rte->relkind != RELKIND_VIEW))
 		return gettext_noop("Views that do not select from a single table or view are not automatically updatable.");
 
+	if (base_rte->tablesample)
+		return gettext_noop("Views containing TABLESAMPLE are not automatically updatable.");
+
 	/*
 	 * Check that the view has at least one updatable column. This is required
 	 * for INSERT/UPDATE but not for DELETE.
diff --git a/src/backend/utils/Makefile b/src/backend/utils/Makefile
index 8374533..9daa2ae 100644
--- a/src/backend/utils/Makefile
+++ b/src/backend/utils/Makefile
@@ -9,7 +9,8 @@ top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS        = fmgrtab.o
-SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time
+SUBDIRS     = adt cache error fmgr hash init mb misc mmgr resowner sort time \
+			  tablesample
 
 # location of Catalog.pm
 catalogdir  = $(top_srcdir)/src/backend/catalog
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 29b5b1b..a6bd34c 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -32,6 +32,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -344,6 +345,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4185,6 +4188,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for tablesample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8453,6 +8500,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 818c2f6..311364c 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -29,6 +29,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_range.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_type.h"
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
@@ -2910,3 +2911,29 @@ get_range_subtype(Oid rangeOid)
 	else
 		return InvalidOid;
 }
+
+/*				---------- PG_TABLESAMPLE_METHOD CACHE ----------			 */
+
+/*
+ * get_tablesample_method_name - given a tablesample method OID,
+ * look up the name or NULL if not found
+ */
+char *
+get_tablesample_method_name(Oid tsmid)
+{
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmid));
+	if (HeapTupleIsValid(tuple))
+	{
+		Form_pg_tablesample_method	tup =
+			(Form_pg_tablesample_method) GETSTRUCT(tuple);
+		char	   *result;
+
+		result = pstrdup(NameStr(tup->tsmname));
+		ReleaseSysCache(tuple);
+		return result;
+	}
+	else
+		return NULL;
+}
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index bd27168..3a8f01e 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
index 1eeabaf..f213c46 100644
--- a/src/backend/utils/misc/sampling.c
+++ b/src/backend/utils/misc/sampling.c
@@ -46,6 +46,8 @@ BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
 	bs->n = samplesize;
 	bs->t = 0;					/* blocks scanned so far */
 	bs->m = 0;					/* blocks selected so far */
+
+	sampler_random_init_state(randseed, bs->randstate);
 }
 
 bool
@@ -92,7 +94,7 @@ BlockSampler_Next(BlockSampler bs)
 	 * less than k, which means that we cannot fail to select enough blocks.
 	 *----------
 	 */
-	V = sampler_random_fract();
+	V = sampler_random_fract(bs->randstate);
 	p = 1.0 - (double) k / (double) K;
 	while (V < p)
 	{
@@ -126,8 +128,14 @@ BlockSampler_Next(BlockSampler bs)
 void
 reservoir_init_selection_state(ReservoirState rs, int n)
 {
+	/*
+	 * Reservoir sampling is not used anywhere where it would need to return
+	 * repeatable results so we can initialize it randomly.
+	 */
+	sampler_random_init_state(random(), rs->randstate);
+
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	*rs = exp(-log(sampler_random_fract()) / n);
+	rs->W = exp(-log(sampler_random_fract(rs->randstate)) / n);
 }
 
 double
@@ -142,7 +150,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 		double		V,
 					quot;
 
-		V = sampler_random_fract(); /* Generate V */
+		V = sampler_random_fract(rs->randstate); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -158,7 +166,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 	else
 	{
 		/* Now apply Algorithm Z */
-		double		W = *rs;
+		double		W = rs->W;
 		double		term = t - (double) n + 1;
 
 		for (;;)
@@ -174,7 +182,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 						tmp;
 
 			/* Generate U and X */
-			U = sampler_random_fract();
+			U = sampler_random_fract(rs->randstate);
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -203,11 +211,11 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract(rs->randstate)) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
-		*rs = W;
+		rs->W = W;
 	}
 	return S;
 }
@@ -217,10 +225,17 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
  * Random number generator used by sampling
  *----------
  */
+void
+sampler_random_init_state(long seed, SamplerRandomState randstate)
+{
+	randstate[0] = 0x330e;
+	randstate[1] = (unsigned short) seed;
+	randstate[2] = (unsigned short) (seed >> 16);
+}
 
 /* Select a random value R uniformly distributed in (0 - 1) */
 double
-sampler_random_fract()
+sampler_random_fract(SamplerRandomState randstate)
 {
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+	return pg_erand48(randstate);
 }
diff --git a/src/backend/utils/tablesample/Makefile b/src/backend/utils/tablesample/Makefile
new file mode 100644
index 0000000..df92939
--- /dev/null
+++ b/src/backend/utils/tablesample/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for utils/tablesample
+#
+# IDENTIFICATION
+#    src/backend/utils/tablesample/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/utils/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = system.o bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/utils/tablesample/bernoulli.c b/src/backend/utils/tablesample/bernoulli.c
new file mode 100644
index 0000000..36f4bcb
--- /dev/null
+++ b/src/backend/utils/tablesample/bernoulli.c
@@ -0,0 +1,224 @@
+/*-------------------------------------------------------------------------
+ *
+ * bernoulli.c
+ *	  interface routines for BERNOULLI tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/relscan.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/* State */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* number of blocks */
+	BlockNumber blockno;		/* current block */
+	float4 probability;			/* probabilty that tuple will be returned (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	HeapScanDesc	scan = scanstate->ss.ss_currentScanDesc;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->startblock = scan->rs_startblock;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->blockno = InvalidBlockNumber;
+	sampler->probability = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	/*
+	 * Bernoulli sampling scans all blocks on the table and supports
+	 * syncscan so loop from startblock to startblock instead of
+	 * from 0 to nblocks.
+	 */
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = sampler->startblock;
+	else
+	{
+		sampler->blockno++;
+
+		if (sampler->blockno >= sampler->nblocks)
+			sampler->blockno = 0;
+
+		if (sampler->blockno == sampler->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+	float4			probability = sampler->probability;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/*
+	 * Loop over tuple offsets until the random generator returns value that
+	 * is within the probability of returning the tuple or until we reach
+	 * end of the block.
+	 *
+	 * (This is our implementation of bernoulli trial)
+	 */
+	while (sampler_random_fract(sampler->randstate) > probability)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData *sampler =
+		(BernoulliSamplerData *) scanstate->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1f;
+	}
+
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/utils/tablesample/system.c b/src/backend/utils/tablesample/system.c
new file mode 100644
index 0000000..07d1f3a
--- /dev/null
+++ b/src/backend/utils/tablesample/system.c
@@ -0,0 +1,185 @@
+/*-------------------------------------------------------------------------
+ *
+ * system.c
+ *	  interface routines for system tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber tblocks;		/* total blocks in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	float4			percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	SystemSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->tblocks =
+		RelationGetNumberOfBlocks(scanstate->ss.ss_currentRelation);
+	sampler->samplesize = 1 + (int) (sampler->tblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	scanstate->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as VACUUM for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	BlockNumber		blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+	OffsetNumber	tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	SystemSamplerData *sampler = (SystemSamplerData *) scanstate->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	BlockSampler_Init(&sampler->bs, sampler->tblocks, sampler->samplesize,
+					  sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1f;
+	}
+
+	*pages = baserel->pages * samplesize;
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 888cce7..69cc702 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -113,8 +113,12 @@ extern HeapScanDesc heap_beginscan_strat(Relation relation, Snapshot snapshot,
 					 bool allow_strat, bool allow_sync);
 extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key);
+extern HeapScanDesc heap_beginscan_ss(Relation relation, Snapshot snapshot,
+				  int nkeys, ScanKey key,
+				  bool allow_strat, bool allow_pagemode);
 extern void heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk,
 		   BlockNumber endBlk);
+extern void heapgetpage(HeapScanDesc scan, BlockNumber page);
 extern void heap_rescan(HeapScanDesc scan, ScanKey key);
 extern void heap_endscan(HeapScanDesc scan);
 extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 9bb6362..e2b2b4f 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -29,6 +29,7 @@ typedef struct HeapScanDescData
 	int			rs_nkeys;		/* number of scan keys */
 	ScanKey		rs_key;			/* array of scan key descriptors */
 	bool		rs_bitmapscan;	/* true if this is really a bitmap scan */
+	bool		rs_samplescan;	/* true if this is really a sample scan */
 	bool		rs_pageatatime; /* verify visibility page-at-a-time? */
 	bool		rs_allow_strat; /* allow or disallow use of access strategy */
 	bool		rs_allow_sync;	/* allow or disallow use of syncscan */
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index a680229..e01bd0c 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3291, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3291
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3292, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3292
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index d90ecc5..91aab0d 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5182,6 +5182,31 @@ DESCR("rank of hypothetical row without gaps");
 DATA(insert OID = 3993 ( dense_rank_final	PGNSP PGUID 12 1 0 2276 0 f f f f f f i 2 0 20 "2281 2276" "{2281,2276}" "{i,v}" _null_ _null_	hypothetical_dense_rank_final _null_ _null_ _null_ ));
 DESCR("aggregate final function");
 
+DATA(insert OID = 3295 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3296 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3297 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3298 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3299 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3300 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3301 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3302 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3303 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3304 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3306 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3307 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 0000000..a58e1cf
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,78 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+#include "catalog/objectaddress.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3290
+
+CATALOG(pg_tablesample_method,3290)
+{
+	NameData	tsmname;		/* tablesample method name */
+	bool		tsmseqscan;		/* does this method scan whole table sequentially? */
+	bool		tsmpagemode;	/* does this method scan page at a time? */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmexaminetuple;	/* optional function which can examine tuple contents and
+								   decide if tuple should be returned or not */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method					10
+#define Anum_pg_tablesample_method_tsmname			1
+#define Anum_pg_tablesample_method_tsmseqscan		2
+#define Anum_pg_tablesample_method_tsmpagemode		3
+#define Anum_pg_tablesample_method_tsminit			4
+#define Anum_pg_tablesample_method_tsmnextblock		5
+#define Anum_pg_tablesample_method_tsmnexttuple		6
+#define Anum_pg_tablesample_method_tsmexaminetuple	7
+#define Anum_pg_tablesample_method_tsmend			8
+#define Anum_pg_tablesample_method_tsmreset			9
+#define Anum_pg_tablesample_method_tsmcost			10
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3293 ( system false true tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3294 ( bernoulli true false tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index ac75f86..20edee4 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1216,6 +1216,24 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState		ss;
+
+	/* Sampling method functions. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmexaminetuple;
+	FmgrInfo		tsmend;
+	FmgrInfo		tsmreset;
+
+	void		   *tsmdata;		/* for use by table scan method */
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 38469ef..caaedbf 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -414,6 +416,8 @@ typedef enum NodeTag
 	T_WithClause,
 	T_CommonTableExpr,
 	T_RoleSpec,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 0e257ac..a4288d1 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -334,6 +334,26 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	bool		tsmseqscan;
+	bool		tsmpagemode;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmexaminetuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -534,6 +554,21 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * We are more generic than SQL Standard so we pass generic function
+ * arguments to the sampling method.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -769,6 +804,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 21cbfa8..ddc3708 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -279,6 +279,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 9c2000b..24003ae 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 9923f0e..89c8ded 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern Path *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+									Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 7c243ec..ae90df8 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 3264691..40c007c 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,11 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args,
+										   int location);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 2f5ede1..78175c1 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -152,6 +152,7 @@ extern void free_attstatsslot(Oid atttype,
 				  float4 *numbers, int nnumbers);
 extern char *get_namespace_name(Oid nspid);
 extern Oid	get_range_subtype(Oid rangeOid);
+extern char *get_tablesample_method_name(Oid tsmid);
 
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 9e17d87..fd40366 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
index e3e7f9c..4ac208d 100644
--- a/src/include/utils/sampling.h
+++ b/src/include/utils/sampling.h
@@ -15,7 +15,12 @@
 
 #include "storage/bufmgr.h"
 
-extern double sampler_random_fract(void);
+/* Random generator for sampling code */
+typedef unsigned short SamplerRandomState[3];
+
+extern void sampler_random_init_state(long seed,
+									  SamplerRandomState randstate);
+extern double sampler_random_fract(SamplerRandomState randstate);
 
 /* Block sampling methods */
 /* Data structure for Algorithm S from Knuth 3.4.2 */
@@ -25,6 +30,7 @@ typedef struct
 	int			n;				/* desired sample size */
 	BlockNumber t;				/* current block number */
 	int			m;				/* blocks selected so far */
+	SamplerRandomState randstate; /* random generator state */
 } BlockSamplerData;
 
 typedef BlockSamplerData *BlockSampler;
@@ -35,7 +41,12 @@ extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
 /* Reservoid sampling methods */
-typedef double ReservoirStateData;
+typedef struct
+{
+	double	W;
+	SamplerRandomState randstate; /* random generator state */
+} ReservoirStateData;
+
 typedef ReservoirStateData *ReservoirState;
 
 extern void reservoir_init_selection_state(ReservoirState rs, int n);
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index ba0b090..6b628f6 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/include/utils/tablesample.h b/src/include/utils/tablesample.h
new file mode 100644
index 0000000..1a24cb6
--- /dev/null
+++ b/src/include/utils/tablesample.h
@@ -0,0 +1,27 @@
+/*--------------------------------------------------------------------------
+ * tablesample.h
+ *	  Header file for builtin table sampling methods.
+ *
+ *	Copyright (c) 2006-2014, PostgreSQL Global Development Group
+ *
+ *	src/include/utils/tablesample.h
+ *--------------------------------------------------------------------------
+ */
+#ifndef TABLESAMPLE_H
+#define TABLESAMPLE_H
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+#endif   /* TABLESAMPLE_H */
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..5946edf 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..6a89689
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,170 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+CLOSE tablesample_cur;
+END;
+-- should fail
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+ERROR:  TABLESAMPLE clause can only be used on tables and materialized views
+LINE 1: SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1)...
+                       ^
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index 6d3b865..300e1fb 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 8326894..d815496 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -153,3 +153,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..d0c069c
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,42 @@
+CREATE TABLE test_tablesample (id INT, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+CLOSE tablesample_cur;
+END;
+
+-- should fail
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+
+DROP TABLE test_tablesample CASCADE;
-- 
1.9.1

>From f5d469e898305ece335dff83ecb66bc59d4df81a Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:51:44 +0100
Subject: [PATCH 3/4] tablesample-ddl v7

---
 doc/src/sgml/ref/allfiles.sgml                     |   2 +
 doc/src/sgml/ref/create_tablesamplemethod.sgml     | 184 ++++++++++
 doc/src/sgml/ref/drop_tablesamplemethod.sgml       |  87 +++++
 doc/src/sgml/reference.sgml                        |   2 +
 src/backend/catalog/dependency.c                   |  15 +-
 src/backend/catalog/objectaddress.c                |  65 +++-
 src/backend/commands/Makefile                      |   6 +-
 src/backend/commands/dropcmds.c                    |   4 +
 src/backend/commands/event_trigger.c               |   3 +
 src/backend/commands/tablecmds.c                   |   1 +
 src/backend/commands/tablesample.c                 | 398 +++++++++++++++++++++
 src/backend/parser/gram.y                          |  14 +-
 src/backend/tcop/utility.c                         |  12 +
 src/backend/utils/cache/lsyscache.c                |  31 ++
 src/bin/pg_dump/common.c                           |   5 +
 src/bin/pg_dump/pg_dump.c                          | 177 +++++++++
 src/bin/pg_dump/pg_dump.h                          |  11 +-
 src/bin/pg_dump/pg_dump_sort.c                     |  11 +-
 src/include/catalog/dependency.h                   |   1 +
 src/include/catalog/pg_tablesample_method.h        |  10 +
 src/include/nodes/parsenodes.h                     |   1 +
 src/include/parser/kwlist.h                        |   1 +
 src/include/utils/lsyscache.h                      |   1 +
 src/test/modules/Makefile                          |   3 +-
 src/test/modules/tablesample/.gitignore            |   4 +
 src/test/modules/tablesample/Makefile              |  21 ++
 .../modules/tablesample/expected/tablesample.out   |  38 ++
 src/test/modules/tablesample/sql/tablesample.sql   |  14 +
 src/test/modules/tablesample/tsm_test--1.0.sql     |  52 +++
 src/test/modules/tablesample/tsm_test.c            | 228 ++++++++++++
 src/test/modules/tablesample/tsm_test.control      |   5 +
 31 files changed, 1396 insertions(+), 11 deletions(-)
 create mode 100644 doc/src/sgml/ref/create_tablesamplemethod.sgml
 create mode 100644 doc/src/sgml/ref/drop_tablesamplemethod.sgml
 create mode 100644 src/backend/commands/tablesample.c
 create mode 100644 src/test/modules/tablesample/.gitignore
 create mode 100644 src/test/modules/tablesample/Makefile
 create mode 100644 src/test/modules/tablesample/expected/tablesample.out
 create mode 100644 src/test/modules/tablesample/sql/tablesample.sql
 create mode 100644 src/test/modules/tablesample/tsm_test--1.0.sql
 create mode 100644 src/test/modules/tablesample/tsm_test.c
 create mode 100644 src/test/modules/tablesample/tsm_test.control

diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index 5b4692f..d31a2db 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -78,6 +78,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY createServer       SYSTEM "create_server.sgml">
 <!ENTITY createTable        SYSTEM "create_table.sgml">
 <!ENTITY createTableAs      SYSTEM "create_table_as.sgml">
+<!ENTITY createTablesampleMethod SYSTEM "create_tablesamplemethod.sgml">
 <!ENTITY createTableSpace   SYSTEM "create_tablespace.sgml">
 <!ENTITY createTrigger      SYSTEM "create_trigger.sgml">
 <!ENTITY createTSConfig     SYSTEM "create_tsconfig.sgml">
@@ -119,6 +120,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY dropSequence       SYSTEM "drop_sequence.sgml">
 <!ENTITY dropServer         SYSTEM "drop_server.sgml">
 <!ENTITY dropTable          SYSTEM "drop_table.sgml">
+<!ENTITY dropTablesampleMethod SYSTEM "drop_tablesamplemethod.sgml">
 <!ENTITY dropTableSpace     SYSTEM "drop_tablespace.sgml">
 <!ENTITY dropTrigger        SYSTEM "drop_trigger.sgml">
 <!ENTITY dropTSConfig       SYSTEM "drop_tsconfig.sgml">
diff --git a/doc/src/sgml/ref/create_tablesamplemethod.sgml b/doc/src/sgml/ref/create_tablesamplemethod.sgml
new file mode 100644
index 0000000..ff105d2
--- /dev/null
+++ b/doc/src/sgml/ref/create_tablesamplemethod.sgml
@@ -0,0 +1,184 @@
+<!--
+doc/src/sgml/ref/create_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-CREATETABLESAMPLEMETHOD">
+ <indexterm zone="sql-createtablesamplemethod">
+  <primary>CREATE TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE TABLESAMPLE METHOD</refname>
+  <refpurpose>define custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE TABLESAMPLE METHOD <replaceable class="parameter">name</replaceable> (
+    INIT = <replaceable class="parameter">init_function</replaceable> ,
+    NEXTBLOCK = <replaceable class="parameter">nextblock_function</replaceable> ,
+    NEXTTUPLE = <replaceable class="parameter">nexttuple_function</replaceable> ,
+    END = <replaceable class="parameter">end_function</replaceable> ,
+    RESET = <replaceable class="parameter">reset_function</replaceable> ,
+    COST = <replaceable class="parameter">cost_function</replaceable>
+    [ , EXAMINETUPLE = <replaceable class="parameter">examinetuple_function</replaceable> ]
+    [ , SEQSCAN = <replaceable class="parameter">seqscan</replaceable> ]
+    [ , PAGEMODE = <replaceable class="parameter">pagemode</replaceable> ]
+)
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE TABLESAMPLE METHOD</command> creates a tablesample method.
+   A tablesample method provides alrorithm for reading sample part of a table
+   when used in <command>TABLESAMPLE</> clause of a <command>SELECT</>
+   statement.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the tablesample method to be created. This name must be
+      unique within the database.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">init_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the init function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nextblock_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-block function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nexttuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-tuple function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">end_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the end function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">reset_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the reset function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">cost_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the costing function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">examinetuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the function for inspecting the tuple contents in order
+      to make decision if it should be returned or not. This parameter
+      is optional.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">seqscan</replaceable></term>
+    <listitem>
+     <para>
+      True if the sampling method will do sequential scan of the whole table.
+      Used for cost estimation and syncscan. The default value if not specified
+      is False.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">pagemode</replaceable></term>
+    <listitem>
+     <para>
+      True if the sampling method will read whole page at a time. The default
+      value if not specified is False.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+  <para>
+   The function names can be schema-qualified if necessary.  Argument types
+   are not given, since the argument list for each type of function is
+   predetermined.  All functions are required.
+  </para>
+
+  <para>
+   The arguments can appear in any order, not only the one shown above.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>CREATE TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-droptablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/ref/drop_tablesamplemethod.sgml b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
new file mode 100644
index 0000000..dffd2ec
--- /dev/null
+++ b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
@@ -0,0 +1,87 @@
+<!--
+doc/src/sgml/ref/drop_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-DROPTABLESAMPLEMETHOD">
+ <indexterm zone="sql-droptablesamplemethod">
+  <primary>DROP TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DROP TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP TABLESAMPLE METHOD</refname>
+  <refpurpose>remove a custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP TABLESAMPLE METHOD [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>DROP TABLESAMPLE METHOD</command> drop an existing tablesample
+   method.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the tablesample method does not exist.
+      A notice is issued in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of an existing tablesample method to be removed.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>DROP TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createtablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index 65ad795..4f55893 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -106,6 +106,7 @@
    &createServer;
    &createTable;
    &createTableAs;
+   &createTablesampleMethod;
    &createTableSpace;
    &createTSConfig;
    &createTSDictionary;
@@ -147,6 +148,7 @@
    &dropSequence;
    &dropServer;
    &dropTable;
+   &dropTablesampleMethod;
    &dropTableSpace;
    &dropTSConfig;
    &dropTSDictionary;
diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index bacb242..6acb5b3 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -46,6 +46,7 @@
 #include "catalog/pg_policy.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -157,7 +158,8 @@ static const Oid object_classes[MAX_OCLASS] = {
 	DefaultAclRelationId,		/* OCLASS_DEFACL */
 	ExtensionRelationId,		/* OCLASS_EXTENSION */
 	EventTriggerRelationId,		/* OCLASS_EVENT_TRIGGER */
-	PolicyRelationId			/* OCLASS_POLICY */
+	PolicyRelationId,			/* OCLASS_POLICY */
+	TableSampleMethodRelationId			/* OCLASS_TABLESAMPLEMETHOD */
 };
 
 
@@ -1265,6 +1267,10 @@ doDeletion(const ObjectAddress *object, int flags)
 			RemovePolicyById(object->objectId);
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			RemoveTablesampleMethodById(object->objectId);
+			break;
+
 		default:
 			elog(ERROR, "unrecognized object class: %u",
 				 object->classId);
@@ -1794,6 +1800,10 @@ find_expr_references_walker(Node *node,
 				case RTE_RELATION:
 					add_object_address(OCLASS_CLASS, rte->relid, 0,
 									   context->addrs);
+					if (rte->tablesample)
+						add_object_address(OCLASS_TABLESAMPLEMETHOD,
+										   rte->tablesample->tsmid, 0,
+										   context->addrs);
 					break;
 				default:
 					break;
@@ -2373,6 +2383,9 @@ getObjectClass(const ObjectAddress *object)
 
 		case PolicyRelationId:
 			return OCLASS_POLICY;
+
+		case TableSampleMethodRelationId:
+			return OCLASS_TABLESAMPLEMETHOD;
 	}
 
 	/* shouldn't get here */
diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index e82a448..3f47076 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -44,6 +44,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_policy.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -429,7 +430,19 @@ static const ObjectPropertyType ObjectProperty[] =
 		Anum_pg_type_typacl,
 		ACL_KIND_TYPE,
 		true
-	}
+	},
+	{
+		TableSampleMethodRelationId,
+		TableSampleMethodOidIndexId,
+		TABLESAMPLEMETHODOID,
+		TABLESAMPLEMETHODNAME,
+		Anum_pg_tablesample_method_tsmname,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		-1,
+		true
+	},
 };
 
 /*
@@ -528,7 +541,9 @@ ObjectTypeMap[] =
 	/* OCLASS_EVENT_TRIGGER */
 	{ "event trigger", OBJECT_EVENT_TRIGGER },
 	/* OCLASS_POLICY */
-	{ "policy", OBJECT_POLICY }
+	{ "policy", OBJECT_POLICY },
+	/* OCLASS_TABLESAMPLEMETHOD */
+	{ "tablesample method", OBJECT_TABLESAMPLEMETHOD }
 };
 
 const ObjectAddress InvalidObjectAddress =
@@ -683,6 +698,7 @@ get_object_address(ObjectType objtype, List *objname, List *objargs,
 			case OBJECT_FDW:
 			case OBJECT_FOREIGN_SERVER:
 			case OBJECT_EVENT_TRIGGER:
+			case OBJECT_TABLESAMPLEMETHOD:
 				address = get_object_address_unqualified(objtype,
 														 objname, missing_ok);
 				break;
@@ -921,6 +937,9 @@ get_object_address_unqualified(ObjectType objtype,
 			case OBJECT_EVENT_TRIGGER:
 				msg = gettext_noop("event trigger name cannot be qualified");
 				break;
+			case OBJECT_TABLESAMPLEMETHOD:
+				msg = gettext_noop("tablesample method name cannot be qualified");
+				break;
 			default:
 				elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 				msg = NULL;		/* placate compiler */
@@ -981,6 +1000,11 @@ get_object_address_unqualified(ObjectType objtype,
 			address.objectId = get_event_trigger_oid(name, missing_ok);
 			address.objectSubId = 0;
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			address.classId = TableSampleMethodRelationId;
+			address.objectId = get_tablesample_method_oid(name, missing_ok);
+			address.objectSubId = 0;
+			break;
 		default:
 			elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 			/* placate compiler, which doesn't know elog won't return */
@@ -2044,6 +2068,7 @@ check_object_ownership(Oid roleid, ObjectType objtype, ObjectAddress address,
 			break;
 		case OBJECT_TSPARSER:
 		case OBJECT_TSTEMPLATE:
+		case OBJECT_TABLESAMPLEMETHOD:
 			/* We treat these object types as being owned by superusers */
 			if (!superuser_arg(roleid))
 				ereport(ERROR,
@@ -2982,6 +3007,21 @@ getObjectDescription(const ObjectAddress *object)
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				appendStringInfo(&buffer, _("tablesample method %s"),
+					 NameStr(((Form_pg_tablesample_method) GETSTRUCT(tup))->tsmname));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
@@ -3459,6 +3499,10 @@ getObjectTypeDescription(const ObjectAddress *object)
 			appendStringInfoString(&buffer, "policy");
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			appendStringInfoString(&buffer, "tablesample method");
+			break;
+
 		default:
 			appendStringInfo(&buffer, "unrecognized %u", object->classId);
 			break;
@@ -4381,6 +4425,23 @@ getObjectIdentityParts(const ObjectAddress *object,
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+				Form_pg_tablesample_method tsmForm;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				tsmForm = (Form_pg_tablesample_method) GETSTRUCT(tup);
+				appendStringInfoString(&buffer,
+							   quote_identifier(NameStr(tsmForm->tsmname)));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index b1ac704..04fcd8c 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -18,8 +18,8 @@ OBJS = aggregatecmds.o alter.o analyze.o async.o cluster.o comment.o  \
 	event_trigger.o explain.o extension.o foreigncmds.o functioncmds.o \
 	indexcmds.o lockcmds.o matview.o operatorcmds.o opclasscmds.o \
 	policy.o portalcmds.o prepare.o proclang.o \
-	schemacmds.o seclabel.o sequence.o tablecmds.o tablespace.o trigger.o \
-	tsearchcmds.o typecmds.o user.o vacuum.o vacuumlazy.o \
-	variable.o view.o
+	schemacmds.o seclabel.o sequence.o tablecmds.o tablesample.o \
+	tablespace.o trigger.o tsearchcmds.o typecmds.o user.o vacuum.o \
+	vacuumlazy.o variable.o view.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/commands/dropcmds.c b/src/backend/commands/dropcmds.c
index a1b0d4d..c307dcf 100644
--- a/src/backend/commands/dropcmds.c
+++ b/src/backend/commands/dropcmds.c
@@ -429,6 +429,10 @@ does_not_exist_skipping(ObjectType objtype, List *objname, List *objargs)
 				}
 			}
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			msg = gettext_noop("tablesample method \"%s\" does not exist, skipping");
+			name = NameListToString(objname);
+			break;
 		default:
 			elog(ERROR, "unexpected object type (%d)", (int) objtype);
 			break;
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index 4bcc327..9e9ef38 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -97,6 +97,7 @@ static event_trigger_support_data event_trigger_support[] = {
 	{"SEQUENCE", true},
 	{"SERVER", true},
 	{"TABLE", true},
+	{"TABLESAMPLE METHOD", true},
 	{"TABLESPACE", false},
 	{"TRIGGER", true},
 	{"TEXT SEARCH CONFIGURATION", true},
@@ -1089,6 +1090,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_SEQUENCE:
 		case OBJECT_TABCONSTRAINT:
 		case OBJECT_TABLE:
+		case OBJECT_TABLESAMPLEMETHOD:
 		case OBJECT_TRIGGER:
 		case OBJECT_TSCONFIGURATION:
 		case OBJECT_TSDICTIONARY:
@@ -1146,6 +1148,7 @@ EventTriggerSupportsObjectClass(ObjectClass objclass)
 		case OCLASS_DEFACL:
 		case OCLASS_EXTENSION:
 		case OCLASS_POLICY:
+		case OCLASS_TABLESAMPLEMETHOD:
 			return true;
 
 		case MAX_OCLASS:
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 06e4332..e527caf 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8236,6 +8236,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 			case OCLASS_USER_MAPPING:
 			case OCLASS_DEFACL:
 			case OCLASS_EXTENSION:
+			case OCLASS_TABLESAMPLEMETHOD:
 
 				/*
 				 * We don't expect any of these sorts of objects to depend on
diff --git a/src/backend/commands/tablesample.c b/src/backend/commands/tablesample.c
new file mode 100644
index 0000000..33581f6
--- /dev/null
+++ b/src/backend/commands/tablesample.c
@@ -0,0 +1,398 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *	  Commands to manipulate tablesample methods
+ *
+ * Table sampling methods provide algorithms for doing sample scan over
+ * the table.
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/tablesample.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "access/heapam.h"
+#include "access/htup_details.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/objectaccess.h"
+#include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
+#include "catalog/pg_type.h"
+#include "commands/defrem.h"
+#include "miscadmin.h"
+#include "parser/parse_func.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+
+static Datum
+get_tablesample_method_func(DefElem *defel, int attnum)
+{
+	List	   *funcName = defGetQualifiedName(defel);
+	/* Big enough size for our needs. */
+	Oid		   *typeId = palloc0(7 * sizeof(Oid));
+	Oid			retTypeId;
+	int			nargs;
+	Oid			procOid = InvalidOid;
+	FuncCandidateList clist;
+
+	switch (attnum)
+	{
+		case Anum_pg_tablesample_method_tsminit:
+			/*
+			 * tsminit needs special handling because it is defined as function
+			 * with 3 or more arguments and only first two arguments must have
+			 * specific type, the rest is up to the tablesample method creator.
+			 */
+			{
+				nargs = 2;
+				typeId[0] = INTERNALOID;
+				typeId[1] = INT4OID;
+				retTypeId = VOIDOID;
+
+				clist = FuncnameGetCandidates(funcName, -1, NIL, false, false, false);
+
+				while (clist)
+				{
+					if (clist->nargs >= 3 &&
+						memcmp(typeId, clist->args, nargs * sizeof(Oid)) == 0)
+					{
+						procOid = clist->oid;
+						/* Save real function signature for future errors. */
+						nargs = clist->nargs;
+						pfree(typeId);
+						typeId = clist->args;
+						break;
+					}
+					clist = clist->next;
+				}
+
+				if (!OidIsValid(procOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_UNDEFINED_FUNCTION),
+							 errmsg("function \"%s\" does not exist or does not have valid signature",
+									NameListToString(funcName)),
+							 errhint("The tamplesample method init function "
+									 "must have at least 3 input parameters "
+									 "with first one of type INTERNAL and second of type INTEGER.")));
+			}
+			break;
+
+		case Anum_pg_tablesample_method_tsmnextblock:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = INT4OID;
+			break;
+		case Anum_pg_tablesample_method_tsmnexttuple:
+			nargs = 3;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INT2OID;
+			retTypeId = INT2OID;
+			break;
+		case Anum_pg_tablesample_method_tsmexaminetuple:
+			nargs = 4;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = BOOLOID;
+			retTypeId = BOOLOID;
+			break;
+		case Anum_pg_tablesample_method_tsmend:
+		case Anum_pg_tablesample_method_tsmreset:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		case Anum_pg_tablesample_method_tsmcost:
+			nargs = 7;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INTERNALOID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = INTERNALOID;
+			typeId[4] = INTERNALOID;
+			typeId[5] = INTERNALOID;
+			typeId[6] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		default:
+			/* should not be here */
+			elog(ERROR, "unrecognized attribute for tablesample method: %d",
+				 attnum);
+			nargs = 0;			/* keep compiler quiet */
+	}
+
+	if (!OidIsValid(procOid))
+		procOid = LookupFuncName(funcName, nargs, typeId, false);
+	if (get_func_rettype(procOid) != retTypeId)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("function %s should return type %s",
+						func_signature_string(funcName, nargs, NIL, typeId),
+						format_type_be(retTypeId))));
+
+	return ObjectIdGetDatum(procOid);
+}
+
+/*
+ * make pg_depend entries for a new pg_tablesample_method entry
+ */
+static void
+makeTablesampleMethodDeps(HeapTuple tuple)
+{
+	Form_pg_tablesample_method tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	ObjectAddress	myself,
+					referenced;
+
+	myself.classId = TableSampleMethodRelationId;
+	myself.objectId = HeapTupleGetOid(tuple);
+	myself.objectSubId = 0;
+
+	/* dependency on extension */
+	recordDependencyOnCurrentExtension(&myself, false);
+
+	/* dependencies on functions */
+	referenced.classId = ProcedureRelationId;
+	referenced.objectSubId = 0;
+
+	referenced.objectId = tsm->tsminit;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnextblock;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnexttuple;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	if (OidIsValid(tsm->tsmexaminetuple))
+	{
+		referenced.objectId = tsm->tsmexaminetuple;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
+
+	referenced.objectId = tsm->tsmend;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmreset;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmcost;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+}
+
+/*
+ * Create a table sampling method
+ *
+ * Only superusers can create a table sampling methods.
+ */
+ObjectAddress
+DefineTablesampleMethod(List *names, List *parameters)
+{
+	char	   *tsmname = strVal(linitial(names));
+	Oid			tsmoid;
+	ListCell   *pl;
+	Relation	rel;
+	Datum		values[Natts_pg_tablesample_method];
+	bool		nulls[Natts_pg_tablesample_method];
+	HeapTuple	tuple;
+	ObjectAddress address;
+
+	/* Must be super user. */
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied to create tablesample method \"%s\"",
+						tsmname),
+				 errhint("Must be superuser to create a tablesample method.")));
+
+	/* Must not already exist. */
+	tsmoid = get_tablesample_method_oid(tsmname, true);
+	if (OidIsValid(tsmoid))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" already exists",
+						tsmname)));
+
+	/* Initialize the values. */
+	memset(values, 0, sizeof(values));
+	memset(nulls, false, sizeof(nulls));
+
+	values[Anum_pg_tablesample_method_tsmname - 1] =
+		DirectFunctionCall1(namein, CStringGetDatum(tsmname));
+
+	/*
+	 * loop over the definition list and extract the information we need.
+	 */
+	foreach(pl, parameters)
+	{
+		DefElem    *defel = (DefElem *) lfirst(pl);
+
+		if (pg_strcasecmp(defel->defname, "seqscan") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmseqscan - 1] =
+				BoolGetDatum(defGetBoolean(defel));
+		}
+		else if (pg_strcasecmp(defel->defname, "pagemode") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmpagemode - 1] =
+				BoolGetDatum(defGetBoolean(defel));
+		}
+		else if (pg_strcasecmp(defel->defname, "init") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsminit - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsminit);
+		}
+		else if (pg_strcasecmp(defel->defname, "nextblock") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnextblock - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnextblock);
+		}
+		else if (pg_strcasecmp(defel->defname, "nexttuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnexttuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnexttuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "examinetuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmexaminetuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmexaminetuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "end") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmend - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmend);
+		}
+		else if (pg_strcasecmp(defel->defname, "reset") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmreset - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmreset);
+		}
+		else if (pg_strcasecmp(defel->defname, "cost") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmcost - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmcost);
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("tablesample method parameter \"%s\" not recognized",
+						defel->defname)));
+	}
+
+	/*
+	 * Validation.
+	 */
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsminit - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method init function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnextblock - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nextblock function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnexttuple - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nexttuple function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmend - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method end function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmreset - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method reset function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmcost - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method cost function is required")));
+
+	/*
+	 * Insert tuple into pg_tablesample_method.
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = heap_form_tuple(rel->rd_att, values, nulls);
+
+	tsmoid = simple_heap_insert(rel, tuple);
+
+	CatalogUpdateIndexes(rel, tuple);
+
+	makeTablesampleMethodDeps(tuple);
+
+	heap_freetuple(tuple);
+
+	/* Post creation hook for new tablesample method */
+	InvokeObjectPostCreateHook(TableSampleMethodRelationId, tsmoid, 0);
+
+	ObjectAddressSet(address, TableSampleMethodRelationId, tsmoid);
+
+	heap_close(rel, RowExclusiveLock);
+
+	return address;
+}
+
+/*
+ * Drop a tablesample method.
+ */
+void
+RemoveTablesampleMethodById(Oid tsmoid)
+{
+	Relation	rel;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+
+	/*
+	 * Find the target tuple
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmoid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for tablesample method %u",
+			 tsmoid);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	/* Can't drop builtin tablesample methods. */
+	if (tsmoid == TABLESAMPLE_METHOD_SYSTEM_OID ||
+		tsmoid == TABLESAMPLE_METHOD_BERNOULLI_OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied for tablesample method %s",
+						NameStr(tsm->tsmname))));
+
+	/*
+	 * Remove the pg_tablespace tuple (this will roll back if we fail below)
+	 */
+	simple_heap_delete(rel, &tuple->t_self);
+
+	ReleaseSysCache(tuple);
+
+	heap_close(rel, RowExclusiveLock);
+}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 8ee6b40..e696ea9 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -590,7 +590,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATERIALIZED MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
+	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P
+	MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEXT NO NONE
 	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
@@ -5103,6 +5104,15 @@ DefineStmt:
 					n->definition = list_make1(makeDefElem("from", (Node *) $5));
 					$$ = (Node *)n;
 				}
+			| CREATE TABLESAMPLE METHOD name definition
+				{
+					DefineStmt *n = makeNode(DefineStmt);
+					n->kind = OBJECT_TABLESAMPLEMETHOD;
+					n->args = NIL;
+					n->defnames = list_make1(makeString($4));
+					n->definition = $5;
+					$$ = (Node *)n;
+				}
 		;
 
 definition: '(' def_list ')'						{ $$ = $2; }
@@ -5557,6 +5567,7 @@ drop_type:	TABLE									{ $$ = OBJECT_TABLE; }
 			| TEXT_P SEARCH DICTIONARY				{ $$ = OBJECT_TSDICTIONARY; }
 			| TEXT_P SEARCH TEMPLATE				{ $$ = OBJECT_TSTEMPLATE; }
 			| TEXT_P SEARCH CONFIGURATION			{ $$ = OBJECT_TSCONFIGURATION; }
+			| TABLESAMPLE METHOD					{ $$ = OBJECT_TABLESAMPLEMETHOD; }
 		;
 
 any_name_list:
@@ -13416,6 +13427,7 @@ unreserved_keyword:
 			| MATCH
 			| MATERIALIZED
 			| MAXVALUE
+			| METHOD
 			| MINUTE_P
 			| MINVALUE
 			| MODE
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index fd09d3a..cadf6b4 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -23,6 +23,7 @@
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/toasting.h"
 #include "commands/alter.h"
 #include "commands/async.h"
@@ -1136,6 +1137,11 @@ ProcessUtilitySlow(Node *parsetree,
 							Assert(stmt->args == NIL);
 							DefineCollation(stmt->defnames, stmt->definition);
 							break;
+						case OBJECT_TABLESAMPLEMETHOD:
+							Assert(stmt->args == NIL);
+							Assert(list_length(stmt->defnames) == 1);
+							DefineTablesampleMethod(stmt->defnames, stmt->definition);
+							break;
 						default:
 							elog(ERROR, "unrecognized define stmt type: %d",
 								 (int) stmt->kind);
@@ -2004,6 +2010,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_POLICY:
 					tag = "DROP POLICY";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "DROP TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
@@ -2100,6 +2109,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_COLLATION:
 					tag = "CREATE COLLATION";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "CREATE TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 311364c..3d2c959 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -2915,6 +2915,37 @@ get_range_subtype(Oid rangeOid)
 /*				---------- PG_TABLESAMPLE_METHOD CACHE ----------			 */
 
