Failure in contrib test _int on loach

commit b233d40c1bd1b270ec0ea1d52887794320a8f595
Author: Anastasia <a.lubennikova@postgrespro.ru>
Date:   Fri Apr 5 19:25:48 2019 +0300

    Test to reproduce gist index problem caused by patch Generate less WAL during GiST, GIN and SP-GiST index build

diff --git a/contrib/intarray/Makefile b/contrib/intarray/Makefile
index 2505294..3535bb1 100644
--- a/contrib/intarray/Makefile
+++ b/contrib/intarray/Makefile
@@ -9,7 +9,7 @@ DATA = intarray--1.2.sql intarray--1.1--1.2.sql intarray--1.0--1.1.sql \
 	intarray--unpackaged--1.0.sql
 PGFILEDESC = "intarray - functions and operators for arrays of integers"
 
-REGRESS = _int
+REGRESS = _int _int2
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
diff --git a/contrib/intarray/expected/_int2.out b/contrib/intarray/expected/_int2.out
new file mode 100644
index 0000000..e88fd34
--- /dev/null
+++ b/contrib/intarray/expected/_int2.out
@@ -0,0 +1,48 @@
+CREATE TABLE test__int2( a int[] );
+\copy test__int2 from 'data/test__int.data'
+ANALYZE test__int2;
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+ count 
+-------
+   403
+(1 row)
+
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+ count 
+-------
+   403
+(1 row)
+
+CREATE INDEX text_idx2 on test__int2 using gist ( a gist__int_ops );
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+ count 
+-------
+   403
+(1 row)
+
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+ count 
+-------
+   403
+(1 row)
+
+SELECT a, t FROM (SELECT a::text, (SELECT COUNT (*) FROM test__int2 t2 WHERE t2.a = t1.a) t from test__int2 t1 WHERE a IS NOT NULL) s WHERE t = 0;
+ a | t 
+---+---
+(0 rows)
+
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+             a             
+---------------------------
+ {193,213,230,266,285,299}
+(1 row)
+
+set enable_indexscan to off;
+set enable_bitmapscan to off;
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+             a             
+---------------------------
+ {193,213,230,266,285,299}
+(1 row)
+
diff --git a/contrib/intarray/sql/_int2.sql b/contrib/intarray/sql/_int2.sql
new file mode 100644
index 0000000..d4adca7
--- /dev/null
+++ b/contrib/intarray/sql/_int2.sql
@@ -0,0 +1,20 @@
+CREATE TABLE test__int2( a int[] );
+\copy test__int2 from 'data/test__int.data'
+ANALYZE test__int2;
+
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+
+CREATE INDEX text_idx2 on test__int2 using gist ( a gist__int_ops );
+
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+
+SELECT a, t FROM (SELECT a::text, (SELECT COUNT (*) FROM test__int2 t2 WHERE t2.a = t1.a) t from test__int2 t1 WHERE a IS NOT NULL) s WHERE t = 0;
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+
+set enable_indexscan to off;
+set enable_bitmapscan to off;
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
diff --git a/src/backend/access/gist/gistutil.c b/src/backend/access/gist/gistutil.c
index 94b6ad6..2183b3a 100644
--- a/src/backend/access/gist/gistutil.c
+++ b/src/backend/access/gist/gistutil.c
@@ -509,6 +509,7 @@ gistchoose(Relation r, Page p, IndexTuple it,	/* it has compressed entry */
 			{
 				/* we didn't make the random choice yet for this old best */
 				keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
+				keep_current_best = 0; /* FIXME only for debugging */
 			}
 			if (keep_current_best == 0)
 			{
@@ -531,6 +532,7 @@ gistchoose(Relation r, Page p, IndexTuple it,	/* it has compressed entry */
 			{
 				/* we didn't make the random choice yet for this old best */
 				keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
+				keep_current_best = 0; /* FIXME only for debugging */
 			}
 			if (keep_current_best == 1)
 				break;

commit 53938b423ec19a88e470b7b9552de13de5e2634a
Author: Anastasia <a.lubennikova@postgrespro.ru>
Date:   Tue Apr 9 18:58:00 2019 +0300

    fix for gist create index WAL optimization. Track splits correctly

diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 2db790c..ff98d13 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -639,6 +639,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
 	/* Start from the root */
 	firststack.blkno = GIST_ROOT_BLKNO;
 	firststack.lsn = 0;
+	firststack.retry_from_parent = false;
 	firststack.parent = NULL;
 	firststack.downlinkoffnum = InvalidOffsetNumber;
 	state.stack = stack = &firststack;
@@ -693,8 +694,15 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
 			continue;
 		}
 
