Renaming of pg_xlog and pg_clog

From 74ff97a9520f496e0df303e777ad93d5eca054f5 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@otacoo.com>
Date: Mon, 29 Aug 2016 15:05:46 +0900
Subject: [PATCH 1/2] Rename pg_clog to pg_trans

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml               |  4 +-
 doc/src/sgml/catalogs.sgml             |  4 +-
 doc/src/sgml/config.sgml               |  2 +-
 doc/src/sgml/func.sgml                 |  2 +-
 doc/src/sgml/maintenance.sgml          |  8 ++--
 doc/src/sgml/ref/pg_resetxlog.sgml     |  4 +-
 doc/src/sgml/ref/pg_rewind.sgml        |  2 +-
 doc/src/sgml/storage.sgml              | 10 ++---
 doc/src/sgml/wal.sgml                  |  2 +-
 src/backend/access/heap/heapam.c       |  4 +-
 src/backend/access/transam/README      | 12 +++---
 src/backend/access/transam/clog.c      |  2 +-
 src/backend/access/transam/commit_ts.c |  2 +-
 src/backend/access/transam/multixact.c |  2 +-
 src/backend/access/transam/subtrans.c  |  4 +-
 src/backend/access/transam/transam.c   |  2 +-
 src/backend/access/transam/twophase.c  |  4 +-
 src/backend/access/transam/xact.c      | 18 ++++----
 src/backend/access/transam/xlog.c      |  2 +-
 src/backend/commands/vacuum.c          | 10 ++---
 src/backend/postmaster/autovacuum.c    |  2 +-
 src/backend/storage/buffer/README      |  2 +-
 src/backend/storage/ipc/procarray.c    |  4 +-
 src/backend/utils/time/tqual.c         |  6 +--
 src/bin/initdb/initdb.c                |  2 +-
 src/bin/pg_upgrade/exec.c              | 79 +++++++++++++++++++++-------------
 src/bin/pg_upgrade/pg_upgrade.c        | 30 +++++++------
 src/include/access/slru.h              |  4 +-
 28 files changed, 127 insertions(+), 102 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 0f09d82..18d4bd5 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -382,10 +382,10 @@ tar -cf backup.tar /usr/local/pgsql/data
       directories. This will <emphasis>not</> work because the
       information contained in these files is not usable without
       the commit log files,
-      <filename>pg_clog/*</filename>, which contain the commit status of
+      <filename>pg_trans/*</filename>, which contain the commit status of
       all transactions. A table file is only usable with this
       information. Of course it is also impossible to restore only a
-      table and the associated <filename>pg_clog</filename> data
+      table and the associated <filename>pg_trans</filename> data
       because that would render all other tables in the database
       cluster useless.  So file system backups only work for complete
       backup and restoration of an entire database cluster.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 4e09e06..783d49c 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1847,7 +1847,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this table.  This is used to track
        whether the table needs to be vacuumed in order to prevent transaction
-       ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
+       ID wraparound or to allow <literal>pg_trans</> to be shrunk.  Zero
        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
       </entry>
      </row>
@@ -2514,7 +2514,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this database.  This is used to
        track whether the database needs to be vacuumed in order to prevent
-       transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
+       transaction ID wraparound or to allow <literal>pg_trans</> to be shrunk.
        It is the minimum of the per-table
        <structname>pg_class</>.<structfield>relfrozenxid</> values.
       </entry>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7c483c6..c32da94 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5816,7 +5816,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
 
        <para>
         Vacuum also allows removal of old files from the
-        <filename>pg_clog</> subdirectory, which is why the default
+        <filename>pg_trans</> subdirectory, which is why the default
         is a relatively low 200 million transactions.
         This parameter can only be set at server start, but the setting
         can be reduced for individual tables by
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 5148095..626e428 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15312,7 +15312,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  postmaster.pid  |  9
  pg_ident.conf   | 10
  global          | 11
- pg_clog         | 12
+ pg_trans        | 12
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index 2713883..75f61cd 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -505,18 +505,18 @@
    <para>
     The sole disadvantage of increasing <varname>autovacuum_freeze_max_age</>
     (and <varname>vacuum_freeze_table_age</> along with it)
-    is that the <filename>pg_clog</> subdirectory of the database cluster
+    is that the <filename>pg_trans</> subdirectory of the database cluster
     will take more space, because it must store the commit status of all
     transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
     The commit status uses two bits per transaction, so if
     <varname>autovacuum_freeze_max_age</> is set to its maximum allowed
-    value of two billion, <filename>pg_clog</> can be expected to
+    value of two billion, <filename>pg_trans</> can be expected to
     grow to about half a gigabyte.  If this is trivial compared to your
     total database size, setting <varname>autovacuum_freeze_max_age</> to
     its maximum allowed value is recommended.  Otherwise, set it depending
-    on what you are willing to allow for <filename>pg_clog</> storage.
+    on what you are willing to allow for <filename>pg_trans</> storage.
     (The default, 200 million transactions, translates to about 50MB of
-    <filename>pg_clog</> storage.)
+    <filename>pg_trans</> storage.)
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index fd9d0be..7253b40 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -256,12 +256,12 @@ PostgreSQL documentation
 
      <para>
       A safe value can be determined by looking for the numerically largest
-      file name in the directory <filename>pg_clog</> under the data directory,
+      file name in the directory <filename>pg_trans</> under the data directory,
       adding one,
       and then multiplying by 1048576 (0x100000).  Note that the file names are in
       hexadecimal.  It is usually easiest to specify the option value in
       hexadecimal too. For example, if <filename>0011</> is the largest entry
-      in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
+      in <filename>pg_trans</>, <literal>-x 0x1200000</> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 42ebfbf..fb64305 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -229,7 +229,7 @@ PostgreSQL documentation
     </step>
     <step>
      <para>
-      Copy all other files such as <filename>pg_clog</filename> and
+      Copy all other files such as <filename>pg_trans</filename> and
       configuration files from the source cluster to the target cluster
       (everything except the relation files).
      </para>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 1b812bd..1528a2e 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -72,11 +72,6 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_clog</></entry>
- <entry>Subdirectory containing transaction commit status data</entry>
-</row>
-
-<row>
  <entry><filename>pg_dynshmem</></entry>
  <entry>Subdirectory containing files used by the dynamic shared memory
   subsystem</entry>
@@ -136,6 +131,11 @@ Item
 </row>
 
 <row>
+ <entry><filename>pg_trans</></entry>
+ <entry>Subdirectory containing transaction commit status data</entry>
+</row>
+
+<row>
  <entry><filename>pg_twophase</></entry>
  <entry>Subdirectory containing state files for prepared transactions</entry>
 </row>
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 503ea8a..fd179ec 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_clog</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_trans</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 6a27ef4..39a3dc3 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -6751,8 +6751,8 @@ heap_prepare_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
  * Note: it might seem we could make the changes without exclusive lock, since
  * TransactionId read/write is assumed atomic anyway.  However there is a race
  * condition: someone who just fetched an old XID that we overwrite here could
- * conceivably not finish checking the XID against pg_clog before we finish
- * the VACUUM and perhaps truncate off the part of pg_clog he needs.  Getting
+ * conceivably not finish checking the XID against pg_trans before we finish
+ * the VACUUM and perhaps truncate off the part of pg_trans he needs.  Getting
  * exclusive lock ensures no other backend is in process of checking the
  * tuple status.  Also, getting exclusive lock makes it safe to adjust the
  * infomask bits.
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index 4ae4715..f941cfd 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -331,17 +331,17 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_clog and pg_subtrans
------------------------
+pg_trans and pg_subtrans
+------------------------
 
-pg_clog and pg_subtrans are permanent (on-disk) storage of transaction related
+pg_trans and pg_subtrans are permanent (on-disk) storage of transaction related
 information.  There is a limited number of pages of each kept in memory, so
 in many cases there is no need to actually read from disk.  However, if
 there's a long running transaction or a backend sitting idle with an open
 transaction, it may be necessary to be able to read and write this information
 from disk.  They also allow information to be permanent across server restarts.
 