 /*
+ * get_tablesample_method_oid - given a tablesample method name,
+ * look up the OID
+ *
+ * If missing_ok is false, throw an error if tablesample method name not found.
+ * If true, just return InvalidOid.
+ */
+Oid
+get_tablesample_method_oid(const char *tsmname, bool missing_ok)
+{
+	Oid			result;
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(tsmname));
+	if (HeapTupleIsValid(tuple))
+	{
+		result = HeapTupleGetOid(tuple);
+		ReleaseSysCache(tuple);
+	}
+	else
+		result = InvalidOid;
+
+	if (!OidIsValid(result) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						tsmname)));
+
+	return result;
+}
+
+/*
  * get_tablesample_method_name - given a tablesample method OID,
  * look up the name or NULL if not found
  */
diff --git a/src/bin/pg_dump/common.c b/src/bin/pg_dump/common.c
index 1a0a587..8a64e4b 100644
--- a/src/bin/pg_dump/common.c
+++ b/src/bin/pg_dump/common.c
@@ -103,6 +103,7 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 	int			numForeignServers;
 	int			numDefaultACLs;
 	int			numEventTriggers;
+	int			numTSMs;
 
 	if (g_verbose)
 		write_msg(NULL, "reading schemas\n");
@@ -251,6 +252,10 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 		write_msg(NULL, "reading policies\n");
 	getPolicies(fout, tblinfo, numTables);
 
+	if (g_verbose)
+		write_msg(NULL, "reading tablesample methods\n");
+	getTableSampleMethods(fout, &numTSMs);
+
 	*numTablesPtr = numTables;
 	return tblinfo;
 }
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 7da5c41..324ca4e 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -182,6 +182,7 @@ static void dumpSequenceData(Archive *fout, TableDataInfo *tdinfo);
 static void dumpIndex(Archive *fout, DumpOptions *dopt, IndxInfo *indxinfo);
 static void dumpConstraint(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
 static void dumpTableConstraintComment(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
+static void dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tbinfo);
 static void dumpTSParser(Archive *fout, DumpOptions *dopt, TSParserInfo *prsinfo);
 static void dumpTSDictionary(Archive *fout, DumpOptions *dopt, TSDictInfo *dictinfo);
 static void dumpTSTemplate(Archive *fout, DumpOptions *dopt, TSTemplateInfo *tmplinfo);
@@ -7134,6 +7135,78 @@ getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tblinfo, int numTable
 }
 
 /*
+ * getTableSampleMethods:
+ *	  read all tablesample methods in the system catalogs and return them
+ *	  in the TSMInfo* structure
+ *
+ *	numTSMs is set to the number of tablesample methods read in
+ */
+TSMInfo *
+getTableSampleMethods(Archive *fout, int *numTSMs)
+{
+	PGresult   *res;
+	int			ntups;
+	int			i;
+	PQExpBuffer query;
+	TSMInfo	   *tsminfo;
+	int			i_tableoid,
+				i_oid,
+				i_tsmname,
+				i_tsmseqscan,
+				i_tsmpagemode;
+
+	/* Before 9.5, there were no tablesample methods */
+	if (fout->remoteVersion < 90500)
+	{
+		*numTSMs = 0;
+		return NULL;
+	}
+
+	query = createPQExpBuffer();
+
+	appendPQExpBuffer(query,
+					  "SELECT tableoid, oid, tsmname, tsmseqscan, tsmpagemode "
+					  "FROM pg_catalog.pg_tablesample_method "
+					  "WHERE oid >= '%u'::pg_catalog.oid",
+					  FirstNormalObjectId);
+
+	res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
+
+	ntups = PQntuples(res);
+	*numTSMs = ntups;
+
+	tsminfo = (TSMInfo *) pg_malloc(ntups * sizeof(TSMInfo));
+
+	i_tableoid = PQfnumber(res, "tableoid");
+	i_oid = PQfnumber(res, "oid");
+	i_tsmname = PQfnumber(res, "tsmname");
+	i_tsmseqscan = PQfnumber(res, "tsmseqscan");
+	i_tsmpagemode = PQfnumber(res, "tsmpagemode");
+
+	for (i = 0; i < ntups; i++)
+	{
+		tsminfo[i].dobj.objType = DO_TABLESAMPLE_METHOD;
+		tsminfo[i].dobj.catId.tableoid = atooid(PQgetvalue(res, i, i_tableoid));
+		tsminfo[i].dobj.catId.oid = atooid(PQgetvalue(res, i, i_oid));
+		AssignDumpId(&tsminfo[i].dobj);
+		tsminfo[i].dobj.name = pg_strdup(PQgetvalue(res, i, i_tsmname));
+		tsminfo[i].dobj.namespace = NULL;
+		tsminfo[i].tsmseqscan = PQgetvalue(res, i, i_tsmseqscan)[0] == 't';
+		tsminfo[i].tsmpagemode = PQgetvalue(res, i, i_tsmpagemode)[0] == 't';
+
+		/* Decide whether we want to dump it */
+		selectDumpableObject(&(tsminfo[i].dobj));
+	}
+
+	PQclear(res);
+
+	destroyPQExpBuffer(query);
+
+	return tsminfo;
+}
+
+
+/*
  * Test whether a column should be printed as part of table's CREATE TABLE.
  * Column number is zero-based.
  *
@@ -8226,6 +8299,9 @@ dumpDumpableObject(Archive *fout, DumpOptions *dopt, DumpableObject *dobj)
 		case DO_POLICY:
 			dumpPolicy(fout, dopt, (PolicyInfo *) dobj);
 			break;
+		case DO_TABLESAMPLE_METHOD:
+			dumpTableSampleMethod(fout, dopt, (TSMInfo *) dobj);
+			break;
 		case DO_PRE_DATA_BOUNDARY:
 		case DO_POST_DATA_BOUNDARY:
 			/* never dumped, nothing to do */
@@ -12226,6 +12302,106 @@ dumpAgg(Archive *fout, DumpOptions *dopt, AggInfo *agginfo)
 }
 
 /*
+ * dumpTableSampleMethod
+ *	  write the declaration of one user-defined tablesample method
+ */
+static void
+dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tsminfo)
+{
+	PGresult   *res;
+	PQExpBuffer q;
+	PQExpBuffer delq;
+	PQExpBuffer labelq;
+	PQExpBuffer query;
+	char	   *tsminit;
+	char	   *tsmnextblock;
+	char	   *tsmnexttuple;
+	char	   *tsmexaminetuple;
+	char	   *tsmend;
+	char	   *tsmreset;
+	char	   *tsmcost;
+
+	/* Skip if not to be dumped */
+	if (!tsminfo->dobj.dump || dopt->dataOnly)
+		return;
+
+	q = createPQExpBuffer();
+	delq = createPQExpBuffer();
+	labelq = createPQExpBuffer();
+	query = createPQExpBuffer();
+
+	/* Make sure we are in proper schema */
+	selectSourceSchema(fout, "pg_catalog");
+
+	appendPQExpBuffer(query, "SELECT tsminit, tsmnextblock, "
+							 "tsmnexttuple, tsmexaminetuple, "
+							 "tsmend, tsmreset, tsmcost "
+							 "FROM pg_catalog.pg_tablesample_method "
+							 "WHERE oid = '%u'::pg_catalog.oid",
+							 tsminfo->dobj.catId.oid);
+
+	res = ExecuteSqlQueryForSingleRow(fout, query->data);
+
+	tsminit = PQgetvalue(res, 0, PQfnumber(res, "tsminit"));
+	tsmnexttuple = PQgetvalue(res, 0, PQfnumber(res, "tsmnexttuple"));
+	tsmnextblock = PQgetvalue(res, 0, PQfnumber(res, "tsmnextblock"));
+	tsmexaminetuple = PQgetvalue(res, 0, PQfnumber(res, "tsmexaminetuple"));
+	tsmend = PQgetvalue(res, 0, PQfnumber(res, "tsmend"));
+	tsmreset = PQgetvalue(res, 0, PQfnumber(res, "tsmreset"));
+	 tsmcost = PQgetvalue(res, 0, PQfnumber(res, "tsmcost"));
+
+	appendPQExpBuffer(q, "CREATE TABLESAMPLE METHOD %s (\n",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(q, "    INIT = %s,\n", tsminit);
+	appendPQExpBuffer(q, "    NEXTTUPLE = %s,\n", tsmnexttuple);
+	appendPQExpBuffer(q, "    NEXTBLOCK = %s,\n", tsmnextblock);
+	appendPQExpBuffer(q, "    END = %s,\n", tsmend);
+	appendPQExpBuffer(q, "    RESET = %s,\n", tsmreset);
+	appendPQExpBuffer(q, "    COST = %s", tsmcost);
+
+	if (strcmp(tsmexaminetuple, "-") != 0)
+		appendPQExpBuffer(q, ",\n    EXAMINETUPLE = %s", tsmexaminetuple);
+
+	if (tsminfo->tsmseqscan)
+		appendPQExpBufferStr(q, ",\n    SEQSCAN = true");
+
+	if (tsminfo->tsmpagemode)
+		appendPQExpBufferStr(q, ",\n    PAGEMODE = true");
+
+	appendPQExpBufferStr(q, "\n);");
+
+	appendPQExpBuffer(delq, "DROP TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(labelq, "TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	if (dopt->binary_upgrade)
+		binary_upgrade_extension_member(q, &tsminfo->dobj, labelq->data);
+
+	ArchiveEntry(fout, tsminfo->dobj.catId, tsminfo->dobj.dumpId,
+				 tsminfo->dobj.name,
+				 NULL,
+				 NULL,
+				 "",
+				 false, "TABLESAMPLE METHOD", SECTION_PRE_DATA,
+				 q->data, delq->data, NULL,
+				 NULL, 0,
+				 NULL, NULL);
+
+	/* Dump Parser Comments */
+	dumpComment(fout, dopt, labelq->data,
+				NULL, "",
+				tsminfo->dobj.catId, 0, tsminfo->dobj.dumpId);
+
+	PQclear(res);
+	destroyPQExpBuffer(q);
+	destroyPQExpBuffer(delq);
+	destroyPQExpBuffer(labelq);
+}
+
+/*
  * dumpTSParser
  *	  write out a single text search parser
  */
@@ -15659,6 +15835,7 @@ addBoundaryDependencies(DumpableObject **dobjs, int numObjs,
 			case DO_FDW:
 			case DO_FOREIGN_SERVER:
 			case DO_BLOB:
+			case DO_TABLESAMPLE_METHOD:
 				/* Pre-data objects: must come before the pre-data boundary */
 				addObjectDependency(preDataBound, dobj->dumpId);
 				break;
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index a9d3c10..87bef24 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -76,7 +76,8 @@ typedef enum
 	DO_POST_DATA_BOUNDARY,
 	DO_EVENT_TRIGGER,
 	DO_REFRESH_MATVIEW,
-	DO_POLICY
+	DO_POLICY,
+	DO_TABLESAMPLE_METHOD
 } DumpableObjectType;
 
 typedef struct _dumpableObject
@@ -383,6 +384,13 @@ typedef struct _inhInfo
 	Oid			inhparent;		/* OID of its parent */
 } InhInfo;
 
+typedef struct _tsmInfo
+{
+	DumpableObject dobj;
+	bool		tsmseqscan;
+	bool		tsmpagemode;
+} TSMInfo;
+
 typedef struct _prsInfo
 {
 	DumpableObject dobj;
@@ -536,6 +544,7 @@ extern ProcLangInfo *getProcLangs(Archive *fout, int *numProcLangs);
 extern CastInfo *getCasts(Archive *fout, DumpOptions *dopt, int *numCasts);
 extern void getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tbinfo, int numTables);
 extern bool shouldPrintColumn(DumpOptions *dopt, TableInfo *tbinfo, int colno);
+extern TSMInfo *getTableSampleMethods(Archive *fout, int *numTSMs);
 extern TSParserInfo *getTSParsers(Archive *fout, int *numTSParsers);
 extern TSDictInfo *getTSDictionaries(Archive *fout, int *numTSDicts);
 extern TSTemplateInfo *getTSTemplates(Archive *fout, int *numTSTemplates);
diff --git a/src/bin/pg_dump/pg_dump_sort.c b/src/bin/pg_dump/pg_dump_sort.c
index c5ed593..9567cf6 100644
--- a/src/bin/pg_dump/pg_dump_sort.c
+++ b/src/bin/pg_dump/pg_dump_sort.c
@@ -73,7 +73,8 @@ static const int oldObjectTypePriority[] =
 	13,							/* DO_POST_DATA_BOUNDARY */
 	20,							/* DO_EVENT_TRIGGER */
 	15,							/* DO_REFRESH_MATVIEW */
-	21							/* DO_POLICY */
+	21,							/* DO_POLICY */
+	5							/* DO_TABLESAMPLE_METHOD */
 };
 
 /*
@@ -122,7 +123,8 @@ static const int newObjectTypePriority[] =
 	25,							/* DO_POST_DATA_BOUNDARY */
 	32,							/* DO_EVENT_TRIGGER */
 	33,							/* DO_REFRESH_MATVIEW */
-	34							/* DO_POLICY */
+	34,							/* DO_POLICY */
+	17							/* DO_TABLESAMPLE_METHOD */
 };
 
 static DumpId preDataBoundId;
@@ -1460,6 +1462,11 @@ describeDumpableObject(DumpableObject *obj, char *buf, int bufsize)
 					 "POLICY (ID %d OID %u)",
 					 obj->dumpId, obj->catId.oid);
 			return;
+		case DO_TABLESAMPLE_METHOD:
+			snprintf(buf, bufsize,
+					 "TABLESAMPLE METHOD %s  (ID %d OID %u)",
+					 obj->name, obj->dumpId, obj->catId.oid);
+			return;
 		case DO_PRE_DATA_BOUNDARY:
 			snprintf(buf, bufsize,
 					 "PRE-DATA BOUNDARY  (ID %d)",
diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 6481ac8..30653f8 100644
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -148,6 +148,7 @@ typedef enum ObjectClass
 	OCLASS_EXTENSION,			/* pg_extension */
 	OCLASS_EVENT_TRIGGER,		/* pg_event_trigger */
 	OCLASS_POLICY,				/* pg_policy */
+	OCLASS_TABLESAMPLEMETHOD,	/* pg_tablesample_method */
 	MAX_OCLASS					/* MUST BE LAST */
 } ObjectClass;
 
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
index a58e1cf..82c15f3 100644
--- a/src/include/catalog/pg_tablesample_method.h
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -72,7 +72,17 @@ typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
 
 DATA(insert OID = 3293 ( system false true tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
 DESCR("SYSTEM table sampling method");
+#define TABLESAMPLE_METHOD_SYSTEM_OID 3293
 DATA(insert OID = 3294 ( bernoulli true false tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
 DESCR("BERNOULLI table sampling method");
+#define TABLESAMPLE_METHOD_BERNOULLI_OID 3294
+
+/* ----------------
+ *		functions for manipulation of pg_tablesample_method
+ * ----------------
+ */
+
+extern ObjectAddress DefineTablesampleMethod(List *names, List *parameters);
+extern void RemoveTablesampleMethodById(Oid tsmoid);
 
 #endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index a4288d1..359119a 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1291,6 +1291,7 @@ typedef enum ObjectType
 	OBJECT_SEQUENCE,
 	OBJECT_TABCONSTRAINT,
 	OBJECT_TABLE,
+	OBJECT_TABLESAMPLEMETHOD,
 	OBJECT_TABLESPACE,
 	OBJECT_TRIGGER,
 	OBJECT_TSCONFIGURATION,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index ae90df8..902c189 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -236,6 +236,7 @@ PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("mode", MODE, UNRESERVED_KEYWORD)
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 78175c1..b1594bb 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -152,6 +152,7 @@ extern void free_attstatsslot(Oid atttype,
 				  float4 *numbers, int nnumbers);
 extern char *get_namespace_name(Oid nspid);
 extern Oid	get_range_subtype(Oid rangeOid);
+extern Oid get_tablesample_method_oid(const char *tsmname, bool missing_ok);
 extern char *get_tablesample_method_name(Oid tsmid);
 
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 93d93af..37ea524 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -9,7 +9,8 @@ SUBDIRS = \
 		  worker_spi \
 		  dummy_seclabel \
 		  test_shm_mq \
-		  test_parser
+		  test_parser \
+		  tablesample
 
 all: submake-errcodes
 
diff --git a/src/test/modules/tablesample/.gitignore b/src/test/modules/tablesample/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/src/test/modules/tablesample/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/src/test/modules/tablesample/Makefile b/src/test/modules/tablesample/Makefile
new file mode 100644
index 0000000..469b004
--- /dev/null
+++ b/src/test/modules/tablesample/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/tsm_test/Makefile
+
+MODULE_big = tsm_test
+OBJS = tsm_test.o $(WIN32RES)
+PGFILEDESC = "tsm_test - example of a custom tablesample method"
+
+EXTENSION = tsm_test
+DATA = tsm_test--1.0.sql
+
+REGRESS = tablesample
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/tablesample/expected/tablesample.out b/src/test/modules/tablesample/expected/tablesample.out
new file mode 100644
index 0000000..ad62e32
--- /dev/null
+++ b/src/test/modules/tablesample/expected/tablesample.out
@@ -0,0 +1,38 @@
+CREATE EXTENSION tsm_test;
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ c81e728d9d4c2f636f067f89cc14862c | 0.5
+ a87ff679a2f3e71d9181a67b7542122c | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ d3d9446802a44259755d38e6d163e820 | 0.5
+(6 rows)
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ e4da3b7fbbce2345d7772b0674a318d5 | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ c9f0f895fb98ab9159f51fd0297e236d | 0.5
+(5 rows)
+
+DROP TABLESAMPLE METHOD tsm_test;
+ERROR:  cannot drop tablesample method tsm_test because extension tsm_test requires it
+HINT:  You can drop extension tsm_test instead.
+DROP EXTENSION tsm_test;
+ERROR:  cannot drop extension tsm_test because other objects depend on it
+DETAIL:  view test_tsm_v depends on tablesample method tsm_test
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+DROP EXTENSION tsm_test CASCADE;
+NOTICE:  drop cascades to view test_tsm_v
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
+ tsmname | tsmseqscan | tsmpagemode | tsminit | tsmnextblock | tsmnexttuple | tsmexaminetuple | tsmend | tsmreset | tsmcost 
+---------+------------+-------------+---------+--------------+--------------+-----------------+--------+----------+---------
+(0 rows)
+
diff --git a/src/test/modules/tablesample/sql/tablesample.sql b/src/test/modules/tablesample/sql/tablesample.sql
new file mode 100644
index 0000000..b1104d6
--- /dev/null
+++ b/src/test/modules/tablesample/sql/tablesample.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_test;
+
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+
+DROP TABLESAMPLE METHOD tsm_test;
+DROP EXTENSION tsm_test;
+DROP EXTENSION tsm_test CASCADE;
+
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
diff --git a/src/test/modules/tablesample/tsm_test--1.0.sql b/src/test/modules/tablesample/tsm_test--1.0.sql
new file mode 100644
index 0000000..e5a9ae8
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test--1.0.sql
@@ -0,0 +1,52 @@
+/* src/test/modules/tablesample/tsm_test--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_test" to load this file. \quit
+
+CREATE FUNCTION tsm_test_init(internal, int4, text)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nextblock(internal)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nexttuple(internal, int4, int2)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_examinetuple(internal, int4, internal, bool)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_cost(internal, internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+
+CREATE TABLESAMPLE METHOD tsm_test (
+	SEQSCAN		= true,
+	PAGEMODE	= true,
+	INIT		= tsm_test_init,
+	NEXTBLOCK	= tsm_test_nextblock,
+	NEXTTUPLE	= tsm_test_nexttuple,
+	EXAMINETUPLE	= tsm_test_examinetuple,
+	END			= tsm_test_end,
+	RESET		= tsm_test_reset,
+	COST		= tsm_test_cost
+);
diff --git a/src/test/modules/tablesample/tsm_test.c b/src/test/modules/tablesample/tsm_test.c
new file mode 100644
index 0000000..be4dcb9
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.c
@@ -0,0 +1,228 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_test.c
+ *	  Simple example of a custom tablesample method
+ *
+ * Copyright (c) 2007-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/test/modules/tablesample/tsm_test.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/htup_details.h"
+#include "access/relscan.h"
+#include "access/tupdesc.h"
+#include "catalog/pg_type.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/builtins.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+#include "utils/sampling.h"
+#include "utils/tablesample.h"
+
+PG_MODULE_MAGIC;
+
+/* State */
+typedef struct
+{
+	uint32		seed;			/* random seed */
+	AttrNumber	attnum;			/* column to check */
+	TupleDesc	tupDesc;		/* tuple descriptor of table */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} tsm_test_state;
+
+
+PG_FUNCTION_INFO_V1(tsm_test_init);
+PG_FUNCTION_INFO_V1(tsm_test_nextblock);
+PG_FUNCTION_INFO_V1(tsm_test_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_test_examinetuple);
+PG_FUNCTION_INFO_V1(tsm_test_end);
+PG_FUNCTION_INFO_V1(tsm_test_reset);
+PG_FUNCTION_INFO_V1(tsm_test_cost);
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_test_init(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	uint32			seed = PG_GETARG_UINT32(1);
+	char		   *attname;
+	AttrNumber		attnum;
+	Oid				atttype;
+	Relation		rel = scanstate->ss.ss_currentRelation;
+	HeapScanDesc	scan = scanstate->ss.ss_currentScanDesc;
+	tsm_test_state *state;
+	TupleDesc		tupDesc = RelationGetDescr(rel);
+
+	if (PG_ARGISNULL(2))
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("attnum cannot be NULL.")));
+
+	attname = text_to_cstring(PG_GETARG_TEXT_P(2));
+
+	attnum = get_attnum(rel->rd_id, attname);
+	if (!AttrNumberIsForUserDefinedAttr(attnum))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s does not exist", attname)));
+
+	atttype = get_atttype(rel->rd_id, attnum);
+	if (atttype != FLOAT8OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s is not of type float.", attname)));
+
+	state = palloc0(sizeof(tsm_test_state));
+
+	/* Remember initial values for reinit */
+	state->seed = seed;
+	state->attnum = attnum;
+	state->tupDesc = tupDesc;
+	state->startblock = scan->rs_startblock;
+	state->nblocks = scan->rs_nblocks;
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+	sampler_random_init_state(state->seed, state->randstate);
+
+	scanstate->tsmdata = (void *) state;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_test_nextblock(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	/* Cycle from startblock to startblock to support syncscan. */
+	if (state->blockno == InvalidBlockNumber)
+		state->blockno = state->startblock;
+	else
+	{
+		state->blockno++;
+
+		if (state->blockno >= state->nblocks)
+			state->blockno = 0;
+
+		if (state->blockno == state->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(state->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ */
+Datum
+tsm_test_nexttuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	OffsetNumber	maxoffset = PG_GETARG_UINT16(2);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+
+	if (state->lt == InvalidOffsetNumber)
+		state->lt = FirstOffsetNumber;
+	else if (++state->lt > maxoffset)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	PG_RETURN_UINT16(state->lt);
+}
+
+/*
+ * Examine tuple and decide if it should be returned.
+ */
+Datum
+tsm_test_examinetuple(PG_FUNCTION_ARGS)
+{
+	SampleScanState	*scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	HeapTuple		tuple = (HeapTuple) PG_GETARG_POINTER(2);
+	bool			visible = PG_GETARG_BOOL(3);
+	tsm_test_state *state = (tsm_test_state *) scanstate->tsmdata;
+	bool			isnull;
+	float8			val, rand;
+
+	if (!visible)
+		PG_RETURN_BOOL(false);
+
+	val = DatumGetFloat8(heap_getattr(tuple, state->attnum, state->tupDesc, &isnull));
+	rand = sampler_random_fract(state->randstate);
+	if (isnull || val < rand)
+		PG_RETURN_BOOL(false);
+	else
+		PG_RETURN_BOOL(true);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_test_end(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+
+	pfree(scanstate->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_test_reset(PG_FUNCTION_ARGS)
+{
+	SampleScanState *scanstate = (SampleScanState *) PG_GETARG_POINTER(0);
+	tsm_test_state  *state = (tsm_test_state *) scanstate->tsmdata;
+
+	state->blockno = InvalidBlockNumber;
+	state->lt = InvalidOffsetNumber;
+
+	sampler_random_init_state(state->seed, state->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_test_cost(PG_FUNCTION_ARGS)
+{
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+
+	*pages = baserel->pages;
+
+	/* This is very bad estimation */
+	*tuples = path->rows = path->rows/2;
+
+	PG_RETURN_VOID();
+}
+
diff --git a/src/test/modules/tablesample/tsm_test.control b/src/test/modules/tablesample/tsm_test.control
new file mode 100644
index 0000000..a7b2741
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.control
@@ -0,0 +1,5 @@
+# tsm_test extension
+comment = 'test module for custom tablesample method'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_test'
+relocatable = true
-- 
1.9.1

>From 53c567c6b456bf30c8f7c580af4ed6fcf59d4eea Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Sun, 15 Mar 2015 17:39:22 +0100
Subject: [PATCH 4/4] tablesample api doc v1

---
 doc/src/sgml/filelist.sgml           |   1 +
 doc/src/sgml/postgres.sgml           |   1 +
 doc/src/sgml/tablesample-method.sgml | 169 +++++++++++++++++++++++++++++++++++
 3 files changed, 171 insertions(+)
 create mode 100644 doc/src/sgml/tablesample-method.sgml

diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index 89fff77..23d932d 100644
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@@ -98,6 +98,7 @@
 <!ENTITY protocol   SYSTEM "protocol.sgml">
 <!ENTITY sources    SYSTEM "sources.sgml">
 <!ENTITY storage    SYSTEM "storage.sgml">
+<!ENTITY tablesample-method SYSTEM "tablesample-method.sgml">
 
 <!-- contrib information -->
 <!ENTITY contrib         SYSTEM "contrib.sgml">
diff --git a/doc/src/sgml/postgres.sgml b/doc/src/sgml/postgres.sgml
index e378d69..dc1f020 100644
--- a/doc/src/sgml/postgres.sgml
+++ b/doc/src/sgml/postgres.sgml
@@ -250,6 +250,7 @@
   &gin;
   &brin;
   &storage;
+  &tablesample-method;
   &bki;
   &planstats;
 
diff --git a/doc/src/sgml/tablesample-method.sgml b/doc/src/sgml/tablesample-method.sgml
new file mode 100644
index 0000000..2d6d323
--- /dev/null
+++ b/doc/src/sgml/tablesample-method.sgml
@@ -0,0 +1,169 @@
+<!-- doc/src/sgml/tablesample-method.sgml -->
+
+<chapter id="tablesample-method">
+ <title>Writing A TABLESAMPLE Sampling Method</title>
+
+ <indexterm zone="tablesample-method">
+  <primary>tablesample method</primary>
+ </indexterm>
+
+ <para>
+  The <command>TABLESAMPLE</command> clause implementation in
+  <productname>PostgreSQL</> supports creating a custom sampling methods.
+  These methods control what sample of the table will be returned when the
+  <command>TABLESAMPLE</command> clause is used.
+ </para>
+
+ <sect1 id="tablesample-method-functions">
+  <title>Tablesample Method Functions</title>
+
+  <para>
+   The tablesample method must provide following set of functions:
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_init (SampleScanState *scanstate,
+         uint32 seed, ...);
+</programlisting>
+   Initialize the tablesample scan. The function is called at the beginning
+   of each relation scan.
+  </para>
+  <para>
+   Note that the first two parameters are required but you can specify
+   additional parameters which then will be used by the <command>TABLESAMPLE</>
+   clause to determine the required user input in the query itself.
+   This means that if your function will specify additional float4 parameter
+   named percent, the user will have to call the tablesample method with
+   expression which evaluates (or can be coerced) to float4.
+   For example this definition:
+<programlisting>
+tsm_init (SampleScanState *scanstate,
+          uint32 seed, float4 pct);
+</programlisting>
+Will lead to SQL call like this:
+<programlisting>
+... TABLESAMPLE yourmethod(0.5) ...
+</programlisting>
+  </para>
+
+  <para>
+<programlisting>
+BlockNumber
+tsm_nextblock (SampleScanState *scanstate);
+</programlisting>
+   Returns the block number of next page to be scanned. InvalidBlockNumber
+   should be returned if the sampling has reached end of the relation.
+  </para>
+
+  <para>
+<programlisting>
+OffsetNumber
+tsm_nexttuple (SampleScanState *scanstate, BlockNumber blockno,
+               OffsetNumber maxoffset);
+</programlisting>
+   Return next tuple offset for the current page. InvalidOffsetNumber should
+   be returned if the sampling has reached end of the page.
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_end (SampleScanState *scanstate);
+</programlisting>
+   The scan has finished, cleanup any left over state.
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_reset (SampleScanState *scanstate);
+</programlisting>
+   The scan needs to rescan the relation again, reset any tablesample method
+   state.
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_cost (PlannerInfo *root, Path *path, RelOptInfo *baserel,
+          List *args, BlockNumber *pages, double *tuples);
+</programlisting>
+   This function is used by optimizer to decide best plan and is also used
+   for output of <command>EXPLAIN</>.
+  </para>
+
+  <para>
+   There is function that tablesampling method can implement in order to gain
+   more fine grained control over sampling. This function is optional:
+  </para>
+
+  <para>
+<programlisting>
+bool
+tsm_examinetuple (SampleScanState *scanstate, BlockNumber blockno,
+                  HeapTuple tuple, bool visible);
+</programlisting>
+   Function that enables the sampling method to examine contents of the tuple
+   (for example to collect some internal statistics). The return value of this
+   function is used to determine if the tuple should be returned to client.
+   Note that this function will receive even invisible tuples but it is not
+   allowed to return true for such tuple (if it does,
+   <productname>PostgreSQL</> will raise an error).
+  </para>
+
+  <para>
+  As you can see most of the tablesample method interfaces get the
+  <structname>SampleScanState</> as a first parameter. This structure holds
+  state of the current scan and also provides storage for the tablesample
+  method's state. It is defined as following:
+<programlisting>
+typedef struct SampleScanState
+{
+    ScanState   ss;
+    FmgrInfo    tsminit;
+    FmgrInfo    tsmnextblock;
+    FmgrInfo    tsmnexttuple;
+    FmgrInfo    tsmexaminetuple;
+    FmgrInfo    tsmend;
+    FmgrInfo    tsmreset;
+    void       *tsmdata;
+} SampleScanState;
+</programlisting>
+  Where <structfield>ss</> is the <structname>ScanState</> itself. From it, you
+  can get <structfield>ss_currentRelation</> (currently scanned relation) and
+  <structfield>ss_currentScanDesc</> (information about the scan).
+  Those are usually useful for the <function>tsm_init</> function.
+  The <structfield>tsminit</>, <structfield>tsmnextblock</>,
+  <structfield>tsmnexttuple</>, <structfield>tsmend</> and
+  <structfield>tsmreset</> are pointers to the tablesample method functions for
+  use by the sample scan itself and the tablesample method does not need to be
+  concerned about these values. The <structfield>tsmdata</> can be used by
+  tablesample method to store any state info it might need during the scan.
+  </para>
+ </sect1>
+
+ <sect1 id="tablesample-method-sql">
+  <title>Tablesample Method Installation</title>
+
+  <para>
+   Once you have written and built the custom tablesample method, you can
+   install it using the SQL statement
+   <xref linkend="sql-createtablesamplemethod"> and removed again using
+   <xref linkend="sql-droptablesamplemethod">.
+  </para>
+
+ </sect1>
+
+ <sect1 id="tablesample-method-example">
+  <title>Tablesample Method Example</title>
+
+  <para>
+   Example of how to implement custom tablesample method can be found in the
+   <productname>PostgreSQL</>'s sources under
+   <filename>src/test/modules/tablesample</> directory.
+  </para>
+ </sect1>
+
+</chapter>
-- 
1.9.1

>From 400fd6f943fe094837bd1ee426d1050fea46f5b2 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 15 Apr 2015 00:45:57 +0200
Subject: [PATCH 4/6] tablesample-contrib: add system_time sampling method