+		/*
+		 * During gistbuild we cannot rely on lsn-nsn comparison,
+		 * since all pages have the same GistBuildLSN value in these fields.
+		 * So use special flag stack->retry_from_parent to detect the fact that
+		 * we need to go back to parent and rechoose the child.
+		 */
 		if (stack->blkno != GIST_ROOT_BLKNO &&
-			stack->parent->lsn < GistPageGetNSN(stack->page))
+			((stack->parent->lsn < GistPageGetNSN(stack->page)) ||
+			 stack->retry_from_parent == true))
 		{
 			/*
 			 * Concurrent split detected. There's no guarantee that the
@@ -786,6 +794,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
 						UnlockReleaseBuffer(stack->buffer);
 						xlocked = false;
 						state.stack = stack = stack->parent;
+						stack->retry_from_parent = true;
 					}
 					continue;
 				}
diff --git a/src/include/access/gist_private.h b/src/include/access/gist_private.h
index 78e2e3f..361a7a8 100644
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -215,6 +215,12 @@ typedef struct GISTInsertStack
 	 */
 	GistNSN		lsn;
 
+	/*
+	 * flag to use during gistbuild to recognize page split
+	 * (instead of lsn-nsn comparison)
+	 */
+	bool retry_from_parent;
+
 	/* offset of the downlink in the parent page, that points to this page */
 	OffsetNumber downlinkoffnum;
 

commit 53f4607b50e0516be05ef27d9369c89bdcb9d82b
Author: Anastasia <a.lubennikova@postgrespro.ru>
Date:   Tue Apr 9 18:56:32 2019 +0300

    test

diff --git a/contrib/intarray/Makefile b/contrib/intarray/Makefile
index 2505294..3535bb1 100644
--- a/contrib/intarray/Makefile
+++ b/contrib/intarray/Makefile
@@ -9,7 +9,7 @@ DATA = intarray--1.2.sql intarray--1.1--1.2.sql intarray--1.0--1.1.sql \
 	intarray--unpackaged--1.0.sql
 PGFILEDESC = "intarray - functions and operators for arrays of integers"
 