-pg_clog records the commit status for each transaction that has been assigned
+pg_trans records the commit status for each transaction that has been assigned
 an XID.  A transaction can be in progress, committed, aborted, or
 "sub-committed".  This last state means that it's a subtransaction that's no
 longer running, but its parent has not updated its state yet.  It is not
@@ -381,9 +381,9 @@ each transaction we keep a "cache" of Xids that are known to be part of the
 transaction tree, so we can skip looking at pg_subtrans unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_clog and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_trans and pg_subtrans.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
-for pg_clog are implemented in transam.c, while the low-level functions are in
+for pg_trans are implemented in transam.c, while the low-level functions are in
 clog.c.  pg_subtrans is contained completely in subtrans.c.
 
 
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 2634476..a6bddd1 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -450,7 +450,7 @@ CLOGShmemInit(void)
 {
 	ClogCtl->PagePrecedes = CLOGPagePrecedes;
 	SimpleLruInit(ClogCtl, "clog", CLOGShmemBuffers(), CLOG_LSNS_PER_PAGE,
-				  CLogControlLock, "pg_clog", LWTRANCHE_CLOG_BUFFERS);
+				  CLogControlLock, "pg_trans", LWTRANCHE_CLOG_BUFFERS);
 }
 
 /*
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index e330105..08a0251 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -3,7 +3,7 @@
  * commit_ts.c
  *		PostgreSQL commit timestamp manager
  *
- * This module is a pg_clog-like system that stores the commit timestamp
+ * This module is a pg_trans-like system that stores the commit timestamp
  * for each transaction.
  *
  * XLOG interactions: this module generates an XLOG record whenever a new
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index e9588a7..303acf6 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3,7 +3,7 @@
  * multixact.c
  *		PostgreSQL multi-transaction-log manager
  *
- * The pg_multixact manager is a pg_clog-like manager that stores an array of
+ * The pg_multixact manager is a pg_trans-like manager that stores an array of
  * MultiXactMember for each MultiXactId.  It is a fundamental part of the
  * shared-row-lock implementation.  Each MultiXactMember is comprised of a
  * TransactionId and a set of flag bits.  The name is a bit historical:
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 908fe2d..8962c26 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,7 +3,7 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_clog-like manager that stores the parent
+ * The pg_subtrans manager is a pg_trans-like manager that stores the parent
  * transaction Id for each transaction.  It is a fundamental part of the
  * nested transactions implementation.  A main transaction has a parent
  * of InvalidTransactionId, and each subtransaction has its immediate parent.
@@ -11,7 +11,7 @@
  * opposite direction.
  *
  * This code is based on clog.c, but the robustness requirements
- * are completely different from pg_clog, because we only need to remember
+ * are completely different from pg_trans, because we only need to remember
  * pg_subtrans information for currently-open transactions.  Thus, there is
  * no need to preserve data over a crash and restart.
  *
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index 1eba49a..108c1da 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -224,7 +224,7 @@ TransactionIdDidAbort(TransactionId transactionId)
  *		True iff transaction associated with the identifier is currently
  *		known to have either committed or aborted.
  *
- * This does NOT look into pg_clog but merely probes our local cache
+ * This does NOT look into pg_trans but merely probes our local cache
  * (and so it's not named TransactionIdDidComplete, which would be the
  * appropriate name for a function that worked that way).  The intended
  * use is just to short-circuit TransactionIdIsInProgress calls when doing
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 9f55adc..2a51f67 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1379,7 +1379,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	/*
 	 * The order of operations here is critical: make the XLOG entry for
 	 * commit or abort, then mark the transaction committed or aborted in
-	 * pg_clog, then remove its PGPROC from the global ProcArray (which means
+	 * pg_trans, then remove its PGPROC from the global ProcArray (which means
 	 * TransactionIdIsInProgress will stop saying the prepared xact is in
 	 * progress), then run the post-commit or post-abort callbacks. The
 	 * callbacks will release the locks the transaction held.
@@ -2089,7 +2089,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	/* Flush XLOG to disk */
 	XLogFlush(recptr);
 
-	/* Mark the transaction committed in pg_clog */
+	/* Mark the transaction committed in pg_trans */
 	TransactionIdCommitTree(xid, nchildren, children);
 
 	/* Checkpoint can proceed now */
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index e11b229..2f5bf34 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1206,8 +1206,8 @@ RecordTransactionCommit(void)
 		/*
 		 * Mark ourselves as within our "commit critical section".  This
 		 * forces any concurrent checkpoint to wait until we've updated
-		 * pg_clog.  Without this, it is possible for the checkpoint to set
-		 * REDO after the XLOG record but fail to flush the pg_clog update to
+		 * pg_trans.  Without this, it is possible for the checkpoint to set
+		 * REDO after the XLOG record but fail to flush the pg_trans update to
 		 * disk, leading to loss of the transaction commit if the system
 		 * crashes a little later.
 		 *
@@ -2033,7 +2033,7 @@ CommitTransaction(void)
 	if (!is_parallel_worker)
 	{
 		/*
-		 * We need to mark our XIDs as committed in pg_clog.  This is where we
+		 * We need to mark our XIDs as committed in pg_trans.  This is where we
 		 * durably commit.
 		 */
 		latestXid = RecordTransactionCommit();
@@ -2539,7 +2539,7 @@ AbortTransaction(void)
 	AtAbort_Twophase();
 
 	/*
-	 * Advertise the fact that we aborted in pg_clog (assuming that we got as
+	 * Advertise the fact that we aborted in pg_trans (assuming that we got as
 	 * far as assigning an XID to advertise).  But if we're inside a parallel
 	 * worker, skip this; the user backend must be the one to write the abort
 	 * record.
@@ -4625,7 +4625,7 @@ AbortSubTransaction(void)
 								s->parent->subTransactionId);
 		AtSubAbort_Notify();
 
-		/* Advertise the fact that we aborted in pg_clog. */
+		/* Advertise the fact that we aborted in pg_trans. */
 		(void) RecordTransactionAbort(true);
 