---
 contrib/tsm_system_time/.gitignore                 |   4 +
 contrib/tsm_system_time/Makefile                   |  21 ++
 .../tsm_system_time/expected/tsm_system_time.out   |  54 ++++
 contrib/tsm_system_time/sql/tsm_system_time.sql    |  14 +
 contrib/tsm_system_time/tsm_system_time--1.0.sql   |  40 +++
 contrib/tsm_system_time/tsm_system_time.c          | 315 +++++++++++++++++++++
 contrib/tsm_system_time/tsm_system_time.control    |   5 +
 7 files changed, 453 insertions(+)
 create mode 100644 contrib/tsm_system_time/.gitignore
 create mode 100644 contrib/tsm_system_time/Makefile
 create mode 100644 contrib/tsm_system_time/expected/tsm_system_time.out
 create mode 100644 contrib/tsm_system_time/sql/tsm_system_time.sql
 create mode 100644 contrib/tsm_system_time/tsm_system_time--1.0.sql
 create mode 100644 contrib/tsm_system_time/tsm_system_time.c
 create mode 100644 contrib/tsm_system_time/tsm_system_time.control

diff --git a/contrib/tsm_system_time/.gitignore b/contrib/tsm_system_time/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/contrib/tsm_system_time/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/contrib/tsm_system_time/Makefile b/contrib/tsm_system_time/Makefile
new file mode 100644
index 0000000..c42c1c6
--- /dev/null
+++ b/contrib/tsm_system_time/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/tsm_system_time/Makefile
+
+MODULE_big = tsm_system_time
+OBJS = tsm_system_time.o $(WIN32RES)
+PGFILEDESC = "tsm_system_time - SYSTEM TABLESAMPLE method which accepts number rows of as a limit"
+
+EXTENSION = tsm_system_time
+DATA = tsm_system_time--1.0.sql
+
+REGRESS = tsm_system_time
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/tsm_system_time
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/tsm_system_time/expected/tsm_system_time.out b/contrib/tsm_system_time/expected/tsm_system_time.out
new file mode 100644
index 0000000..32ad03c
--- /dev/null
+++ b/contrib/tsm_system_time/expected/tsm_system_time.out
@@ -0,0 +1,54 @@
+CREATE EXTENSION tsm_system_time;
+CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000) FROM generate_series(0, 30) s(i) ORDER BY i;
+ANALYZE test_tablesample;
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (1000);
+ count 
+-------
+    31
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE system_time (1000) REPEATABLE (5432);
+ id 
+----
+  7
+ 14
+ 21
+ 28
+  4
+ 11
+ 18
+ 25
+  1
+  8
+ 15
+ 22
+ 29
+  5
+ 12
+ 19
+ 26
+  2
+  9
+ 16
+ 23
+ 30
+  6
+ 13
+ 20
+ 27
+  3
+ 10
+ 17
+ 24
+  0
+(31 rows)
+
+EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE system_time (100) REPEATABLE (10);
+                                     QUERY PLAN                                     
+------------------------------------------------------------------------------------
+ Sample Scan (system_time) on test_tablesample  (cost=0.00..100.25 rows=25 width=4)
+(1 row)
+
+-- done
+DROP TABLE test_tablesample CASCADE;
diff --git a/contrib/tsm_system_time/sql/tsm_system_time.sql b/contrib/tsm_system_time/sql/tsm_system_time.sql
new file mode 100644
index 0000000..68dbbf9
--- /dev/null
+++ b/contrib/tsm_system_time/sql/tsm_system_time.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_system_time;
+
+CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000) FROM generate_series(0, 30) s(i) ORDER BY i;
+ANALYZE test_tablesample;
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_time (1000);
+SELECT id FROM test_tablesample TABLESAMPLE system_time (1000) REPEATABLE (5432);
+
+EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE system_time (100) REPEATABLE (10);
+
+-- done
+DROP TABLE test_tablesample CASCADE;
diff --git a/contrib/tsm_system_time/tsm_system_time--1.0.sql b/contrib/tsm_system_time/tsm_system_time--1.0.sql
new file mode 100644
index 0000000..834ee77
--- /dev/null
+++ b/contrib/tsm_system_time/tsm_system_time--1.0.sql
@@ -0,0 +1,40 @@
+/* src/test/modules/tablesample/tsm_system_time--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_system_time" to load this file. \quit
+
+CREATE FUNCTION tsm_system_time_init(internal, int4, int4)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_time_nextblock(internal)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_time_nexttuple(internal, int4, int2)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_time_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_time_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_time_cost(internal, internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+INSERT INTO pg_tablesample_method VALUES('system_time', false, true,
+	'tsm_system_time_init', 'tsm_system_time_nextblock',
+	'tsm_system_time_nexttuple', '-', 'tsm_system_time_end',
+	'tsm_system_time_reset', 'tsm_system_time_cost');
+
diff --git a/contrib/tsm_system_time/tsm_system_time.c b/contrib/tsm_system_time/tsm_system_time.c
new file mode 100644
index 0000000..efb127c
--- /dev/null
+++ b/contrib/tsm_system_time/tsm_system_time.c
@@ -0,0 +1,315 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_system_time.c
+ *	  interface routines for system_time tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  contrib/tsm_system_time_rowlimit/tsm_system_time.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tablesample.h"
+#include "access/relscan.h"
+#include "miscadmin.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+#include "utils/spccache.h"
+#include "utils/timestamp.h"
+
+PG_MODULE_MAGIC;
+
+/*
+ * State
+ */
+typedef struct
+{
+	SamplerRandomState randstate;
+	uint32			seed;			/* random seed */
+	BlockNumber		nblocks;		/* number of block in relation */
+	int32			time;			/* time limit for sampling */
+	TimestampTz		start_time;		/* start time of sampling */
+	TimestampTz		end_time;		/* end time of sampling */
+	OffsetNumber	lt;				/* last tuple returned from current block */
+	BlockNumber		step;			/* step size */
+	BlockNumber		lb;				/* last block visited */
+	BlockNumber		estblocks;		/* estimated number of returned blocks (moving) */
+	BlockNumber		doneblocks;		/* number of already returned blocks */
+} SystemSamplerData;
+
+
+PG_FUNCTION_INFO_V1(tsm_system_time_init);
+PG_FUNCTION_INFO_V1(tsm_system_time_nextblock);
+PG_FUNCTION_INFO_V1(tsm_system_time_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_system_time_end);
+PG_FUNCTION_INFO_V1(tsm_system_time_reset);
+PG_FUNCTION_INFO_V1(tsm_system_time_cost);
+
+static uint32 random_relative_prime(uint32 n, SamplerRandomState randstate);
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_time_init(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	uint32				seed = PG_GETARG_UINT32(1);
+	int32				time = PG_ARGISNULL(2) ? -1 : PG_GETARG_INT32(2);
+	HeapScanDesc		scan = tsdesc->heapScan;
+	SystemSamplerData  *sampler;
+
+	if (time < 1)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid time limit"),
+				 errhint("Time limit must be positive integer value.")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->lt = InvalidOffsetNumber;
+	sampler->estblocks = 2;
+	sampler->doneblocks = 0;
+	sampler->time = time;
+	sampler->start_time = GetCurrentTimestamp();
+	sampler->end_time = TimestampTzPlusMilliseconds(sampler->start_time,
+													sampler->time);
+
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	/* Find relative prime as step size for linear probing. */
+	sampler->step = random_relative_prime(sampler->nblocks, sampler->randstate);
+	/*
+	 * Randomize start position so that blocks close to step size don't have
+	 * higher probability of being chosen on very short scan.
+	 */
+	sampler->lb = sampler_random_fract(sampler->randstate) * (sampler->nblocks / sampler->step);
+
+	tsdesc->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses linear probing algorithm for picking next block.
+ */
+Datum
+tsm_system_time_nextblock(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+
+	sampler->lb = (sampler->lb + sampler->step) % sampler->nblocks;
+	sampler->doneblocks++;
+
+	/* All blocks have been read, we're done */
+	if (sampler->doneblocks > sampler->nblocks)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	/*
+	 * Update the estimations for time limit at least 10 times per estimated
+	 * number of returned blocks to handle variations in block read speed.
+	 */
+	if (sampler->doneblocks % Max(sampler->estblocks/10, 1) == 0)
+	{
+		TimestampTz	now = GetCurrentTimestamp();
+		long        secs;
+		int         usecs;
+		int			usecs_remaining;
+		int			time_per_block;
+
+		TimestampDifference(sampler->start_time, now, &secs, &usecs);
+		usecs += (int) secs * 1000000;
+
+		time_per_block = usecs / sampler->doneblocks;
+
+		/* No time left, end. */
+		TimestampDifference(now, sampler->end_time, &secs, &usecs);
+		if (secs <= 0 && usecs <= 0)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+
+		/* Remaining microseconds */
+		usecs_remaining = usecs + (int) secs * 1000000;
+
+		/* Recalculate estimated returned number of blocks */
+		if (time_per_block < usecs_remaining && time_per_block > 0)
+			sampler->estblocks = sampler->time * time_per_block;
+	}
+
+	PG_RETURN_UINT32(sampler->lb);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_time_nexttuple(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	OffsetNumber		maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+	OffsetNumber		tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_time_end(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+
+	pfree(tsdesc->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_time_reset(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	sampler->start_time = GetCurrentTimestamp();
+	sampler->end_time = TimestampTzPlusMilliseconds(sampler->start_time,
+													sampler->time);
+	sampler->estblocks = 2;
+	sampler->doneblocks = 0;
+
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+	sampler->step = random_relative_prime(sampler->nblocks, sampler->randstate);
+	sampler->lb = sampler_random_fract(sampler->randstate) * (sampler->nblocks / sampler->step);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_time_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *limitnode;
+	int32			time;
+	BlockNumber		relpages;
+	double			reltuples;
+	double			density;
+	double			spc_random_page_cost;
+
+	limitnode = linitial(args);
+	limitnode = estimate_expression_value(root, limitnode);
+
+	if (IsA(limitnode, RelabelType))
+		limitnode = (Node *) ((RelabelType *) limitnode)->arg;
+
+	if (IsA(limitnode, Const))
+		time = DatumGetInt32(((Const *) limitnode)->constvalue);
+	else
+	{
+		/* Default time (1s) if the estimation didn't return Const. */
+		time = 1000;
+	}
+
+	relpages = baserel->pages;
+	reltuples = baserel->tuples;
+
+	/* estimate the tuple density */
+	if (relpages > 0)
+		density = reltuples / (double) relpages;
+	else
+		density = (BLCKSZ - SizeOfPageHeaderData) / baserel->width;
+
+	/*
+	 * We equal random page cost value to number of ms it takes to read the
+	 * random page here which is far from accurate but we don't have anything
+	 * better to base our predicted page reads.
+	 */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  NULL);
+
+	/*
+	 * Assumption here is that we'll never read less then 1% of table pages,
+	 * this is here mainly because it is much less bad to overestimate than
+	 * underestimate and using just spc_random_page_cost will probably lead
+	 * to underestimations in general.
+	 */
+	*pages = Min(baserel->pages, Max(time/spc_random_page_cost, baserel->pages/100));
+	*tuples = rint(density * (double) *pages * path->rows / baserel->tuples);
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
+
+static uint32
+gcd (uint32 a, uint32 b)
+{
+	uint32 c;
+
+	while (a != 0)
+	{
+		c = a;
+		a = b % a;
+		b = c;
+	}
+
+	return b;
+}
+
+static uint32
+random_relative_prime(uint32 n, SamplerRandomState randstate)
+{
+	/* Pick random starting number, with some limits on what it can be. */
+	uint32 r = (uint32) sampler_random_fract(randstate) * n/2 + n/4,
+		   t;
+
+	/*
+	 * This should only take 2 or 3 iterations as the probability of 2 numbers
+	 * being relatively prime is ~61%.
+	 */
+	while ((t = gcd(r, n)) > 1)
+	{
+		CHECK_FOR_INTERRUPTS();
+		r /= t;
+	}
+
+	return r;
+}
diff --git a/contrib/tsm_system_time/tsm_system_time.control b/contrib/tsm_system_time/tsm_system_time.control
new file mode 100644
index 0000000..ebcee19
--- /dev/null
+++ b/contrib/tsm_system_time/tsm_system_time.control
@@ -0,0 +1,5 @@
+# tsm_system_time extension
+comment = 'SYSTEM TABLESAMPLE method which accepts time in milliseconds as a limit'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_system_time'
+relocatable = true
-- 
1.9.1

>From 275f7ad324bdd372517427b9a282573b6a6c2ffa Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Mon, 13 Apr 2015 18:20:16 +0200
Subject: [PATCH 3/6] tablesample-contrib: add system_rows sampling method

---
 contrib/tsm_system_rows/.gitignore                 |   4 +
 contrib/tsm_system_rows/Makefile                   |  21 ++
 .../tsm_system_rows/expected/tsm_system_rows.out   |  31 +++
 contrib/tsm_system_rows/sql/tsm_system_rows.sql    |  14 ++
 contrib/tsm_system_rows/tsm_system_rows--1.0.sql   |  45 ++++
 contrib/tsm_system_rows/tsm_system_rows.c          | 270 +++++++++++++++++++++
 contrib/tsm_system_rows/tsm_system_rows.control    |   5 +
 7 files changed, 390 insertions(+)
 create mode 100644 contrib/tsm_system_rows/.gitignore
 create mode 100644 contrib/tsm_system_rows/Makefile
 create mode 100644 contrib/tsm_system_rows/expected/tsm_system_rows.out
 create mode 100644 contrib/tsm_system_rows/sql/tsm_system_rows.sql
 create mode 100644 contrib/tsm_system_rows/tsm_system_rows--1.0.sql
 create mode 100644 contrib/tsm_system_rows/tsm_system_rows.c
 create mode 100644 contrib/tsm_system_rows/tsm_system_rows.control

diff --git a/contrib/tsm_system_rows/.gitignore b/contrib/tsm_system_rows/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/contrib/tsm_system_rows/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/contrib/tsm_system_rows/Makefile b/contrib/tsm_system_rows/Makefile
new file mode 100644
index 0000000..700ab27
--- /dev/null
+++ b/contrib/tsm_system_rows/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/tsm_system_rows/Makefile
+
+MODULE_big = tsm_system_rows
+OBJS = tsm_system_rows.o $(WIN32RES)
+PGFILEDESC = "tsm_system_rows - SYSTEM TABLESAMPLE method which accepts number of rows as a limit"
+
+EXTENSION = tsm_system_rows
+DATA = tsm_system_rows--1.0.sql
+
+REGRESS = tsm_system_rows
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/tsm_system_rows
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/tsm_system_rows/expected/tsm_system_rows.out b/contrib/tsm_system_rows/expected/tsm_system_rows.out
new file mode 100644
index 0000000..7e0f72b
--- /dev/null
+++ b/contrib/tsm_system_rows/expected/tsm_system_rows.out
@@ -0,0 +1,31 @@
+CREATE EXTENSION tsm_system_rows;
+CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000) FROM generate_series(0, 30) s(i) ORDER BY i;
+ANALYZE test_tablesample;
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (1000);
+ count 
+-------
+    31
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE system_rows (8) REPEATABLE (5432);
+ id 
+----
+  7
+ 14
+ 21
+ 28
+  4
+ 11
+ 18
+ 25
+(8 rows)
+
+EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE system_rows (20) REPEATABLE (10);
+                                    QUERY PLAN                                     
+-----------------------------------------------------------------------------------
+ Sample Scan (system_rows) on test_tablesample  (cost=0.00..80.20 rows=20 width=4)
+(1 row)
+
+-- done
+DROP TABLE test_tablesample CASCADE;
diff --git a/contrib/tsm_system_rows/sql/tsm_system_rows.sql b/contrib/tsm_system_rows/sql/tsm_system_rows.sql
new file mode 100644
index 0000000..bd812220e
--- /dev/null
+++ b/contrib/tsm_system_rows/sql/tsm_system_rows.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_system_rows;
+
+CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 1000) FROM generate_series(0, 30) s(i) ORDER BY i;
+ANALYZE test_tablesample;
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE system_rows (1000);
+SELECT id FROM test_tablesample TABLESAMPLE system_rows (8) REPEATABLE (5432);
+
+EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE system_rows (20) REPEATABLE (10);
+
+-- done
+DROP TABLE test_tablesample CASCADE;
diff --git a/contrib/tsm_system_rows/tsm_system_rows--1.0.sql b/contrib/tsm_system_rows/tsm_system_rows--1.0.sql
new file mode 100644
index 0000000..9d1b7e2
--- /dev/null
+++ b/contrib/tsm_system_rows/tsm_system_rows--1.0.sql
@@ -0,0 +1,45 @@
+/* src/test/modules/tablesample/tsm_system_rows--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_system_rows" to load this file. \quit
+
+CREATE FUNCTION tsm_system_rows_init(internal, int4, int4)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_rows_nextblock(internal)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_rows_nexttuple(internal, int4, int2)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_rows_examinetuple(internal, int4, internal, bool)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_rows_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_rows_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_system_rows_cost(internal, internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+INSERT INTO pg_tablesample_method VALUES('system_rows', false, true,
+	'tsm_system_rows_init', 'tsm_system_rows_nextblock',
+	'tsm_system_rows_nexttuple', 'tsm_system_rows_examinetuple',
+	'tsm_system_rows_end', 'tsm_system_rows_reset', 'tsm_system_rows_cost');
+
diff --git a/contrib/tsm_system_rows/tsm_system_rows.c b/contrib/tsm_system_rows/tsm_system_rows.c
new file mode 100644
index 0000000..14efb27
--- /dev/null
+++ b/contrib/tsm_system_rows/tsm_system_rows.c
@@ -0,0 +1,270 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_system_rows.c
+ *	  interface routines for system_rows tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  contrib/tsm_system_rows_rowlimit/tsm_system_rows.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tablesample.h"
+#include "access/relscan.h"
+#include "miscadmin.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+
+PG_MODULE_MAGIC;
+
+/*
+ * State
+ */
+typedef struct
+{
+	SamplerRandomState randstate;
+	uint32			seed;			/* random seed */
+	BlockNumber		nblocks;		/* number of block in relation */
+	int32			ntuples;		/* number of tuples to return */
+	int32			donetuples;		/* tuples already returned */
+	OffsetNumber	lt;				/* last tuple returned from current block */
+	BlockNumber		step;			/* step size */
+	BlockNumber		lb;				/* last block visited */
+	BlockNumber		doneblocks;		/* number of already returned blocks */
+} SystemSamplerData;
+
+
+PG_FUNCTION_INFO_V1(tsm_system_rows_init);
+PG_FUNCTION_INFO_V1(tsm_system_rows_nextblock);
+PG_FUNCTION_INFO_V1(tsm_system_rows_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_system_rows_examinetuple);
+PG_FUNCTION_INFO_V1(tsm_system_rows_end);
+PG_FUNCTION_INFO_V1(tsm_system_rows_reset);
+PG_FUNCTION_INFO_V1(tsm_system_rows_cost);
+
+static uint32 random_relative_prime(uint32 n, SamplerRandomState randstate);
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_rows_init(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	uint32				seed = PG_GETARG_UINT32(1);
+	int32				ntuples = PG_ARGISNULL(2) ? -1 : PG_GETARG_INT32(2);
+	HeapScanDesc		scan = tsdesc->heapScan;
+	SystemSamplerData  *sampler;
+
+	if (ntuples < 1)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be positive integer value.")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->ntuples = ntuples;
+	sampler->donetuples = 0;
+	sampler->lt = InvalidOffsetNumber;
+	sampler->doneblocks = 0;
+
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	/* Find relative prime as step size for linear probing. */
+	sampler->step = random_relative_prime(sampler->nblocks, sampler->randstate);
+	/*
+	 * Randomize start position so that blocks close to step size don't have
+	 * higher probability of being chosen on very short scan.
+	 */
+	sampler->lb = sampler_random_fract(sampler->randstate) *
+		(sampler->nblocks / sampler->step);
+
+	tsdesc->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses linear probing algorithm for picking next block.
+ */
+Datum
+tsm_system_rows_nextblock(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+
+	sampler->lb = (sampler->lb + sampler->step) % sampler->nblocks;
+	sampler->doneblocks++;
+
+	/* All blocks have been read, we're done */
+	if (sampler->doneblocks > sampler->nblocks ||
+		sampler->donetuples >= sampler->ntuples)
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	PG_RETURN_UINT32(sampler->lb);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_rows_nexttuple(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	OffsetNumber		maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+	OffsetNumber		tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset ||
+		sampler->donetuples >= sampler->ntuples)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Examine tuple and decide if it should be returned.
+ */
+Datum
+tsm_system_rows_examinetuple(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	bool				visible = PG_GETARG_BOOL(3);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+
+	if (!visible)
+		PG_RETURN_BOOL(false);
+
+	sampler->donetuples++;
+
+	PG_RETURN_BOOL(true);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_rows_end(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+
+	pfree(tsdesc->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_rows_reset(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	sampler->donetuples = 0;
+	sampler->doneblocks = 0;
+
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+	sampler->step = random_relative_prime(sampler->nblocks, sampler->randstate);
+	sampler->lb = sampler_random_fract(sampler->randstate) * (sampler->nblocks / sampler->step);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_rows_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *limitnode;
+	int32			ntuples;
+
+	limitnode = linitial(args);
+	limitnode = estimate_expression_value(root, limitnode);
+
+	if (IsA(limitnode, RelabelType))
+		limitnode = (Node *) ((RelabelType *) limitnode)->arg;
+
+	if (IsA(limitnode, Const))
+		ntuples = DatumGetInt32(((Const *) limitnode)->constvalue);
+	else
+	{
+		/* Default ntuples if the estimation didn't return Const. */
+		ntuples = 1000;
+	}
+
+	*pages = Min(baserel->pages, ntuples);
+	*tuples = ntuples;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
+
+
+static uint32
+gcd (uint32 a, uint32 b)
+{
+	uint32 c;
+
+	while (a != 0)
+	{
+		c = a;
+		a = b % a;
+		b = c;
+	}
+
+	return b;
+}
+
+static uint32
+random_relative_prime(uint32 n, SamplerRandomState randstate)
+{
+	/* Pick random starting number, with some limits on what it can be. */
+	uint32 r = (uint32) sampler_random_fract(randstate) * n/2 + n/4,
+		   t;
+
+	/*
+	 * This should only take 2 or 3 iterations as the probability of 2 numbers
+	 * being relatively prime is ~61%.
+	 */
+	while ((t = gcd(r, n)) > 1)
+	{
+		CHECK_FOR_INTERRUPTS();
+		r /= t;
+	}
+
+	return r;
+}
diff --git a/contrib/tsm_system_rows/tsm_system_rows.control b/contrib/tsm_system_rows/tsm_system_rows.control
new file mode 100644
index 0000000..84ea7ad
--- /dev/null
+++ b/contrib/tsm_system_rows/tsm_system_rows.control
@@ -0,0 +1,5 @@
+# tsm_system_rows extension
+comment = 'SYSTEM TABLESAMPLE method which accepts number rows as a limit'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_system_rows'
+relocatable = true
-- 
1.9.1

>From cb0618e8e21d040c53c501b80cffff17207c1286 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:37:55 +0100
Subject: [PATCH 2/6] tablesample v13

---
 contrib/file_fdw/file_fdw.c                  |   2 +-
 contrib/postgres_fdw/postgres_fdw.c          |   2 +-
 doc/src/sgml/catalogs.sgml                   | 120 +++++++++
 doc/src/sgml/ref/select.sgml                 |  61 ++++-
 src/backend/access/Makefile                  |   3 +-
 src/backend/access/heap/heapam.c             |  41 ++-
 src/backend/access/tablesample/Makefile      |  17 ++
 src/backend/access/tablesample/bernoulli.c   | 235 +++++++++++++++++
 src/backend/access/tablesample/system.c      | 186 ++++++++++++++
 src/backend/access/tablesample/tablesample.c | 368 +++++++++++++++++++++++++++
 src/backend/catalog/Makefile                 |   2 +-
 src/backend/commands/analyze.c               |   2 +-
 src/backend/commands/explain.c               |  19 ++
 src/backend/executor/Makefile                |   2 +-
 src/backend/executor/execAmi.c               |   8 +
 src/backend/executor/execCurrent.c           |   1 +
 src/backend/executor/execProcnode.c          |  14 +
 src/backend/executor/nodeSamplescan.c        | 256 +++++++++++++++++++
 src/backend/nodes/copyfuncs.c                |  60 +++++
 src/backend/nodes/equalfuncs.c               |  37 +++
 src/backend/nodes/nodeFuncs.c                |  12 +
 src/backend/nodes/outfuncs.c                 |  48 ++++
 src/backend/nodes/readfuncs.c                |  45 ++++
 src/backend/optimizer/path/allpaths.c        |  49 ++++
 src/backend/optimizer/path/costsize.c        |  67 +++++
 src/backend/optimizer/plan/createplan.c      |  69 +++++
 src/backend/optimizer/plan/setrefs.c         |  11 +
 src/backend/optimizer/plan/subselect.c       |   1 +
 src/backend/optimizer/util/pathnode.c        |  22 ++
 src/backend/parser/gram.y                    |  36 ++-
 src/backend/parser/parse_clause.c            |  56 ++++
 src/backend/parser/parse_func.c              | 143 +++++++++++
 src/backend/rewrite/rewriteHandler.c         |   3 +
 src/backend/utils/adt/ruleutils.c            |  50 ++++
 src/backend/utils/cache/lsyscache.c          |  27 ++
 src/backend/utils/cache/syscache.c           |  23 ++
 src/backend/utils/misc/sampling.c            |  33 ++-
 src/include/access/heapam.h                  |   4 +
 src/include/access/relscan.h                 |   1 +
 src/include/access/tablesample.h             |  60 +++++
 src/include/catalog/indexing.h               |   5 +
 src/include/catalog/pg_proc.h                |  26 ++
 src/include/catalog/pg_tablesample_method.h  |  78 ++++++
 src/include/executor/nodeSamplescan.h        |  24 ++
 src/include/nodes/execnodes.h                |   9 +
 src/include/nodes/nodes.h                    |   4 +
 src/include/nodes/parsenodes.h               |  37 +++
 src/include/nodes/plannodes.h                |   6 +
 src/include/optimizer/cost.h                 |   1 +
 src/include/optimizer/pathnode.h             |   2 +
 src/include/parser/kwlist.h                  |   1 +
 src/include/parser/parse_func.h              |   5 +
 src/include/port.h                           |   4 +
 src/include/utils/lsyscache.h                |   1 +
 src/include/utils/rel.h                      |   1 -
 src/include/utils/sampling.h                 |  15 +-
 src/include/utils/syscache.h                 |   2 +
 src/port/erand48.c                           |   3 -
 src/test/regress/expected/rowsecurity.out    |  26 ++
 src/test/regress/expected/sanity_check.out   |   1 +
 src/test/regress/expected/tablesample.out    | 216 ++++++++++++++++
 src/test/regress/parallel_schedule           |   2 +-
 src/test/regress/serial_schedule             |   1 +
 src/test/regress/sql/rowsecurity.sql         |   4 +
 src/test/regress/sql/tablesample.sql         |  61 +++++
 65 files changed, 2694 insertions(+), 37 deletions(-)
 create mode 100644 src/backend/access/tablesample/Makefile
 create mode 100644 src/backend/access/tablesample/bernoulli.c
 create mode 100644 src/backend/access/tablesample/system.c
 create mode 100644 src/backend/access/tablesample/tablesample.c
 create mode 100644 src/backend/executor/nodeSamplescan.c
 create mode 100644 src/include/access/tablesample.h
 create mode 100644 src/include/catalog/pg_tablesample_method.h
 create mode 100644 src/include/executor/nodeSamplescan.h
 create mode 100644 src/test/regress/expected/tablesample.out
 create mode 100644 src/test/regress/sql/tablesample.sql

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 249d541..6a813a3 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -1096,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * sampler_random_fract());
+				int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 74ef792..5903384 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -2543,7 +2543,7 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * sampler_random_fract());
+			pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index d0b78f2..ce4bcc4 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -269,6 +269,11 @@
      </row>
 
      <row>
+      <entry><link linkend="catalog-pg-tablesample-method"><structname>pg_tablesample_method</structname></link></entry>
+      <entry>table sampling methods</entry>
+     </row>
+
+     <row>
       <entry><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link></entry>
       <entry>tablespaces within this database cluster</entry>
      </row>
@@ -5980,6 +5985,121 @@
  </sect1>
 
 
+ <sect1 id="catalog-pg-tablesample-method">
+  <title><structname>pg_tabesample_method</structname></title>
+
+  <indexterm zone="catalog-pg-tablesample-method">
+   <primary>pg_am</primary>
+  </indexterm>
+
+  <para>
+   The catalog <structname>pg_tablesample_method</structname> stores
+   information about table sampling methods which can be used in
+   <command>TABLESAMPLE</command> clause of a <command>SELECT</command>
+   statement.
+  </para>
+
+  <table>
+   <title><structname>pg_tablesample_method</> Columns</title>
+
+   <tgroup cols="4">
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Type</entry>
+      <entry>References</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+    <tbody>
+
+     <row>
+      <entry><structfield>oid</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry></entry>
+      <entry>Row identifier (hidden attribute; must be explicitly selected)</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmname</structfield></entry>
+      <entry><type>name</type></entry>
+      <entry></entry>
+      <entry>Name of the sampling method</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmseqscan</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry></entry>
+      <entry>If true, the sampling method scans the whole table sequentially.
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmpagemode</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry></entry>
+      <entry>If true, the sampling method always reads the pages completely.
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsminit</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Initialize the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnextblock</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next block number</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmnexttuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Get next tuple offset</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmexaminetuple</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Function which examines the tuple contents and decides if to
+        return it, or zero if none</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmend</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>End the sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmreset</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry><quote>Restart the state of sampling scan</quote> function</entry>
+     </row>
+
+     <row>
+      <entry><structfield>tsmcost</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Costing function</entry>
+     </row>
+
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect1>
+
+
  <sect1 id="catalog-pg-tablespace">
   <title><structname>pg_tablespace</structname></title>
 
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 2295f63..42e0466 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -49,7 +49,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
 
 <phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
 
-    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
+    [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ] [ TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ] ]
     [ LATERAL ] ( <replaceable class="parameter">select</replaceable> ) [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ]
     <replaceable class="parameter">with_query_name</replaceable> [ [ AS ] <replaceable class="parameter">alias</replaceable> [ ( <replaceable class="parameter">column_alias</replaceable> [, ...] ) ] ]
     [ LATERAL ] <replaceable class="parameter">function_name</replaceable> ( [ <replaceable class="parameter">argument</replaceable> [, ...] ] )
@@ -317,6 +317,50 @@ TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ]
      </varlistentry>
 
      <varlistentry>
+      <term>TABLESAMPLE <replaceable class="parameter">sampling_method</replaceable> ( <replaceable class="parameter">argument</replaceable> [, ...] ) [ REPEATABLE ( <replaceable class="parameter">seed</replaceable> ) ]</term>
+      <listitem>
+       <para>
+        Table sample clause after
+        <replaceable class="parameter">table_name</replaceable> indicates that
+        a <replaceable class="parameter">sampling_method</replaceable> should
+        be used to retrieve subset of rows in the table.
+        The <replaceable class="parameter">sampling_method</replaceable> can be
+        any sampling method installed in the database. There are currently two
+        sampling methods available in the standard
+        <productname>PostgreSQL</productname> distribution:
+        <itemizedlist>
+         <listitem>
+          <para><literal>SYSTEM</literal></para>
+         </listitem>
+         <listitem>
+          <para><literal>BERNOULLI</literal></para>
+         </listitem>
+        </itemizedlist>
+        Both of these sampling methods currently accept only single argument
+        which is the percent (floating point from 0 to 100) of the rows to
+        be returned.
+        The <literal>SYSTEM</literal> sampling method does block level
+        sampling with each block having the same chance of being selected and
+        returns all rows from each selected block.
+        The <literal>BERNOULLI</literal> scans whole table and returns
+        individual rows with equal probability. Additional sampling methods
+        may be installed in the database via extensions.
+       </para>
+       <para>
+        The optional parameter <literal>REPEATABLE</literal> uses the seed
+        parameter, which can be a number or expression producing a number, as
+        a random seed for sampling. Note that subsequent commands may return
+        different results even if same <literal>REPEATABLE</literal> clause was
+        specified. This happens because <acronym>DML</acronym> statements and
+        maintenance operations such as <command>VACUUM</> may affect physical
+        distribution of data. The <function>setseed()</> function will not
+        affect the sampling result when the <literal>REPEATABLE</literal>
+        parameter is used.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><replaceable class="parameter">alias</replaceable></term>
       <listitem>
        <para>
@@ -1927,5 +1971,20 @@ SELECT distributors.* WHERE distributors.name = 'Westward';
     <literal>ROWS FROM( ... )</> is an extension of the SQL standard.
    </para>
   </refsect2>
+
+  <refsect2>
+   <title><literal>TABLESAMPLE</literal> clause</title>
+
+   <para>
+    The <literal>TABLESAMPLE</> clause is currently accepted only on physical
+    relations and materialized views.
+   </para>
+
+   <para>
+    Additional modules allow you to install custom sampling methods and use
+    them instead of the SQL standard methods.
+   </para>
+  </refsect2>
+
  </refsect1>
 </refentry>
diff --git a/src/backend/access/Makefile b/src/backend/access/Makefile
index 21721b4..bd93a6a 100644
--- a/src/backend/access/Makefile
+++ b/src/backend/access/Makefile
@@ -8,6 +8,7 @@ subdir = src/backend/access
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist transam
+SUBDIRS	    = brin common gin gist hash heap index nbtree rmgrdesc spgist \
+			  tablesample transam
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 457cd70..ef39cf2 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -79,8 +79,9 @@ bool		synchronize_seqscans = true;
 static HeapScanDesc heap_beginscan_internal(Relation relation,
 						Snapshot snapshot,
 						int nkeys, ScanKey key,
-						bool allow_strat, bool allow_sync,
-						bool is_bitmapscan, bool temp_snap);
+						bool allow_strat, bool allow_sync, bool allow_pagemode,
+						bool is_bitmapscan, bool is_samplescan,
+						bool temp_snap);
 static HeapTuple heap_prepare_insert(Relation relation, HeapTuple tup,
 					TransactionId xid, CommandId cid, int options);
 static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf,
@@ -293,9 +294,10 @@ initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
 
 	/*
 	 * Currently, we don't have a stats counter for bitmap heap scans (but the
-	 * underlying bitmap index scans will be counted).
+	 * underlying bitmap index scans will be counted) or sample scans (we only
+	 * update stats for tuple fetches there)
 	 */
-	if (!scan->rs_bitmapscan)
+	if (!scan->rs_bitmapscan && !scan->rs_samplescan)
 		pgstat_count_heap_scan(scan->rs_rd);
 }
 
@@ -314,7 +316,7 @@ heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk, BlockNumber numBlks)
  * In page-at-a-time mode it performs additional work, namely determining
  * which tuples on the page are visible.
  */
-static void
+void
 heapgetpage(HeapScanDesc scan, BlockNumber page)
 {
 	Buffer		buffer;
@@ -1297,6 +1299,9 @@ heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
  * HeapScanDesc for a bitmap heap scan.  Although that scan technology is
  * really quite unlike a standard seqscan, there is just enough commonality
  * to make it worth using the same data structure.
+ *
+ * heap_beginscan_samplingscan is alternate entry point for setting up a
+ * HeapScanDesc for a TABLESAMPLE scan.
  * ----------------
  */
 HeapScanDesc
@@ -1304,7 +1309,7 @@ heap_beginscan(Relation relation, Snapshot snapshot,
 			   int nkeys, ScanKey key)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   true, true, false, false);
+								   true, true, true, false, false, false);
 }
 
 HeapScanDesc
@@ -1314,7 +1319,7 @@ heap_beginscan_catalog(Relation relation, int nkeys, ScanKey key)
 	Snapshot	snapshot = RegisterSnapshot(GetCatalogSnapshot(relid));
 
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   true, true, false, true);
+								   true, true, true, false, false, true);
 }
 
 HeapScanDesc
@@ -1323,7 +1328,8 @@ heap_beginscan_strat(Relation relation, Snapshot snapshot,
 					 bool allow_strat, bool allow_sync)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   allow_strat, allow_sync, false, false);
+								   allow_strat, allow_sync, true,
+								   false, false, false);
 }
 
 HeapScanDesc
@@ -1331,14 +1337,24 @@ heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key)
 {
 	return heap_beginscan_internal(relation, snapshot, nkeys, key,
-								   false, false, true, false);
+								   false, false, true, true, false, false);
+}
+
+HeapScanDesc
+heap_beginscan_sampling(Relation relation, Snapshot snapshot,
+						int nkeys, ScanKey key,
+						bool allow_strat, bool allow_pagemode)
+{
+	return heap_beginscan_internal(relation, snapshot, nkeys, key,
+								   allow_strat, false, allow_pagemode,
+								   false, true, false);
 }
 
 static HeapScanDesc
 heap_beginscan_internal(Relation relation, Snapshot snapshot,
 						int nkeys, ScanKey key,
-						bool allow_strat, bool allow_sync,
-						bool is_bitmapscan, bool temp_snap)
+						bool allow_strat, bool allow_sync, bool allow_pagemode,
+						bool is_bitmapscan, bool is_samplescan, bool temp_snap)
 {
 	HeapScanDesc scan;
 
@@ -1360,6 +1376,7 @@ heap_beginscan_internal(Relation relation, Snapshot snapshot,
 	scan->rs_snapshot = snapshot;
 	scan->rs_nkeys = nkeys;
 	scan->rs_bitmapscan = is_bitmapscan;
+	scan->rs_samplescan = is_samplescan;
 	scan->rs_strategy = NULL;	/* set in initscan */
 	scan->rs_allow_strat = allow_strat;
 	scan->rs_allow_sync = allow_sync;
@@ -1368,7 +1385,7 @@ heap_beginscan_internal(Relation relation, Snapshot snapshot,
 	/*
 	 * we can use page-at-a-time mode if it's an MVCC-safe snapshot
 	 */
-	scan->rs_pageatatime = IsMVCCSnapshot(snapshot);
+	scan->rs_pageatatime = allow_pagemode && IsMVCCSnapshot(snapshot);
 