-REGRESS = _int
+REGRESS = _int _int2
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
diff --git a/contrib/intarray/expected/_int2.out b/contrib/intarray/expected/_int2.out
new file mode 100644
index 0000000..8346334
--- /dev/null
+++ b/contrib/intarray/expected/_int2.out
@@ -0,0 +1,47 @@
+CREATE TABLE test__int2( a int[] );
+\copy test__int2 from 'data/test__int.data'
+ANALYZE test__int2;
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+ count 
+-------
+   403
+(1 row)
+
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+ count 
+-------
+   403
+(1 row)
+
+CREATE INDEX text_idx2 on test__int2 using gist ( a gist__int_ops );
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+ count 
+-------
+   403
+(1 row)
+
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+ count 
+-------
+   403
+(1 row)
+
+SELECT a, t FROM (SELECT a::text, (SELECT COUNT (*) FROM test__int2 t2 WHERE t2.a = t1.a) t from test__int2 t1 WHERE a IS NOT NULL) s WHERE t = 0;
+ a | t 
+---+---
+(0 rows)
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+             a             
+---------------------------
+ {193,213,230,266,285,299}
+(1 row)
+
+set enable_indexscan to off;
+set enable_bitmapscan to off;
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+             a             
+---------------------------
+ {193,213,230,266,285,299}
+(1 row)
+
diff --git a/contrib/intarray/sql/_int2.sql b/contrib/intarray/sql/_int2.sql
new file mode 100644
index 0000000..d4adca7
--- /dev/null
+++ b/contrib/intarray/sql/_int2.sql
@@ -0,0 +1,20 @@
+CREATE TABLE test__int2( a int[] );
+\copy test__int2 from 'data/test__int.data'
+ANALYZE test__int2;
+
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+
+CREATE INDEX text_idx2 on test__int2 using gist ( a gist__int_ops );
+
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+
+SELECT a, t FROM (SELECT a::text, (SELECT COUNT (*) FROM test__int2 t2 WHERE t2.a = t1.a) t from test__int2 t1 WHERE a IS NOT NULL) s WHERE t = 0;
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+
+set enable_indexscan to off;
+set enable_bitmapscan to off;
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
diff --git a/src/backend/access/gist/gistutil.c b/src/backend/access/gist/gistutil.c
index 94b6ad6..2183b3a 100644
--- a/src/backend/access/gist/gistutil.c
+++ b/src/backend/access/gist/gistutil.c
@@ -509,6 +509,7 @@ gistchoose(Relation r, Page p, IndexTuple it,	/* it has compressed entry */
 			{
 				/* we didn't make the random choice yet for this old best */
 				keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
+				keep_current_best = 0; /* FIXME only for debugging */
 			}
 			if (keep_current_best == 0)
 			{
@@ -531,6 +532,7 @@ gistchoose(Relation r, Page p, IndexTuple it,	/* it has compressed entry */
 			{
 				/* we didn't make the random choice yet for this old best */
 				keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
+				keep_current_best = 0; /* FIXME only for debugging */
 			}
 			if (keep_current_best == 1)
 				break;

From 59e1519a0a48b879777820ff68116c68ed31e684 Mon Sep 17 00:00:00 2001
From: "Andrey V. Lepikhov" <a.lepikhov@postgrespro.ru>
Date: Thu, 11 Apr 2019 10:52:39 +0500
Subject: [PATCH] Alt fix for gist_optimized_wal_intarray_test bug

---
 src/backend/access/gin/gininsert.c      |  2 +-
 src/backend/access/gist/gist.c          |  4 ++--
 src/backend/access/gist/gistbuild.c     | 17 +++++++++++++++--
 src/backend/access/spgist/spginsert.c   |  2 +-
 src/backend/access/transam/xloginsert.c |  4 +++-
 src/include/access/gist.h               |  6 ------
 src/include/access/gist_private.h       |  2 ++
 src/include/access/xloginsert.h         |  6 +++++-
 8 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/src/backend/access/gin/gininsert.c b/src/backend/access/gin/gininsert.c
index 55eab14617..a63f33b429 100644
--- a/src/backend/access/gin/gininsert.c
+++ b/src/backend/access/gin/gininsert.c
@@ -413,7 +413,7 @@ ginbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	{
 		log_newpage_range(index, MAIN_FORKNUM,
 						  0, RelationGetNumberOfBlocks(index),
-						  true);
+						  true, NULL);
 	}
 
 	/*
diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 2db790c840..56f6ce04db 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -492,7 +492,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 		 * we don't need to be able to detect concurrent splits yet.)
 		 */
 		if (is_build)
-			recptr = GistBuildLSN;
+			recptr = gistBuildLSN++;
 		else
 		{
 			if (RelationNeedsWAL(rel))
@@ -559,7 +559,7 @@ gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
 			MarkBufferDirty(leftchildbuf);
 
 		if (is_build)
-			recptr = GistBuildLSN;
+			recptr = gistBuildLSN++;
 		else
 		{
 			if (RelationNeedsWAL(rel))
diff --git a/src/backend/access/gist/gistbuild.c b/src/backend/access/gist/gistbuild.c
index 8e81eda517..31118b54cf 100644
--- a/src/backend/access/gist/gistbuild.c
+++ b/src/backend/access/gist/gistbuild.c
@@ -76,6 +76,13 @@ typedef struct
 	GistBufferingMode bufferingMode;
 } GISTBuildState;
 