 		/* Post-abort cleanup */
@@ -5371,7 +5371,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 	if (standbyState == STANDBY_DISABLED)
 	{
 		/*
-		 * Mark the transaction committed in pg_clog.
+		 * Mark the transaction committed in pg_trans.
 		 */
 		TransactionIdCommitTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
@@ -5389,7 +5389,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		RecordKnownAssignedTransactionIds(max_xid);
 
 		/*
-		 * Mark the transaction committed in pg_clog. We use async commit
+		 * Mark the transaction committed in pg_trans. We use async commit
 		 * protocol during recovery to provide information on database
 		 * consistency for when users try to set hint bits. It is important
 		 * that we do not set hint bits until the minRecoveryPoint is past
@@ -5526,7 +5526,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 
 	if (standbyState == STANDBY_DISABLED)
 	{
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_trans, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
 	else
@@ -5542,7 +5542,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 		 */
 		RecordKnownAssignedTransactionIds(max_xid);
 
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_trans, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 
 		/*
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index acd95aa..4333903 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8392,7 +8392,7 @@ CreateCheckPoint(int flags)
 	 * that are currently in commit critical sections.  If an xact inserted
 	 * its commit record into XLOG just before the REDO point, then a crash
 	 * restart from the REDO point would not replay that record, which means
-	 * that our flushing had better include the xact's update of pg_clog.  So
+	 * that our flushing had better include the xact's update of pg_trans.  So
 	 * we wait till he's out of his commit critical section before proceeding.
 	 * See notes in RecordTransactionCommit().
 	 *
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 58bbf55..a5babef 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -356,7 +356,7 @@ vacuum(int options, RangeVar *relation, Oid relid, VacuumParams *params,
 	if ((options & VACOPT_VACUUM) && !IsAutoVacuumWorkerProcess())
 	{
 		/*
-		 * Update pg_database.datfrozenxid, and truncate pg_clog if possible.
+		 * Update pg_database.datfrozenxid, and truncate pg_trans if possible.
 		 * (autovacuum.c does this for itself.)
 		 */
 		vac_update_datfrozenxid();
@@ -880,7 +880,7 @@ vac_update_relstats(Relation relation,
  *		pg_class.relminmxid values.
  *
  *		If we are able to advance either pg_database value, also try to
- *		truncate pg_clog and pg_multixact.
+ *		truncate pg_trans and pg_multixact.
  *
  *		We violate transaction semantics here by overwriting the database's
  *		existing pg_database tuple with the new values.  This is reasonably
@@ -1026,7 +1026,7 @@ vac_update_datfrozenxid(void)
 
 	/*
 	 * If we were able to advance datfrozenxid or datminmxid, see if we can
-	 * truncate pg_clog and/or pg_multixact.  Also do it if the shared
+	 * truncate pg_trans and/or pg_multixact.  Also do it if the shared
 	 * XID-wrap-limit info is stale, since this action will update that too.
 	 */
 	if (dirty || ForceTransactionIdLimitUpdate())
@@ -1039,7 +1039,7 @@ vac_update_datfrozenxid(void)
  *	vac_truncate_clog() -- attempt to truncate the commit log
  *
  *		Scan pg_database to determine the system-wide oldest datfrozenxid,
- *		and use it to truncate the transaction commit log (pg_clog).
+ *		and use it to truncate the transaction commit log (pg_trans).
  *		Also update the XID wrap limit info maintained by varsup.c.
  *		Likewise for datminmxid.
  *
@@ -1086,7 +1086,7 @@ vac_truncate_clog(TransactionId frozenXID,
 	 * of the interlock against copying a DB containing an active backend.
 	 * Hence the new entry will not reduce the minimum.  Also, if two VACUUMs
 	 * concurrently modify the datfrozenxid's of different databases, the
-	 * worst possible outcome is that pg_clog is not truncated as aggressively
+	 * worst possible outcome is that pg_trans is not truncated as aggressively
 	 * as it could be.
 	 */
 	relation = heap_open(DatabaseRelationId, AccessShareLock);
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 1a92ca1..f77aa01 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2394,7 +2394,7 @@ deleted:
 	 */
 
 	/*
-	 * Update pg_database.datfrozenxid, and truncate pg_clog if possible. We
+	 * Update pg_database.datfrozenxid, and truncate pg_trans if possible. We
 	 * only need to do this once, not after each table.
 	 */
 	vac_update_datfrozenxid();
diff --git a/src/backend/storage/buffer/README b/src/backend/storage/buffer/README
index 248883f..e7dda01 100644
--- a/src/backend/storage/buffer/README
+++ b/src/backend/storage/buffer/README
@@ -63,7 +63,7 @@ at about the same time would OR the same bits into the field, so there
 is little or no risk of conflicting update; what's more, if there did
 manage to be a conflict it would merely mean that one bit-update would
 be lost and need to be done again later.  These four bits are only hints
-(they cache the results of transaction status lookups in pg_clog), so no
+(they cache the results of transaction status lookups in pg_trans), so no
 great harm is done if they get reset to zero by conflicting updates.
 Note, however, that a tuple is frozen by setting both HEAP_XMIN_INVALID
 and HEAP_XMIN_COMMITTED; this is a critical update and accordingly requires
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index e5d487d..5ce3a44 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -388,7 +388,7 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
  * ProcArrayEndTransaction -- mark a transaction as no longer running
  *
  * This is used interchangeably for commit and abort cases.  The transaction
- * commit/abort must already be reported to WAL and pg_clog.
+ * commit/abort must already be reported to WAL and pg_trans.
  *
  * proc is currently always MyProc, but we pass it explicitly for flexibility.
  * latestXid is the latest Xid among the transaction's main XID and
@@ -1180,7 +1180,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
 	 * subtransaction, we want to say "not running" even though its parent may
-	 * still be running.  So first, check pg_clog to see if it's been aborted.
+	 * still be running.  So first, check pg_trans to see if it's been aborted.
 	 */
 	xc_slow_answer_inc();
 
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 26a3be3..c4202e5 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -13,9 +13,9 @@
  * NOTE: When using a non-MVCC snapshot, we must check
  * TransactionIdIsInProgress (which looks in the PGXACT array)
  * before TransactionIdDidCommit/TransactionIdDidAbort (which look in
- * pg_clog).  Otherwise we have a race condition: we might decide that a
+ * pg_trans).  Otherwise we have a race condition: we might decide that a
  * just-committed transaction crashed, because none of the tests succeed.
- * xact.c is careful to record commit/abort in pg_clog before it unsets
+ * xact.c is careful to record commit/abort in pg_trans before it unsets
  * MyPgXact->xid in the PGXACT array.  That fixes that problem, but it
  * also means there is a window where TransactionIdIsInProgress and
  * TransactionIdDidCommit will both return true.  If we check only
@@ -29,7 +29,7 @@
  *
  * When using an MVCC snapshot, we rely on XidInMVCCSnapshot rather than
  * TransactionIdIsInProgress, but the logic is otherwise the same: do not
- * check pg_clog until after deciding that the xact is no longer in progress.
+ * check pg_trans until after deciding that the xact is no longer in progress.
  *
  *
  * Summary of visibility functions:
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index aad6ba5..ec06e34 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -201,7 +201,6 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 static const char *const subdirs[] = {
 	"global",
 	"pg_xlog/archive_status",
-	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
 	"pg_notify",
@@ -218,6 +217,7 @@ static const char *const subdirs[] = {
 	"pg_tblspc",
 	"pg_stat",
 	"pg_stat_tmp",
+	"pg_trans",
 	"pg_logical",
 	"pg_logical/snapshots",
 	"pg_logical/mappings"
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index dd30952..5f6a6ea 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -14,7 +14,7 @@
 #include <fcntl.h>
 #include <sys/types.h>
 