 	/*
 	 * For a seqscan in a serializable transaction, acquire a predicate lock
diff --git a/src/backend/access/tablesample/Makefile b/src/backend/access/tablesample/Makefile
new file mode 100644
index 0000000..46eeb59
--- /dev/null
+++ b/src/backend/access/tablesample/Makefile
@@ -0,0 +1,17 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for utils/tablesample
+#
+# IDENTIFICATION
+#    src/backend/utils/tablesample/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/access/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = tablesample.o system.o bernoulli.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/access/tablesample/bernoulli.c b/src/backend/access/tablesample/bernoulli.c
new file mode 100644
index 0000000..c91f3f5
--- /dev/null
+++ b/src/backend/access/tablesample/bernoulli.c
@@ -0,0 +1,235 @@
+/*-------------------------------------------------------------------------
+ *
+ * bernoulli.c
+ *	  interface routines for BERNOULLI tablesample method
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/bernoulli.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tablesample.h"
+#include "access/relscan.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+
+
+/* tsdesc */
+typedef struct
+{
+	uint32 seed;				/* random seed */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* number of blocks */
+	BlockNumber blockno;		/* current block */
+	float4 probability;			/* probabilty that tuple will be returned (0.0-1.0) */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator tsdesc */
+} BernoulliSamplerData;
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_bernoulli_init(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	uint32				seed = PG_GETARG_UINT32(1);
+	float4				percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	HeapScanDesc		scan = tsdesc->heapScan;
+	BernoulliSamplerData *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(BernoulliSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->startblock = scan->rs_startblock;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->blockno = InvalidBlockNumber;
+	sampler->probability = percent / 100;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	tsdesc->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_bernoulli_nextblock(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc		   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData   *sampler =
+		(BernoulliSamplerData *) tsdesc->tsmdata;
+
+	/*
+	 * Bernoulli sampling scans all blocks on the table and supports
+	 * syncscan so loop from startblock to startblock instead of
+	 * from 0 to nblocks.
+	 */
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = sampler->startblock;
+	else
+	{
+		sampler->blockno++;
+
+		if (sampler->blockno >= sampler->nblocks)
+			sampler->blockno = 0;
+
+		if (sampler->blockno == sampler->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ *
+ * This method implements the main logic in bernoulli sampling.
+ * The algorithm simply generates new random number (in 0.0-1.0 range) and if
+ * it falls within user specified probability (in the same range) return the
+ * tuple offset.
+ *
+ * It is ok here to return tuple offset without knowing if tuple is visible
+ * and not check it via examinetuple. The reason for that is that we do the
+ * coinflip (random number generation) for every tuple in the table. Since all
+ * tuples have same probability of being returned the visible and invisible
+ * tuples will be returned in same ratio as they have in the actual table.
+ * This means that there is no skew towards either visible or invisible tuples
+ * and the  number returned visible tuples to from the executor node is the
+ * fraction of visible tuples which was specified in input.
+ *
+ * This is faster than doing the coinflip in the examinetuple because we don't
+ * have to do visibility checks on uninteresting tuples.
+ *
+ * If we reach end of the block return InvalidOffsetNumber which tells
+ * SampleScan to go to next block.
+ */
+Datum
+tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc		   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	OffsetNumber			maxoffset = PG_GETARG_UINT16(2);
+	BernoulliSamplerData   *sampler =
+		(BernoulliSamplerData *) tsdesc->tsmdata;
+	OffsetNumber			tupoffset = sampler->lt;
+	float4					probability = sampler->probability;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	/*
+	 * Loop over tuple offsets until the random generator returns value that
+	 * is within the probability of returning the tuple or until we reach
+	 * end of the block.
+	 *
+	 * (This is our implementation of bernoulli trial)
+	 */
+	while (sampler_random_fract(sampler->randstate) > probability)
+	{
+		tupoffset++;
+
+		if (tupoffset > maxoffset)
+			break;
+	}
+
+	if (tupoffset > maxoffset)
+		/* Tell SampleScan that we want next block. */
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_bernoulli_end(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+
+	pfree(tsdesc->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset tsdesc (called by ReScan).
+ */
+Datum
+tsm_bernoulli_reset(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc		   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	BernoulliSamplerData   *sampler =
+		(BernoulliSamplerData *) tsdesc->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_bernoulli_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	*pages = baserel->pages;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1f;
+	}
+
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/access/tablesample/system.c b/src/backend/access/tablesample/system.c
new file mode 100644
index 0000000..1412e51
--- /dev/null
+++ b/src/backend/access/tablesample/system.c
@@ -0,0 +1,186 @@
+/*-------------------------------------------------------------------------
+ *
+ * system.c
+ *	  interface routines for system tablesample method
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/tablesample/system.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tablesample.h"
+#include "access/relscan.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/sampling.h"
+
+
+/*
+ * State
+ */
+typedef struct
+{
+	BlockSamplerData bs;
+	uint32 seed;				/* random seed */
+	BlockNumber nblocks;		/* number of block in relation */
+	int samplesize;				/* number of blocks to return */
+	OffsetNumber lt;			/* last tuple returned from current block */
+} SystemSamplerData;
+
+
+/*
+ * Initializes the state.
+ */
+Datum
+tsm_system_init(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	uint32				seed = PG_GETARG_UINT32(1);
+	float4				percent = PG_ARGISNULL(2) ? -1 : PG_GETARG_FLOAT4(2);
+	HeapScanDesc		scan = tsdesc->heapScan;
+	SystemSamplerData  *sampler;
+
+	if (percent < 0 || percent > 100)
+		ereport(ERROR,
+				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+				 errmsg("invalid sample size"),
+				 errhint("Sample size must be numeric value between 0 and 100 (inclusive).")));
+
+	sampler = palloc0(sizeof(SystemSamplerData));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->samplesize = 1 + (int) (sampler->nblocks * (percent / 100.0));
+	sampler->lt = InvalidOffsetNumber;
+
+	BlockSampler_Init(&sampler->bs, sampler->nblocks, sampler->samplesize,
+					  sampler->seed);
+
+	tsdesc->tsmdata = (void *) sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number or InvalidBlockNumber when we're done.
+ *
+ * Uses the same logic as ANALYZE for picking the random blocks.
+ */
+Datum
+tsm_system_nextblock(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+	BlockNumber			blockno;
+
+	if (!BlockSampler_HasMore(&sampler->bs))
+		PG_RETURN_UINT32(InvalidBlockNumber);
+
+	blockno = BlockSampler_Next(&sampler->bs);
+
+	PG_RETURN_UINT32(blockno);
+}
+
+/*
+ * Get next tuple offset in current block or InvalidOffsetNumber if we are done
+ * with this block.
+ */
+Datum
+tsm_system_nexttuple(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	OffsetNumber		maxoffset = PG_GETARG_UINT16(2);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+	OffsetNumber		tupoffset = sampler->lt;
+
+	if (tupoffset == InvalidOffsetNumber)
+		tupoffset = FirstOffsetNumber;
+	else
+		tupoffset++;
+
+	if (tupoffset > maxoffset)
+		tupoffset = InvalidOffsetNumber;
+
+	sampler->lt = tupoffset;
+
+	PG_RETURN_UINT16(tupoffset);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_system_end(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+
+	pfree(tsdesc->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_system_reset(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	SystemSamplerData  *sampler = (SystemSamplerData *) tsdesc->tsmdata;
+
+	sampler->lt = InvalidOffsetNumber;
+	BlockSampler_Init(&sampler->bs, sampler->nblocks, sampler->samplesize,
+					  sampler->seed);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_system_cost(PG_FUNCTION_ARGS)
+{
+	PlannerInfo	   *root = (PlannerInfo *) PG_GETARG_POINTER(0);
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	List		   *args = (List *) PG_GETARG_POINTER(3);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+	Node		   *pctnode;
+	float4			samplesize;
+
+	pctnode = linitial(args);
+	pctnode = estimate_expression_value(root, pctnode);
+
+	if (IsA(pctnode, RelabelType))
+		pctnode = (Node *) ((RelabelType *) pctnode)->arg;
+
+	if (IsA(pctnode, Const))
+	{
+		samplesize = DatumGetFloat4(((Const *) pctnode)->constvalue);
+		samplesize /= 100.0;
+	}
+	else
+	{
+		/* Default samplesize if the estimation didn't return Const. */
+		samplesize = 0.1f;
+	}
+
+	*pages = baserel->pages * samplesize;
+	*tuples = path->rows * samplesize;
+	path->rows = *tuples;
+
+	PG_RETURN_VOID();
+}
diff --git a/src/backend/access/tablesample/tablesample.c b/src/backend/access/tablesample/tablesample.c
new file mode 100644
index 0000000..ef55d06
--- /dev/null
+++ b/src/backend/access/tablesample/tablesample.c
@@ -0,0 +1,368 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *        TABLESAMPLE internal API
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *        src/backend/access/tablesample/tablesample.c
+ *
+ * TABLESAMPLE is the SQL standard clause for sampling the relations.
+ *
+ * The API is interface between the Executor and the TABLESAMPLE Methods.
+ *
+ * TABLESAMPLE Methods are implementations of actual sampling algorithms which
+ * can be used for returning a sample of the source relation.
+ * Methods don't read the table directly but are asked for block number and
+ * tuple offset which they want to examine (or return) and the tablesample
+ * interface implemented here does the reading for them.
+ *
+ * We currently only support sampling of the physical relations, but in the
+ * future we might extend the API to support subqueries as well.
+ *
+ * -------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/tablesample.h"
+
+#include "catalog/pg_tablesample_method.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "storage/bufmgr.h"
+#include "storage/predicate.h"
+#include "utils/rel.h"
+#include "utils/tqual.h"
+
+
+static bool SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan);
+
+
+/*
+ * Initialize the TABLESAMPLE Descriptor and the TABLESAMPLE Method.
+ */
+TableSampleDesc *
+tablesample_init(SampleScanState *scanstate, TableSampleClause *tablesample)
+{
+	FunctionCallInfoData fcinfo;
+	int			i;
+	List	   *args = tablesample->args;
+	ListCell   *arg;
+	ExprContext *econtext = scanstate->ss.ps.ps_ExprContext;
+	TableSampleDesc	*tsdesc = (TableSampleDesc *) palloc0(sizeof(TableSampleDesc));
+
+	/* Load functions */
+	fmgr_info(tablesample->tsminit, &(tsdesc->tsminit));
+	fmgr_info(tablesample->tsmnextblock, &(tsdesc->tsmnextblock));
+	fmgr_info(tablesample->tsmnexttuple, &(tsdesc->tsmnexttuple));
+	if (OidIsValid(tablesample->tsmexaminetuple))
+		fmgr_info(tablesample->tsmexaminetuple, &(tsdesc->tsmexaminetuple));
+	else
+		tsdesc->tsmexaminetuple.fn_oid = InvalidOid;
+	fmgr_info(tablesample->tsmreset, &(tsdesc->tsmreset));
+	fmgr_info(tablesample->tsmend, &(tsdesc->tsmend));
+
+	InitFunctionCallInfoData(fcinfo, &tsdesc->tsminit,
+							 list_length(args) + 2,
+							 InvalidOid, NULL, NULL);
+
+	tsdesc->tupDesc = scanstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
+	tsdesc->heapScan = scanstate->ss.ss_currentScanDesc;
+
+	/* First argument for init function is always TableSampleDesc */
+	fcinfo.arg[0] = PointerGetDatum(tsdesc);
+	fcinfo.argnull[0] = false;
+
+	/*
+	 * Second arg for init function is always REPEATABLE
+	 * When tablesample->repeatable is NULL then REPEATABLE clause was not
+	 * specified.
+	 * When specified, the expression cannot evaluate to NULL.
+	 */
+	if (tablesample->repeatable)
+	{
+		ExprState  *argstate = ExecInitExpr((Expr *) tablesample->repeatable,
+											(PlanState *) scanstate);
+		fcinfo.arg[1] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[1], NULL);
+		if (fcinfo.argnull[1])
+			ereport(ERROR,
+					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+					 errmsg("REPEATABLE clause must be NOT NULL numeric value")));
+	}
+	else
+	{
+		fcinfo.arg[1] = UInt32GetDatum(random());
+		fcinfo.argnull[1] = false;
+	}
+
+	/* Rest of the arguments come from user.  */
+	i = 2;
+	foreach(arg, args)
+	{
+		Expr	   *argexpr = (Expr *) lfirst(arg);
+		ExprState  *argstate = ExecInitExpr(argexpr, (PlanState *) scanstate);
+
+		if (argstate == NULL)
+		{
+			fcinfo.argnull[i] = true;
+			fcinfo.arg[i] = (Datum) 0;;
+		}
+
+		fcinfo.arg[i] = ExecEvalExpr(argstate, econtext,
+									 &fcinfo.argnull[i], NULL);
+		i++;
+	}
+	Assert(i == fcinfo.nargs);
+
+	(void) FunctionCallInvoke(&fcinfo);
+
+	return tsdesc;
+}
+
+/*
+ * Get next tuple from TABLESAMPLE Method.
+ */
+HeapTuple
+tablesample_getnext(TableSampleDesc *desc)
+{
+	HeapScanDesc	scan = desc->heapScan;
+	HeapTuple		tuple = &(scan->rs_ctup);
+	bool			pagemode = scan->rs_pageatatime;
+	BlockNumber		blockno;
+	Page			page;
+	bool			page_all_visible;
+	ItemId			itemid;
+	OffsetNumber	tupoffset,
+					maxoffset;
+
+	if (!scan->rs_inited)
+	{
+		/*
+		 * return null immediately if relation is empty
+		 */
+		if (scan->rs_nblocks == 0)
+		{
+			Assert(!BufferIsValid(scan->rs_cbuf));
+			tuple->t_data = NULL;
+			return NULL;
+		}
+		blockno = DatumGetInt32(FunctionCall1(&desc->tsmnextblock,
+											PointerGetDatum(desc)));
+		if (!BlockNumberIsValid(blockno))
+		{
+			tuple->t_data = NULL;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+		scan->rs_inited = true;
+	}
+	else
+	{
+		/* continue from previously returned page/tuple */
+		blockno = scan->rs_cblock;		/* current page */
+	}
+
+	/*
+	 * When pagemode is disabled, the scan will do visibility checks for each
+	 * tuple it finds so the buffer needs to be locked.
+	 */
+	if (!pagemode)
+		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+	page = (Page) BufferGetPage(scan->rs_cbuf);
+	page_all_visible = PageIsAllVisible(page);
+	maxoffset = PageGetMaxOffsetNumber(page);
+
+	for (;;)
+	{
+		CHECK_FOR_INTERRUPTS();
+
+		tupoffset = DatumGetUInt16(FunctionCall3(&desc->tsmnexttuple,
+											 PointerGetDatum(desc),
+											 UInt32GetDatum(blockno),
+											 UInt16GetDatum(maxoffset)));
+
+		if (OffsetNumberIsValid(tupoffset))
+		{
+			bool	visible;
+			bool	found;
+
+			/* Skip invalid tuple pointers. */
+			itemid = PageGetItemId(page, tupoffset);
+			if (!ItemIdIsNormal(itemid))
+				continue;
+
+			tuple->t_data = (HeapTupleHeader) PageGetItem((Page) page, itemid);
+			tuple->t_len = ItemIdGetLength(itemid);
+			ItemPointerSet(&(tuple->t_self), blockno, tupoffset);
+
+			if (page_all_visible)
+				visible = true;
+			else
+				visible = SampleTupleVisible(tuple, tupoffset, scan);
+
+			/*
+			 * Let the sampling method examine the actual tuple and decide if we
+			 * should return it.
+			 *
+			 * Note that we let it examine even invisible tuples for
+			 * statistical purposes, but not return them since user should
+			 * never see invisible tuples.
+			 */
+			if (OidIsValid(desc->tsmexaminetuple.fn_oid))
+			{
+				found = DatumGetBool(FunctionCall4(&desc->tsmexaminetuple,
+											   PointerGetDatum(desc),
+											   UInt32GetDatum(blockno),
+											   PointerGetDatum(tuple),
+											   BoolGetDatum(visible)));
+				/* Should not happen if sampling method is well written. */
+				if (found && !visible)
+					elog(ERROR, "Sampling method wanted to return invisible tuple");
+			}
+			else
+				found = visible;
+
+			/* Found visible tuple, return it. */
+			if (found)
+			{
+				if (!pagemode)
+					LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+				break;
+			}
+			else
+			{
+				/* Try next tuple from same page. */
+				continue;
+			}
+		}
+
+
+		if (!pagemode)
+			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+
+		blockno = DatumGetInt32(FunctionCall1(&desc->tsmnextblock,
+										  PointerGetDatum(desc)));
+
+		/*
+		 * Report our new scan position for synchronization purposes. We
+		 * don't do that when moving backwards, however. That would just
+		 * mess up any other forward-moving scanners.
+		 *
+		 * Note: we do this before checking for end of scan so that the
+		 * final state of the position hint is back at the start of the
+		 * rel.  That's not strictly necessary, but otherwise when you run
+		 * the same query multiple times the starting position would shift
+		 * a little bit backwards on every invocation, which is confusing.
+		 * We don't guarantee any specific ordering in general, though.
+		 */
+		if (scan->rs_syncscan)
+			ss_report_location(scan->rs_rd, BlockNumberIsValid(blockno) ?
+							   blockno : scan->rs_startblock);
+
+		/*
+		 * Reached end of scan.
+		 */
+		if (!BlockNumberIsValid(blockno))
+		{
+			if (BufferIsValid(scan->rs_cbuf))
+				ReleaseBuffer(scan->rs_cbuf);
+			scan->rs_cbuf = InvalidBuffer;
+			scan->rs_cblock = InvalidBlockNumber;
+			tuple->t_data = NULL;
+			scan->rs_inited = false;
+			return NULL;
+		}
+
+		heapgetpage(scan, blockno);
+
+		if (!pagemode)
+			LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+
+		page = (Page) BufferGetPage(scan->rs_cbuf);
+		page_all_visible = PageIsAllVisible(page);
+		maxoffset = PageGetMaxOffsetNumber(page);
+	}
+
+	pgstat_count_heap_getnext(scan->rs_rd);
+
+	return &(scan->rs_ctup);
+}
+
+/*
+ * Reset the sampling to starting state
+ */
+void
+tablesample_reset(TableSampleDesc *desc)
+{
+	(void) FunctionCall1(&desc->tsmreset, PointerGetDatum(desc));
+}
+
+/*
+ * Signal the sampling method that the scan has finished.
+ */
+void
+tablesample_end(TableSampleDesc *desc)
+{
+	(void) FunctionCall1(&desc->tsmend, PointerGetDatum(desc));
+}
+
+/*
+ * Check visibility of the tuple.
+ */
+static bool
+SampleTupleVisible(HeapTuple tuple, OffsetNumber tupoffset, HeapScanDesc scan)
+{
+	/*
+	 * If this scan is reading whole pages at a time, there is already
+	 * visibility info present in rs_vistuples so we can just search it
+	 * for the tupoffset.
+	 */
+	if (scan->rs_pageatatime)
+	{
+		int start = 0,
+			end = scan->rs_ntuples - 1;
+
+		/*
+		 * Do the binary search over rs_vistuples, it's already sorted by
+		 * OffsetNumber so we don't need to do any sorting ourselves here.
+		 *
+		 * We could use bsearch() here but it's slower for integers because
+		 * of the function call overhead and because it needs boiler plate code
+		 * it would not save us anything code-wise anyway.
+		 */
+		while (start <= end)
+		{
+			int mid = start + (end - start) / 2;
+			OffsetNumber curoffset = scan->rs_vistuples[mid];
+
+			if (curoffset == tupoffset)
+				return true;
+			else if (curoffset > tupoffset)
+				end = mid - 1;
+			else
+				start = mid + 1;
+		}
+
+		return false;
+	}
+	else
+	{
+		/* No pagemode, we have to check the tuple itself. */
+		Snapshot	snapshot = scan->rs_snapshot;
+		Buffer		buffer = scan->rs_cbuf;
+
+		bool visible = HeapTupleSatisfiesVisibility(tuple, snapshot, buffer);
+
+		CheckForSerializableConflictOut(visible, scan->rs_rd, tuple, buffer,
+										snapshot);
+
+		return visible;
+	}
+}
diff --git a/src/backend/catalog/Makefile b/src/backend/catalog/Makefile
index a403c64..34db3e6 100644
--- a/src/backend/catalog/Makefile
+++ b/src/backend/catalog/Makefile
@@ -39,7 +39,7 @@ POSTGRES_BKI_SRCS = $(addprefix $(top_srcdir)/src/include/catalog/,\
 	pg_ts_config.h pg_ts_config_map.h pg_ts_dict.h \
 	pg_ts_parser.h pg_ts_template.h pg_extension.h \
 	pg_foreign_data_wrapper.h pg_foreign_server.h pg_user_mapping.h \
-	pg_foreign_table.h pg_policy.h \
+	pg_foreign_table.h pg_policy.h pg_tablesample_method.h \
 	pg_default_acl.h pg_seclabel.h pg_shseclabel.h pg_collation.h pg_range.h \
 	toasting.h indexing.h \
     )
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 952cf20..65e329e 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1150,7 +1150,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * sampler_random_fract());
+						int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 315a528..17088f3 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -732,6 +732,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			*rels_used = bms_add_member(*rels_used,
 										((Scan *) plan)->scanrelid);
 			break;
@@ -957,6 +958,21 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			else
 				pname = sname;
 			break;
+		case T_SampleScan:
+			{
+				/*
+				 * Fetch the tablesample method name from RTE.
+				 *
+				 * It would be nice to also show parameters, but since we
+				 * support arbitrary expressions as parameter it might get
+				 * quite messy.
+				 */
+				RangeTblEntry *rte;
+				rte = rt_fetch(((SampleScan *) plan)->scanrelid, es->rtable);
+				custom_name = get_tablesample_method_name(rte->tablesample->tsmid);
+				pname = psprintf("Sample Scan (%s)", custom_name);
+			}
+			break;
 		case T_Material:
 			pname = sname = "Materialize";
 			break;
@@ -1074,6 +1090,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_WorkTableScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
 		case T_IndexScan:
@@ -1326,6 +1343,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_CteScan:
 		case T_WorkTableScan:
 		case T_SubqueryScan:
+		case T_SampleScan:
 			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
@@ -2224,6 +2242,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 		case T_TidScan:
 		case T_ForeignScan:
 		case T_CustomScan:
+		case T_SampleScan:
 		case T_ModifyTable:
 			/* Assert it's on a real relation */
 			Assert(rte->rtekind == RTE_RELATION);
diff --git a/src/backend/executor/Makefile b/src/backend/executor/Makefile
index af707b0..75f799c 100644
--- a/src/backend/executor/Makefile
+++ b/src/backend/executor/Makefile
@@ -21,7 +21,7 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
-       nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
+       nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o nodeCtescan.o nodeWorktablescan.o \
        nodeGroup.o nodeSubplan.o nodeSubqueryscan.o nodeTidscan.o \
        nodeForeignscan.o nodeWindowAgg.o tstoreReceiver.o spi.o
diff --git a/src/backend/executor/execAmi.c b/src/backend/executor/execAmi.c
index 6ebad2f..4948a26 100644
--- a/src/backend/executor/execAmi.c
+++ b/src/backend/executor/execAmi.c
@@ -39,6 +39,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecReScanSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
@@ -480,6 +485,9 @@ ExecSupportsBackwardScan(Plan *node)
 			}
 			return false;
 
+		case T_SampleScan:
+			return false;
+
 		case T_Material:
 		case T_Sort:
 			/* these don't evaluate tlist */
diff --git a/src/backend/executor/execCurrent.c b/src/backend/executor/execCurrent.c
index d87be96..bcd287f 100644
--- a/src/backend/executor/execCurrent.c
+++ b/src/backend/executor/execCurrent.c
@@ -261,6 +261,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 * Relation scan nodes can all be treated alike
 			 */
 		case T_SeqScanState:
+		case T_SampleScanState:
 		case T_IndexScanState:
 		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 9892499..03c2feb 100644
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -102,6 +102,7 @@
 #include "executor/nodeNestloop.h"
 #include "executor/nodeRecursiveunion.h"
 #include "executor/nodeResult.h"
+#include "executor/nodeSamplescan.h"
 #include "executor/nodeSeqscan.h"
 #include "executor/nodeSetOp.h"
 #include "executor/nodeSort.h"
@@ -190,6 +191,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 												   estate, eflags);
 			break;
 
+		case T_SampleScan:
+			result = (PlanState *) ExecInitSampleScan((SampleScan *) node,
+													  estate, eflags);
+			break;
+
 		case T_IndexScan:
 			result = (PlanState *) ExecInitIndexScan((IndexScan *) node,
 													 estate, eflags);
@@ -406,6 +412,10 @@ ExecProcNode(PlanState *node)
 			result = ExecSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			result = ExecSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
@@ -644,6 +654,10 @@ ExecEndNode(PlanState *node)
 			ExecEndSeqScan((SeqScanState *) node);
 			break;
 
+		case T_SampleScanState:
+			ExecEndSampleScan((SampleScanState *) node);
+			break;
+
 		case T_IndexScanState:
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
diff --git a/src/backend/executor/nodeSamplescan.c b/src/backend/executor/nodeSamplescan.c
new file mode 100644
index 0000000..fc89d1d
--- /dev/null
+++ b/src/backend/executor/nodeSamplescan.c
@@ -0,0 +1,256 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.c
+ *	  Support routines for sample scans of relations (table sampling).
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeSamplescan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/tablesample.h"
+#include "executor/executor.h"
+#include "executor/nodeSamplescan.h"
+#include "miscadmin.h"
+#include "parser/parsetree.h"
+#include "pgstat.h"
+#include "storage/bufmgr.h"
+#include "storage/predicate.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+#include "utils/tqual.h"
+
+static void InitScanRelation(SampleScanState *node, EState *estate,
+							 int eflags, TableSampleClause *tablesample);
+static TupleTableSlot *SampleNext(SampleScanState *node);
+
+
+/* ----------------------------------------------------------------
+ *						Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		SampleNext
+ *
+ *		This is a workhorse for ExecSampleScan
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+SampleNext(SampleScanState *node)
+{
+	TupleTableSlot	   *slot;
+	TableSampleDesc	   *tsdesc;
+	HeapTuple			tuple;
+
+	/*
+	 * get information from the scan state
+	 */
+	slot = node->ss.ss_ScanTupleSlot;
+	tsdesc = node->tsdesc;
+
+	tuple = tablesample_getnext(tsdesc);
+
+	if (tuple)
+		ExecStoreTuple(tuple,	/* tuple to store */
+					   slot,	/* slot to store in */
+					   tsdesc->heapScan->rs_cbuf,	/* buffer associated with this tuple */
+					   false);	/* don't pfree this pointer */
+	else
+		ExecClearTuple(slot);
+
+	return slot;
+}
+
+/*
+ * SampleRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ */
+static bool
+SampleRecheck(SampleScanState *node, TupleTableSlot *slot)
+{
+	/* No need to recheck for SampleScan */
+	return true;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSampleScan(node)
+ *
+ *		Scans the relation using the sampling method and returns
+ *		the next qualifying tuple.
+ *		We call the ExecScan() routine and pass it the appropriate
+ *		access method functions.
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecSampleScan(SampleScanState *node)
+{
+	return ExecScan((ScanState *) node,
+					(ExecScanAccessMtd) SampleNext,
+					(ExecScanRecheckMtd) SampleRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		InitScanRelation
+ *
+ *		Set up to access the scan relation.
+ * ----------------------------------------------------------------
+ */
+static void
+InitScanRelation(SampleScanState *node, EState *estate, int eflags,
+				 TableSampleClause *tablesample)
+{
+	Relation	currentRelation;
+
+	/*
+	 * get the relation object id from the relid'th entry in the range table,
+	 * open that relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate,
+										   ((SampleScan *) node->ss.ps.plan)->scanrelid,
+										   eflags);
+
+	node->ss.ss_currentRelation = currentRelation;
+
+	/*
+	 * Even though we aren't going to do a conventional seqscan, it is useful
+	 * to create a HeapScanDesc --- many of the fields in it are usable.
+	 */
+	node->ss.ss_currentScanDesc =
+		heap_beginscan_sampling(currentRelation, estate->es_snapshot, 0, NULL,
+								tablesample->tsmseqscan,
+								tablesample->tsmpagemode);
+
+	/* and report the scan tuple slot's rowtype */
+	ExecAssignScanType(&node->ss, RelationGetDescr(currentRelation));
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecInitSampleScan
+ * ----------------------------------------------------------------
+ */
+SampleScanState *
+ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
+{
+	SampleScanState *scanstate;
+	RangeTblEntry *rte = rt_fetch(node->scanrelid,
+								  estate->es_range_table);
+
+	Assert(outerPlan(node) == NULL);
+	Assert(innerPlan(node) == NULL);
+	Assert(rte->tablesample != NULL);
+
+	/*
+	 * create state structure
+	 */
+	scanstate = makeNode(SampleScanState);
+	scanstate->ss.ps.plan = (Plan *) node;
+	scanstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &scanstate->ss.ps);
+
+	/*
+	 * initialize child expressions
+	 */
+	scanstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->plan.targetlist,
+					 (PlanState *) scanstate);
+	scanstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->plan.qual,
+					 (PlanState *) scanstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &scanstate->ss);
+
+	/*
+	 * initialize scan relation
+	 */
+	InitScanRelation(scanstate, estate, eflags, rte->tablesample);
+
+	scanstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * Initialize result tuple type and projection info.
+	 */
+	ExecAssignResultTypeFromTL(&scanstate->ss.ps);
+	ExecAssignScanProjectionInfo(&scanstate->ss);
+
+	scanstate->tsdesc = tablesample_init(scanstate, rte->tablesample);
+
+	return scanstate;
+}
+
+/* ----------------------------------------------------------------
+ *		ExecEndSampleScan
+ *
+ *		frees any storage allocated through C routines.
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndSampleScan(SampleScanState *node)
+{
+	/*
+	 * Tell sampling function that we finished the scan.
+	 */
+	tablesample_end(node->tsdesc);
+
+	/*
+	 * Free the exprcontext
+	 */
+	ExecFreeExprContext(&node->ss.ps);
+
+	/*
+	 * clean out the tuple table
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close heap scan
+	 */
+	heap_endscan(node->ss.ss_currentScanDesc);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(node->ss.ss_currentRelation);
+}
+
+/* ----------------------------------------------------------------
+ *						Join Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecReScanSampleScan
+ *
+ *		Rescans the relation.
+ *
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanSampleScan(SampleScanState *node)
+{
+	heap_rescan(node->ss.ss_currentScanDesc, NULL);
+
+	/*
+	 * Tell sampling function to reset its state for rescan.
+	 */
+	tablesample_reset(node->tsdesc);
+
+	ExecScanReScan(&node->ss);
+}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 029761e..1a4c85b 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -630,6 +630,22 @@ _copyCustomScan(const CustomScan *from)
 }
 
 /*
+ * _copySampleScan
+ */
+static SampleScan *
+_copySampleScan(const SampleScan *from)
+{
+	SampleScan *newnode = makeNode(SampleScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	return newnode;
+}
+
+/*
  * CopyJoinFields
  *
  *		This function copies the fields of the Join node.  It is used by
@@ -2015,6 +2031,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(rtekind);
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
+	COPY_NODE_FIELD(tablesample);
 	COPY_NODE_FIELD(subquery);
 	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
@@ -2147,6 +2164,40 @@ _copyCommonTableExpr(const CommonTableExpr *from)
 	return newnode;
 }
 
+static RangeTableSample *
+_copyRangeTableSample(const RangeTableSample *from)
+{
+	RangeTableSample *newnode = makeNode(RangeTableSample);
+
+	COPY_NODE_FIELD(relation);
+	COPY_STRING_FIELD(method);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
+static TableSampleClause *
+_copyTableSampleClause(const TableSampleClause *from)
+{
+	TableSampleClause *newnode = makeNode(TableSampleClause);
+
+	COPY_SCALAR_FIELD(tsmid);
+	COPY_SCALAR_FIELD(tsmseqscan);
+	COPY_SCALAR_FIELD(tsmpagemode);
+	COPY_SCALAR_FIELD(tsminit);
+	COPY_SCALAR_FIELD(tsmnextblock);
+	COPY_SCALAR_FIELD(tsmnexttuple);
+	COPY_SCALAR_FIELD(tsmexaminetuple);
+	COPY_SCALAR_FIELD(tsmend);
+	COPY_SCALAR_FIELD(tsmreset);
+	COPY_SCALAR_FIELD(tsmcost);
+	COPY_NODE_FIELD(repeatable);
+	COPY_NODE_FIELD(args);
+
+	return newnode;
+}
+
 static A_Expr *
 _copyAExpr(const A_Expr *from)
 {
@@ -4084,6 +4135,9 @@ copyObject(const void *from)
 		case T_CustomScan:
 			retval = _copyCustomScan(from);
 			break;
+		case T_SampleScan:
+			retval = _copySampleScan(from);
+			break;
 		case T_Join:
 			retval = _copyJoin(from);
 			break;
@@ -4732,6 +4786,12 @@ copyObject(const void *from)
 		case T_CommonTableExpr:
 			retval = _copyCommonTableExpr(from);
 			break;
+		case T_RangeTableSample:
+			retval = _copyRangeTableSample(from);
+			break;
+		case T_TableSampleClause:
+			retval = _copyTableSampleClause(from);
+			break;
 		case T_FuncWithArgs:
 			retval = _copyFuncWithArgs(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 190e50a..27626b5 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2318,6 +2318,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(rtekind);
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
+	COMPARE_NODE_FIELD(tablesample);
 	COMPARE_NODE_FIELD(subquery);
 	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
@@ -2437,6 +2438,36 @@ _equalCommonTableExpr(const CommonTableExpr *a, const CommonTableExpr *b)
 }
 
 static bool
+_equalRangeTableSample(const RangeTableSample *a, const RangeTableSample *b)
+{
+	COMPARE_NODE_FIELD(relation);
+	COMPARE_STRING_FIELD(method);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
+_equalTableSampleClause(const TableSampleClause *a, const TableSampleClause *b)
+{
+	COMPARE_SCALAR_FIELD(tsmid);
+	COMPARE_SCALAR_FIELD(tsmseqscan);
+	COMPARE_SCALAR_FIELD(tsmpagemode);
+	COMPARE_SCALAR_FIELD(tsminit);
+	COMPARE_SCALAR_FIELD(tsmnextblock);
+	COMPARE_SCALAR_FIELD(tsmnexttuple);
+	COMPARE_SCALAR_FIELD(tsmexaminetuple);
+	COMPARE_SCALAR_FIELD(tsmend);
+	COMPARE_SCALAR_FIELD(tsmreset);
+	COMPARE_SCALAR_FIELD(tsmcost);
+	COMPARE_NODE_FIELD(repeatable);
+	COMPARE_NODE_FIELD(args);
+
+	return true;
+}
+
+static bool
 _equalXmlSerialize(const XmlSerialize *a, const XmlSerialize *b)
 {
 	COMPARE_SCALAR_FIELD(xmloption);
@@ -3155,6 +3186,12 @@ equal(const void *a, const void *b)
 		case T_CommonTableExpr:
 			retval = _equalCommonTableExpr(a, b);
 			break;
+		case T_RangeTableSample:
+			retval = _equalRangeTableSample(a, b);
+			break;
+		case T_TableSampleClause:
+			retval = _equalTableSampleClause(a, b);
+			break;
 		case T_FuncWithArgs:
 			retval = _equalFuncWithArgs(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index d6f1f5b..7742189 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3219,6 +3219,18 @@ raw_expression_tree_walker(Node *node,
 			return walker(((WithClause *) node)->ctes, context);
 		case T_CommonTableExpr:
 			return walker(((CommonTableExpr *) node)->ctequery, context);
+		case T_RangeTableSample:
+			{
+				RangeTableSample *rts = (RangeTableSample *) node;
+
+				if (walker(rts->relation, context))
+					return true;
+				if (walker(rts->repeatable, context))
+					return true;
+				if (walker(rts->args, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 385b289..e26dbf0 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -580,6 +580,14 @@ _outCustomScan(StringInfo str, const CustomScan *node)
 }
 
 static void
+_outSampleScan(StringInfo str, const SampleScan *node)
+{
+	WRITE_NODE_TYPE("SAMPLESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+}
+
+static void
 _outJoin(StringInfo str, const Join *node)
 {
 	WRITE_NODE_TYPE("JOIN");
@@ -2404,6 +2412,36 @@ _outCommonTableExpr(StringInfo str, const CommonTableExpr *node)
 }
 
 static void
+_outRangeTableSample(StringInfo str, const RangeTableSample *node)
+{
+	WRITE_NODE_TYPE("RANGETABLESAMPLE");
+
+	WRITE_NODE_FIELD(relation);
+	WRITE_STRING_FIELD(method);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
+_outTableSampleClause(StringInfo str, const TableSampleClause *node)
+{
+	WRITE_NODE_TYPE("TABLESAMPLECLAUSE");
+
+	WRITE_OID_FIELD(tsmid);
+	WRITE_BOOL_FIELD(tsmseqscan);
+	WRITE_BOOL_FIELD(tsmpagemode);
+	WRITE_OID_FIELD(tsminit);
+	WRITE_OID_FIELD(tsmnextblock);
+	WRITE_OID_FIELD(tsmnexttuple);
+	WRITE_OID_FIELD(tsmexaminetuple);
+	WRITE_OID_FIELD(tsmend);
+	WRITE_OID_FIELD(tsmreset);
+	WRITE_OID_FIELD(tsmcost);
+	WRITE_NODE_FIELD(repeatable);
+	WRITE_NODE_FIELD(args);
+}
+
+static void
 _outSetOperationStmt(StringInfo str, const SetOperationStmt *node)
 {
 	WRITE_NODE_TYPE("SETOPERATIONSTMT");
@@ -2433,6 +2471,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 		case RTE_RELATION:
 			WRITE_OID_FIELD(relid);
 			WRITE_CHAR_FIELD(relkind);
+			WRITE_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
@@ -2931,6 +2970,9 @@ _outNode(StringInfo str, const void *obj)
 			case T_CustomScan:
 				_outCustomScan(str, obj);
 				break;
+			case T_SampleScan:
+				_outSampleScan(str, obj);
+				break;
 			case T_Join:
 				_outJoin(str, obj);
 				break;
@@ -3272,6 +3314,12 @@ _outNode(StringInfo str, const void *obj)
 			case T_CommonTableExpr:
 				_outCommonTableExpr(str, obj);
 				break;
+			case T_RangeTableSample:
+				_outRangeTableSample(str, obj);
+				break;
+			case T_TableSampleClause:
+				_outTableSampleClause(str, obj);
+				break;
 			case T_SetOperationStmt:
 				_outSetOperationStmt(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 563209c..05ed9a8 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -350,6 +350,46 @@ _readCommonTableExpr(void)
 }
 