+/*
+ * A bogus LSN / NSN value used during index build. Must be smaller than any
+ * real or fake unlogged LSN, so that after an index build finishes, all the
+ * splits are considered completed.
+ */
+XLogRecPtr gistBuildLSN = 0;
+
 /* prototypes for private functions */
 static void gistInitBuffering(GISTBuildState *buildstate);
 static int	calculatePagesPerBuffer(GISTBuildState *buildstate, int levelStep);
@@ -107,6 +114,12 @@ static void gistMemorizeParent(GISTBuildState *buildstate, BlockNumber child,
 static void gistMemorizeAllDownlinks(GISTBuildState *buildstate, Buffer parent);
 static BlockNumber gistGetParent(GISTBuildState *buildstate, BlockNumber child);
 
+static void
+gistbuild_log_mask(char *page)
+{
+	GistPageSetNSN((Page) page, (uint64) 1);
+}
+
 /*
  * Main entry point to GiST index build. Initially calls insert over and over,
  * but switches to more efficient buffering build algorithm after a certain
@@ -180,7 +193,7 @@ gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	GISTInitBuffer(buffer, F_LEAF);
 
 	MarkBufferDirty(buffer);
-	PageSetLSN(page, GistBuildLSN);
+	PageSetLSN(page, gistBuildLSN++);
 
 	UnlockReleaseBuffer(buffer);
 
@@ -222,7 +235,7 @@ gistbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	{
 		log_newpage_range(index, MAIN_FORKNUM,
 						  0, RelationGetNumberOfBlocks(index),
-						  true);
+						  true, gistbuild_log_mask);
 	}
 
 	/*
diff --git a/src/backend/access/spgist/spginsert.c b/src/backend/access/spgist/spginsert.c
index b40bd440cf..50f302d045 100644
--- a/src/backend/access/spgist/spginsert.c
+++ b/src/backend/access/spgist/spginsert.c
@@ -139,7 +139,7 @@ spgbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	{
 		log_newpage_range(index, MAIN_FORKNUM,
 						  0, RelationGetNumberOfBlocks(index),
-						  true);
+						  true, NULL);
 	}
 
 	result = (IndexBuildResult *) palloc0(sizeof(IndexBuildResult));
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index 1c76dcfa0d..ab8af41d99 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -1041,7 +1041,7 @@ log_newpage_buffer(Buffer buffer, bool page_std)
 void
 log_newpage_range(Relation rel, ForkNumber forkNum,
 				  BlockNumber startblk, BlockNumber endblk,
-				  bool page_std)
+				  bool page_std, log_mask_callback mask)
 {
 	BlockNumber blkno;
 
@@ -1089,6 +1089,8 @@ log_newpage_range(Relation rel, ForkNumber forkNum,
 		for (i = 0; i < nbufs; i++)
 		{
 			XLogRegisterBuffer(i, bufpack[i], REGBUF_FORCE_IMAGE | REGBUF_STANDARD);
+			if (mask)
+				mask(BufferGetPage(bufpack[i]));
 			MarkBufferDirty(bufpack[i]);
 		}
 
diff --git a/src/include/access/gist.h b/src/include/access/gist.h
index 6902f4115b..d09f992e1f 100644
--- a/src/include/access/gist.h
+++ b/src/include/access/gist.h
@@ -49,12 +49,6 @@
 
 typedef XLogRecPtr GistNSN;
 
-/*
- * A bogus LSN / NSN value used during index build. Must be smaller than any
- * real or fake unlogged LSN, so that after an index build finishes, all the
- * splits are considered completed.
- */
-#define GistBuildLSN	((XLogRecPtr) 1)
 
 /*
  * For on-disk compatibility with pre-9.3 servers, NSN is stored as two
diff --git a/src/include/access/gist_private.h b/src/include/access/gist_private.h
index 78e2e3fb31..64469640e4 100644
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -381,6 +381,8 @@ typedef struct GiSTOptions
 	int			bufferingModeOffset;	/* use buffering build? */
 } GiSTOptions;
 
+extern XLogRecPtr gistBuildLSN;
+
 /* gist.c */
 extern void gistbuildempty(Relation index);
 extern bool gistinsert(Relation r, Datum *values, bool *isnull,
diff --git a/src/include/access/xloginsert.h b/src/include/access/xloginsert.h
index 30c4ff7bea..0d56ee2266 100644
--- a/src/include/access/xloginsert.h
+++ b/src/include/access/xloginsert.h
@@ -38,6 +38,8 @@
 #define REGBUF_KEEP_DATA	0x10	/* include data even if a full-page image
 									 * is taken */
 