-static void check_data_dir(const char *pg_data);
+static void check_data_dir(ClusterInfo *cluster);
 static void check_bin_dir(ClusterInfo *cluster);
 static void validate_exec(const char *dir, const char *cmdName);
 
@@ -220,9 +220,9 @@ verify_directories(void)
 		pg_fatal("You must have read and write access in the current directory.\n");
 
 	check_bin_dir(&old_cluster);
-	check_data_dir(old_cluster.pgdata);
+	check_data_dir(&old_cluster);
 	check_bin_dir(&new_cluster);
-	check_data_dir(new_cluster.pgdata);
+	check_data_dir(&new_cluster);
 }
 
 
@@ -253,6 +253,31 @@ win32_check_directory_write_permissions(void)
 
 
 /*
+ * check_single_dir()
+ *
+ *  Check for the presence of a single directory in PGDATA, and fail if
+ * is it missing or not accessible.
+ */
+static void
+check_single_dir(const char *pg_data, const char *subdir)
+{
+	struct stat statBuf;
+	char        subDirName[MAXPGPATH];
+
+	snprintf(subDirName, sizeof(subDirName), "%s%s%s", pg_data,
+	/* Win32 can't stat() a directory with a trailing slash. */
+				 *subdir ? "/" : "",
+				 subdir);
+
+	if (stat(subDirName, &statBuf) != 0)
+		report_status(PG_FATAL, "check for \"%s\" failed: %s\n",
+					  subDirName, getErrorText());
+	else if (!S_ISDIR(statBuf.st_mode))
+		report_status(PG_FATAL, "%s is not a directory\n",
+					  subDirName);
+}
+
+/*
  * check_data_dir()
  *
  *	This function validates the given cluster directory - we search for a
@@ -262,34 +287,28 @@ win32_check_directory_write_permissions(void)
  *
  */
 static void
-check_data_dir(const char *pg_data)
+check_data_dir(ClusterInfo *cluster)
 {
-	char		subDirName[MAXPGPATH];
-	int			subdirnum;
-
-	/* start check with top-most directory */
-	const char *requiredSubdirs[] = {"", "base", "global", "pg_clog",
-		"pg_multixact", "pg_subtrans", "pg_tblspc", "pg_twophase",
-	"pg_xlog"};
-
-	for (subdirnum = 0;
-		 subdirnum < sizeof(requiredSubdirs) / sizeof(requiredSubdirs[0]);
-		 ++subdirnum)
-	{
-		struct stat statBuf;
-
-		snprintf(subDirName, sizeof(subDirName), "%s%s%s", pg_data,
-		/* Win32 can't stat() a directory with a trailing slash. */
-				 *requiredSubdirs[subdirnum] ? "/" : "",
-				 requiredSubdirs[subdirnum]);
-
-		if (stat(subDirName, &statBuf) != 0)
-			report_status(PG_FATAL, "check for \"%s\" failed: %s\n",
-						  subDirName, getErrorText());
-		else if (!S_ISDIR(statBuf.st_mode))
-			report_status(PG_FATAL, "%s is not a directory\n",
-						  subDirName);
-	}
+	const char *pg_data = cluster->pgdata;
+
+	/* get old and new cluster versions */
+	old_cluster.major_version = get_major_server_version(&old_cluster);
+	new_cluster.major_version = get_major_server_version(&new_cluster);
+
+	check_single_dir(pg_data, "");
+	check_single_dir(pg_data, "base");
+	check_single_dir(pg_data, "global");
+	check_single_dir(pg_data, "pg_multixact");
+	check_single_dir(pg_data, "pg_subtrans");
+	check_single_dir(pg_data, "pg_tblspc");
+	check_single_dir(pg_data, "pg_twophase");
+	check_single_dir(pg_data, "pg_xlog");
+
+	/* pg_clog has been renamed to pg_trans in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_clog");
+	else
+		check_single_dir(pg_data, "pg_trans");
 }
 
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index fa118e9..dd7a54b 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -47,7 +47,7 @@
 static void prepare_new_cluster(void);
 static void prepare_new_databases(void);
 static void create_new_objects(void);
-static void copy_clog_xlog_xid(void);
+static void copy_trans_xlog_xid(void);
 static void set_frozenxids(bool minmxid_only);
 static void setup(char *argv0, bool *live_check);
 static void cleanup(void);
@@ -113,7 +113,7 @@ main(int argc, char **argv)
 	 * Destructive Changes to New Cluster
 	 */
 
-	copy_clog_xlog_xid();
+	copy_trans_xlog_xid();
 
 	/* New now using xids of the old system */
 
@@ -374,17 +374,17 @@ remove_new_subdir(char *subdir, bool rmtopdir)
  * Copy the files from the old cluster into it
  */
 static void
-copy_subdir_files(char *subdir)
+copy_subdir_files(char *old_subdir, char *new_subdir)
 {
 	char		old_path[MAXPGPATH];
 	char		new_path[MAXPGPATH];
 
-	remove_new_subdir(subdir, true);
+	remove_new_subdir(new_subdir, true);
 
-	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, subdir);
-	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, subdir);
+	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, old_subdir);
+	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, new_subdir);
 
-	prep_status("Copying old %s to new server", subdir);
+	prep_status("Copying old %s to new server", old_subdir);
 
 	exec_prog(UTILITY_LOG_FILE, NULL, true,
 #ifndef WIN32
@@ -399,10 +399,16 @@ copy_subdir_files(char *subdir)
 }
 
 static void
-copy_clog_xlog_xid(void)
+copy_trans_xlog_xid(void)
 {
-	/* copy old commit logs to new data dir */
-	copy_subdir_files("pg_clog");
+	/*
+	 * Copy old commit logs to new data dir. pg_clog has been renamed to
+	 * pg_trans in post-10 clusters.
+	 */
+	copy_subdir_files(GET_MAJOR_VERSION(old_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_trans",
+					  GET_MAJOR_VERSION(new_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_trans");
 