 /*
+ * _readRangeTableSample
+ */
+static RangeTableSample *
+_readRangeTableSample(void)
+{
+	READ_LOCALS(RangeTableSample);
+
+	READ_NODE_FIELD(relation);
+	READ_STRING_FIELD(method);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
+ * _readTableSampleClause
+ */
+static TableSampleClause *
+_readTableSampleClause(void)
+{
+	READ_LOCALS(TableSampleClause);
+
+	READ_OID_FIELD(tsmid);
+	READ_BOOL_FIELD(tsmseqscan);
+	READ_BOOL_FIELD(tsmpagemode);
+	READ_OID_FIELD(tsminit);
+	READ_OID_FIELD(tsmnextblock);
+	READ_OID_FIELD(tsmnexttuple);
+	READ_OID_FIELD(tsmexaminetuple);
+	READ_OID_FIELD(tsmend);
+	READ_OID_FIELD(tsmreset);
+	READ_OID_FIELD(tsmcost);
+	READ_NODE_FIELD(repeatable);
+	READ_NODE_FIELD(args);
+
+	READ_DONE();
+}
+
+/*
  * _readSetOperationStmt
  */
 static SetOperationStmt *
@@ -1218,6 +1258,7 @@ _readRangeTblEntry(void)
 		case RTE_RELATION:
 			READ_OID_FIELD(relid);
 			READ_CHAR_FIELD(relkind);
+			READ_NODE_FIELD(tablesample);
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
@@ -1313,6 +1354,10 @@ parseNodeString(void)
 		return_value = _readRowMarkClause();
 	else if (MATCH("COMMONTABLEEXPR", 15))
 		return_value = _readCommonTableExpr();
+	else if (MATCH("RANGETABLESAMPLE", 16))
+		return_value = _readRangeTableSample();
+	else if (MATCH("TABLESAMPLECLAUSE", 17))
+		return_value = _readTableSampleClause();
 	else if (MATCH("SETOPERATIONSTMT", 16))
 		return_value = _readSetOperationStmt();
 	else if (MATCH("ALIAS", 5))
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 58d78e6..5f12477 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -71,6 +71,10 @@ static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
 				   RangeTblEntry *rte);
 static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					   RangeTblEntry *rte);
+static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
+				   RangeTblEntry *rte);
+static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
+										 RangeTblEntry *rte);
 static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
 				 RangeTblEntry *rte);
 static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -265,6 +269,11 @@ set_rel_size(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_size(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Sampled relation */
+					set_tablesample_rel_size(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -332,6 +341,11 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_pathlist(root, rel, rte);
 				}
+				else if (rte->tablesample != NULL)
+				{
+					/* Build sample scan on relation */
+					set_tablesample_rel_pathlist(root, rel, rte);
+				}
 				else
 				{
 					/* Plain relation */
@@ -418,6 +432,41 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 }
 
 /*
+ * set_tablesample_rel_size
+ *	  Set size estimates for a sampled relation.
+ */
+static void
+set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	/* Mark rel with estimated output rows, width, etc */
+	set_baserel_size_estimates(root, rel);
+}
+
+/*
+ * set_tablesample_rel_pathlist
+ *	  Build access paths for a sampled relation
+ *
+ * There is only one possible path - sampling scan
+ */
+static void
+set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
+{
+	Relids	required_outer;
+	Path   *path;
+
+	/*
+	 * We don't support pushing join clauses into the quals of a seqscan, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	required_outer = rel->lateral_relids;
+
+	/* We only do sample scan if it was requested */
+	path = create_samplescan_path(root, rel, required_outer);
+	rel->pathlist = list_make1(path);
+}
+
+/*
  * set_foreign_size
  *		Set size estimates for a foreign table RTE
  */
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 1a0d358..c2b2b76 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -220,6 +220,73 @@ cost_seqscan(Path *path, PlannerInfo *root,
 }
 
 /*
+ * cost_samplescan
+ *	  Determines and returns the cost of scanning a relation using sampling.
+ *
+ * From planner/optimizer perspective, we don't care all that much about cost
+ * itself since there is always only one scan path to consider when sampling
+ * scan is present, but number of rows estimation is still important.
+ *
+ * 'baserel' is the relation to be scanned
+ * 'param_info' is the ParamPathInfo if this is a parameterized path, else NULL
+ */
+void
+cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel)
+{
+	Cost		startup_cost = 0;
+	Cost		run_cost = 0;
+	double		spc_seq_page_cost,
+				spc_random_page_cost,
+				spc_page_cost;
+	QualCost	qpqual_cost;
+	Cost		cpu_per_tuple;
+	BlockNumber pages;
+	double		tuples;
+	RangeTblEntry		   *rte = planner_rt_fetch(baserel->relid, root);
+	TableSampleClause	   *tablesample = rte->tablesample;
+
+	/* Should only be applied to base relations */
+	Assert(baserel->relid > 0);
+	Assert(baserel->rtekind == RTE_RELATION);
+
+	/* Mark the path with the correct row estimate */
+	if (path->param_info)
+		path->rows = path->param_info->ppi_rows;
+	else
+		path->rows = baserel->rows;
+
+	/* Call the sampling method's costing function. */
+	OidFunctionCall6(tablesample->tsmcost, PointerGetDatum(root),
+					 PointerGetDatum(path), PointerGetDatum(baserel),
+					 PointerGetDatum(tablesample->args),
+					 PointerGetDatum(&pages), PointerGetDatum(&tuples));
+
+	/* fetch estimated page cost for tablespace containing table */
+	get_tablespace_page_costs(baserel->reltablespace,
+							  &spc_random_page_cost,
+							  &spc_seq_page_cost);
+
+
+	spc_page_cost = tablesample->tsmseqscan ? spc_seq_page_cost :
+					spc_random_page_cost;
+
+	/*
+	 * disk costs
+	 */
+	run_cost += spc_page_cost * pages;
+
+	/* CPU costs */
+	get_restriction_qual_cost(root, baserel, path->param_info, &qpqual_cost);
+
+	startup_cost += qpqual_cost.startup;
+	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+	run_cost += cpu_per_tuple * tuples;
+
+	path->startup_cost = startup_cost;
+	path->total_cost = startup_cost + run_cost;
+}
+
+/*
  * cost_index
  *	  Determines and returns the cost of scanning a relation using an index.
  *
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index cb69c03..3fc84e2 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -58,6 +58,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
+static SampleScan *create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses);
 static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
 					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
@@ -100,6 +102,7 @@ static List *order_qual_clauses(PlannerInfo *root, List *clauses);
 static void copy_path_costsize(Plan *dest, Path *src);
 static void copy_plan_costsize(Plan *dest, Plan *src);
 static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
+static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
@@ -228,6 +231,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	switch (best_path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -343,6 +347,13 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 												scan_clauses);
 			break;
 
+		case T_SampleScan:
+			plan = (Plan *) create_samplescan_plan(root,
+												   best_path,
+												   tlist,
+												   scan_clauses);
+			break;
+
 		case T_IndexScan:
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
@@ -546,6 +557,7 @@ disuse_physical_tlist(PlannerInfo *root, Plan *plan, Path *path)
 	switch (path->pathtype)
 	{
 		case T_SeqScan:
+		case T_SampleScan:
 		case T_IndexScan:
 		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
@@ -1133,6 +1145,45 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
 }
 
 /*
+ * create_samplescan_plan
+ *	 Returns a samplecan plan for the base relation scanned by 'best_path'
+ *	 with restriction clauses 'scan_clauses' and targetlist 'tlist'.
+ */
+static SampleScan *
+create_samplescan_plan(PlannerInfo *root, Path *best_path,
+					List *tlist, List *scan_clauses)
+{
+	SampleScan *scan_plan;
+	Index		scan_relid = best_path->parent->relid;
+
+	/* it should be a base rel with tablesample clause... */
+	Assert(scan_relid > 0);
+	Assert(best_path->parent->rtekind == RTE_RELATION);
+	Assert(best_path->pathtype == T_SampleScan);
+
+	/* Sort clauses into best execution order */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/* Reduce RestrictInfo list to bare expressions; ignore pseudoconstants */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Replace any outer-relation variables with nestloop params */
+	if (best_path->param_info)
+	{
+		scan_clauses = (List *)
+			replace_nestloop_params(root, (Node *) scan_clauses);
+	}
+
+	scan_plan = make_samplescan(tlist,
+								scan_clauses,
+								scan_relid);
+
+	copy_path_costsize(&scan_plan->plan, best_path);
+
+	return scan_plan;
+}
+
+/*
  * create_indexscan_plan
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
@@ -3321,6 +3372,24 @@ make_seqscan(List *qptlist,
 	return node;
 }
 
+static SampleScan *
+make_samplescan(List *qptlist,
+				List *qpqual,
+				Index scanrelid)
+{
+	SampleScan *node = makeNode(SampleScan);
+	Plan	   *plan = &node->plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scanrelid = scanrelid;
+
+	return node;
+}
+
 static IndexScan *
 make_indexscan(List *qptlist,
 			   List *qpqual,
diff --git a/src/backend/optimizer/plan/setrefs.c b/src/backend/optimizer/plan/setrefs.c
index 94b12ab..a2ae940 100644
--- a/src/backend/optimizer/plan/setrefs.c
+++ b/src/backend/optimizer/plan/setrefs.c
@@ -445,6 +445,17 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->plan.qual, rtoffset);
 			}
 			break;
+		case T_SampleScan:
+			{
+				SampleScan	   *splan = (SampleScan *) plan;
+
+				splan->scanrelid += rtoffset;
+				splan->plan.targetlist =
+					fix_scan_list(root, splan->plan.targetlist, rtoffset);
+				splan->plan.qual =
+					fix_scan_list(root, splan->plan.qual, rtoffset);
+			}
+			break;
 		case T_IndexScan:
 			{
 				IndexScan  *splan = (IndexScan *) plan;
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index acfd0bc..9971b54 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -2167,6 +2167,7 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			break;
 
 		case T_SeqScan:
+		case T_SampleScan:
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index faca30b..ea7a47b 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -706,6 +706,26 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
 }
 
 /*
+ * create_samplescan_path
+ *	  Like seqscan but uses sampling function while scanning.
+ */
+Path *
+create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
+{
+	Path		   *pathnode = makeNode(Path);
+
+	pathnode->pathtype = T_SampleScan;
+	pathnode->parent = rel;
+	pathnode->param_info = get_baserel_parampathinfo(root, rel,
+													 required_outer);
+	pathnode->pathkeys = NIL;	/* samplescan has unordered result */
+
+	cost_samplescan(pathnode, root, rel);
+
+	return pathnode;
+}
+
+/*
  * create_index_path
  *	  Creates a path node for an index scan.
  *
@@ -1778,6 +1798,8 @@ reparameterize_path(PlannerInfo *root, Path *path,
 		case T_SubqueryScan:
 			return create_subqueryscan_path(root, rel, path->pathkeys,
 											required_outer);
+		case T_SampleScan:
+			return (Path *) create_samplescan_path(root, rel, required_outer);
 		default:
 			break;
 	}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 5818858..d5405ad 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -448,6 +448,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <range>	relation_expr
 %type <range>	relation_expr_opt_alias
 %type <target>	target_el single_set_clause set_target insert_column_item
+%type <node>	relation_expr_tablesample tablesample_clause opt_repeatable_clause
 
 %type <str>		generic_option_name
 %type <node>	generic_option_arg
@@ -615,8 +616,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
 	SYMMETRIC SYSID SYSTEM_P
 
-	TABLE TABLES TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN TIME TIMESTAMP
-	TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
+	TABLE TABLES TABLESAMPLE TABLESPACE TEMP TEMPLATE TEMPORARY TEXT_P THEN
+	TIME TIMESTAMP TO TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P TYPES_P
 
 	UNBOUNDED UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNLOGGED
@@ -10191,6 +10192,10 @@ table_ref:	relation_expr opt_alias_clause
 					$1->alias = $2;
 					$$ = (Node *) $1;
 				}
+			| relation_expr_tablesample
+				{
+					$$ = (Node *) $1;
+				}
 			| func_table func_alias_clause
 				{
 					RangeFunction *n = (RangeFunction *) $1;
@@ -10516,6 +10521,32 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
+
+relation_expr_tablesample: relation_expr opt_alias_clause tablesample_clause
+				{
+					RangeTableSample *n = (RangeTableSample *) $3;
+					n->relation = $1;
+					n->relation->alias = $2;
+					$$ = (Node *) n;
+				}
+		;
+
+tablesample_clause:
+			TABLESAMPLE ColId '(' expr_list ')' opt_repeatable_clause
+				{
+					RangeTableSample *n = makeNode(RangeTableSample);
+					n->method = $2;
+					n->args = $4;
+					n->repeatable = $6;
+					$$ = (Node *) n;
+				}
+		;
+
+opt_repeatable_clause:
+			REPEATABLE '(' a_expr ')'	{ $$ = (Node *) $3; }
+			| /*EMPTY*/					{ $$ = NULL; }
+		;
+
 /*
  * func_table represents a function invocation in a FROM list. It can be
  * a plain function call, like "foo(...)", or a ROWS FROM expression with
@@ -13606,6 +13637,7 @@ type_func_name_keyword:
 			| OVERLAPS
 			| RIGHT
 			| SIMILAR
+			| TABLESAMPLE
 			| VERBOSE
 		;
 
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 8d90b50..d512ce1 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
 #include "catalog/heap.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -29,6 +30,7 @@
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
 #include "parser/parse_expr.h"
+#include "parser/parse_func.h"
 #include "parser/parse_oper.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
@@ -36,6 +38,7 @@
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 /* Convenience macro for the most common makeNamespaceItem() case */
@@ -414,6 +417,39 @@ transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
 	return result;
 }
 
+static RangeTblEntry *
+transformTableSampleEntry(ParseState *pstate, RangeTableSample *rv)
+{
+	RangeTblEntry   *rte = NULL;
+	CommonTableExpr *cte = NULL;
+	TableSampleClause *tablesample = NULL;
+
+	/* if relation has an unqualified name, it might be a CTE reference */
+	if (!rv->relation->schemaname)
+	{
+		Index	levelsup;
+		cte = scanNameSpaceForCTE(pstate, rv->relation->relname, &levelsup);
+	}
+
+	/* We first need to build a range table entry */
+	if (!cte)
+		rte = transformTableEntry(pstate, rv->relation);
+
+	if (!rte ||
+		(rte->relkind != RELKIND_RELATION &&
+		rte->relkind != RELKIND_MATVIEW))
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("TABLESAMPLE clause can only be used on tables and materialized views"),
+				 parser_errposition(pstate, rv->relation->location)));
+
+	tablesample = ParseTableSample(pstate, rv->method, rv->repeatable,
+								   rv->args, rv->relation->location);
+	rte->tablesample = tablesample;
+
+	return rte;
+}
+
 /*
  * transformTableEntry --- transform a RangeVar (simple relation reference)
  */
@@ -1122,6 +1158,26 @@ transformFromClauseItem(ParseState *pstate, Node *n,
 
 		return (Node *) j;
 	}
+	else if (IsA(n, RangeTableSample))
+	{
+		/* Tablesample reference */
+		RangeTableSample   *rv = (RangeTableSample *) n;
+		RangeTblRef *rtr;
+		RangeTblEntry *rte = NULL;
+		int			rtindex;
+
+		rte = transformTableSampleEntry(pstate, rv);
+
+		/* assume new rte is at end */
+		rtindex = list_length(pstate->p_rtable);
+		Assert(rte == rt_fetch(rtindex, pstate->p_rtable));
+		*top_rte = rte;
+		*top_rti = rtindex;
+		*namespace = list_make1(makeDefaultNSItem(rte));
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = rtindex;
+		return (Node *) rtr;
+	}
 	else
 		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
 	return NULL;				/* can't get here, keep compiler quiet */
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 1385776..ab87635 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -18,6 +18,7 @@
 #include "catalog/pg_aggregate.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_type.h"
+#include "catalog/pg_tablesample_method.h"
 #include "funcapi.h"
 #include "lib/stringinfo.h"
 #include "nodes/makefuncs.h"
@@ -26,6 +27,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
+#include "parser/parse_expr.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
@@ -767,6 +769,147 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 }
 
 
+/*
+ * ParseTableSample
+ *
+ * Parse TABLESAMPLE clause and process the arguments
+ */
+TableSampleClause *
+ParseTableSample(ParseState *pstate, char *samplemethod, Node *repeatable,
+				 List *sampleargs, int location)
+{
+	HeapTuple		tuple;
+	Form_pg_tablesample_method tsm;
+	Form_pg_proc procform;
+	TableSampleClause *tablesample;
+	List		   *fargs;
+	ListCell	   *larg;
+	int				nargs, initnargs;
+	Oid				init_arg_types[FUNC_MAX_ARGS];
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(samplemethod));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						samplemethod),
+				 parser_errposition(pstate, location)));
+
+	tablesample = makeNode(TableSampleClause);
+	tablesample->tsmid = HeapTupleGetOid(tuple);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+
+	tablesample->tsmseqscan = tsm->tsmseqscan;
+	tablesample->tsmpagemode = tsm->tsmpagemode;
+	tablesample->tsminit = tsm->tsminit;
+	tablesample->tsmnextblock = tsm->tsmnextblock;
+	tablesample->tsmnexttuple = tsm->tsmnexttuple;
+	tablesample->tsmexaminetuple = tsm->tsmexaminetuple;
+	tablesample->tsmend = tsm->tsmend;
+	tablesample->tsmreset = tsm->tsmreset;
+	tablesample->tsmcost = tsm->tsmcost;
+
+	ReleaseSysCache(tuple);
+
+	/* Validate the parameters against init function definition. */
+	tuple = SearchSysCache1(PROCOID,
+							ObjectIdGetDatum(tablesample->tsminit));
+
+	if (!HeapTupleIsValid(tuple))	/* should not happen */
+		elog(ERROR, "cache lookup failed for function %u",
+			 tablesample->tsminit);
+
+	procform = (Form_pg_proc) GETSTRUCT(tuple);
+	initnargs = procform->pronargs;
+	Assert(initnargs >= 3);
+
+	/*
+	 * First parameter is used to pass the SampleScanState, second is
+	 * seed (REPEATABLE), skip the processing for them here, just assert
+	 * that the types are correct.
+	 */
+	Assert(procform->proargtypes.values[0] == INTERNALOID);
+	Assert(procform->proargtypes.values[1] == INT4OID);
+	initnargs -= 2;
+	memcpy(init_arg_types, procform->proargtypes.values + 2,
+				   initnargs * sizeof(Oid));
+
+	/* Now we are done with the catalog */
+	ReleaseSysCache(tuple);
+
+	/* Process repeatable (seed) */
+	if (repeatable != NULL)
+	{
+		Node   *arg = repeatable;
+
+		if (arg && IsA(arg, A_Const))
+		{
+			A_Const    *con = (A_Const *) arg;
+
+			if (con->val.type == T_Null)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("REPEATABLE clause must be NOT NULL numeric value"),
+						 parser_errposition(pstate, con->location)));
+
+		}
+
+		arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
+		arg = coerce_to_specific_type(pstate, arg, INT4OID, "REPEATABLE");
+		tablesample->repeatable = arg;
+	}
+	else
+		tablesample->repeatable = NULL;
+
+	/* Check user provided expected number of arguments. */
+	if (list_length(sampleargs) != initnargs)
+		ereport(ERROR,
+				(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
+		 errmsg_plural("tablesample method \"%s\" expects %d argument got %d",
+					   "tablesample method \"%s\" expects %d arguments got %d",
+					   initnargs,
+					   samplemethod,
+					   initnargs, list_length(sampleargs)),
+		 parser_errposition(pstate, location)));
+
+	/* Transform the arguments, typecasting them as needed. */
+	fargs = NIL;
+	nargs = 0;
+	foreach(larg, sampleargs)
+	{
+		Node   *inarg = (Node *) lfirst(larg);
+		Node   *arg = transformExpr(pstate, inarg, EXPR_KIND_FROM_FUNCTION);
+		Oid		argtype = exprType(arg);
+
+		if (argtype != init_arg_types[nargs])
+		{
+			if (!can_coerce_type(1, &argtype, &init_arg_types[nargs],
+								 COERCION_IMPLICIT))
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("wrong parameter %d for tablesample method \"%s\"",
+							nargs + 1, samplemethod),
+					 errdetail("Expected type %s got %s.",
+							   format_type_be(init_arg_types[nargs]),
+							   format_type_be(argtype)),
+					 parser_errposition(pstate, exprLocation(inarg))));
+
+			arg = coerce_type(pstate, arg, argtype, init_arg_types[nargs], -1,
+							  COERCION_IMPLICIT, COERCE_IMPLICIT_CAST, -1);
+		}
+
+		fargs = lappend(fargs, arg);
+		nargs++;
+	}
+
+	/* Pass the arguments down */
+	tablesample->args = fargs;
+
+	return tablesample;
+}
+
 /* func_match_argtypes()
  *
  * Given a list of candidate functions (having the right name and number
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index 9d2c280..385ae9c 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -2160,6 +2160,9 @@ view_query_is_auto_updatable(Query *viewquery, bool check_cols)
 		 base_rte->relkind != RELKIND_VIEW))
 		return gettext_noop("Views that do not select from a single table or view are not automatically updatable.");
 
+	if (base_rte->tablesample)
+		return gettext_noop("Views containing TABLESAMPLE are not automatically updatable.");
+
 	/*
 	 * Check that the view has at least one updatable column. This is required
 	 * for INSERT/UPDATE but not for DELETE.
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 29b5b1b..a6bd34c 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -32,6 +32,7 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
 #include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
@@ -344,6 +345,8 @@ static void make_ruledef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags);
 static void make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 			 int prettyFlags, int wrapColumn);
+static void get_tablesample_def(TableSampleClause *tablesample,
+								deparse_context *context);
 static void get_query_def(Query *query, StringInfo buf, List *parentnamespace,
 			  TupleDesc resultDesc,
 			  int prettyFlags, int wrapColumn, int startIndent);
@@ -4185,6 +4188,50 @@ make_viewdef(StringInfo buf, HeapTuple ruletup, TupleDesc rulettc,
 	heap_close(ev_relation, AccessShareLock);
 }
 
+/* ----------
+ * get_tablesample_def			- Convert TableSampleClause back to SQL
+ * ----------
+ */
+static void
+get_tablesample_def(TableSampleClause *tablesample, deparse_context *context)
+{
+	StringInfo	buf = context->buf;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+	char	   *tsmname;
+	int			nargs;
+	ListCell   *l;
+
+	/* Load the tablesample method */
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tablesample->tsmid));
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("cache lookup failed for tablesample method %u",
+						tablesample->tsmid)));
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	tsmname = NameStr(tsm->tsmname);
+	appendStringInfo(buf, " TABLESAMPLE %s (", quote_identifier(tsmname));
+
+	ReleaseSysCache(tuple);
+
+	nargs = 0;
+	foreach(l, tablesample->args)
+	{
+		if (nargs++ > 0)
+			appendStringInfoString(buf, ", ");
+		get_rule_expr((Node *) lfirst(l), context, true);
+	}
+	appendStringInfoChar(buf, ')');
+
+	if (tablesample->repeatable != NULL)
+	{
+		appendStringInfoString(buf, " REPEATABLE (");
+		get_rule_expr(tablesample->repeatable, context, true);
+		appendStringInfoChar(buf, ')');
+	}
+}
 
 /* ----------
  * get_query_def			- Parse back one query parsetree
@@ -8453,6 +8500,9 @@ get_from_clause_item(Node *jtnode, Query *query, deparse_context *context)
 								 only_marker(rte),
 								 generate_relation_name(rte->relid,
 														context->namespaces));
+
+				if (rte->tablesample)
+					get_tablesample_def(rte->tablesample, context);
 				break;
 			case RTE_SUBQUERY:
 				/* Subquery RTE */
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 6a39863..9be3d64 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -30,6 +30,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_range.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_type.h"
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
@@ -2925,3 +2926,29 @@ get_range_subtype(Oid rangeOid)
 	else
 		return InvalidOid;
 }
+
+/*				---------- PG_TABLESAMPLE_METHOD CACHE ----------			 */
+
+/*
+ * get_tablesample_method_name - given a tablesample method OID,
+ * look up the name or NULL if not found
+ */
+char *
+get_tablesample_method_name(Oid tsmid)
+{
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmid));
+	if (HeapTupleIsValid(tuple))
+	{
+		Form_pg_tablesample_method	tup =
+			(Form_pg_tablesample_method) GETSTRUCT(tuple);
+		char	   *result;
+
+		result = pstrdup(NameStr(tup->tsmname));
+		ReleaseSysCache(tuple);
+		return result;
+	}
+	else
+		return NULL;
+}
diff --git a/src/backend/utils/cache/syscache.c b/src/backend/utils/cache/syscache.c
index bd27168..3a8f01e 100644
--- a/src/backend/utils/cache/syscache.c
+++ b/src/backend/utils/cache/syscache.c
@@ -55,6 +55,7 @@
 #include "catalog/pg_shdescription.h"
 #include "catalog/pg_shseclabel.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_ts_config.h"
 #include "catalog/pg_ts_config_map.h"
@@ -642,6 +643,28 @@ static const struct cachedesc cacheinfo[] = {
 		},
 		128
 	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODNAME */
+		TableSampleMethodNameIndexId,
+		1,
+		{
+			Anum_pg_tablesample_method_tsmname,
+			0,
+			0,
+			0,
+		},
+		2
+	},
+	{TableSampleMethodRelationId,		/* TABLESAMPLEMETHODOID */
+		TableSampleMethodOidIndexId,
+		1,
+		{
+			ObjectIdAttributeNumber,
+			0,
+			0,
+			0,
+		},
+		2
+	},
 	{TableSpaceRelationId,		/* TABLESPACEOID */
 		TablespaceOidIndexId,
 		1,
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
index 1eeabaf..9becc63 100644
--- a/src/backend/utils/misc/sampling.c
+++ b/src/backend/utils/misc/sampling.c
@@ -46,6 +46,8 @@ BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
 	bs->n = samplesize;
 	bs->t = 0;					/* blocks scanned so far */
 	bs->m = 0;					/* blocks selected so far */
+
+	sampler_random_init_state(randseed, bs->randstate);
 }
 
 bool
@@ -92,7 +94,7 @@ BlockSampler_Next(BlockSampler bs)
 	 * less than k, which means that we cannot fail to select enough blocks.
 	 *----------
 	 */
-	V = sampler_random_fract();
+	V = sampler_random_fract(bs->randstate);
 	p = 1.0 - (double) k / (double) K;
 	while (V < p)
 	{
@@ -126,8 +128,14 @@ BlockSampler_Next(BlockSampler bs)
 void
 reservoir_init_selection_state(ReservoirState rs, int n)
 {
+	/*
+	 * Reservoir sampling is not used anywhere where it would need to return
+	 * repeatable results so we can initialize it randomly.
+	 */
+	sampler_random_init_state(random(), rs->randstate);
+
 	/* Initial value of W (for use when Algorithm Z is first applied) */
-	*rs = exp(-log(sampler_random_fract()) / n);
+	rs->W = exp(-log(sampler_random_fract(rs->randstate)) / n);
 }
 
 double
@@ -142,7 +150,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 		double		V,
 					quot;
 
-		V = sampler_random_fract(); /* Generate V */
+		V = sampler_random_fract(rs->randstate); /* Generate V */
 		S = 0;
 		t += 1;
 		/* Note: "num" in Vitter's code is always equal to t - n */
@@ -158,7 +166,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 	else
 	{
 		/* Now apply Algorithm Z */
-		double		W = *rs;
+		double		W = rs->W;
 		double		term = t - (double) n + 1;
 
 		for (;;)
@@ -174,7 +182,7 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 						tmp;
 
 			/* Generate U and X */
-			U = sampler_random_fract();
+			U = sampler_random_fract(rs->randstate);
 			X = t * (W - 1.0);
 			S = floor(X);		/* S is tentatively set to floor(X) */
 			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
@@ -203,11 +211,11 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
 				y *= numer / denom;
 				denom -= 1;
 			}
-			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			W = exp(-log(sampler_random_fract(rs->randstate)) / n);		/* Generate W in advance */
 			if (exp(log(y) / n) <= (t + X) / t)
 				break;
 		}
-		*rs = W;
+		rs->W = W;
 	}
 	return S;
 }
@@ -217,10 +225,17 @@ reservoir_get_next_S(ReservoirState rs, double t, int n)
  * Random number generator used by sampling
  *----------
  */
+void
+sampler_random_init_state(long seed, SamplerRandomState randstate)
+{
+	randstate[0] = RAND48_SEED_0;
+	randstate[1] = (unsigned short) seed;
+	randstate[2] = (unsigned short) (seed >> 16);
+}
 
 /* Select a random value R uniformly distributed in (0 - 1) */
 double
-sampler_random_fract()
+sampler_random_fract(SamplerRandomState randstate)
 {
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+	return pg_erand48(randstate);
 }
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 888cce7..3174cc1 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -113,8 +113,12 @@ extern HeapScanDesc heap_beginscan_strat(Relation relation, Snapshot snapshot,
 					 bool allow_strat, bool allow_sync);
 extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
 				  int nkeys, ScanKey key);
+extern HeapScanDesc heap_beginscan_sampling(Relation relation,
+						Snapshot snapshot, int nkeys, ScanKey key,
+						bool allow_strat, bool allow_pagemode);
 extern void heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk,
 		   BlockNumber endBlk);
+extern void heapgetpage(HeapScanDesc scan, BlockNumber page);
 extern void heap_rescan(HeapScanDesc scan, ScanKey key);
 extern void heap_endscan(HeapScanDesc scan);
 extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 9bb6362..e2b2b4f 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -29,6 +29,7 @@ typedef struct HeapScanDescData
 	int			rs_nkeys;		/* number of scan keys */
 	ScanKey		rs_key;			/* array of scan key descriptors */
 	bool		rs_bitmapscan;	/* true if this is really a bitmap scan */
+	bool		rs_samplescan;	/* true if this is really a sample scan */
 	bool		rs_pageatatime; /* verify visibility page-at-a-time? */
 	bool		rs_allow_strat; /* allow or disallow use of access strategy */
 	bool		rs_allow_sync;	/* allow or disallow use of syncscan */
diff --git a/src/include/access/tablesample.h b/src/include/access/tablesample.h
new file mode 100644
index 0000000..222fa8d
--- /dev/null
+++ b/src/include/access/tablesample.h
@@ -0,0 +1,60 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.h
+ *        Public header file for TABLESAMPLE clause interface
+ *
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/tablesample.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef TABLESAMPLE_H
+#define TABLESAMPLE_H
+
+#include "access/relscan.h"
+#include "executor/executor.h"
+
+typedef struct TableSampleDesc {
+	HeapScanDesc	heapScan;
+	TupleDesc		tupDesc;	/* Mostly useful for tsmexaminetuple */
+
+	void		   *tsmdata;	/* private method data */
+
+	/* These point to he function of the TABLESAMPLE Method. */
+	FmgrInfo		tsminit;
+	FmgrInfo		tsmnextblock;
+	FmgrInfo		tsmnexttuple;
+	FmgrInfo		tsmexaminetuple;
+	FmgrInfo		tsmreset;
+	FmgrInfo		tsmend;
+} TableSampleDesc;
+
+
+extern TableSampleDesc *tablesample_init(SampleScanState *scanstate,
+										 TableSampleClause *tablesample);
+extern HeapTuple tablesample_getnext(TableSampleDesc *desc);
+extern void tablesample_reset(TableSampleDesc *desc);
+extern void tablesample_end(TableSampleDesc *desc);
+extern HeapTuple tablesample_source_getnext(TableSampleDesc *desc);
+extern HeapTuple tablesample_source_gettup(TableSampleDesc *desc, ItemPointer tid,
+										   bool *visible);
+
+extern Datum tsm_system_init(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_system_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_system_end(PG_FUNCTION_ARGS);
+extern Datum tsm_system_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_system_cost(PG_FUNCTION_ARGS);
+
+extern Datum tsm_bernoulli_init(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nextblock(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_nexttuple(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_end(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_reset(PG_FUNCTION_ARGS);
+extern Datum tsm_bernoulli_cost(PG_FUNCTION_ARGS);
+
+
+#endif
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index a680229..e01bd0c 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -305,6 +305,11 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_name_index, 3291, on pg_tablesample_method using btree(tsmname name_ops));
+#define TableSampleMethodNameIndexId  3291
+DECLARE_UNIQUE_INDEX(pg_tablesample_method_oid_index, 3292, on pg_tablesample_method using btree(oid oid_ops));
+#define TableSampleMethodOidIndexId  3292
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 8469c82..1ef8198 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5201,6 +5201,32 @@ DESCR("for use by pg_upgrade");
 DATA(insert OID = 3591 ( binary_upgrade_create_empty_extension PGNSP PGUID  12 1 0 0 0 f f f f t f v 7 0 2278 "25 25 16 25 1028 1009 1009" _null_ _null_ _null_ _null_ binary_upgrade_create_empty_extension _null_ _null_ _null_ ));
 DESCR("for use by pg_upgrade");
 
+/* tablesample */
+DATA(insert OID = 3295 (  tsm_system_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_system_init _null_ _null_ _null_ ));
+DESCR("tsm_system_init(internal)");
+DATA(insert OID = 3296 (  tsm_system_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_system_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_system_nextblock(internal)");
+DATA(insert OID = 3297 (  tsm_system_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_system_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_system_nexttuple(internal)");
+DATA(insert OID = 3298 (  tsm_system_end		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_end _null_ _null_ _null_ ));
+DESCR("tsm_system_end(internal)");
+DATA(insert OID = 3299 (  tsm_system_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_system_reset _null_ _null_ _null_ ));
+DESCR("tsm_system_reset(internal)");
+DATA(insert OID = 3300 (  tsm_system_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_system_cost _null_ _null_ _null_ ));
+DESCR("tsm_system_cost(internal)");
+
+DATA(insert OID = 3301 (  tsm_bernoulli_init		PGNSP PGUID 12 1 0 0 0 f f f f t f v 3 0 2278 "2281 23 700" _null_ _null_ _null_ _null_	tsm_bernoulli_init _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_init(internal)");
+DATA(insert OID = 3302 (  tsm_bernoulli_nextblock	PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 23 "2281 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nextblock _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nextblock(internal)");
+DATA(insert OID = 3303 (  tsm_bernoulli_nexttuple	PGNSP PGUID 12 1 0 0 0 f f f f t f v 4 0 21 "2281 23 21 16" _null_ _null_ _null_ _null_	tsm_bernoulli_nexttuple _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_nexttuple(internal)");
+DATA(insert OID = 3304 (  tsm_bernoulli_end			PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_end _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_end(internal)");
+DATA(insert OID = 3306 (  tsm_bernoulli_reset		PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "2281" _null_ _null_ _null_ _null_	tsm_bernoulli_reset _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_reset(internal)");
+DATA(insert OID = 3307 (  tsm_bernoulli_cost		PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_	tsm_bernoulli_cost _null_ _null_ _null_ ));
+DESCR("tsm_bernoulli_cost(internal)");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
new file mode 100644
index 0000000..a58e1cf
--- /dev/null
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -0,0 +1,78 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_tablesample_method.h
+ *	  definition of the table scan methods.
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_tablesample_method.h
+ *
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_TABLESAMPLE_METHOD_H
+#define PG_TABLESAMPLE_METHOD_H
+
+#include "catalog/genbki.h"
+#include "catalog/objectaddress.h"
+
+/* ----------------
+ *		pg_tablesample_method definition.  cpp turns this into
+ *		typedef struct FormData_pg_tablesample_method
+ * ----------------
+ */
+#define TableSampleMethodRelationId	3290
+
+CATALOG(pg_tablesample_method,3290)
+{
+	NameData	tsmname;		/* tablesample method name */
+	bool		tsmseqscan;		/* does this method scan whole table sequentially? */
+	bool		tsmpagemode;	/* does this method scan page at a time? */
+	regproc		tsminit;		/* init scan function */
+	regproc		tsmnextblock;	/* function returning next block to sample
+								   or InvalidBlockOffset if finished */
+	regproc		tsmnexttuple;	/* function returning next tuple offset from current block
+								   or InvalidOffsetNumber if end of the block was reacher */
+	regproc		tsmexaminetuple;	/* optional function which can examine tuple contents and
+								   decide if tuple should be returned or not */
+	regproc		tsmend;			/* end scan function*/
+	regproc		tsmreset;		/* reset state - used by rescan */
+	regproc		tsmcost;		/* costing function */
+} FormData_pg_tablesample_method;
+
+/* ----------------
+ *		Form_pg_tablesample_method corresponds to a pointer to a tuple with
+ *		the format of pg_tablesample_method relation.
+ * ----------------
+ */
+typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
+
+/* ----------------
+ *		compiler constants for pg_tablesample_method
+ * ----------------
+ */
+#define Natts_pg_tablesample_method					10
+#define Anum_pg_tablesample_method_tsmname			1
+#define Anum_pg_tablesample_method_tsmseqscan		2
+#define Anum_pg_tablesample_method_tsmpagemode		3
+#define Anum_pg_tablesample_method_tsminit			4
+#define Anum_pg_tablesample_method_tsmnextblock		5
+#define Anum_pg_tablesample_method_tsmnexttuple		6
+#define Anum_pg_tablesample_method_tsmexaminetuple	7
+#define Anum_pg_tablesample_method_tsmend			8
+#define Anum_pg_tablesample_method_tsmreset			9
+#define Anum_pg_tablesample_method_tsmcost			10
+
+/* ----------------
+ *		initial contents of pg_tablesample_method
+ * ----------------
+ */
+
+DATA(insert OID = 3293 ( system false true tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
+DESCR("SYSTEM table sampling method");
+DATA(insert OID = 3294 ( bernoulli true false tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
+DESCR("BERNOULLI table sampling method");
+
+#endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/executor/nodeSamplescan.h b/src/include/executor/nodeSamplescan.h
new file mode 100644
index 0000000..4b769da
--- /dev/null
+++ b/src/include/executor/nodeSamplescan.h
@@ -0,0 +1,24 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeSamplescan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeSamplescan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODESAMPLESCAN_H
+#define NODESAMPLESCAN_H
+
+#include "nodes/execnodes.h"
+
+extern SampleScanState *ExecInitSampleScan(SampleScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecSampleScan(SampleScanState *node);
+extern void ExecEndSampleScan(SampleScanState *node);
+extern void ExecReScanSampleScan(SampleScanState *node);
+
+#endif   /* NODESAMPLESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index ac75f86..3697e21 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1216,6 +1216,15 @@ typedef struct ScanState
 typedef ScanState SeqScanState;
 