+typedef void (*log_mask_callback)(char *page);
+
 /* prototypes for public functions in xloginsert.c: */
 extern void XLogBeginInsert(void);
 extern void XLogSetRecordFlags(uint8 flags);
@@ -55,8 +57,10 @@ extern bool XLogCheckBufferNeedsBackup(Buffer buffer);
 extern XLogRecPtr log_newpage(RelFileNode *rnode, ForkNumber forkNum,
 			BlockNumber blk, char *page, bool page_std);
 extern XLogRecPtr log_newpage_buffer(Buffer buffer, bool page_std);
+
 extern void log_newpage_range(Relation rel, ForkNumber forkNum,
-				  BlockNumber startblk, BlockNumber endblk, bool page_std);
+				  BlockNumber startblk, BlockNumber endblk, bool page_std,
+				  log_mask_callback mask);
 extern XLogRecPtr XLogSaveBufferForHint(Buffer buffer, bool buffer_std);
 
 extern void InitXLogInsert(void);
-- 
2.17.1

commit 53938b423ec19a88e470b7b9552de13de5e2634a
Author: Anastasia <a.lubennikova@postgrespro.ru>
Date:   Tue Apr 9 18:58:00 2019 +0300

    fix for gist create index WAL optimization. Track splits correctly

diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 2db790c..ff98d13 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -639,6 +639,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
 	/* Start from the root */
 	firststack.blkno = GIST_ROOT_BLKNO;
 	firststack.lsn = 0;
+	firststack.retry_from_parent = false;
 	firststack.parent = NULL;
 	firststack.downlinkoffnum = InvalidOffsetNumber;
 	state.stack = stack = &firststack;
@@ -693,8 +694,15 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
 			continue;
 		}
 
+		/*
+		 * During gistbuild we cannot rely on lsn-nsn comparison,
+		 * since all pages have the same GistBuildLSN value in these fields.
+		 * So use special flag stack->retry_from_parent to detect the fact that
+		 * we need to go back to parent and rechoose the child.
+		 */
 		if (stack->blkno != GIST_ROOT_BLKNO &&
-			stack->parent->lsn < GistPageGetNSN(stack->page))
+			((stack->parent->lsn < GistPageGetNSN(stack->page)) ||
+			 stack->retry_from_parent == true))
 		{
 			/*
 			 * Concurrent split detected. There's no guarantee that the
@@ -786,6 +794,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
 						UnlockReleaseBuffer(stack->buffer);
 						xlocked = false;
 						state.stack = stack = stack->parent;
+						stack->retry_from_parent = true;
 					}
 					continue;
 				}
diff --git a/src/include/access/gist_private.h b/src/include/access/gist_private.h
index 78e2e3f..361a7a8 100644
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -215,6 +215,12 @@ typedef struct GISTInsertStack
 	 */
 	GistNSN		lsn;
 
+	/*
+	 * flag to use during gistbuild to recognize page split
+	 * (instead of lsn-nsn comparison)
+	 */
+	bool retry_from_parent;
+
 	/* offset of the downlink in the parent page, that points to this page */
 	OffsetNumber downlinkoffnum;
 

commit 53f4607b50e0516be05ef27d9369c89bdcb9d82b
Author: Anastasia <a.lubennikova@postgrespro.ru>
Date:   Tue Apr 9 18:56:32 2019 +0300

    test

diff --git a/contrib/intarray/Makefile b/contrib/intarray/Makefile
index 2505294..3535bb1 100644
--- a/contrib/intarray/Makefile
+++ b/contrib/intarray/Makefile
@@ -9,7 +9,7 @@ DATA = intarray--1.2.sql intarray--1.1--1.2.sql intarray--1.0--1.1.sql \
 	intarray--unpackaged--1.0.sql
 PGFILEDESC = "intarray - functions and operators for arrays of integers"
 