 	/* set the next transaction id and epoch of the new cluster */
 	prep_status("Setting next transaction ID and epoch for new cluster");
@@ -432,8 +438,8 @@ copy_clog_xlog_xid(void)
 	if (old_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER &&
 		new_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER)
 	{
-		copy_subdir_files("pg_multixact/offsets");
-		copy_subdir_files("pg_multixact/members");
+		copy_subdir_files("pg_multixact/offsets", "pg_multixact/offsets");
+		copy_subdir_files("pg_multixact/members", "pg_multixact/members");
 
 		prep_status("Setting next multixact ID and offset for new cluster");
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 5fcebc5..e279d0d 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,7 +76,7 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_clog, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
+	 * for pg_trans, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
 	 * has lsn_groups_per_page entries per buffer slot, each containing the
 	 * highest LSN known for a contiguous group of SLRU entries on that slot's
 	 * page.
@@ -120,7 +120,7 @@ typedef struct SlruCtlData
 	SlruShared	shared;
 
 	/*
-	 * This flag tells whether to fsync writes (true for pg_clog and multixact
+	 * This flag tells whether to fsync writes (true for pg_trans and multixact
 	 * stuff, false for pg_subtrans and pg_notify).
 	 */
 	bool		do_fsync;
-- 
2.9.3

From 02687ad0239f3ba617b78f88cf1630c2b0886a73 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@otacoo.com>
Date: Mon, 29 Aug 2016 15:26:38 +0900
Subject: [PATCH 2/2] Rename pg_xlog to pg_wal

Additional check handling is needed in pg_upgrade regarding the clusters
worked on, except that it is a very mechanical patch.
---
 doc/src/sgml/backup.sgml                     |  28 ++++----
 doc/src/sgml/config.sgml                     |   6 +-
 doc/src/sgml/func.sgml                       |   2 +-
 doc/src/sgml/high-availability.sgml          |  14 ++--
 doc/src/sgml/perform.sgml                    |   2 +-
 doc/src/sgml/protocol.sgml                   |   6 +-
 doc/src/sgml/ref/pg_resetxlog.sgml           |  10 +--
 doc/src/sgml/ref/pg_rewind.sgml              |   4 +-
 doc/src/sgml/ref/pg_xlogdump.sgml            |   2 +-
 doc/src/sgml/ref/pgtestfsync.sgml            |   4 +-
 doc/src/sgml/ref/pgupgrade.sgml              |   4 +-
 doc/src/sgml/storage.sgml                    |   2 +-
 doc/src/sgml/wal.sgml                        |  10 +--
 src/backend/access/transam/timeline.c        |   4 +-
 src/backend/access/transam/xlog.c            | 100 +++++++++++++--------------
 src/backend/access/transam/xlogarchive.c     |   2 +-
 src/backend/access/transam/xlogfuncs.c       |   2 +-
 src/backend/replication/README               |   2 +-
 src/backend/replication/basebackup.c         |  20 +++---
 src/backend/replication/walreceiver.c        |   6 +-
 src/backend/replication/walsender.c          |   4 +-
 src/backend/storage/file/fd.c                |  16 ++---
 src/bin/initdb/initdb.c                      |  26 +++----
 src/bin/pg_basebackup/pg_basebackup.c        |  16 ++---
 src/bin/pg_basebackup/t/010_pg_basebackup.pl |   6 +-
 src/bin/pg_resetxlog/pg_resetxlog.c          |   2 +-
 src/bin/pg_rewind/copy_fetch.c               |   4 +-
 src/bin/pg_rewind/filemap.c                  |   8 +--
 src/bin/pg_rewind/parsexlog.c                |   2 +-
 src/bin/pg_rewind/t/004_pg_xlog_symlink.pl   |  10 +--
 src/bin/pg_upgrade/exec.c                    |   7 +-
 src/bin/pg_xlogdump/pg_xlogdump.c            |   2 +-
 src/include/access/xlog_internal.h           |   2 +-
 src/include/postmaster/pgarch.h              |   2 +-
 34 files changed, 171 insertions(+), 166 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 18d4bd5..1fa4d0e 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -472,7 +472,7 @@ tar -cf backup.tar /usr/local/pgsql/data
 
   <para>
    At all times, <productname>PostgreSQL</> maintains a
-   <firstterm>write ahead log</> (WAL) in the <filename>pg_xlog/</>
+   <firstterm>write ahead log</> (WAL) in the <filename>pg_wal/</>
    subdirectory of the cluster's data directory. The log records
    every change made to the database's data files.  This log exists
    primarily for crash-safety purposes: if the system crashes, the
@@ -616,7 +616,7 @@ archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"'  # Windows
     <literal>%p</> and <literal>%f</> parameters have been replaced,
     the actual command executed might look like this:
 <programlisting>
-test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065
+test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_wal/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065
 </programlisting>
     A similar command will be generated for each new file to be archived.
    </para>
@@ -668,9 +668,9 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     fills, nothing further can be archived until the tape is swapped.
     You should ensure that any error condition or request to a human operator
     is reported appropriately so that the situation can be
-    resolved reasonably quickly. The <filename>pg_xlog/</> directory will
+    resolved reasonably quickly. The <filename>pg_wal/</> directory will
     continue to fill with WAL segment files until the situation is resolved.
-    (If the file system containing <filename>pg_xlog/</> fills up,
+    (If the file system containing <filename>pg_wal/</> fills up,
     <productname>PostgreSQL</> will do a PANIC shutdown.  No committed
     transactions will be lost, but the database will remain offline until
     you free some space.)
@@ -682,7 +682,7 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     operation continues even if the archiving process falls a little behind.
     If archiving falls significantly behind, this will increase the amount of
     data that would be lost in the event of a disaster. It will also mean that
-    the <filename>pg_xlog/</> directory will contain large numbers of
+    the <filename>pg_wal/</> directory will contain large numbers of
     not-yet-archived segment files, which could eventually exceed available
     disk space. You are advised to monitor the archiving process to ensure that
     it is working as you intend.
@@ -743,7 +743,7 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     configuration file reload.  If you wish to temporarily stop archiving,
     one way to do it is to set <varname>archive_command</> to the empty
     string (<literal>''</>).
-    This will cause WAL files to accumulate in <filename>pg_xlog/</> until a
+    This will cause WAL files to accumulate in <filename>pg_wal/</> until a
     working <varname>archive_command</> is re-established.
    </para>
   </sect2>
@@ -1062,10 +1062,10 @@ SELECT pg_stop_backup();
 