 /*
+ * SampleScan
+ */
+typedef struct SampleScanState
+{
+	ScanState	ss;
+	struct TableSampleDesc *tsdesc;
+} SampleScanState;
+
+/*
  * These structs store information about index quals that don't have simple
  * constant right-hand sides.  See comments for ExecIndexBuildScanKeys()
  * for discussion.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 38469ef..caaedbf 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -61,6 +61,7 @@ typedef enum NodeTag
 	T_ValuesScan,
 	T_CteScan,
 	T_WorkTableScan,
+	T_SampleScan,
 	T_ForeignScan,
 	T_CustomScan,
 	T_Join,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_BitmapOrState,
 	T_ScanState,
 	T_SeqScanState,
+	T_SampleScanState,
 	T_IndexScanState,
 	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
@@ -414,6 +416,8 @@ typedef enum NodeTag
 	T_WithClause,
 	T_CommonTableExpr,
 	T_RoleSpec,
+	T_RangeTableSample,
+	T_TableSampleClause,
 
 	/*
 	 * TAGS FOR REPLICATION GRAMMAR PARSE NODES (replnodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 0e257ac..aea499e 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -334,6 +334,26 @@ typedef struct FuncCall
 } FuncCall;
 
 /*
+ * TableSampleClause - a sampling method information
+ */
+typedef struct TableSampleClause
+{
+	NodeTag		type;
+	Oid			tsmid;
+	bool		tsmseqscan;
+	bool		tsmpagemode;
+	Oid			tsminit;
+	Oid			tsmnextblock;
+	Oid			tsmnexttuple;
+	Oid			tsmexaminetuple;
+	Oid			tsmend;
+	Oid			tsmreset;
+	Oid			tsmcost;
+	Node	   *repeatable;
+	List	   *args;
+} TableSampleClause;
+
+/*
  * A_Star - '*' representing all columns of a table or compound field
  *
  * This can appear within ColumnRef.fields, A_Indirection.indirection, and
@@ -534,6 +554,22 @@ typedef struct RangeFunction
 } RangeFunction;
 
 /*
+ * RangeTableSample - represents <table> TABLESAMPLE <method> (<params>) REPEATABLE (<num>)
+ *
+ * SQL Standard specifies only one parameter which is percentage. But we allow
+ * custom tablesample methods which may need different input arguments so we
+ * accept list of arguments.
+ */
+typedef struct RangeTableSample
+{
+	NodeTag		type;
+	RangeVar   *relation;
+	char	   *method;		/* sampling method */
+	Node	   *repeatable;
+	List	   *args;		/* arguments for sampling method */
+} RangeTableSample;
+
+/*
  * ColumnDef - column definition (used in various creates)
  *
  * If the column has a default value, we may have the value expression
@@ -769,6 +805,7 @@ typedef struct RangeTblEntry
 	 */
 	Oid			relid;			/* OID of the relation */
 	char		relkind;		/* relation kind (see pg_class.relkind) */
+	TableSampleClause	*tablesample;	/* sampling method and parameters */
 
 	/*
 	 * Fields valid for a subquery RTE (else NULL):
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 21cbfa8..ddc3708 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -279,6 +279,12 @@ typedef struct Scan
 typedef Scan SeqScan;
 
 /* ----------------
+ *		table sample scan node
+ * ----------------
+ */
+typedef Scan SampleScan;
+
+/* ----------------
  *		index scan node
  *
  * indexqualorig is an implicitly-ANDed list of index qual expressions, each
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 9c2000b..24003ae 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -68,6 +68,7 @@ extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
 					double index_pages, PlannerInfo *root);
 extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
 			 ParamPathInfo *param_info);
+extern void cost_samplescan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
 extern void cost_index(IndexPath *path, PlannerInfo *root,
 		   double loop_count);
 extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 9923f0e..89c8ded 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -32,6 +32,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
 
 extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
 					Relids required_outer);
+extern Path *create_samplescan_path(PlannerInfo *root, RelOptInfo *rel,
+									Relids required_outer);
 extern IndexPath *create_index_path(PlannerInfo *root,
 				  IndexOptInfo *index,
 				  List *indexclauses,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 7c243ec..ae90df8 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -366,6 +366,7 @@ PG_KEYWORD("sysid", SYSID, UNRESERVED_KEYWORD)
 PG_KEYWORD("system", SYSTEM_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("table", TABLE, RESERVED_KEYWORD)
 PG_KEYWORD("tables", TABLES, UNRESERVED_KEYWORD)
+PG_KEYWORD("tablesample", TABLESAMPLE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("tablespace", TABLESPACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("temp", TEMP, UNRESERVED_KEYWORD)
 PG_KEYWORD("template", TEMPLATE, UNRESERVED_KEYWORD)
diff --git a/src/include/parser/parse_func.h b/src/include/parser/parse_func.h
index 3264691..40c007c 100644
--- a/src/include/parser/parse_func.h
+++ b/src/include/parser/parse_func.h
@@ -33,6 +33,11 @@ typedef enum
 extern Node *ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 				  FuncCall *fn, int location);
 
+extern TableSampleClause *ParseTableSample(ParseState *pstate,
+										   char *samplemethod,
+										   Node *repeatable, List *args,
+										   int location);
+
 extern FuncDetailCode func_get_detail(List *funcname,
 				List *fargs, List *fargnames,
 				int nargs, Oid *argtypes,
diff --git a/src/include/port.h b/src/include/port.h
index 3787cbf..71113c0 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -357,6 +357,10 @@ extern off_t ftello(FILE *stream);
 #endif
 #endif
 
+#define RAND48_SEED_0	(0x330e)
+#define RAND48_SEED_1	(0xabcd)
+#define RAND48_SEED_2	(0x1234)
+
 extern double pg_erand48(unsigned short xseed[3]);
 extern long pg_lrand48(void);
 extern void pg_srand48(long seed);
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 15bb6d9..ea1aa11 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -153,6 +153,7 @@ extern void free_attstatsslot(Oid atttype,
 extern char *get_namespace_name(Oid nspid);
 extern char *get_namespace_name_or_temp(Oid nspid);
 extern Oid	get_range_subtype(Oid rangeOid);
+extern char *get_tablesample_method_name(Oid tsmid);
 
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 9e17d87..fd40366 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -63,7 +63,6 @@ typedef struct RelationAmInfo
 	FmgrInfo	amcanreturn;
 } RelationAmInfo;
 
-
 /*
  * Here are the contents of a relation cache entry.
  */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
index e3e7f9c..4ac208d 100644
--- a/src/include/utils/sampling.h
+++ b/src/include/utils/sampling.h
@@ -15,7 +15,12 @@
 
 #include "storage/bufmgr.h"
 
-extern double sampler_random_fract(void);
+/* Random generator for sampling code */
+typedef unsigned short SamplerRandomState[3];
+
+extern void sampler_random_init_state(long seed,
+									  SamplerRandomState randstate);
+extern double sampler_random_fract(SamplerRandomState randstate);
 
 /* Block sampling methods */
 /* Data structure for Algorithm S from Knuth 3.4.2 */
@@ -25,6 +30,7 @@ typedef struct
 	int			n;				/* desired sample size */
 	BlockNumber t;				/* current block number */
 	int			m;				/* blocks selected so far */
+	SamplerRandomState randstate; /* random generator state */
 } BlockSamplerData;
 
 typedef BlockSamplerData *BlockSampler;
@@ -35,7 +41,12 @@ extern bool BlockSampler_HasMore(BlockSampler bs);
 extern BlockNumber BlockSampler_Next(BlockSampler bs);
 
 /* Reservoid sampling methods */
-typedef double ReservoirStateData;
+typedef struct
+{
+	double	W;
+	SamplerRandomState randstate; /* random generator state */
+} ReservoirStateData;
+
 typedef ReservoirStateData *ReservoirState;
 
 extern void reservoir_init_selection_state(ReservoirState rs, int n);
diff --git a/src/include/utils/syscache.h b/src/include/utils/syscache.h
index ba0b090..6b628f6 100644
--- a/src/include/utils/syscache.h
+++ b/src/include/utils/syscache.h
@@ -79,6 +79,8 @@ enum SysCacheIdentifier
 	RELOID,
 	RULERELNAME,
 	STATRELATTINH,
+	TABLESAMPLEMETHODNAME,
+	TABLESAMPLEMETHODOID,
 	TABLESPACEOID,
 	TSCONFIGMAP,
 	TSCONFIGNAMENSP,
diff --git a/src/port/erand48.c b/src/port/erand48.c
index 9d47119..12efd81 100644
--- a/src/port/erand48.c
+++ b/src/port/erand48.c
@@ -33,9 +33,6 @@
 
 #include <math.h>
 
-#define RAND48_SEED_0	(0x330e)
-#define RAND48_SEED_1	(0xabcd)
-#define RAND48_SEED_2	(0x1234)
 #define RAND48_MULT_0	(0xe66d)
 #define RAND48_MULT_1	(0xdeec)
 #define RAND48_MULT_2	(0x0005)
diff --git a/src/test/regress/expected/rowsecurity.out b/src/test/regress/expected/rowsecurity.out
index 44e8dab..79e98f7 100644
--- a/src/test/regress/expected/rowsecurity.out
+++ b/src/test/regress/expected/rowsecurity.out
@@ -101,6 +101,17 @@ NOTICE:  f_leak => great manga
   44 |   8 |      1 | rls_regress_user2 | great manga           | manga
 (4 rows)
 
+SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
+NOTICE:  f_leak => my first novel
+NOTICE:  f_leak => my first manga
+NOTICE:  f_leak => great science fiction
+ did | cid | dlevel |      dauthor      |        dtitle         
+-----+-----+--------+-------------------+-----------------------
+   1 |  11 |      1 | rls_regress_user1 | my first novel
+   4 |  44 |      1 | rls_regress_user1 | my first manga
+   6 |  22 |      1 | rls_regress_user2 | great science fiction
+(3 rows)
+
 -- viewpoint from rls_regress_user2
 SET SESSION AUTHORIZATION rls_regress_user2;
 SELECT * FROM document WHERE f_leak(dtitle) ORDER BY did;
@@ -145,6 +156,21 @@ NOTICE:  f_leak => great manga
   44 |   8 |      1 | rls_regress_user2 | great manga           | manga
 (8 rows)
 
+SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
+NOTICE:  f_leak => my first novel
+NOTICE:  f_leak => my second novel
+NOTICE:  f_leak => my first manga
+NOTICE:  f_leak => great science fiction
+NOTICE:  f_leak => great technology book
+ did | cid | dlevel |      dauthor      |        dtitle         
+-----+-----+--------+-------------------+-----------------------
+   1 |  11 |      1 | rls_regress_user1 | my first novel
+   2 |  11 |      2 | rls_regress_user1 | my second novel
+   4 |  44 |      1 | rls_regress_user1 | my first manga
+   6 |  22 |      1 | rls_regress_user2 | great science fiction
+   7 |  33 |      2 | rls_regress_user2 | great technology book
+(5 rows)
+
 EXPLAIN (COSTS OFF) SELECT * FROM document WHERE f_leak(dtitle);
                         QUERY PLAN                        
 ----------------------------------------------------------
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index c7be273..5946edf 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -127,6 +127,7 @@ pg_shdepend|t
 pg_shdescription|t
 pg_shseclabel|t
 pg_statistic|t
+pg_tablesample_method|t
 pg_tablespace|t
 pg_trigger|t
 pg_ts_config|t
diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
new file mode 100644
index 0000000..271638d
--- /dev/null
+++ b/src/test/regress/expected/tablesample.out
@@ -0,0 +1,216 @@
+CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+ id 
+----
+  6
+  7
+  8
+(3 rows)
+
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+ count 
+-------
+    10
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  2
+  6
+  7
+  8
+  9
+(7 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+ id 
+----
+  0
+  1
+  3
+  4
+  5
+(5 rows)
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ id 
+----
+  0
+  5
+(2 rows)
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+                                 pg_get_viewdef                                 
+--------------------------------------------------------------------------------
+  SELECT test_tablesample.id                                                   +
+    FROM test_tablesample TABLESAMPLE system (((10 * 2))::real) REPEATABLE (2);
+(1 row)
+
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+                      pg_get_viewdef                       
+-----------------------------------------------------------
+  SELECT test_tablesample.id                              +
+    FROM test_tablesample TABLESAMPLE system ((99)::real);
+(1 row)
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+ id 
+----
+  0
+  1
+  2
+  3
+  4
+  5
+  9
+(7 rows)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+FETCH FIRST FROM tablesample_cur;
+ id 
+----
+  0
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  1
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  2
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  6
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  7
+(1 row)
+
+FETCH NEXT FROM tablesample_cur;
+ id 
+----
+  8
+(1 row)
+
+CLOSE tablesample_cur;
+END;
+EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+                                  QUERY PLAN                                   
+-------------------------------------------------------------------------------
+ Sample Scan (system) on test_tablesample  (cost=0.00..26.35 rows=635 width=4)
+(1 row)
+
+EXPLAIN SELECT * FROM test_tablesample_v1;
+                                  QUERY PLAN                                   
+-------------------------------------------------------------------------------
+ Sample Scan (system) on test_tablesample  (cost=0.00..10.54 rows=254 width=4)
+(1 row)
+
+-- errors
+SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
+ERROR:  tablesample method "foobar" does not exist
+LINE 1: SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
+                       ^
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
+ERROR:  REPEATABLE clause must be NOT NULL numeric value
+LINE 1: ... test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
+                                                                 ^
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (-1);
+ERROR:  invalid sample size
+HINT:  Sample size must be numeric value between 0 and 100 (inclusive).
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (200);
+ERROR:  invalid sample size
+HINT:  Sample size must be numeric value between 0 and 100 (inclusive).
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (-1);
+ERROR:  invalid sample size
+HINT:  Sample size must be numeric value between 0 and 100 (inclusive).
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (200);
+ERROR:  invalid sample size
+HINT:  Sample size must be numeric value between 0 and 100 (inclusive).
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+ERROR:  TABLESAMPLE clause can only be used on tables and materialized views
+LINE 1: SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1)...
+                       ^
+INSERT INTO test_tablesample_v1 VALUES(1);
+ERROR:  cannot insert into view "test_tablesample_v1"
+DETAIL:  Views containing TABLESAMPLE are not automatically updatable.
+HINT:  To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule.
+WITH query_select AS (SELECT * FROM test_tablesample)
+SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+ERROR:  TABLESAMPLE clause can only be used on tables and materialized views
+LINE 2: SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEA...
+                      ^
+SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);
+ERROR:  syntax error at or near "TABLESAMPLE"
+LINE 1: ...CT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPL...
+                                                             ^
+-- done
+DROP TABLE test_tablesample CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to view test_tablesample_v1
+drop cascades to view test_tablesample_v2
diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index 6d3b865..300e1fb 100644
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -83,7 +83,7 @@ test: select_into select_distinct select_distinct_on select_implicit select_havi
 # ----------
 # Another group of parallel tests
 # ----------
-test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address
+test: brin gin gist spgist privileges security_label collate matview lock replica_identity rowsecurity object_address tablesample
 
 # ----------
 # Another group of parallel tests
diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index 8326894..d815496 100644
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -153,3 +153,4 @@ test: with
 test: xml
 test: event_trigger
 test: stats
+test: tablesample
diff --git a/src/test/regress/sql/rowsecurity.sql b/src/test/regress/sql/rowsecurity.sql
index ed7adbf..71ad21f 100644
--- a/src/test/regress/sql/rowsecurity.sql
+++ b/src/test/regress/sql/rowsecurity.sql
@@ -94,11 +94,15 @@ SET row_security TO ON;
 SELECT * FROM document WHERE f_leak(dtitle) ORDER BY did;
 SELECT * FROM document NATURAL JOIN category WHERE f_leak(dtitle) ORDER BY did;
 
+SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
+
 -- viewpoint from rls_regress_user2
 SET SESSION AUTHORIZATION rls_regress_user2;
 SELECT * FROM document WHERE f_leak(dtitle) ORDER BY did;
 SELECT * FROM document NATURAL JOIN category WHERE f_leak(dtitle) ORDER BY did;
 
+SELECT * FROM document TABLESAMPLE BERNOULLI (50) REPEATABLE(1) WHERE f_leak(dtitle) ORDER BY did;
+
 EXPLAIN (COSTS OFF) SELECT * FROM document WHERE f_leak(dtitle);
 EXPLAIN (COSTS OFF) SELECT * FROM document NATURAL JOIN category WHERE f_leak(dtitle);
 
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
new file mode 100644
index 0000000..2f4b7de
--- /dev/null
+++ b/src/test/regress/sql/tablesample.sql
@@ -0,0 +1,61 @@
+CREATE TABLE test_tablesample (id int, name text) WITH (fillfactor=10); -- force smaller pages so we don't have to load too much data to get multiple pages
+
+INSERT INTO test_tablesample SELECT i, repeat(i::text, 200) FROM generate_series(0, 9) s(i) ORDER BY i;
+
+SELECT t.id FROM test_tablesample AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (100.0/11) REPEATABLE (9999);
+SELECT count(*) FROM test_tablesample TABLESAMPLE SYSTEM (100);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (50) REPEATABLE (100);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+CREATE VIEW test_tablesample_v1 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (10*2) REPEATABLE (2);
+CREATE VIEW test_tablesample_v2 AS SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (99);
+SELECT pg_get_viewdef('test_tablesample_v1'::regclass);
+SELECT pg_get_viewdef('test_tablesample_v2'::regclass);
+
+BEGIN;
+DECLARE tablesample_cur CURSOR FOR SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (100);
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+FETCH FIRST FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+FETCH NEXT FROM tablesample_cur;
+
+CLOSE tablesample_cur;
+END;
+
+EXPLAIN SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (10);
+EXPLAIN SELECT * FROM test_tablesample_v1;
+
+-- errors
+SELECT id FROM test_tablesample TABLESAMPLE FOOBAR (1);
+
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (50) REPEATABLE (NULL);
+
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (-1);
+SELECT id FROM test_tablesample TABLESAMPLE BERNOULLI (200);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (-1);
+SELECT id FROM test_tablesample TABLESAMPLE SYSTEM (200);
+
+SELECT id FROM test_tablesample_v1 TABLESAMPLE BERNOULLI (1);
+INSERT INTO test_tablesample_v1 VALUES(1);
+
+WITH query_select AS (SELECT * FROM test_tablesample)
+SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
+
+SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);
+
+-- done
+DROP TABLE test_tablesample CASCADE;
-- 
1.9.1

>From eb0e40665f3bb2946cac2d539dc4e9dd4d135ca8 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:51:44 +0100
Subject: [PATCH 6/6] tablesample-ddl v8

---
 doc/src/sgml/ref/allfiles.sgml                     |   2 +
 doc/src/sgml/ref/create_tablesamplemethod.sgml     | 184 ++++++++++
 doc/src/sgml/ref/drop_tablesamplemethod.sgml       |  87 +++++
 doc/src/sgml/reference.sgml                        |   2 +
 src/backend/catalog/dependency.c                   |  15 +-
 src/backend/catalog/objectaddress.c                |  65 +++-
 src/backend/commands/Makefile                      |   6 +-
 src/backend/commands/dropcmds.c                    |   4 +
 src/backend/commands/event_trigger.c               |   3 +
 src/backend/commands/tablecmds.c                   |   1 +
 src/backend/commands/tablesample.c                 | 398 +++++++++++++++++++++
 src/backend/parser/gram.y                          |  14 +-
 src/backend/tcop/utility.c                         |  12 +
 src/backend/utils/cache/lsyscache.c                |  31 ++
 src/bin/pg_dump/common.c                           |   5 +
 src/bin/pg_dump/pg_dump.c                          | 177 +++++++++
 src/bin/pg_dump/pg_dump.h                          |  11 +-
 src/bin/pg_dump/pg_dump_sort.c                     |  11 +-
 src/include/catalog/dependency.h                   |   1 +
 src/include/catalog/pg_tablesample_method.h        |  10 +
 src/include/nodes/parsenodes.h                     |   1 +
 src/include/parser/kwlist.h                        |   1 +
 src/include/utils/lsyscache.h                      |   1 +
 src/test/modules/Makefile                          |   3 +-
 src/test/modules/tablesample/.gitignore            |   4 +
 src/test/modules/tablesample/Makefile              |  21 ++
 .../modules/tablesample/expected/tablesample.out   |  38 ++
 src/test/modules/tablesample/sql/tablesample.sql   |  14 +
 src/test/modules/tablesample/tsm_test--1.0.sql     |  52 +++
 src/test/modules/tablesample/tsm_test.c            | 224 ++++++++++++
 src/test/modules/tablesample/tsm_test.control      |   5 +
 31 files changed, 1392 insertions(+), 11 deletions(-)
 create mode 100644 doc/src/sgml/ref/create_tablesamplemethod.sgml
 create mode 100644 doc/src/sgml/ref/drop_tablesamplemethod.sgml
 create mode 100644 src/backend/commands/tablesample.c
 create mode 100644 src/test/modules/tablesample/.gitignore
 create mode 100644 src/test/modules/tablesample/Makefile
 create mode 100644 src/test/modules/tablesample/expected/tablesample.out
 create mode 100644 src/test/modules/tablesample/sql/tablesample.sql
 create mode 100644 src/test/modules/tablesample/tsm_test--1.0.sql
 create mode 100644 src/test/modules/tablesample/tsm_test.c
 create mode 100644 src/test/modules/tablesample/tsm_test.control

diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index 211a3c4..93950c5 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -78,6 +78,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY createServer       SYSTEM "create_server.sgml">
 <!ENTITY createTable        SYSTEM "create_table.sgml">
 <!ENTITY createTableAs      SYSTEM "create_table_as.sgml">
+<!ENTITY createTablesampleMethod SYSTEM "create_tablesamplemethod.sgml">
 <!ENTITY createTableSpace   SYSTEM "create_tablespace.sgml">
 <!ENTITY createTrigger      SYSTEM "create_trigger.sgml">
 <!ENTITY createTSConfig     SYSTEM "create_tsconfig.sgml">
@@ -119,6 +120,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY dropSequence       SYSTEM "drop_sequence.sgml">
 <!ENTITY dropServer         SYSTEM "drop_server.sgml">
 <!ENTITY dropTable          SYSTEM "drop_table.sgml">
+<!ENTITY dropTablesampleMethod SYSTEM "drop_tablesamplemethod.sgml">
 <!ENTITY dropTableSpace     SYSTEM "drop_tablespace.sgml">
 <!ENTITY dropTrigger        SYSTEM "drop_trigger.sgml">
 <!ENTITY dropTSConfig       SYSTEM "drop_tsconfig.sgml">
diff --git a/doc/src/sgml/ref/create_tablesamplemethod.sgml b/doc/src/sgml/ref/create_tablesamplemethod.sgml
new file mode 100644
index 0000000..ff105d2
--- /dev/null
+++ b/doc/src/sgml/ref/create_tablesamplemethod.sgml
@@ -0,0 +1,184 @@
+<!--
+doc/src/sgml/ref/create_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-CREATETABLESAMPLEMETHOD">
+ <indexterm zone="sql-createtablesamplemethod">
+  <primary>CREATE TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE TABLESAMPLE METHOD</refname>
+  <refpurpose>define custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE TABLESAMPLE METHOD <replaceable class="parameter">name</replaceable> (
+    INIT = <replaceable class="parameter">init_function</replaceable> ,
+    NEXTBLOCK = <replaceable class="parameter">nextblock_function</replaceable> ,
+    NEXTTUPLE = <replaceable class="parameter">nexttuple_function</replaceable> ,
+    END = <replaceable class="parameter">end_function</replaceable> ,
+    RESET = <replaceable class="parameter">reset_function</replaceable> ,
+    COST = <replaceable class="parameter">cost_function</replaceable>
+    [ , EXAMINETUPLE = <replaceable class="parameter">examinetuple_function</replaceable> ]
+    [ , SEQSCAN = <replaceable class="parameter">seqscan</replaceable> ]
+    [ , PAGEMODE = <replaceable class="parameter">pagemode</replaceable> ]
+)
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE TABLESAMPLE METHOD</command> creates a tablesample method.
+   A tablesample method provides alrorithm for reading sample part of a table
+   when used in <command>TABLESAMPLE</> clause of a <command>SELECT</>
+   statement.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the tablesample method to be created. This name must be
+      unique within the database.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">init_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the init function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nextblock_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-block function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">nexttuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the get-next-tuple function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">end_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the end function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">reset_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the reset function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">cost_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the costing function for the tablesample method.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">examinetuple_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of the function for inspecting the tuple contents in order
+      to make decision if it should be returned or not. This parameter
+      is optional.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">seqscan</replaceable></term>
+    <listitem>
+     <para>
+      True if the sampling method will do sequential scan of the whole table.
+      Used for cost estimation and syncscan. The default value if not specified
+      is False.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">pagemode</replaceable></term>
+    <listitem>
+     <para>
+      True if the sampling method will read whole page at a time. The default
+      value if not specified is False.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+  <para>
+   The function names can be schema-qualified if necessary.  Argument types
+   are not given, since the argument list for each type of function is
+   predetermined.  All functions are required.
+  </para>
+
+  <para>
+   The arguments can appear in any order, not only the one shown above.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>CREATE TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-droptablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/ref/drop_tablesamplemethod.sgml b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
new file mode 100644
index 0000000..dffd2ec
--- /dev/null
+++ b/doc/src/sgml/ref/drop_tablesamplemethod.sgml
@@ -0,0 +1,87 @@
+<!--
+doc/src/sgml/ref/drop_tablesamplemethod.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-DROPTABLESAMPLEMETHOD">
+ <indexterm zone="sql-droptablesamplemethod">
+  <primary>DROP TABLESAMPLE METHOD</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DROP TABLESAMPLE METHOD</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP TABLESAMPLE METHOD</refname>
+  <refpurpose>remove a custom tablesample method</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP TABLESAMPLE METHOD [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>DROP TABLESAMPLE METHOD</command> drop an existing tablesample
+   method.
+  </para>
+
+  <para>
+   You must be a superuser to use <command>CREATE TABLESAMPLE METHOD</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the tablesample method does not exist.
+      A notice is issued in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name of an existing tablesample method to be removed.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   There is no
+   <command>DROP TABLESAMPLE METHOD</command> statement in the SQL
+   standard.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createtablesamplemethod"></member>
+   <member><xref linkend="sql-select"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index fb18d94..0b576ad 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -106,6 +106,7 @@
    &createServer;
    &createTable;
    &createTableAs;
+   &createTablesampleMethod;
    &createTableSpace;
    &createTSConfig;
    &createTSDictionary;
@@ -147,6 +148,7 @@
    &dropSequence;
    &dropServer;
    &dropTable;
+   &dropTablesampleMethod;
    &dropTableSpace;
    &dropTSConfig;
    &dropTSDictionary;
diff --git a/src/backend/catalog/dependency.c b/src/backend/catalog/dependency.c
index bacb242..6acb5b3 100644
--- a/src/backend/catalog/dependency.c
+++ b/src/backend/catalog/dependency.c
@@ -46,6 +46,7 @@
 #include "catalog/pg_policy.h"
 #include "catalog/pg_proc.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -157,7 +158,8 @@ static const Oid object_classes[MAX_OCLASS] = {
 	DefaultAclRelationId,		/* OCLASS_DEFACL */
 	ExtensionRelationId,		/* OCLASS_EXTENSION */
 	EventTriggerRelationId,		/* OCLASS_EVENT_TRIGGER */
-	PolicyRelationId			/* OCLASS_POLICY */
+	PolicyRelationId,			/* OCLASS_POLICY */
+	TableSampleMethodRelationId			/* OCLASS_TABLESAMPLEMETHOD */
 };
 
 
@@ -1265,6 +1267,10 @@ doDeletion(const ObjectAddress *object, int flags)
 			RemovePolicyById(object->objectId);
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			RemoveTablesampleMethodById(object->objectId);
+			break;
+
 		default:
 			elog(ERROR, "unrecognized object class: %u",
 				 object->classId);
@@ -1794,6 +1800,10 @@ find_expr_references_walker(Node *node,
 				case RTE_RELATION:
 					add_object_address(OCLASS_CLASS, rte->relid, 0,
 									   context->addrs);
+					if (rte->tablesample)
+						add_object_address(OCLASS_TABLESAMPLEMETHOD,
+										   rte->tablesample->tsmid, 0,
+										   context->addrs);
 					break;
 				default:
 					break;
@@ -2373,6 +2383,9 @@ getObjectClass(const ObjectAddress *object)
 
 		case PolicyRelationId:
 			return OCLASS_POLICY;
+
+		case TableSampleMethodRelationId:
+			return OCLASS_TABLESAMPLEMETHOD;
 	}
 
 	/* shouldn't get here */
diff --git a/src/backend/catalog/objectaddress.c b/src/backend/catalog/objectaddress.c
index 30cb699..f936332 100644
--- a/src/backend/catalog/objectaddress.c
+++ b/src/backend/catalog/objectaddress.c
@@ -44,6 +44,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_policy.h"
 #include "catalog/pg_rewrite.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_ts_config.h"
@@ -429,7 +430,19 @@ static const ObjectPropertyType ObjectProperty[] =
 		Anum_pg_type_typacl,
 		ACL_KIND_TYPE,
 		true
-	}
+	},
+	{
+		TableSampleMethodRelationId,
+		TableSampleMethodOidIndexId,
+		TABLESAMPLEMETHODOID,
+		TABLESAMPLEMETHODNAME,
+		Anum_pg_tablesample_method_tsmname,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		InvalidAttrNumber,
+		-1,
+		true
+	},
 };
 
 /*
@@ -528,7 +541,9 @@ ObjectTypeMap[] =
 	/* OCLASS_EVENT_TRIGGER */
 	{ "event trigger", OBJECT_EVENT_TRIGGER },
 	/* OCLASS_POLICY */
-	{ "policy", OBJECT_POLICY }
+	{ "policy", OBJECT_POLICY },
+	/* OCLASS_TABLESAMPLEMETHOD */
+	{ "tablesample method", OBJECT_TABLESAMPLEMETHOD }
 };
 
 const ObjectAddress InvalidObjectAddress =
@@ -683,6 +698,7 @@ get_object_address(ObjectType objtype, List *objname, List *objargs,
 			case OBJECT_FDW:
 			case OBJECT_FOREIGN_SERVER:
 			case OBJECT_EVENT_TRIGGER:
+			case OBJECT_TABLESAMPLEMETHOD:
 				address = get_object_address_unqualified(objtype,
 														 objname, missing_ok);
 				break;
@@ -921,6 +937,9 @@ get_object_address_unqualified(ObjectType objtype,
 			case OBJECT_EVENT_TRIGGER:
 				msg = gettext_noop("event trigger name cannot be qualified");
 				break;
+			case OBJECT_TABLESAMPLEMETHOD:
+				msg = gettext_noop("tablesample method name cannot be qualified");
+				break;
 			default:
 				elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 				msg = NULL;		/* placate compiler */
@@ -981,6 +1000,11 @@ get_object_address_unqualified(ObjectType objtype,
 			address.objectId = get_event_trigger_oid(name, missing_ok);
 			address.objectSubId = 0;
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			address.classId = TableSampleMethodRelationId;
+			address.objectId = get_tablesample_method_oid(name, missing_ok);
+			address.objectSubId = 0;
+			break;
 		default:
 			elog(ERROR, "unrecognized objtype: %d", (int) objtype);
 			/* placate compiler, which doesn't know elog won't return */
@@ -2044,6 +2068,7 @@ check_object_ownership(Oid roleid, ObjectType objtype, ObjectAddress address,
 			break;
 		case OBJECT_TSPARSER:
 		case OBJECT_TSTEMPLATE:
+		case OBJECT_TABLESAMPLEMETHOD:
 			/* We treat these object types as being owned by superusers */
 			if (!superuser_arg(roleid))
 				ereport(ERROR,
@@ -2982,6 +3007,21 @@ getObjectDescription(const ObjectAddress *object)
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				appendStringInfo(&buffer, _("tablesample method %s"),
+					 NameStr(((Form_pg_tablesample_method) GETSTRUCT(tup))->tsmname));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
@@ -3459,6 +3499,10 @@ getObjectTypeDescription(const ObjectAddress *object)
 			appendStringInfoString(&buffer, "policy");
 			break;
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			appendStringInfoString(&buffer, "tablesample method");
+			break;
+
 		default:
 			appendStringInfo(&buffer, "unrecognized %u", object->classId);
 			break;
@@ -4381,6 +4425,23 @@ getObjectIdentityParts(const ObjectAddress *object,
 				break;
 			}
 
+		case OCLASS_TABLESAMPLEMETHOD:
+			{
+				HeapTuple	tup;
+				Form_pg_tablesample_method tsmForm;
+
+				tup = SearchSysCache1(TABLESAMPLEMETHODOID,
+									  ObjectIdGetDatum(object->objectId));
+				if (!HeapTupleIsValid(tup))
+					elog(ERROR, "cache lookup failed for tablesample method %u",
+						 object->objectId);
+				tsmForm = (Form_pg_tablesample_method) GETSTRUCT(tup);
+				appendStringInfoString(&buffer,
+							   quote_identifier(NameStr(tsmForm->tsmname)));
+				ReleaseSysCache(tup);
+				break;
+			}
+
 		default:
 			appendStringInfo(&buffer, "unrecognized object %u %u %d",
 							 object->classId,
diff --git a/src/backend/commands/Makefile b/src/backend/commands/Makefile
index b1ac704..04fcd8c 100644
--- a/src/backend/commands/Makefile
+++ b/src/backend/commands/Makefile
@@ -18,8 +18,8 @@ OBJS = aggregatecmds.o alter.o analyze.o async.o cluster.o comment.o  \
 	event_trigger.o explain.o extension.o foreigncmds.o functioncmds.o \
 	indexcmds.o lockcmds.o matview.o operatorcmds.o opclasscmds.o \
 	policy.o portalcmds.o prepare.o proclang.o \
-	schemacmds.o seclabel.o sequence.o tablecmds.o tablespace.o trigger.o \
-	tsearchcmds.o typecmds.o user.o vacuum.o vacuumlazy.o \
-	variable.o view.o
+	schemacmds.o seclabel.o sequence.o tablecmds.o tablesample.o \
+	tablespace.o trigger.o tsearchcmds.o typecmds.o user.o vacuum.o \
+	vacuumlazy.o variable.o view.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/commands/dropcmds.c b/src/backend/commands/dropcmds.c
index a1b0d4d..c307dcf 100644
--- a/src/backend/commands/dropcmds.c
+++ b/src/backend/commands/dropcmds.c
@@ -429,6 +429,10 @@ does_not_exist_skipping(ObjectType objtype, List *objname, List *objargs)
 				}
 			}
 			break;
+		case OBJECT_TABLESAMPLEMETHOD:
+			msg = gettext_noop("tablesample method \"%s\" does not exist, skipping");
+			name = NameListToString(objname);
+			break;
 		default:
 			elog(ERROR, "unexpected object type (%d)", (int) objtype);
 			break;
diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c
index f07fd06..5a8d286 100644
--- a/src/backend/commands/event_trigger.c
+++ b/src/backend/commands/event_trigger.c
@@ -97,6 +97,7 @@ static event_trigger_support_data event_trigger_support[] = {
 	{"SEQUENCE", true},
 	{"SERVER", true},
 	{"TABLE", true},
+	{"TABLESAMPLE METHOD", true},
 	{"TABLESPACE", false},
 	{"TRIGGER", true},
 	{"TEXT SEARCH CONFIGURATION", true},
@@ -1090,6 +1091,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_SEQUENCE:
 		case OBJECT_TABCONSTRAINT:
 		case OBJECT_TABLE:
+		case OBJECT_TABLESAMPLEMETHOD:
 		case OBJECT_TRIGGER:
 		case OBJECT_TSCONFIGURATION:
 		case OBJECT_TSDICTIONARY:
@@ -1147,6 +1149,7 @@ EventTriggerSupportsObjectClass(ObjectClass objclass)
 		case OCLASS_DEFACL:
 		case OCLASS_EXTENSION:
 		case OCLASS_POLICY:
+		case OCLASS_TABLESAMPLEMETHOD:
 			return true;
 
 		case MAX_OCLASS:
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 06e4332..e527caf 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8236,6 +8236,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 			case OCLASS_USER_MAPPING:
 			case OCLASS_DEFACL:
 			case OCLASS_EXTENSION:
+			case OCLASS_TABLESAMPLEMETHOD:
 