-REGRESS = _int
+REGRESS = _int _int2
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
diff --git a/contrib/intarray/expected/_int2.out b/contrib/intarray/expected/_int2.out
new file mode 100644
index 0000000..8346334
--- /dev/null
+++ b/contrib/intarray/expected/_int2.out
@@ -0,0 +1,47 @@
+CREATE TABLE test__int2( a int[] );
+\copy test__int2 from 'data/test__int.data'
+ANALYZE test__int2;
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+ count 
+-------
+   403
+(1 row)
+
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+ count 
+-------
+   403
+(1 row)
+
+CREATE INDEX text_idx2 on test__int2 using gist ( a gist__int_ops );
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+ count 
+-------
+   403
+(1 row)
+
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+ count 
+-------
+   403
+(1 row)
+
+SELECT a, t FROM (SELECT a::text, (SELECT COUNT (*) FROM test__int2 t2 WHERE t2.a = t1.a) t from test__int2 t1 WHERE a IS NOT NULL) s WHERE t = 0;
+ a | t 
+---+---
+(0 rows)
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+             a             
+---------------------------
+ {193,213,230,266,285,299}
+(1 row)
+
+set enable_indexscan to off;
+set enable_bitmapscan to off;
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+             a             
+---------------------------
+ {193,213,230,266,285,299}
+(1 row)
+
diff --git a/contrib/intarray/sql/_int2.sql b/contrib/intarray/sql/_int2.sql
new file mode 100644
index 0000000..d4adca7
--- /dev/null
+++ b/contrib/intarray/sql/_int2.sql
@@ -0,0 +1,20 @@
+CREATE TABLE test__int2( a int[] );
+\copy test__int2 from 'data/test__int.data'
+ANALYZE test__int2;
+
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+
+CREATE INDEX text_idx2 on test__int2 using gist ( a gist__int_ops );
+
+SELECT count(*) from test__int2 WHERE a && '{23,50}';
+SELECT count(*) from test__int2 WHERE a @@ '23|50';
+
+SELECT a, t FROM (SELECT a::text, (SELECT COUNT (*) FROM test__int2 t2 WHERE t2.a = t1.a) t from test__int2 t1 WHERE a IS NOT NULL) s WHERE t = 0;
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
+
+set enable_indexscan to off;
+set enable_bitmapscan to off;
+
+select * from test__int2 where a = '{193,213,230,266,285,299}';
diff --git a/src/backend/access/gist/gistutil.c b/src/backend/access/gist/gistutil.c
index 94b6ad6..2183b3a 100644
--- a/src/backend/access/gist/gistutil.c
+++ b/src/backend/access/gist/gistutil.c
@@ -509,6 +509,7 @@ gistchoose(Relation r, Page p, IndexTuple it,	/* it has compressed entry */
 			{
 				/* we didn't make the random choice yet for this old best */
 				keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
+				keep_current_best = 0; /* FIXME only for debugging */
 			}
 			if (keep_current_best == 0)
 			{
@@ -531,6 +532,7 @@ gistchoose(Relation r, Page p, IndexTuple it,	/* it has compressed entry */
 			{
 				/* we didn't make the random choice yet for this old best */
 				keep_current_best = (random() <= (MAX_RANDOM_VALUE / 2)) ? 1 : 0;
+				keep_current_best = 0; /* FIXME only for debugging */
 			}
 			if (keep_current_best == 1)
 				break;

From 7e0b7fa120b9c4c3e0f0f71dc7a5f35ba806ea7f Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Wed, 8 May 2019 01:29:52 +0300
Subject: [PATCH 1/1] Detect internal GiST page splits correctly during index
 build.

As we descend the GiST tree during insertion, we modify any downlinks on
the way down to include the new tuple we're about to insert (if they don't
cover it already). Modifying an existing downlink might cause an internal
page to split, if the new downlink tuple is larger than the old one. If
that happens, we need to back up to the parent and re-choose a page to
insert to. We used to detect that situation, thanks to the NSN-LSN
interlock normally used to detect concurrent page splits, but that got
broken by commit 9155580fd5. With that commit, we now use a dummy constant
LSN value for every page during index build, so the LSN-NSN interlock no
longer works. I thought that was OK because there can't be any other
backends modifying the index during index build, but missed that the
insertion itself can modify the page we're inserting to. The consequence
was that we would sometimes insert the new tuple to an incorrect page, one
whose downlink doesn't cover the new tuple.