    <para>
     You should, however, omit from the backup the files within the
-    cluster's <filename>pg_xlog/</> subdirectory.  This
+    cluster's <filename>pg_wal/</> subdirectory.  This
     slight adjustment is worthwhile because it reduces the risk
     of mistakes when restoring.  This is easy to arrange if
-    <filename>pg_xlog/</> is a symbolic link pointing to someplace outside
+    <filename>pg_wal/</> is a symbolic link pointing to someplace outside
     the cluster directory, which is a common setup anyway for performance
     reasons.  You might also want to exclude <filename>postmaster.pid</>
     and <filename>postmaster.opts</>, which record information
@@ -1133,7 +1133,7 @@ SELECT pg_stop_backup();
      location in case you need them later. Note that this precaution will
      require that you have enough free space on your system to hold two
      copies of your existing database. If you do not have enough space,
-     you should at least save the contents of the cluster's <filename>pg_xlog</>
+     you should at least save the contents of the cluster's <filename>pg_wal</>
      subdirectory, as it might contain logs which
      were not archived before the system went down.
     </para>
@@ -1156,9 +1156,9 @@ SELECT pg_stop_backup();
    </listitem>
    <listitem>
     <para>
-     Remove any files present in <filename>pg_xlog/</>; these came from the
+     Remove any files present in <filename>pg_wal/</>; these came from the
      file system backup and are therefore probably obsolete rather than current.
-     If you didn't archive <filename>pg_xlog/</> at all, then recreate
+     If you didn't archive <filename>pg_wal/</> at all, then recreate
      it with proper permissions,
      being careful to ensure that you re-establish it as a symbolic link
      if you had it set up that way before.
@@ -1167,7 +1167,7 @@ SELECT pg_stop_backup();
    <listitem>
     <para>
      If you have unarchived WAL segment files that you saved in step 2,
-     copy them into <filename>pg_xlog/</>.  (It is best to copy them,
+     copy them into <filename>pg_wal/</>.  (It is best to copy them,
      not move them, so you still have the unmodified files if a
      problem occurs and you have to start over.)
     </para>
@@ -1249,9 +1249,9 @@ restore_command = 'cp /mnt/server/archivedir/%f %p'
 
    <para>
     WAL segments that cannot be found in the archive will be sought in
-    <filename>pg_xlog/</>; this allows use of recent un-archived segments.
+    <filename>pg_wal/</>; this allows use of recent un-archived segments.
     However, segments that are available from the archive will be used in
-    preference to files in <filename>pg_xlog/</>.
+    preference to files in <filename>pg_wal/</>.
    </para>
 
    <para>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index c32da94..dff2945 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2926,7 +2926,7 @@ include_dir 'conf.d'
        <listitem>
        <para>
         Specifies the minimum number of past log file segments kept in the
-        <filename>pg_xlog</>
+        <filename>pg_wal</>
         directory, in case a standby server needs to fetch them for streaming
         replication. Each segment is normally 16 megabytes. If a standby
         server connected to the sending server falls behind by more than
@@ -2940,7 +2940,7 @@ include_dir 'conf.d'
 
        <para>
         This sets only the minimum number of segments retained in
-        <filename>pg_xlog</>; the system might need to retain more segments
+        <filename>pg_wal</>; the system might need to retain more segments
         for WAL archival or to recover from a checkpoint. If
         <varname>wal_keep_segments</> is zero (the default), the system
         doesn't keep any extra segments for standby purposes, so the number
@@ -3316,7 +3316,7 @@ include_dir 'conf.d'
        <para>
         Specify how long the standby server should wait when WAL data is not
         available from any sources (streaming replication,
-        local <filename>pg_xlog</> or WAL archive) before retrying to
+        local <filename>pg_wal</> or WAL archive) before retrying to
         retrieve WAL data.  This parameter can only be set in the
         <filename>postgresql.conf</> file or on the server command line.
         The default value is 5 seconds. Units are milliseconds if not specified.
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 626e428..0fd06d6 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15316,7 +15316,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
- pg_xlog         | 16
+ pg_wal          | 16
  pg_hba.conf     | 17
  pg_stat_tmp     | 18
  pg_subtrans     | 19
diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index 06f49db..5bedaf2 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -594,24 +594,24 @@ protocol to make nodes agree on a serializable transactional order.
     (see <xref linkend="restore-command">) or directly from the master
     over a TCP connection (streaming replication). The standby server will
     also attempt to restore any WAL found in the standby cluster's
-    <filename>pg_xlog</> directory. That typically happens after a server
+    <filename>pg_wal</> directory. That typically happens after a server
     restart, when the standby replays again WAL that was streamed from the
     master before the restart, but you can also manually copy files to
-    <filename>pg_xlog</> at any time to have them replayed.
+    <filename>pg_wal</> at any time to have them replayed.
    </para>
 
    <para>
     At startup, the standby begins by restoring all WAL available in the
     archive location, calling <varname>restore_command</>. Once it
     reaches the end of WAL available there and <varname>restore_command</>
-    fails, it tries to restore any WAL available in the <filename>pg_xlog</> directory.
+    fails, it tries to restore any WAL available in the <filename>pg_wal</> directory.
     If that fails, and streaming replication has been configured, the
     standby tries to connect to the primary server and start streaming WAL
-    from the last valid record found in archive or <filename>pg_xlog</>. If that fails
+    from the last valid record found in archive or <filename>pg_wal</>. If that fails
     or streaming replication is not configured, or if the connection is
     later disconnected, the standby goes back to step 1 and tries to
     restore the file from the archive again. This loop of retries from the
-    archive, <filename>pg_xlog</>, and via streaming replication goes on until the server
+    archive, <filename>pg_wal</>, and via streaming replication goes on until the server
     is stopped or failover is triggered by a trigger file.
    </para>
 
@@ -619,7 +619,7 @@ protocol to make nodes agree on a serializable transactional order.
     Standby mode is exited and the server switches to normal operation
     when <command>pg_ctl promote</> is run or a trigger file is found
     (<varname>trigger_file</>). Before failover,
-    any WAL immediately available in the archive or in <filename>pg_xlog</> will be
+    any WAL immediately available in the archive or in <filename>pg_wal</> will be
     restored, but no attempt is made to connect to the master.
    </para>
   </sect2>
@@ -895,7 +895,7 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass'
     However, these methods often result in retaining more WAL segments than
     required, whereas replication slots retain only the number of segments
     known to be needed.  An advantage of these methods is that they bound
-    the space requirement for <literal>pg_xlog</>; there is currently no way
+    the space requirement for <literal>pg_wal</>; there is currently no way
     to do this using replication slots.
    </para>
    <para>
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml
index 7bcbfa7..8d30fd1 100644
--- a/doc/src/sgml/perform.sgml
+++ b/doc/src/sgml/perform.sgml
@@ -1612,7 +1612,7 @@ SELECT * FROM x, y, a, b, c WHERE something AND somethingelse;
        Increase <xref linkend="guc-max-wal-size"> and <xref
        linkend="guc-checkpoint-timeout"> ; this reduces the frequency
        of checkpoints, but increases the storage requirements of
-       <filename>/pg_xlog</>.
+       <filename>/pg_wal</>.
       </para>
      </listitem>
 