 				/*
 				 * We don't expect any of these sorts of objects to depend on
diff --git a/src/backend/commands/tablesample.c b/src/backend/commands/tablesample.c
new file mode 100644
index 0000000..33581f6
--- /dev/null
+++ b/src/backend/commands/tablesample.c
@@ -0,0 +1,398 @@
+/*-------------------------------------------------------------------------
+ *
+ * tablesample.c
+ *	  Commands to manipulate tablesample methods
+ *
+ * Table sampling methods provide algorithms for doing sample scan over
+ * the table.
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/tablesample.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "access/heapam.h"
+#include "access/htup_details.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/objectaccess.h"
+#include "catalog/pg_proc.h"
+#include "catalog/pg_tablesample_method.h"
+#include "catalog/pg_type.h"
+#include "commands/defrem.h"
+#include "miscadmin.h"
+#include "parser/parse_func.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+
+
+static Datum
+get_tablesample_method_func(DefElem *defel, int attnum)
+{
+	List	   *funcName = defGetQualifiedName(defel);
+	/* Big enough size for our needs. */
+	Oid		   *typeId = palloc0(7 * sizeof(Oid));
+	Oid			retTypeId;
+	int			nargs;
+	Oid			procOid = InvalidOid;
+	FuncCandidateList clist;
+
+	switch (attnum)
+	{
+		case Anum_pg_tablesample_method_tsminit:
+			/*
+			 * tsminit needs special handling because it is defined as function
+			 * with 3 or more arguments and only first two arguments must have
+			 * specific type, the rest is up to the tablesample method creator.
+			 */
+			{
+				nargs = 2;
+				typeId[0] = INTERNALOID;
+				typeId[1] = INT4OID;
+				retTypeId = VOIDOID;
+
+				clist = FuncnameGetCandidates(funcName, -1, NIL, false, false, false);
+
+				while (clist)
+				{
+					if (clist->nargs >= 3 &&
+						memcmp(typeId, clist->args, nargs * sizeof(Oid)) == 0)
+					{
+						procOid = clist->oid;
+						/* Save real function signature for future errors. */
+						nargs = clist->nargs;
+						pfree(typeId);
+						typeId = clist->args;
+						break;
+					}
+					clist = clist->next;
+				}
+
+				if (!OidIsValid(procOid))
+					ereport(ERROR,
+							(errcode(ERRCODE_UNDEFINED_FUNCTION),
+							 errmsg("function \"%s\" does not exist or does not have valid signature",
+									NameListToString(funcName)),
+							 errhint("The tamplesample method init function "
+									 "must have at least 3 input parameters "
+									 "with first one of type INTERNAL and second of type INTEGER.")));
+			}
+			break;
+
+		case Anum_pg_tablesample_method_tsmnextblock:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = INT4OID;
+			break;
+		case Anum_pg_tablesample_method_tsmnexttuple:
+			nargs = 3;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INT2OID;
+			retTypeId = INT2OID;
+			break;
+		case Anum_pg_tablesample_method_tsmexaminetuple:
+			nargs = 4;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INT4OID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = BOOLOID;
+			retTypeId = BOOLOID;
+			break;
+		case Anum_pg_tablesample_method_tsmend:
+		case Anum_pg_tablesample_method_tsmreset:
+			nargs = 1;
+			typeId[0] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		case Anum_pg_tablesample_method_tsmcost:
+			nargs = 7;
+			typeId[0] = INTERNALOID;
+			typeId[1] = INTERNALOID;
+			typeId[2] = INTERNALOID;
+			typeId[3] = INTERNALOID;
+			typeId[4] = INTERNALOID;
+			typeId[5] = INTERNALOID;
+			typeId[6] = INTERNALOID;
+			retTypeId = VOIDOID;
+			break;
+		default:
+			/* should not be here */
+			elog(ERROR, "unrecognized attribute for tablesample method: %d",
+				 attnum);
+			nargs = 0;			/* keep compiler quiet */
+	}
+
+	if (!OidIsValid(procOid))
+		procOid = LookupFuncName(funcName, nargs, typeId, false);
+	if (get_func_rettype(procOid) != retTypeId)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("function %s should return type %s",
+						func_signature_string(funcName, nargs, NIL, typeId),
+						format_type_be(retTypeId))));
+
+	return ObjectIdGetDatum(procOid);
+}
+
+/*
+ * make pg_depend entries for a new pg_tablesample_method entry
+ */
+static void
+makeTablesampleMethodDeps(HeapTuple tuple)
+{
+	Form_pg_tablesample_method tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	ObjectAddress	myself,
+					referenced;
+
+	myself.classId = TableSampleMethodRelationId;
+	myself.objectId = HeapTupleGetOid(tuple);
+	myself.objectSubId = 0;
+
+	/* dependency on extension */
+	recordDependencyOnCurrentExtension(&myself, false);
+
+	/* dependencies on functions */
+	referenced.classId = ProcedureRelationId;
+	referenced.objectSubId = 0;
+
+	referenced.objectId = tsm->tsminit;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnextblock;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmnexttuple;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	if (OidIsValid(tsm->tsmexaminetuple))
+	{
+		referenced.objectId = tsm->tsmexaminetuple;
+		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+	}
+
+	referenced.objectId = tsm->tsmend;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmreset;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+
+	referenced.objectId = tsm->tsmcost;
+	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
+}
+
+/*
+ * Create a table sampling method
+ *
+ * Only superusers can create a table sampling methods.
+ */
+ObjectAddress
+DefineTablesampleMethod(List *names, List *parameters)
+{
+	char	   *tsmname = strVal(linitial(names));
+	Oid			tsmoid;
+	ListCell   *pl;
+	Relation	rel;
+	Datum		values[Natts_pg_tablesample_method];
+	bool		nulls[Natts_pg_tablesample_method];
+	HeapTuple	tuple;
+	ObjectAddress address;
+
+	/* Must be super user. */
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied to create tablesample method \"%s\"",
+						tsmname),
+				 errhint("Must be superuser to create a tablesample method.")));
+
+	/* Must not already exist. */
+	tsmoid = get_tablesample_method_oid(tsmname, true);
+	if (OidIsValid(tsmoid))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" already exists",
+						tsmname)));
+
+	/* Initialize the values. */
+	memset(values, 0, sizeof(values));
+	memset(nulls, false, sizeof(nulls));
+
+	values[Anum_pg_tablesample_method_tsmname - 1] =
+		DirectFunctionCall1(namein, CStringGetDatum(tsmname));
+
+	/*
+	 * loop over the definition list and extract the information we need.
+	 */
+	foreach(pl, parameters)
+	{
+		DefElem    *defel = (DefElem *) lfirst(pl);
+
+		if (pg_strcasecmp(defel->defname, "seqscan") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmseqscan - 1] =
+				BoolGetDatum(defGetBoolean(defel));
+		}
+		else if (pg_strcasecmp(defel->defname, "pagemode") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmpagemode - 1] =
+				BoolGetDatum(defGetBoolean(defel));
+		}
+		else if (pg_strcasecmp(defel->defname, "init") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsminit - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsminit);
+		}
+		else if (pg_strcasecmp(defel->defname, "nextblock") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnextblock - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnextblock);
+		}
+		else if (pg_strcasecmp(defel->defname, "nexttuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmnexttuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmnexttuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "examinetuple") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmexaminetuple - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmexaminetuple);
+		}
+		else if (pg_strcasecmp(defel->defname, "end") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmend - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmend);
+		}
+		else if (pg_strcasecmp(defel->defname, "reset") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmreset - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmreset);
+		}
+		else if (pg_strcasecmp(defel->defname, "cost") == 0)
+		{
+			values[Anum_pg_tablesample_method_tsmcost - 1] =
+				get_tablesample_method_func(defel,
+					Anum_pg_tablesample_method_tsmcost);
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("tablesample method parameter \"%s\" not recognized",
+						defel->defname)));
+	}
+
+	/*
+	 * Validation.
+	 */
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsminit - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method init function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnextblock - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nextblock function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmnexttuple - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method nexttuple function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmend - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method end function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmreset - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method reset function is required")));
+
+	if (!OidIsValid(DatumGetObjectId(values[Anum_pg_tablesample_method_tsmcost - 1])))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("tablesample method cost function is required")));
+
+	/*
+	 * Insert tuple into pg_tablesample_method.
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = heap_form_tuple(rel->rd_att, values, nulls);
+
+	tsmoid = simple_heap_insert(rel, tuple);
+
+	CatalogUpdateIndexes(rel, tuple);
+
+	makeTablesampleMethodDeps(tuple);
+
+	heap_freetuple(tuple);
+
+	/* Post creation hook for new tablesample method */
+	InvokeObjectPostCreateHook(TableSampleMethodRelationId, tsmoid, 0);
+
+	ObjectAddressSet(address, TableSampleMethodRelationId, tsmoid);
+
+	heap_close(rel, RowExclusiveLock);
+
+	return address;
+}
+
+/*
+ * Drop a tablesample method.
+ */
+void
+RemoveTablesampleMethodById(Oid tsmoid)
+{
+	Relation	rel;
+	HeapTuple	tuple;
+	Form_pg_tablesample_method tsm;
+
+	/*
+	 * Find the target tuple
+	 */
+	rel = heap_open(TableSampleMethodRelationId, RowExclusiveLock);
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODOID, ObjectIdGetDatum(tsmoid));
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for tablesample method %u",
+			 tsmoid);
+
+	tsm = (Form_pg_tablesample_method) GETSTRUCT(tuple);
+	/* Can't drop builtin tablesample methods. */
+	if (tsmoid == TABLESAMPLE_METHOD_SYSTEM_OID ||
+		tsmoid == TABLESAMPLE_METHOD_BERNOULLI_OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("permission denied for tablesample method %s",
+						NameStr(tsm->tsmname))));
+
+	/*
+	 * Remove the pg_tablespace tuple (this will roll back if we fail below)
+	 */
+	simple_heap_delete(rel, &tuple->t_self);
+
+	ReleaseSysCache(tuple);
+
+	heap_close(rel, RowExclusiveLock);
+}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index d5405ad..acb1f18 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -590,7 +590,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
-	MAPPING MATCH MATERIALIZED MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
+	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P
+	MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEXT NO NONE
 	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
@@ -5103,6 +5104,15 @@ DefineStmt:
 					n->definition = list_make1(makeDefElem("from", (Node *) $5));
 					$$ = (Node *)n;
 				}
+			| CREATE TABLESAMPLE METHOD name definition
+				{
+					DefineStmt *n = makeNode(DefineStmt);
+					n->kind = OBJECT_TABLESAMPLEMETHOD;
+					n->args = NIL;
+					n->defnames = list_make1(makeString($4));
+					n->definition = $5;
+					$$ = (Node *)n;
+				}
 		;
 
 definition: '(' def_list ')'						{ $$ = $2; }
@@ -5557,6 +5567,7 @@ drop_type:	TABLE									{ $$ = OBJECT_TABLE; }
 			| TEXT_P SEARCH DICTIONARY				{ $$ = OBJECT_TSDICTIONARY; }
 			| TEXT_P SEARCH TEMPLATE				{ $$ = OBJECT_TSTEMPLATE; }
 			| TEXT_P SEARCH CONFIGURATION			{ $$ = OBJECT_TSCONFIGURATION; }
+			| TABLESAMPLE METHOD					{ $$ = OBJECT_TABLESAMPLEMETHOD; }
 		;
 
 any_name_list:
@@ -13410,6 +13421,7 @@ unreserved_keyword:
 			| MATCH
 			| MATERIALIZED
 			| MAXVALUE
+			| METHOD
 			| MINUTE_P
 			| MINVALUE
 			| MODE
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index fd09d3a..cadf6b4 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -23,6 +23,7 @@
 #include "access/xlog.h"
 #include "catalog/catalog.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_tablesample_method.h"
 #include "catalog/toasting.h"
 #include "commands/alter.h"
 #include "commands/async.h"
@@ -1136,6 +1137,11 @@ ProcessUtilitySlow(Node *parsetree,
 							Assert(stmt->args == NIL);
 							DefineCollation(stmt->defnames, stmt->definition);
 							break;
+						case OBJECT_TABLESAMPLEMETHOD:
+							Assert(stmt->args == NIL);
+							Assert(list_length(stmt->defnames) == 1);
+							DefineTablesampleMethod(stmt->defnames, stmt->definition);
+							break;
 						default:
 							elog(ERROR, "unrecognized define stmt type: %d",
 								 (int) stmt->kind);
@@ -2004,6 +2010,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_POLICY:
 					tag = "DROP POLICY";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "DROP TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
@@ -2100,6 +2109,9 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_COLLATION:
 					tag = "CREATE COLLATION";
 					break;
+				case OBJECT_TABLESAMPLEMETHOD:
+					tag = "CREATE TABLESAMPLE METHOD";
+					break;
 				default:
 					tag = "???";
 			}
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 9be3d64..2c90997 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -2930,6 +2930,37 @@ get_range_subtype(Oid rangeOid)
 /*				---------- PG_TABLESAMPLE_METHOD CACHE ----------			 */
 
 /*
+ * get_tablesample_method_oid - given a tablesample method name,
+ * look up the OID
+ *
+ * If missing_ok is false, throw an error if tablesample method name not found.
+ * If true, just return InvalidOid.
+ */
+Oid
+get_tablesample_method_oid(const char *tsmname, bool missing_ok)
+{
+	Oid			result;
+	HeapTuple	tuple;
+
+	tuple = SearchSysCache1(TABLESAMPLEMETHODNAME, PointerGetDatum(tsmname));
+	if (HeapTupleIsValid(tuple))
+	{
+		result = HeapTupleGetOid(tuple);
+		ReleaseSysCache(tuple);
+	}
+	else
+		result = InvalidOid;
+
+	if (!OidIsValid(result) && !missing_ok)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("tablesample method \"%s\" does not exist",
+						tsmname)));
+
+	return result;
+}
+
+/*
  * get_tablesample_method_name - given a tablesample method OID,
  * look up the name or NULL if not found
  */
diff --git a/src/bin/pg_dump/common.c b/src/bin/pg_dump/common.c
index 1a0a587..8a64e4b 100644
--- a/src/bin/pg_dump/common.c
+++ b/src/bin/pg_dump/common.c
@@ -103,6 +103,7 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 	int			numForeignServers;
 	int			numDefaultACLs;
 	int			numEventTriggers;
+	int			numTSMs;
 
 	if (g_verbose)
 		write_msg(NULL, "reading schemas\n");
@@ -251,6 +252,10 @@ getSchemaData(Archive *fout, DumpOptions *dopt, int *numTablesPtr)
 		write_msg(NULL, "reading policies\n");
 	getPolicies(fout, tblinfo, numTables);
 
+	if (g_verbose)
+		write_msg(NULL, "reading tablesample methods\n");
+	getTableSampleMethods(fout, &numTSMs);
+
 	*numTablesPtr = numTables;
 	return tblinfo;
 }
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index fe08c1b..69ca267 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -182,6 +182,7 @@ static void dumpSequenceData(Archive *fout, TableDataInfo *tdinfo);
 static void dumpIndex(Archive *fout, DumpOptions *dopt, IndxInfo *indxinfo);
 static void dumpConstraint(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
 static void dumpTableConstraintComment(Archive *fout, DumpOptions *dopt, ConstraintInfo *coninfo);
+static void dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tbinfo);
 static void dumpTSParser(Archive *fout, DumpOptions *dopt, TSParserInfo *prsinfo);
 static void dumpTSDictionary(Archive *fout, DumpOptions *dopt, TSDictInfo *dictinfo);
 static void dumpTSTemplate(Archive *fout, DumpOptions *dopt, TSTemplateInfo *tmplinfo);
@@ -7134,6 +7135,78 @@ getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tblinfo, int numTable
 }
 
 /*
+ * getTableSampleMethods:
+ *	  read all tablesample methods in the system catalogs and return them
+ *	  in the TSMInfo* structure
+ *
+ *	numTSMs is set to the number of tablesample methods read in
+ */
+TSMInfo *
+getTableSampleMethods(Archive *fout, int *numTSMs)
+{
+	PGresult   *res;
+	int			ntups;
+	int			i;
+	PQExpBuffer query;
+	TSMInfo	   *tsminfo;
+	int			i_tableoid,
+				i_oid,
+				i_tsmname,
+				i_tsmseqscan,
+				i_tsmpagemode;
+
+	/* Before 9.5, there were no tablesample methods */
+	if (fout->remoteVersion < 90500)
+	{
+		*numTSMs = 0;
+		return NULL;
+	}
+
+	query = createPQExpBuffer();
+
+	appendPQExpBuffer(query,
+					  "SELECT tableoid, oid, tsmname, tsmseqscan, tsmpagemode "
+					  "FROM pg_catalog.pg_tablesample_method "
+					  "WHERE oid >= '%u'::pg_catalog.oid",
+					  FirstNormalObjectId);
+
+	res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
+
+	ntups = PQntuples(res);
+	*numTSMs = ntups;
+
+	tsminfo = (TSMInfo *) pg_malloc(ntups * sizeof(TSMInfo));
+
+	i_tableoid = PQfnumber(res, "tableoid");
+	i_oid = PQfnumber(res, "oid");
+	i_tsmname = PQfnumber(res, "tsmname");
+	i_tsmseqscan = PQfnumber(res, "tsmseqscan");
+	i_tsmpagemode = PQfnumber(res, "tsmpagemode");
+
+	for (i = 0; i < ntups; i++)
+	{
+		tsminfo[i].dobj.objType = DO_TABLESAMPLE_METHOD;
+		tsminfo[i].dobj.catId.tableoid = atooid(PQgetvalue(res, i, i_tableoid));
+		tsminfo[i].dobj.catId.oid = atooid(PQgetvalue(res, i, i_oid));
+		AssignDumpId(&tsminfo[i].dobj);
+		tsminfo[i].dobj.name = pg_strdup(PQgetvalue(res, i, i_tsmname));
+		tsminfo[i].dobj.namespace = NULL;
+		tsminfo[i].tsmseqscan = PQgetvalue(res, i, i_tsmseqscan)[0] == 't';
+		tsminfo[i].tsmpagemode = PQgetvalue(res, i, i_tsmpagemode)[0] == 't';
+
+		/* Decide whether we want to dump it */
+		selectDumpableObject(&(tsminfo[i].dobj));
+	}
+
+	PQclear(res);
+
+	destroyPQExpBuffer(query);
+
+	return tsminfo;
+}
+
+
+/*
  * Test whether a column should be printed as part of table's CREATE TABLE.
  * Column number is zero-based.
  *
@@ -8226,6 +8299,9 @@ dumpDumpableObject(Archive *fout, DumpOptions *dopt, DumpableObject *dobj)
 		case DO_POLICY:
 			dumpPolicy(fout, dopt, (PolicyInfo *) dobj);
 			break;
+		case DO_TABLESAMPLE_METHOD:
+			dumpTableSampleMethod(fout, dopt, (TSMInfo *) dobj);
+			break;
 		case DO_PRE_DATA_BOUNDARY:
 		case DO_POST_DATA_BOUNDARY:
 			/* never dumped, nothing to do */
@@ -12226,6 +12302,106 @@ dumpAgg(Archive *fout, DumpOptions *dopt, AggInfo *agginfo)
 }
 
 /*
+ * dumpTableSampleMethod
+ *	  write the declaration of one user-defined tablesample method
+ */
+static void
+dumpTableSampleMethod(Archive *fout, DumpOptions *dopt, TSMInfo *tsminfo)
+{
+	PGresult   *res;
+	PQExpBuffer q;
+	PQExpBuffer delq;
+	PQExpBuffer labelq;
+	PQExpBuffer query;
+	char	   *tsminit;
+	char	   *tsmnextblock;
+	char	   *tsmnexttuple;
+	char	   *tsmexaminetuple;
+	char	   *tsmend;
+	char	   *tsmreset;
+	char	   *tsmcost;
+
+	/* Skip if not to be dumped */
+	if (!tsminfo->dobj.dump || dopt->dataOnly)
+		return;
+
+	q = createPQExpBuffer();
+	delq = createPQExpBuffer();
+	labelq = createPQExpBuffer();
+	query = createPQExpBuffer();
+
+	/* Make sure we are in proper schema */
+	selectSourceSchema(fout, "pg_catalog");
+
+	appendPQExpBuffer(query, "SELECT tsminit, tsmnextblock, "
+							 "tsmnexttuple, tsmexaminetuple, "
+							 "tsmend, tsmreset, tsmcost "
+							 "FROM pg_catalog.pg_tablesample_method "
+							 "WHERE oid = '%u'::pg_catalog.oid",
+							 tsminfo->dobj.catId.oid);
+
+	res = ExecuteSqlQueryForSingleRow(fout, query->data);
+
+	tsminit = PQgetvalue(res, 0, PQfnumber(res, "tsminit"));
+	tsmnexttuple = PQgetvalue(res, 0, PQfnumber(res, "tsmnexttuple"));
+	tsmnextblock = PQgetvalue(res, 0, PQfnumber(res, "tsmnextblock"));
+	tsmexaminetuple = PQgetvalue(res, 0, PQfnumber(res, "tsmexaminetuple"));
+	tsmend = PQgetvalue(res, 0, PQfnumber(res, "tsmend"));
+	tsmreset = PQgetvalue(res, 0, PQfnumber(res, "tsmreset"));
+	 tsmcost = PQgetvalue(res, 0, PQfnumber(res, "tsmcost"));
+
+	appendPQExpBuffer(q, "CREATE TABLESAMPLE METHOD %s (\n",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(q, "    INIT = %s,\n", tsminit);
+	appendPQExpBuffer(q, "    NEXTTUPLE = %s,\n", tsmnexttuple);
+	appendPQExpBuffer(q, "    NEXTBLOCK = %s,\n", tsmnextblock);
+	appendPQExpBuffer(q, "    END = %s,\n", tsmend);
+	appendPQExpBuffer(q, "    RESET = %s,\n", tsmreset);
+	appendPQExpBuffer(q, "    COST = %s", tsmcost);
+
+	if (strcmp(tsmexaminetuple, "-") != 0)
+		appendPQExpBuffer(q, ",\n    EXAMINETUPLE = %s", tsmexaminetuple);
+
+	if (tsminfo->tsmseqscan)
+		appendPQExpBufferStr(q, ",\n    SEQSCAN = true");
+
+	if (tsminfo->tsmpagemode)
+		appendPQExpBufferStr(q, ",\n    PAGEMODE = true");
+
+	appendPQExpBufferStr(q, "\n);");
+
+	appendPQExpBuffer(delq, "DROP TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	appendPQExpBuffer(labelq, "TABLESAMPLE METHOD %s",
+					  fmtId(tsminfo->dobj.name));
+
+	if (dopt->binary_upgrade)
+		binary_upgrade_extension_member(q, &tsminfo->dobj, labelq->data);
+
+	ArchiveEntry(fout, tsminfo->dobj.catId, tsminfo->dobj.dumpId,
+				 tsminfo->dobj.name,
+				 NULL,
+				 NULL,
+				 "",
+				 false, "TABLESAMPLE METHOD", SECTION_PRE_DATA,
+				 q->data, delq->data, NULL,
+				 NULL, 0,
+				 NULL, NULL);
+
+	/* Dump Parser Comments */
+	dumpComment(fout, dopt, labelq->data,
+				NULL, "",
+				tsminfo->dobj.catId, 0, tsminfo->dobj.dumpId);
+
+	PQclear(res);
+	destroyPQExpBuffer(q);
+	destroyPQExpBuffer(delq);
+	destroyPQExpBuffer(labelq);
+}
+
+/*
  * dumpTSParser
  *	  write out a single text search parser
  */
@@ -15659,6 +15835,7 @@ addBoundaryDependencies(DumpableObject **dobjs, int numObjs,
 			case DO_FDW:
 			case DO_FOREIGN_SERVER:
 			case DO_BLOB:
+			case DO_TABLESAMPLE_METHOD:
 				/* Pre-data objects: must come before the pre-data boundary */
 				addObjectDependency(preDataBound, dobj->dumpId);
 				break;
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index a9d3c10..87bef24 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -76,7 +76,8 @@ typedef enum
 	DO_POST_DATA_BOUNDARY,
 	DO_EVENT_TRIGGER,
 	DO_REFRESH_MATVIEW,
-	DO_POLICY
+	DO_POLICY,
+	DO_TABLESAMPLE_METHOD
 } DumpableObjectType;
 
 typedef struct _dumpableObject
@@ -383,6 +384,13 @@ typedef struct _inhInfo
 	Oid			inhparent;		/* OID of its parent */
 } InhInfo;
 
+typedef struct _tsmInfo
+{
+	DumpableObject dobj;
+	bool		tsmseqscan;
+	bool		tsmpagemode;
+} TSMInfo;
+
 typedef struct _prsInfo
 {
 	DumpableObject dobj;
@@ -536,6 +544,7 @@ extern ProcLangInfo *getProcLangs(Archive *fout, int *numProcLangs);
 extern CastInfo *getCasts(Archive *fout, DumpOptions *dopt, int *numCasts);
 extern void getTableAttrs(Archive *fout, DumpOptions *dopt, TableInfo *tbinfo, int numTables);
 extern bool shouldPrintColumn(DumpOptions *dopt, TableInfo *tbinfo, int colno);
+extern TSMInfo *getTableSampleMethods(Archive *fout, int *numTSMs);
 extern TSParserInfo *getTSParsers(Archive *fout, int *numTSParsers);
 extern TSDictInfo *getTSDictionaries(Archive *fout, int *numTSDicts);
 extern TSTemplateInfo *getTSTemplates(Archive *fout, int *numTSTemplates);
diff --git a/src/bin/pg_dump/pg_dump_sort.c b/src/bin/pg_dump/pg_dump_sort.c
index c5ed593..9567cf6 100644
--- a/src/bin/pg_dump/pg_dump_sort.c
+++ b/src/bin/pg_dump/pg_dump_sort.c
@@ -73,7 +73,8 @@ static const int oldObjectTypePriority[] =
 	13,							/* DO_POST_DATA_BOUNDARY */
 	20,							/* DO_EVENT_TRIGGER */
 	15,							/* DO_REFRESH_MATVIEW */
-	21							/* DO_POLICY */
+	21,							/* DO_POLICY */
+	5							/* DO_TABLESAMPLE_METHOD */
 };
 
 /*
@@ -122,7 +123,8 @@ static const int newObjectTypePriority[] =
 	25,							/* DO_POST_DATA_BOUNDARY */
 	32,							/* DO_EVENT_TRIGGER */
 	33,							/* DO_REFRESH_MATVIEW */
-	34							/* DO_POLICY */
+	34,							/* DO_POLICY */
+	17							/* DO_TABLESAMPLE_METHOD */
 };
 
 static DumpId preDataBoundId;
@@ -1460,6 +1462,11 @@ describeDumpableObject(DumpableObject *obj, char *buf, int bufsize)
 					 "POLICY (ID %d OID %u)",
 					 obj->dumpId, obj->catId.oid);
 			return;
+		case DO_TABLESAMPLE_METHOD:
+			snprintf(buf, bufsize,
+					 "TABLESAMPLE METHOD %s  (ID %d OID %u)",
+					 obj->name, obj->dumpId, obj->catId.oid);
+			return;
 		case DO_PRE_DATA_BOUNDARY:
 			snprintf(buf, bufsize,
 					 "PRE-DATA BOUNDARY  (ID %d)",
diff --git a/src/include/catalog/dependency.h b/src/include/catalog/dependency.h
index 6481ac8..30653f8 100644
--- a/src/include/catalog/dependency.h
+++ b/src/include/catalog/dependency.h
@@ -148,6 +148,7 @@ typedef enum ObjectClass
 	OCLASS_EXTENSION,			/* pg_extension */
 	OCLASS_EVENT_TRIGGER,		/* pg_event_trigger */
 	OCLASS_POLICY,				/* pg_policy */
+	OCLASS_TABLESAMPLEMETHOD,	/* pg_tablesample_method */
 	MAX_OCLASS					/* MUST BE LAST */
 } ObjectClass;
 
diff --git a/src/include/catalog/pg_tablesample_method.h b/src/include/catalog/pg_tablesample_method.h
index a58e1cf..82c15f3 100644
--- a/src/include/catalog/pg_tablesample_method.h
+++ b/src/include/catalog/pg_tablesample_method.h
@@ -72,7 +72,17 @@ typedef FormData_pg_tablesample_method *Form_pg_tablesample_method;
 
 DATA(insert OID = 3293 ( system false true tsm_system_init tsm_system_nextblock tsm_system_nexttuple - tsm_system_end tsm_system_reset tsm_system_cost ));
 DESCR("SYSTEM table sampling method");
+#define TABLESAMPLE_METHOD_SYSTEM_OID 3293
 DATA(insert OID = 3294 ( bernoulli true false tsm_bernoulli_init tsm_bernoulli_nextblock tsm_bernoulli_nexttuple - tsm_bernoulli_end tsm_bernoulli_reset tsm_bernoulli_cost ));
 DESCR("BERNOULLI table sampling method");
+#define TABLESAMPLE_METHOD_BERNOULLI_OID 3294
+
+/* ----------------
+ *		functions for manipulation of pg_tablesample_method
+ * ----------------
+ */
+
+extern ObjectAddress DefineTablesampleMethod(List *names, List *parameters);
+extern void RemoveTablesampleMethodById(Oid tsmoid);
 
 #endif   /* PG_TABLESAMPLE_METHOD_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index aea499e..a2bb920 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1292,6 +1292,7 @@ typedef enum ObjectType
 	OBJECT_SEQUENCE,
 	OBJECT_TABCONSTRAINT,
 	OBJECT_TABLE,
+	OBJECT_TABLESAMPLEMETHOD,
 	OBJECT_TABLESPACE,
 	OBJECT_TRIGGER,
 	OBJECT_TSCONFIGURATION,
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index ae90df8..902c189 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -236,6 +236,7 @@ PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
 PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
 PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
 PG_KEYWORD("maxvalue", MAXVALUE, UNRESERVED_KEYWORD)
+PG_KEYWORD("method", METHOD, UNRESERVED_KEYWORD)
 PG_KEYWORD("minute", MINUTE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("minvalue", MINVALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("mode", MODE, UNRESERVED_KEYWORD)
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index ea1aa11..518f27f 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -153,6 +153,7 @@ extern void free_attstatsslot(Oid atttype,
 extern char *get_namespace_name(Oid nspid);
 extern char *get_namespace_name_or_temp(Oid nspid);
 extern Oid	get_range_subtype(Oid rangeOid);
+extern Oid get_tablesample_method_oid(const char *tsmname, bool missing_ok);
 extern char *get_tablesample_method_name(Oid tsmid);
 