Thomas Munro noticed that the contrib/intarray regression test started
failing occasionally on the buildfarm after commit 9155580fd5. The failure
was intermittent, because the gistchoose() function is not deterministic,
and would only occasionally create the right circumstances for this bug to
cause the failure.

To fix, add a flag to the stack that keeps track of the state while
descending tree, to indicate that a page was split, and we need to retry
the descend from the parent.

Patch by Anastasia Lubennikova, with some changes by me to make it work
correctly also when the internal page split also causes the "grandparent"
to be split.

Discussion: https://www.postgresql.org/message-id/CA%2BhUKGJRzLo7tZExWfSbwM3XuK7aAK7FhdBV0FLkbUG%2BW0v0zg%40mail.gmail.com
---
 src/backend/access/gist/gist.c    | 33 +++++++++++++++++++++++++++++++
 src/include/access/gist_private.h |  7 +++++++
 2 files changed, 40 insertions(+)

diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index 769aca42e3..d70a138f54 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -639,6 +639,7 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
 	/* Start from the root */
 	firststack.blkno = GIST_ROOT_BLKNO;
 	firststack.lsn = 0;
+	firststack.retry_from_parent = false;
 	firststack.parent = NULL;
 	firststack.downlinkoffnum = InvalidOffsetNumber;
 	state.stack = stack = &firststack;
@@ -651,6 +652,21 @@ gistdoinsert(Relation r, IndexTuple itup, Size freespace,
 	 */
 	for (;;)
 	{
+		/*
+		 * If we split an internal page while descending the tree, we have to
+		 * retry at the parent. (Normally, the LSN-NSN interlock below would
+		 * also catch this and cause us to retry. But LSNs are not updated
+		 * during index build.)
+		 */
+		while (stack->retry_from_parent)
+		{
+			if (xlocked)
+				LockBuffer(stack->buffer, GIST_UNLOCK);
+			xlocked = false;
+			ReleaseBuffer(stack->buffer);
+			state.stack = stack = stack->parent;
+		}
+
 		if (XLogRecPtrIsInvalid(stack->lsn))
 			stack->buffer = ReadBuffer(state.r, stack->blkno);
 
@@ -1376,6 +1392,23 @@ gistfinishsplit(GISTInsertState *state, GISTInsertStack *stack,
 					 unlockbuf	/* Unlock stack->buffer if caller wants that */
 		);
 	Assert(left->buf == stack->buffer);
+
+	/*
+	 * If we split the page because we had to adjust the downlink on an
+	 * internal page, while descending the tree for inserting a new tuple,
+	 * then this might no longer be the correct page for the new tuple. The
+	 * downlink to this page might not cover the new tuple anymore, it might
+	 * need to go to the newly-created right sibling instead. Tell the caller
+	 * to walk back up the stack, to re-check at the parent which page to
+	 * insert to.
+	 *
+	 * Normally, the LSN-NSN interlock during the tree descend would also
+	 * detect that a concurrent split happened (by ourselves), and cause us to
+	 * retry at the parent. But that mechanism doesn't work during index
+	 * build, because we don't do WAL-logging, and don't update LSNs, during
+	 * index build.
+	 */
+	stack->retry_from_parent = true;
 }
 
 /*
diff --git a/src/include/access/gist_private.h b/src/include/access/gist_private.h
index ccf050cd62..614d9996ec 100644
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -215,6 +215,13 @@ typedef struct GISTInsertStack
 	 */
 	GistNSN		lsn;
 
+	/*
+	 * If set, we split the page while descending the tree to find an
+	 * insertion target. It means that we need to retry from the parent,
+	 * because the downlink of this page might no longer cover the new key.
+	 */
+	bool		retry_from_parent;
+
 	/* offset of the downlink in the parent page, that points to this page */
 	OffsetNumber downlinkoffnum;
 
-- 
2.20.1