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 68b0941..800e39d 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -1947,7 +1947,7 @@ The commands accepted in walsender mode are:
          <para>
           Include the necessary WAL segments in the backup. This will include
           all the files between start and stop backup in the
-          <filename>pg_xlog</filename> directory of the base directory tar
+          <filename>pg_wal</filename> directory of the base directory tar
           file.
          </para>
         </listitem>
@@ -2074,8 +2074,8 @@ The commands accepted in walsender mode are:
        </listitem>
        <listitem>
         <para>
-         <filename>pg_xlog</>, including subdirectories. If the backup is run
-         with WAL files included, a synthesized version of <filename>pg_xlog</filename> will be
+         <filename>pg_wal</>, including subdirectories. If the backup is run
+         with WAL files included, a synthesized version of <filename>pg_wal</filename> will be
          included, but it will only contain the files necessary for the
          backup to work, not the rest of the contents.
         </para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index 7253b40..6226a33 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -173,22 +173,22 @@ PostgreSQL documentation
      <para>
       The WAL starting address should be
       larger than any WAL segment file name currently existing in
-      the directory <filename>pg_xlog</> under the data directory.
+      the directory <filename>pg_wal</> under the data directory.
       These names are also in hexadecimal and have three parts.  The first
       part is the <quote>timeline ID</> and should usually be kept the same.
       For example, if <filename>00000001000000320000004A</> is the
-      largest entry in <filename>pg_xlog</>, use <literal>-l 00000001000000320000004B</> or higher.
+      largest entry in <filename>pg_wal</>, use <literal>-l 00000001000000320000004B</> or higher.
      </para>
 
      <note>
       <para>
        <command>pg_resetxlog</command> itself looks at the files in
-       <filename>pg_xlog</> and chooses a default <option>-l</> setting
+       <filename>pg_wal</> and chooses a default <option>-l</> setting
        beyond the last existing file name.  Therefore, manual adjustment of
        <option>-l</> should only be needed if you are aware of WAL segment
-       files that are not currently present in <filename>pg_xlog</>, such as
+       files that are not currently present in <filename>pg_wal</>, such as
        entries in an offline archive; or if the contents of
-       <filename>pg_xlog</> have been lost entirely.
+       <filename>pg_wal</> have been lost entirely.
       </para>
      </note>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index fb64305..57ba80f 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -61,14 +61,14 @@ PostgreSQL documentation
   <para>
    <application>pg_rewind</> examines the timeline histories of the source
    and target clusters to determine the point where they diverged, and
-   expects to find WAL in the target cluster's <filename>pg_xlog</> directory
+   expects to find WAL in the target cluster's <filename>pg_wal</> directory
    reaching all the way back to the point of divergence. The point of divergence
    can be found either on the target timeline, the source timeline, or their common
    ancestor. In the typical failover scenario where the target cluster was
    shut down soon after the divergence, this is not a problem, but if the
    target cluster ran for a long time after the divergence, the old WAL
    files might no longer be present. In that case, they can be manually
-   copied from the WAL archive to the <filename>pg_xlog</> directory, or
+   copied from the WAL archive to the <filename>pg_wal</> directory, or
    fetched on startup by configuring <filename>recovery.conf</>.  The use of
    <application>pg_rewind</> is not limited to failover, e.g.  a standby
    server can be promoted, run some write transactions, and then rewinded
diff --git a/doc/src/sgml/ref/pg_xlogdump.sgml b/doc/src/sgml/ref/pg_xlogdump.sgml
index 177caab..cfb6d87 100644
--- a/doc/src/sgml/ref/pg_xlogdump.sgml
+++ b/doc/src/sgml/ref/pg_xlogdump.sgml
@@ -118,7 +118,7 @@ PostgreSQL documentation
       <listitem>
        <para>
         Directory in which to find log segment files.  The default is to search
-        for them in the <literal>pg_xlog</literal> subdirectory of the current
+        for them in the <literal>pg_wal</literal> subdirectory of the current
         directory.
        </para>
       </listitem>
diff --git a/doc/src/sgml/ref/pgtestfsync.sgml b/doc/src/sgml/ref/pgtestfsync.sgml
index 6e134c7..5856356 100644
--- a/doc/src/sgml/ref/pgtestfsync.sgml
+++ b/doc/src/sgml/ref/pgtestfsync.sgml
@@ -57,8 +57,8 @@
        <para>
         Specifies the file name to write test data in.
         This file should be in the same file system that the
-        <filename>pg_xlog</> directory is or will be placed in.
-        (<filename>pg_xlog</> contains the <acronym>WAL</> files.)
+        <filename>pg_wal</> directory is or will be placed in.
+        (<filename>pg_wal</> contains the <acronym>WAL</> files.)
         The default is <filename>pg_test_fsync.out</> in the current
         directory.
        </para>
diff --git a/doc/src/sgml/ref/pgupgrade.sgml b/doc/src/sgml/ref/pgupgrade.sgml
index 9685193..4b9aab2 100644
--- a/doc/src/sgml/ref/pgupgrade.sgml
+++ b/doc/src/sgml/ref/pgupgrade.sgml
@@ -345,7 +345,7 @@ NET STOP postgresql-9.0
      your old cluster
      once you start the new cluster after the upgrade.  Link mode also
      requires that the old and new cluster data directories be in the
-     same file system.  (Tablespaces and <filename>pg_xlog</> can be on
+     same file system.  (Tablespaces and <filename>pg_wal</> can be on
      different file systems.)  See <literal>pg_upgrade --help</> for a full
      list of options.
     </para>
@@ -508,7 +508,7 @@ rsync --archive --delete --hard-links --size-only old_pgdata new_pgdata remote_d
       <para>
        If you have tablespaces, you will need to run a similar
        <application>rsync</> command for each tablespace directory.  If you
-       have relocated <filename>pg_xlog</> outside the data directories,
+       have relocated <filename>pg_wal</> outside the data directories,
        <application>rsync</> must be run on those directories too.
       </para>
      </step>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 1528a2e..000f3fd 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -141,7 +141,7 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_xlog</></entry>
+ <entry><filename>pg_wal</></entry>
  <entry>Subdirectory containing WAL (Write Ahead Log) files</entry>
 </row>
 
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index fd179ec..79d9986 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -557,7 +557,7 @@
   </para>
 
   <para>
-   The number of WAL segment files in <filename>pg_xlog</> directory depends on
+   The number of WAL segment files in <filename>pg_wal</> directory depends on
    <varname>min_wal_size</>, <varname>max_wal_size</> and
    the amount of WAL generated in previous checkpoint cycles. When old log
    segment files are no longer needed, they are removed or recycled (that is,
@@ -582,7 +582,7 @@
    kept at all times. Also, if WAL archiving is used, old segments can not be
    removed or recycled until they are archived. If WAL archiving cannot keep up
    with the pace that WAL is generated, or if <varname>archive_command</varname>
-   fails repeatedly, old WAL files will accumulate in <filename>pg_xlog</>
+   fails repeatedly, old WAL files will accumulate in <filename>pg_wal</>
    until the situation is resolved. A slow or failed standby server that
    uses a replication slot will have the same effect (see
    <xref linkend="streaming-replication-slots">).
@@ -594,7 +594,7 @@
    which are similar to checkpoints in normal operation: the server forces
    all its state to disk, updates the <filename>pg_control</> file to
    indicate that the already-processed WAL data need not be scanned again,
-   and then recycles any old log segment files in the <filename>pg_xlog</>
+   and then recycles any old log segment files in the <filename>pg_wal</>
    directory.
    Restartpoints can't be performed more frequently than checkpoints in the
    master because restartpoints can only be performed at checkpoint records.
@@ -734,7 +734,7 @@
 