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 93d93af..37ea524 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -9,7 +9,8 @@ SUBDIRS = \
 		  worker_spi \
 		  dummy_seclabel \
 		  test_shm_mq \
-		  test_parser
+		  test_parser \
+		  tablesample
 
 all: submake-errcodes
 
diff --git a/src/test/modules/tablesample/.gitignore b/src/test/modules/tablesample/.gitignore
new file mode 100644
index 0000000..5dcb3ff
--- /dev/null
+++ b/src/test/modules/tablesample/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/src/test/modules/tablesample/Makefile b/src/test/modules/tablesample/Makefile
new file mode 100644
index 0000000..469b004
--- /dev/null
+++ b/src/test/modules/tablesample/Makefile
@@ -0,0 +1,21 @@
+# src/test/modules/tsm_test/Makefile
+
+MODULE_big = tsm_test
+OBJS = tsm_test.o $(WIN32RES)
+PGFILEDESC = "tsm_test - example of a custom tablesample method"
+
+EXTENSION = tsm_test
+DATA = tsm_test--1.0.sql
+
+REGRESS = tablesample
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/tablesample
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/tablesample/expected/tablesample.out b/src/test/modules/tablesample/expected/tablesample.out
new file mode 100644
index 0000000..ad62e32
--- /dev/null
+++ b/src/test/modules/tablesample/expected/tablesample.out
@@ -0,0 +1,38 @@
+CREATE EXTENSION tsm_test;
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ c81e728d9d4c2f636f067f89cc14862c | 0.5
+ a87ff679a2f3e71d9181a67b7542122c | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ d3d9446802a44259755d38e6d163e820 | 0.5
+(6 rows)
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+                a                 |  b  
+----------------------------------+-----
+ c4ca4238a0b923820dcc509a6f75849b | 0.5
+ e4da3b7fbbce2345d7772b0674a318d5 | 0.5
+ 1679091c5a880faf6fb5e6087eb1b2dc | 0.5
+ 8f14e45fceea167a5a36dedd4bea2543 | 0.5
+ c9f0f895fb98ab9159f51fd0297e236d | 0.5
+(5 rows)
+
+DROP TABLESAMPLE METHOD tsm_test;
+ERROR:  cannot drop tablesample method tsm_test because extension tsm_test requires it
+HINT:  You can drop extension tsm_test instead.
+DROP EXTENSION tsm_test;
+ERROR:  cannot drop extension tsm_test because other objects depend on it
+DETAIL:  view test_tsm_v depends on tablesample method tsm_test
+HINT:  Use DROP ... CASCADE to drop the dependent objects too.
+DROP EXTENSION tsm_test CASCADE;
+NOTICE:  drop cascades to view test_tsm_v
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
+ tsmname | tsmseqscan | tsmpagemode | tsminit | tsmnextblock | tsmnexttuple | tsmexaminetuple | tsmend | tsmreset | tsmcost 
+---------+------------+-------------+---------+--------------+--------------+-----------------+--------+----------+---------
+(0 rows)
+
diff --git a/src/test/modules/tablesample/sql/tablesample.sql b/src/test/modules/tablesample/sql/tablesample.sql
new file mode 100644
index 0000000..b1104d6
--- /dev/null
+++ b/src/test/modules/tablesample/sql/tablesample.sql
@@ -0,0 +1,14 @@
+CREATE EXTENSION tsm_test;
+
+CREATE TABLE test_tsm AS SELECT md5(i::text) a, 0.5::float b FROM generate_series(1,10) g(i);
+
+SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (1);
+
+CREATE VIEW test_tsm_v AS SELECT * FROM test_tsm TABLESAMPLE tsm_test('b') REPEATABLE (9999);
+SELECT * FROM test_tsm_v;
+
+DROP TABLESAMPLE METHOD tsm_test;
+DROP EXTENSION tsm_test;
+DROP EXTENSION tsm_test CASCADE;
+
+SELECT * FROM pg_tablesample_method WHERE tsmname = 'tsm_test';
diff --git a/src/test/modules/tablesample/tsm_test--1.0.sql b/src/test/modules/tablesample/tsm_test--1.0.sql
new file mode 100644
index 0000000..e5a9ae8
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test--1.0.sql
@@ -0,0 +1,52 @@
+/* src/test/modules/tablesample/tsm_test--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION tsm_test" to load this file. \quit
+
+CREATE FUNCTION tsm_test_init(internal, int4, text)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nextblock(internal)
+RETURNS int4
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_nexttuple(internal, int4, int2)
+RETURNS int2
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_examinetuple(internal, int4, internal, bool)
+RETURNS bool
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_end(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_reset(internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION tsm_test_cost(internal, internal, internal, internal, internal, internal, internal)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+
+CREATE TABLESAMPLE METHOD tsm_test (
+	SEQSCAN		= true,
+	PAGEMODE	= true,
+	INIT		= tsm_test_init,
+	NEXTBLOCK	= tsm_test_nextblock,
+	NEXTTUPLE	= tsm_test_nexttuple,
+	EXAMINETUPLE	= tsm_test_examinetuple,
+	END			= tsm_test_end,
+	RESET		= tsm_test_reset,
+	COST		= tsm_test_cost
+);
diff --git a/src/test/modules/tablesample/tsm_test.c b/src/test/modules/tablesample/tsm_test.c
new file mode 100644
index 0000000..5d76c78
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.c
@@ -0,0 +1,224 @@
+/*-------------------------------------------------------------------------
+ *
+ * tsm_test.c
+ *	  Simple example of a custom tablesample method
+ *
+ * Copyright (c) 2007-2014, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/test/modules/tablesample/tsm_test.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "fmgr.h"
+
+#include "access/tablesample.h"
+#include "access/htup_details.h"
+#include "access/relscan.h"
+#include "access/tupdesc.h"
+#include "catalog/pg_type.h"
+#include "nodes/execnodes.h"
+#include "nodes/relation.h"
+#include "optimizer/clauses.h"
+#include "storage/bufmgr.h"
+#include "utils/builtins.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+#include "utils/sampling.h"
+
+PG_MODULE_MAGIC;
+
+/* State */
+typedef struct
+{
+	uint32		seed;			/* random seed */
+	AttrNumber	attnum;			/* column to check */
+	BlockNumber startblock;		/* starting block, we use ths for syncscan support */
+	BlockNumber nblocks;		/* total blocks in relation */
+	BlockNumber blockno;		/* current block */
+	OffsetNumber lt;			/* last tuple returned from current block */
+	SamplerRandomState randstate; /* random generator state */
+} TestSamplerState;
+
+
+PG_FUNCTION_INFO_V1(tsm_test_init);
+PG_FUNCTION_INFO_V1(tsm_test_nextblock);
+PG_FUNCTION_INFO_V1(tsm_test_nexttuple);
+PG_FUNCTION_INFO_V1(tsm_test_examinetuple);
+PG_FUNCTION_INFO_V1(tsm_test_end);
+PG_FUNCTION_INFO_V1(tsm_test_reset);
+PG_FUNCTION_INFO_V1(tsm_test_cost);
+
+/*
+ * Initialize the state.
+ */
+Datum
+tsm_test_init(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	uint32				seed = PG_GETARG_UINT32(1);
+	char			   *attname;
+	AttrNumber			attnum;
+	Oid					atttype;
+	HeapScanDesc		scan = tsdesc->heapScan;
+	TestSamplerState   *sampler;
+
+	if (PG_ARGISNULL(2))
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("attnum cannot be NULL.")));
+
+	attname = text_to_cstring(PG_GETARG_TEXT_P(2));
+
+	attnum = get_attnum(scan->rs_rd->rd_id, attname);
+	if (!AttrNumberIsForUserDefinedAttr(attnum))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s does not exist", attname)));
+
+	atttype = get_atttype(scan->rs_rd->rd_id, attnum);
+	if (atttype != FLOAT8OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid parameter for tablesample method tsm_test"),
+				 errhint("column %s is not of type float.", attname)));
+
+	sampler = palloc0(sizeof(TestSamplerState));
+
+	/* Remember initial values for reinit */
+	sampler->seed = seed;
+	sampler->attnum = attnum;
+	sampler->startblock = scan->rs_startblock;
+	sampler->nblocks = scan->rs_nblocks;
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	tsdesc->tsmdata = sampler;
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Get next block number to read or InvalidBlockNumber if we are at the
+ * end of the relation.
+ */
+Datum
+tsm_test_nextblock(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	TestSamplerState   *sampler = (TestSamplerState *) tsdesc->tsmdata;
+
+	/* Cycle from startblock to startblock to support syncscan. */
+	if (sampler->blockno == InvalidBlockNumber)
+		sampler->blockno = sampler->startblock;
+	else
+	{
+		sampler->blockno++;
+
+		if (sampler->blockno >= sampler->nblocks)
+			sampler->blockno = 0;
+
+		if (sampler->blockno == sampler->startblock)
+			PG_RETURN_UINT32(InvalidBlockNumber);
+	}
+
+	PG_RETURN_UINT32(sampler->blockno);
+}
+
+/*
+ * Get next tuple from current block.
+ */
+Datum
+tsm_test_nexttuple(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	OffsetNumber		maxoffset = PG_GETARG_UINT16(2);
+	TestSamplerState   *sampler = (TestSamplerState *) tsdesc->tsmdata;
+
+	if (sampler->lt == InvalidOffsetNumber)
+		sampler->lt = FirstOffsetNumber;
+	else if (++sampler->lt > maxoffset)
+		PG_RETURN_UINT16(InvalidOffsetNumber);
+
+	PG_RETURN_UINT16(sampler->lt);
+}
+
+/*
+ * Examine tuple and decide if it should be returned.
+ */
+Datum
+tsm_test_examinetuple(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	HeapTuple			tuple = (HeapTuple) PG_GETARG_POINTER(2);
+	bool				visible = PG_GETARG_BOOL(3);
+	TestSamplerState   *sampler = (TestSamplerState *) tsdesc->tsmdata;
+	bool				isnull;
+	float8				val, rand;
+
+	if (!visible)
+		PG_RETURN_BOOL(false);
+
+	val = DatumGetFloat8(heap_getattr(tuple, sampler->attnum, tsdesc->tupDesc, &isnull));
+	rand = sampler_random_fract(sampler->randstate);
+	if (isnull || val < rand)
+		PG_RETURN_BOOL(false);
+	else
+		PG_RETURN_BOOL(true);
+}
+
+/*
+ * Cleanup method.
+ */
+Datum
+tsm_test_end(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+
+	pfree(tsdesc->tsmdata);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Reset state (called by ReScan).
+ */
+Datum
+tsm_test_reset(PG_FUNCTION_ARGS)
+{
+	TableSampleDesc	   *tsdesc = (TableSampleDesc *) PG_GETARG_POINTER(0);
+	TestSamplerState   *sampler = (TestSamplerState *) tsdesc->tsmdata;
+
+	sampler->blockno = InvalidBlockNumber;
+	sampler->lt = InvalidOffsetNumber;
+
+	sampler_random_init_state(sampler->seed, sampler->randstate);
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Costing function.
+ */
+Datum
+tsm_test_cost(PG_FUNCTION_ARGS)
+{
+	Path		   *path = (Path *) PG_GETARG_POINTER(1);
+	RelOptInfo	   *baserel = (RelOptInfo *) PG_GETARG_POINTER(2);
+	BlockNumber	   *pages = (BlockNumber *) PG_GETARG_POINTER(4);
+	double		   *tuples = (double *) PG_GETARG_POINTER(5);
+
+	*pages = baserel->pages;
+
+	/* This is very bad estimation */
+	*tuples = path->rows = path->rows/2;
+
+	PG_RETURN_VOID();
+}
+
diff --git a/src/test/modules/tablesample/tsm_test.control b/src/test/modules/tablesample/tsm_test.control
new file mode 100644
index 0000000..a7b2741
--- /dev/null
+++ b/src/test/modules/tablesample/tsm_test.control
@@ -0,0 +1,5 @@
+# tsm_test extension
+comment = 'test module for custom tablesample method'
+default_version = '1.0'
+module_pathname = '$libdir/tsm_test'
+relocatable = true
-- 
1.9.1

>From c36749fe10ceb98f2cd787ed5ad1659b8497ffc0 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Thu, 16 Apr 2015 20:35:14 +0200
Subject: [PATCH 5/6] tablesample-api-doc v2

---
 doc/src/sgml/filelist.sgml           |   1 +
 doc/src/sgml/postgres.sgml           |   1 +
 doc/src/sgml/tablesample-method.sgml | 139 +++++++++++++++++++++++++++++++++++
 3 files changed, 141 insertions(+)
 create mode 100644 doc/src/sgml/tablesample-method.sgml

diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index 2d7514c..4f6d868 100644
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@@ -98,6 +98,7 @@
 <!ENTITY protocol   SYSTEM "protocol.sgml">
 <!ENTITY sources    SYSTEM "sources.sgml">
 <!ENTITY storage    SYSTEM "storage.sgml">
+<!ENTITY tablesample-method SYSTEM "tablesample-method">
 
 <!-- contrib information -->
 <!ENTITY contrib         SYSTEM "contrib.sgml">
diff --git a/doc/src/sgml/postgres.sgml b/doc/src/sgml/postgres.sgml
index e378d69..46c2f93 100644
--- a/doc/src/sgml/postgres.sgml
+++ b/doc/src/sgml/postgres.sgml
@@ -249,6 +249,7 @@
   &spgist;
   &gin;
   &brin;
+  &tablesample-method;
   &storage;
   &bki;
   &planstats;
diff --git a/doc/src/sgml/tablesample-method.sgml b/doc/src/sgml/tablesample-method.sgml
new file mode 100644
index 0000000..48eb7fe
--- /dev/null
+++ b/doc/src/sgml/tablesample-method.sgml
@@ -0,0 +1,139 @@
+<!-- doc/src/sgml/tablesample-method.sgml -->
+
+<chapter id="tablesample-method">
+ <title>Writing A TABLESAMPLE Sampling Method</title>
+
+ <indexterm zone="tablesample-method">
+  <primary>tablesample method</primary>
+ </indexterm>
+
+ <para>
+  The <command>TABLESAMPLE</command> clause implementation in
+  <productname>PostgreSQL</> supports creating a custom sampling methods.
+  These methods control what sample of the table will be returned when the
+  <command>TABLESAMPLE</command> clause is used.
+ </para>
+
+ <sect1 id="tablesample-method-functions">
+  <title>Tablesample Method Functions</title>
+
+  <para>
+   The tablesample method must provide following set of functions:
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_init (TableSampleDesc *desc,
+         uint32 seed, ...);
+</programlisting>
+   Initialize the tablesample scan. The function is called at the beginning
+   of each relation scan.
+  </para>
+  <para>
+   Note that the first two parameters are required but you can specify
+   additional parameters which then will be used by the <command>TABLESAMPLE</>
+   clause to determine the required user input in the query itself.
+   This means that if your function will specify additional float4 parameter
+   named percent, the user will have to call the tablesample method with
+   expression which evaluates (or can be coerced) to float4.
+   For example this definition:
+<programlisting>
+tsm_init (TableSampleDesc *desc,
+          uint32 seed, float4 pct);
+</programlisting>
+Will lead to SQL call like this:
+<programlisting>
+... TABLESAMPLE yourmethod(0.5) ...
+</programlisting>
+  </para>
+
+  <para>
+<programlisting>
+BlockNumber
+tsm_nextblock (TableSampleDesc *desc);
+</programlisting>
+   Returns the block number of next page to be scanned. InvalidBlockNumber
+   should be returned if the sampling has reached end of the relation.
+  </para>
+
+  <para>
+<programlisting>
+OffsetNumber
+tsm_nexttuple (TableSampleDesc *desc, BlockNumber blockno,
+               OffsetNumber maxoffset);
+</programlisting>
+   Return next tuple offset for the current page. InvalidOffsetNumber should
+   be returned if the sampling has reached end of the page.
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_end (TableSampleDesc *desc);
+</programlisting>
+   The scan has finished, cleanup any left over state.
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_reset (TableSampleDesc *desc);
+</programlisting>
+   The scan needs to rescan the relation again, reset any tablesample method
+   state.
+  </para>
+
+  <para>
+<programlisting>
+void
+tsm_cost (PlannerInfo *root, Path *path, RelOptInfo *baserel,
+          List *args, BlockNumber *pages, double *tuples);
+</programlisting>
+   This function is used by optimizer to decide best plan and is also used
+   for output of <command>EXPLAIN</>.
+  </para>
+
+  <para>
+   There is one more function which tablesampling method can implement in order
+   to gain more fine grained control over sampling. This function is optional:
+  </para>
+
+  <para>
+<programlisting>
+bool
+tsm_examinetuple (TableSampleDesc *desc, BlockNumber blockno,
+                  HeapTuple tuple, bool visible);
+</programlisting>
+   Function that enables the sampling method to examine contents of the tuple
+   (for example to collect some internal statistics). The return value of this
+   function is used to determine if the tuple should be returned to client.
+   Note that this function will receive even invisible tuples but it is not
+   allowed to return true for such tuple (if it does,
+   <productname>PostgreSQL</> will raise an error).
+  </para>
+
+  <para>
+  As you can see most of the tablesample method interfaces get the
+  <structname>TableSampleDesc</> as a first parameter. This structure holds
+  state of the current scan and also provides storage for the tablesample
+  method's state. It is defined as following:
+<programlisting>
+typedef struct TableSampleDesc {
+    HeapScanDesc    heapScan;
+    TupleDesc       tupDesc;
+
+    void           *tsmdata;
+} TableSampleDesc;
+</programlisting>
+  Where <structfield>heapScan</> is the descriptor of the physical table scan.
+  It's possible to get table size info from it. The <structfield>tupDesc</>
+  represents the tuple descriptor of the tuples returned by the scan and passed
+  to the <function>tsm_examinetuple()</> interface. The <structfield>tsmdata</>
+  can be used by tablesample method itself to store any state info it might
+  need during the scan. If used by the method, it should be <function>pfree</>d
+  in <function>tsm_end()</> function.
+  </para>
+ </sect1>
+
+</chapter>
-- 
1.9.1

>From 686f1adc77833f1d28f1a6d7dac5f3d65fd3e9e2 Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 7 Jan 2015 23:36:56 +0100
Subject: [PATCH 1/6] separate block sampling functions v2

---
 contrib/file_fdw/file_fdw.c         |   9 +-
 contrib/postgres_fdw/postgres_fdw.c |  10 +-
 src/backend/commands/analyze.c      | 225 +----------------------------------
 src/backend/utils/misc/Makefile     |   2 +-
 src/backend/utils/misc/sampling.c   | 226 ++++++++++++++++++++++++++++++++++++
 src/include/commands/vacuum.h       |   3 -
 src/include/utils/sampling.h        |  44 +++++++
 7 files changed, 287 insertions(+), 232 deletions(-)
 create mode 100644 src/backend/utils/misc/sampling.c
 create mode 100644 src/include/utils/sampling.h

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
index 4368897..249d541 100644
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@@ -34,6 +34,7 @@
 #include "optimizer/var.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -1005,7 +1006,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 {
 	int			numrows = 0;
 	double		rowstoskip = -1;	/* -1 means not set yet */
-	double		rstate;
+	ReservoirStateData rstate;
 	TupleDesc	tupDesc;
 	Datum	   *values;
 	bool	   *nulls;
@@ -1043,7 +1044,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 									   ALLOCSET_DEFAULT_MAXSIZE);
 
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Set up callback to identify error line number. */
 	errcallback.callback = CopyFromErrorCallback;
@@ -1087,7 +1088,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 			 * not-yet-incremented value of totalrows as t.
 			 */
 			if (rowstoskip < 0)
-				rowstoskip = anl_get_next_S(*totalrows, targrows, &rstate);
+				rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
 
 			if (rowstoskip <= 0)
 			{
@@ -1095,7 +1096,7 @@ file_acquire_sample_rows(Relation onerel, int elevel,
 				 * Found a suitable tuple, so save it, replacing one old tuple
 				 * at random
 				 */
-				int			k = (int) (targrows * anl_random_fract());
+				int			k = (int) (targrows * sampler_random_fract());
 
 				Assert(k >= 0 && k < targrows);
 				heap_freetuple(rows[k]);
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 478e124..74ef792 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -37,6 +37,7 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
+#include "utils/sampling.h"
 
 PG_MODULE_MAGIC;
 
@@ -202,7 +203,7 @@ typedef struct PgFdwAnalyzeState
 	/* for random sampling */
 	double		samplerows;		/* # of rows fetched */
 	double		rowstoskip;		/* # of rows to skip before next sample */
-	double		rstate;			/* random state */
+	ReservoirStateData rstate;		/* state for reservoir sampling*/
 
 	/* working memory contexts */
 	MemoryContext anl_cxt;		/* context for per-analyze lifespan data */
@@ -2397,7 +2398,7 @@ postgresAcquireSampleRowsFunc(Relation relation, int elevel,
 	astate.numrows = 0;
 	astate.samplerows = 0;
 	astate.rowstoskip = -1;		/* -1 means not set yet */
-	astate.rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&astate.rstate, targrows);
 
 	/* Remember ANALYZE context, and create a per-tuple temp context */
 	astate.anl_cxt = CurrentMemoryContext;
@@ -2537,13 +2538,12 @@ analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
 		 * analyze.c; see Jeff Vitter's paper.
 		 */
 		if (astate->rowstoskip < 0)
-			astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
-												&astate->rstate);
+			astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
 
 		if (astate->rowstoskip <= 0)
 		{
 			/* Choose a random reservoir element to replace. */
-			pos = (int) (targrows * anl_random_fract());
+			pos = (int) (targrows * sampler_random_fract());
 			Assert(pos >= 0 && pos < targrows);
 			heap_freetuple(astate->rows[pos]);
 		}
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 15ec0ad..952cf20 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -50,23 +50,13 @@
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/pg_rusage.h"
+#include "utils/sampling.h"
 #include "utils/sortsupport.h"
 #include "utils/syscache.h"
 #include "utils/timestamp.h"
 #include "utils/tqual.h"
 
 
-/* Data structure for Algorithm S from Knuth 3.4.2 */
-typedef struct
-{
-	BlockNumber N;				/* number of blocks, known in advance */
-	int			n;				/* desired sample size */
-	BlockNumber t;				/* current block number */
-	int			m;				/* blocks selected so far */
-} BlockSamplerData;
-
-typedef BlockSamplerData *BlockSampler;
-
 /* Per-index data for ANALYZE */
 typedef struct AnlIndexData
 {
@@ -89,10 +79,6 @@ static void do_analyze_rel(Relation onerel, int options,
 			   VacuumParams *params, List *va_cols,
 			   AcquireSampleRowsFunc acquirefunc, BlockNumber relpages,
 			   bool inh, bool in_outer_xact, int elevel);
-static void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
-				  int samplesize);
-static bool BlockSampler_HasMore(BlockSampler bs);
-static BlockNumber BlockSampler_Next(BlockSampler bs);
 static void compute_index_stats(Relation onerel, double totalrows,
 					AnlIndexData *indexdata, int nindexes,
 					HeapTuple *rows, int numrows,
@@ -951,94 +937,6 @@ examine_attribute(Relation onerel, int attnum, Node *index_expr)
 }
 
 /*
- * BlockSampler_Init -- prepare for random sampling of blocknumbers
- *
- * BlockSampler is used for stage one of our new two-stage tuple
- * sampling mechanism as discussed on pgsql-hackers 2004-04-02 (subject
- * "Large DB").  It selects a random sample of samplesize blocks out of
- * the nblocks blocks in the table.  If the table has less than
- * samplesize blocks, all blocks are selected.
- *
- * Since we know the total number of blocks in advance, we can use the
- * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
- * algorithm.
- */
-static void
-BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize)
-{
-	bs->N = nblocks;			/* measured table size */
-
-	/*
-	 * If we decide to reduce samplesize for tables that have less or not much
-	 * more than samplesize blocks, here is the place to do it.
-	 */
-	bs->n = samplesize;
-	bs->t = 0;					/* blocks scanned so far */
-	bs->m = 0;					/* blocks selected so far */
-}
-
-static bool
-BlockSampler_HasMore(BlockSampler bs)
-{
-	return (bs->t < bs->N) && (bs->m < bs->n);
-}
-
-static BlockNumber
-BlockSampler_Next(BlockSampler bs)
-{
-	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
-	int			k = bs->n - bs->m;		/* blocks still to sample */
-	double		p;				/* probability to skip block */
-	double		V;				/* random */
-
-	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
-
-	if ((BlockNumber) k >= K)
-	{
-		/* need all the rest */
-		bs->m++;
-		return bs->t++;
-	}
-
-	/*----------
-	 * It is not obvious that this code matches Knuth's Algorithm S.
-	 * Knuth says to skip the current block with probability 1 - k/K.
-	 * If we are to skip, we should advance t (hence decrease K), and
-	 * repeat the same probabilistic test for the next block.  The naive
-	 * implementation thus requires an anl_random_fract() call for each block
-	 * number.  But we can reduce this to one anl_random_fract() call per
-	 * selected block, by noting that each time the while-test succeeds,
-	 * we can reinterpret V as a uniform random number in the range 0 to p.
-	 * Therefore, instead of choosing a new V, we just adjust p to be
-	 * the appropriate fraction of its former value, and our next loop
-	 * makes the appropriate probabilistic test.
-	 *
-	 * We have initially K > k > 0.  If the loop reduces K to equal k,
-	 * the next while-test must fail since p will become exactly zero
-	 * (we assume there will not be roundoff error in the division).
-	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
-	 * to be doubly sure about roundoff error.)  Therefore K cannot become
-	 * less than k, which means that we cannot fail to select enough blocks.
-	 *----------
-	 */
-	V = anl_random_fract();
-	p = 1.0 - (double) k / (double) K;
-	while (V < p)
-	{
-		/* skip */
-		bs->t++;
-		K--;					/* keep K == N - t */
-
-		/* adjust p to be new cutoff point in reduced range */
-		p *= 1.0 - (double) k / (double) K;
-	}
-
-	/* select */
-	bs->m++;
-	return bs->t++;
-}
-
-/*
  * acquire_sample_rows -- acquire a random sample of rows from the table
  *
  * Selected rows are returned in the caller-allocated array rows[], which
@@ -1084,7 +982,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	BlockNumber totalblocks;
 	TransactionId OldestXmin;
 	BlockSamplerData bs;
-	double		rstate;
+	ReservoirStateData rstate;
 
 	Assert(targrows > 0);
 
@@ -1094,9 +992,9 @@ acquire_sample_rows(Relation onerel, int elevel,
 	OldestXmin = GetOldestXmin(onerel, true);
 
 	/* Prepare for sampling block numbers */
-	BlockSampler_Init(&bs, totalblocks, targrows);
+	BlockSampler_Init(&bs, totalblocks, targrows, random());
 	/* Prepare for sampling rows */
-	rstate = anl_init_selection_state(targrows);
+	reservoir_init_selection_state(&rstate, targrows);
 
 	/* Outer loop over blocks to sample */
 	while (BlockSampler_HasMore(&bs))
@@ -1244,8 +1142,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 					 * t.
 					 */
 					if (rowstoskip < 0)
-						rowstoskip = anl_get_next_S(samplerows, targrows,
-													&rstate);
+						rowstoskip = reservoir_get_next_S(&rstate, samplerows, targrows);
 
 					if (rowstoskip <= 0)
 					{
@@ -1253,7 +1150,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 						 * Found a suitable tuple, so save it, replacing one
 						 * old tuple at random
 						 */
-						int			k = (int) (targrows * anl_random_fract());
+						int			k = (int) (targrows * sampler_random_fract());
 
 						Assert(k >= 0 && k < targrows);
 						heap_freetuple(rows[k]);
@@ -1312,116 +1209,6 @@ acquire_sample_rows(Relation onerel, int elevel,
 	return numrows;
 }
 
-/* Select a random value R uniformly distributed in (0 - 1) */
-double
-anl_random_fract(void)
-{
-	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
-}
-
-/*
- * These two routines embody Algorithm Z from "Random sampling with a
- * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
- * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
- * of the count S of records to skip before processing another record.
- * It is computed primarily based on t, the number of records already read.
- * The only extra state needed between calls is W, a random state variable.
- *
- * anl_init_selection_state computes the initial W value.
- *
- * Given that we've already read t records (t >= n), anl_get_next_S
- * determines the number of records to skip before the next record is
- * processed.
- */
-double
-anl_init_selection_state(int n)
-{
-	/* Initial value of W (for use when Algorithm Z is first applied) */
-	return exp(-log(anl_random_fract()) / n);
-}
-
-double
-anl_get_next_S(double t, int n, double *stateptr)
-{
-	double		S;
-
-	/* The magic constant here is T from Vitter's paper */
-	if (t <= (22.0 * n))
-	{
-		/* Process records using Algorithm X until t is large enough */
-		double		V,
-					quot;
-
-		V = anl_random_fract(); /* Generate V */
-		S = 0;
-		t += 1;
-		/* Note: "num" in Vitter's code is always equal to t - n */
-		quot = (t - (double) n) / t;
-		/* Find min S satisfying (4.1) */
-		while (quot > V)
-		{
-			S += 1;
-			t += 1;
-			quot *= (t - (double) n) / t;
-		}
-	}
-	else
-	{
-		/* Now apply Algorithm Z */
-		double		W = *stateptr;
-		double		term = t - (double) n + 1;
-
-		for (;;)
-		{
-			double		numer,
-						numer_lim,
-						denom;
-			double		U,
-						X,
-						lhs,
-						rhs,
-						y,
-						tmp;
-
-			/* Generate U and X */
-			U = anl_random_fract();
-			X = t * (W - 1.0);
-			S = floor(X);		/* S is tentatively set to floor(X) */
-			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
-			tmp = (t + 1) / term;
-			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
-			rhs = (((t + X) / (term + S)) * term) / t;
-			if (lhs <= rhs)
-			{
-				W = rhs / lhs;
-				break;
-			}
-			/* Test if U <= f(S)/cg(X) */
-			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
-			if ((double) n < S)
-			{
-				denom = t;
-				numer_lim = term + S;
-			}
-			else
-			{
-				denom = t - (double) n + S;
-				numer_lim = t + 1;
-			}
-			for (numer = t + S; numer >= numer_lim; numer -= 1)
-			{
-				y *= numer / denom;
-				denom -= 1;
-			}
-			W = exp(-log(anl_random_fract()) / n);		/* Generate W in advance */
-			if (exp(log(y) / n) <= (t + X) / t)
-				break;
-		}
-		*stateptr = W;
-	}
-	return S;
-}
-
 /*
  * qsort comparator for sorting rows[] array
  */
diff --git a/src/backend/utils/misc/Makefile b/src/backend/utils/misc/Makefile
index 378b77e..7889101 100644
--- a/src/backend/utils/misc/Makefile
+++ b/src/backend/utils/misc/Makefile
@@ -15,7 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = guc.o help_config.o pg_rusage.o ps_status.o rls.o \
-       superuser.o timeout.o tzparser.o
+       sampling.o superuser.o timeout.o tzparser.o
 
 # This location might depend on the installation directories. Therefore
 # we can't subsitute it into pg_config.h.
diff --git a/src/backend/utils/misc/sampling.c b/src/backend/utils/misc/sampling.c
new file mode 100644
index 0000000..1eeabaf
--- /dev/null
+++ b/src/backend/utils/misc/sampling.c
@@ -0,0 +1,226 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.c
+ *	  Relation block sampling routines.
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/misc/sampling.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/sampling.h"
+
+
+/*
+ * BlockSampler_Init -- prepare for random sampling of blocknumbers
+ *
+ * BlockSampler provides algorithm for block level sampling of a relation
+ * as discussed on pgsql-hackers 2004-04-02 (subject "Large DB")
+ * It selects a random sample of samplesize blocks out of
+ * the nblocks blocks in the table. If the table has less than
+ * samplesize blocks, all blocks are selected.
+ *
+ * Since we know the total number of blocks in advance, we can use the
+ * straightforward Algorithm S from Knuth 3.4.2, rather than Vitter's
+ * algorithm.
+ */
+void
+BlockSampler_Init(BlockSampler bs, BlockNumber nblocks, int samplesize,
+				  long randseed)
+{
+	bs->N = nblocks;			/* measured table size */
+
+	/*
+	 * If we decide to reduce samplesize for tables that have less or not much
+	 * more than samplesize blocks, here is the place to do it.
+	 */
+	bs->n = samplesize;
+	bs->t = 0;					/* blocks scanned so far */
+	bs->m = 0;					/* blocks selected so far */
+}
+
+bool
+BlockSampler_HasMore(BlockSampler bs)
+{
+	return (bs->t < bs->N) && (bs->m < bs->n);
+}
+
+BlockNumber
+BlockSampler_Next(BlockSampler bs)
+{
+	BlockNumber K = bs->N - bs->t;		/* remaining blocks */
+	int			k = bs->n - bs->m;		/* blocks still to sample */
+	double		p;				/* probability to skip block */
+	double		V;				/* random */
+
+	Assert(BlockSampler_HasMore(bs));	/* hence K > 0 and k > 0 */
+
+	if ((BlockNumber) k >= K)
+	{
+		/* need all the rest */
+		bs->m++;
+		return bs->t++;
+	}
+
+	/*----------
+	 * It is not obvious that this code matches Knuth's Algorithm S.
+	 * Knuth says to skip the current block with probability 1 - k/K.
+	 * If we are to skip, we should advance t (hence decrease K), and
+	 * repeat the same probabilistic test for the next block.  The naive
+	 * implementation thus requires an sampler_random_fract() call for each
+	 * block number.  But we can reduce this to one sampler_random_fract()
+	 * call per selected block, by noting that each time the while-test
+	 * succeeds, we can reinterpret V as a uniform random number in the range
+	 * 0 to p. Therefore, instead of choosing a new V, we just adjust p to be
+	 * the appropriate fraction of its former value, and our next loop
+	 * makes the appropriate probabilistic test.
+	 *
+	 * We have initially K > k > 0.  If the loop reduces K to equal k,
+	 * the next while-test must fail since p will become exactly zero
+	 * (we assume there will not be roundoff error in the division).
+	 * (Note: Knuth suggests a "<=" loop condition, but we use "<" just
+	 * to be doubly sure about roundoff error.)  Therefore K cannot become
+	 * less than k, which means that we cannot fail to select enough blocks.
+	 *----------
+	 */
+	V = sampler_random_fract();
+	p = 1.0 - (double) k / (double) K;
+	while (V < p)
+	{
+		/* skip */
+		bs->t++;
+		K--;					/* keep K == N - t */
+
+		/* adjust p to be new cutoff point in reduced range */
+		p *= 1.0 - (double) k / (double) K;
+	}
+
+	/* select */
+	bs->m++;
+	return bs->t++;
+}
+
+/*
+ * These two routines embody Algorithm Z from "Random sampling with a
+ * reservoir" by Jeffrey S. Vitter, in ACM Trans. Math. Softw. 11, 1
+ * (Mar. 1985), Pages 37-57.  Vitter describes his algorithm in terms
+ * of the count S of records to skip before processing another record.
+ * It is computed primarily based on t, the number of records already read.
+ * The only extra state needed between calls is W, a random state variable.
+ *
+ * reservoir_init_selection_state computes the initial W value.
+ *
+ * Given that we've already read t records (t >= n), reservoir_get_next_S
+ * determines the number of records to skip before the next record is
+ * processed.
+ */
+void
+reservoir_init_selection_state(ReservoirState rs, int n)
+{
+	/* Initial value of W (for use when Algorithm Z is first applied) */
+	*rs = exp(-log(sampler_random_fract()) / n);
+}
+
+double
+reservoir_get_next_S(ReservoirState rs, double t, int n)
+{
+	double		S;
+
+	/* The magic constant here is T from Vitter's paper */
+	if (t <= (22.0 * n))
+	{
+		/* Process records using Algorithm X until t is large enough */
+		double		V,
+					quot;
+
+		V = sampler_random_fract(); /* Generate V */
+		S = 0;
+		t += 1;
+		/* Note: "num" in Vitter's code is always equal to t - n */
+		quot = (t - (double) n) / t;
+		/* Find min S satisfying (4.1) */
+		while (quot > V)
+		{
+			S += 1;
+			t += 1;
+			quot *= (t - (double) n) / t;
+		}
+	}
+	else
+	{
+		/* Now apply Algorithm Z */
+		double		W = *rs;
+		double		term = t - (double) n + 1;
+
+		for (;;)
+		{
+			double		numer,
+						numer_lim,
+						denom;
+			double		U,
+						X,
+						lhs,
+						rhs,
+						y,
+						tmp;
+
+			/* Generate U and X */
+			U = sampler_random_fract();
+			X = t * (W - 1.0);
+			S = floor(X);		/* S is tentatively set to floor(X) */
+			/* Test if U <= h(S)/cg(X) in the manner of (6.3) */
+			tmp = (t + 1) / term;
+			lhs = exp(log(((U * tmp * tmp) * (term + S)) / (t + X)) / n);
+			rhs = (((t + X) / (term + S)) * term) / t;
+			if (lhs <= rhs)
+			{
+				W = rhs / lhs;
+				break;
+			}
+			/* Test if U <= f(S)/cg(X) */
+			y = (((U * (t + 1)) / term) * (t + S + 1)) / (t + X);
+			if ((double) n < S)
+			{
+				denom = t;
+				numer_lim = term + S;
+			}
+			else
+			{
+				denom = t - (double) n + S;
+				numer_lim = t + 1;
+			}
+			for (numer = t + S; numer >= numer_lim; numer -= 1)
+			{
+				y *= numer / denom;
+				denom -= 1;
+			}
+			W = exp(-log(sampler_random_fract()) / n);		/* Generate W in advance */
+			if (exp(log(y) / n) <= (t + X) / t)
+				break;
+		}
+		*rs = W;
+	}
+	return S;
+}
+
+
+/*----------
+ * Random number generator used by sampling
+ *----------
+ */
+
+/* Select a random value R uniformly distributed in (0 - 1) */
+double
+sampler_random_fract()
+{
+	return ((double) random() + 1) / ((double) MAX_RANDOM_VALUE + 2);
+}
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index 71f0165..ce7b28d 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -197,8 +197,5 @@ extern void analyze_rel(Oid relid, RangeVar *relation, int options,
 			VacuumParams *params, List *va_cols, bool in_outer_xact,
 			BufferAccessStrategy bstrategy);
 extern bool std_typanalyze(VacAttrStats *stats);
-extern double anl_random_fract(void);
-extern double anl_init_selection_state(int n);
-extern double anl_get_next_S(double t, int n, double *stateptr);
 
 #endif   /* VACUUM_H */
diff --git a/src/include/utils/sampling.h b/src/include/utils/sampling.h
new file mode 100644
index 0000000..e3e7f9c
--- /dev/null
+++ b/src/include/utils/sampling.h
@@ -0,0 +1,44 @@
+/*-------------------------------------------------------------------------
+ *
+ * sampling.h
+ *	  definitions for sampling functions
+ *
+ * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/utils/sampling.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SAMPLING_H
+#define SAMPLING_H
+
+#include "storage/bufmgr.h"
+
+extern double sampler_random_fract(void);
+
+/* Block sampling methods */
+/* Data structure for Algorithm S from Knuth 3.4.2 */
+typedef struct
+{
+	BlockNumber N;				/* number of blocks, known in advance */
+	int			n;				/* desired sample size */
+	BlockNumber t;				/* current block number */
+	int			m;				/* blocks selected so far */
+} BlockSamplerData;
+
+typedef BlockSamplerData *BlockSampler;
+
+extern void BlockSampler_Init(BlockSampler bs, BlockNumber nblocks,
+				  int samplesize, long randseed);
+extern bool BlockSampler_HasMore(BlockSampler bs);
+extern BlockNumber BlockSampler_Next(BlockSampler bs);
+
+/* Reservoid sampling methods */
+typedef double ReservoirStateData;
+typedef ReservoirStateData *ReservoirState;
+
+extern void reservoir_init_selection_state(ReservoirState rs, int n);
+extern double reservoir_get_next_S(ReservoirState rs, double t, int n);
+
+#endif /* SAMPLING_H */
-- 
1.9.1

>From d059c792a1e864e38f321cea51169ea0b3c5caab Mon Sep 17 00:00:00 2001
From: Petr Jelinek <pjmodos@pjmodos.net>
Date: Wed, 22 Apr 2015 21:28:29 +0200
Subject: [PATCH 7/7] tablesample: add catalog regression test

---
 src/test/regress/expected/tablesample.out | 15 +++++++++++++++
 src/test/regress/sql/tablesample.sql      | 13 +++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/src/test/regress/expected/tablesample.out b/src/test/regress/expected/tablesample.out
index 271638d..04e5eb8 100644
--- a/src/test/regress/expected/tablesample.out
+++ b/src/test/regress/expected/tablesample.out
@@ -209,6 +209,21 @@ SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);
 ERROR:  syntax error at or near "TABLESAMPLE"
 LINE 1: ...CT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPL...
                                                              ^
+-- catalog sanity
+SELECT *
+FROM pg_tablesample_method
+WHERE tsminit IS NULL
+   OR tsmseqscan IS NULL
+   OR tsmpagemode IS NULL
+   OR tsmnextblock IS NULL
+   OR tsmnexttuple IS NULL
+   OR tsmend IS NULL
+   OR tsmreset IS NULL
+   OR tsmcost IS NULL;
+ tsmname | tsmseqscan | tsmpagemode | tsminit | tsmnextblock | tsmnexttuple | tsmexaminetuple | tsmend | tsmreset | tsmcost 
+---------+------------+-------------+---------+--------------+--------------+-----------------+--------+----------+---------
+(0 rows)
+
 -- done
 DROP TABLE test_tablesample CASCADE;
 NOTICE:  drop cascades to 2 other objects
diff --git a/src/test/regress/sql/tablesample.sql b/src/test/regress/sql/tablesample.sql
index 2f4b7de..7b3eb9b 100644
--- a/src/test/regress/sql/tablesample.sql
+++ b/src/test/regress/sql/tablesample.sql
@@ -57,5 +57,18 @@ SELECT * FROM query_select TABLESAMPLE BERNOULLI (5.5) REPEATABLE (1);
 
 SELECT q.* FROM (SELECT * FROM test_tablesample) as q TABLESAMPLE BERNOULLI (5);
 
+-- catalog sanity
+
+SELECT *
+FROM pg_tablesample_method
+WHERE tsminit IS NULL
+   OR tsmseqscan IS NULL
+   OR tsmpagemode IS NULL
+   OR tsmnextblock IS NULL
+   OR tsmnexttuple IS NULL
+   OR tsmend IS NULL
+   OR tsmreset IS NULL
+   OR tsmcost IS NULL;
+
 -- done
 DROP TABLE test_tablesample CASCADE;
-- 
1.9.1