   <para>
    <acronym>WAL</acronym> logs are stored in the directory
-   <filename>pg_xlog</filename> under the data directory, as a set of
+   <filename>pg_wal</filename> under the data directory, as a set of
    segment files, normally each 16 MB in size (but the size can be changed
    by altering the <option>--with-wal-segsize</> configure option when
    building the server).  Each segment is divided into pages, normally
@@ -751,7 +751,7 @@
   <para>
    It is advantageous if the log is located on a different disk from the
    main database files.  This can be achieved by moving the
-   <filename>pg_xlog</filename> directory to another location (while the server
+   <filename>pg_wal</filename> directory to another location (while the server
    is shut down, of course) and creating a symbolic link from the
    original location in the main data directory to the new location.
   </para>
diff --git a/src/backend/access/transam/timeline.c b/src/backend/access/transam/timeline.c
index bd91573..43436a9 100644
--- a/src/backend/access/transam/timeline.c
+++ b/src/backend/access/transam/timeline.c
@@ -43,7 +43,7 @@
 
 /*
  * Copies all timeline history files with id's between 'begin' and 'end'
- * from archive to pg_xlog.
+ * from archive to pg_wal.
  */
 void
 restoreTimeLineHistoryFiles(TimeLineID begin, TimeLineID end)
@@ -191,7 +191,7 @@ readTimeLineHistory(TimeLineID targetTLI)
 	result = lcons(entry, result);
 
 	/*
-	 * If the history file was fetched from archive, save it in pg_xlog for
+	 * If the history file was fetched from archive, save it in pg_wal for
 	 * future reference.
 	 */
 	if (fromArchive)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 4333903..6946d4a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -234,9 +234,9 @@ static int	LocalXLogInsertAllowed = -1;
  * valid in the startup process.
  *
  * When ArchiveRecoveryRequested is true, but InArchiveRecovery is false, we're
- * currently performing crash recovery using only XLOG files in pg_xlog, but
+ * currently performing crash recovery using only XLOG files in pg_wal, but
  * will switch to using offline XLOG archives as soon as we reach the end of
- * WAL in pg_xlog.
+ * WAL in pg_wal.
 */
 bool		ArchiveRecoveryRequested = false;
 bool		InArchiveRecovery = false;
@@ -697,12 +697,12 @@ typedef enum
 {
 	XLOG_FROM_ANY = 0,			/* request to read WAL from any source */
 	XLOG_FROM_ARCHIVE,			/* restored using restore_command */
-	XLOG_FROM_PG_XLOG,			/* existing file in pg_xlog */
+	XLOG_FROM_PG_WAL,			/* existing file in pg_wal */
 	XLOG_FROM_STREAM			/* streamed from master */
 } XLogSource;
 
 /* human-readable names for XLogSources, for debugging output */
-static const char *xlogSourceNames[] = {"any", "archive", "pg_xlog", "stream"};
+static const char *xlogSourceNames[] = {"any", "archive", "pg_wal", "stream"};
 
 /*
  * openLogFile is -1 or a kernel FD for an open log file segment.
@@ -3342,7 +3342,7 @@ XLogFileOpen(XLogSegNo segno)
  * Open a logfile segment for reading (during recovery).
  *
  * If source == XLOG_FROM_ARCHIVE, the segment is retrieved from archive.
- * Otherwise, it's assumed to be already available in pg_xlog.
+ * Otherwise, it's assumed to be already available in pg_wal.
  */
 static int
 XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
@@ -3371,7 +3371,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 				return -1;
 			break;
 
-		case XLOG_FROM_PG_XLOG:
+		case XLOG_FROM_PG_WAL:
 		case XLOG_FROM_STREAM:
 			XLogFilePath(path, tli, segno);
 			restoredFromArchive = false;
@@ -3390,7 +3390,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 		KeepFileRestoredFromArchive(path, xlogfname);
 
 		/*
-		 * Set path to point at the new file in pg_xlog.
+		 * Set path to point at the new file in pg_wal.
 		 */
 		snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlogfname);
 	}
@@ -3478,10 +3478,10 @@ XLogFileReadAnyTLI(XLogSegNo segno, int emode, int source)
 			}
 		}
 
-		if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_XLOG)
+		if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_WAL)
 		{
 			fd = XLogFileRead(segno, emode, tli,
-							  XLOG_FROM_PG_XLOG, true);
+							  XLOG_FROM_PG_WAL, true);
 			if (fd != -1)
 			{
 				if (!expectedTLEs)
@@ -3690,10 +3690,10 @@ RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
  *
  * This is called during recovery, whenever we switch to follow a new
  * timeline, and at the end of recovery when we create a new timeline. We
- * wouldn't otherwise care about extra WAL files lying in pg_xlog, but they
+ * wouldn't otherwise care about extra WAL files lying in pg_wal, but they
  * might be leftover pre-allocated or recycled WAL segments on the old timeline
  * that we haven't used yet, and contain garbage. If we just leave them in
- * pg_xlog, they will eventually be archived, and we can't let that happen.
+ * pg_wal, they will eventually be archived, and we can't let that happen.
  * Files that belong to our timeline history are valid, because we have
  * successfully replayed them, but from others we can't be sure.
  *
@@ -3850,15 +3850,15 @@ RemoveXlogFile(const char *segname, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
 }
 
 /*
- * Verify whether pg_xlog and pg_xlog/archive_status exist.
+ * Verify whether pg_wal and pg_wal/archive_status exist.
  * If the latter does not exist, recreate it.
  *
  * It is not the goal of this function to verify the contents of these
  * directories, but to help in cases where someone has performed a cluster
- * copy for PITR purposes but omitted pg_xlog from the copy.
+ * copy for PITR purposes but omitted pg_wal from the copy.
  *
- * We could also recreate pg_xlog if it doesn't exist, but a deliberate
- * policy decision was made not to.  It is fairly common for pg_xlog to be
+ * We could also recreate pg_wal if it doesn't exist, but a deliberate
+ * policy decision was made not to.  It is fairly common for pg_wal to be
  * a symlink, and if that was the DBA's intent then automatically making a
  * plain directory would result in degraded performance with no notice.
  */
@@ -3868,7 +3868,7 @@ ValidateXLOGDirectoryStructure(void)
 	char		path[MAXPGPATH];
 	struct stat stat_buf;
 
-	/* Check for pg_xlog; if it doesn't exist, error out */
+	/* Check for pg_wal; if it doesn't exist, error out */
 	if (stat(XLOGDIR, &stat_buf) != 0 ||
 		!S_ISDIR(stat_buf.st_mode))
 		ereport(FATAL,
@@ -4024,11 +4024,11 @@ ReadRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int emode,
 			 * If archive recovery was requested, but we were still doing
 			 * crash recovery, switch to archive recovery and retry using the
 			 * offline archive. We have now replayed all the valid WAL in
-			 * pg_xlog, so we are presumably now consistent.
+			 * pg_wal, so we are presumably now consistent.
 			 *
 			 * We require that there's at least some valid WAL present in
-			 * pg_xlog, however (!fetch_ckpt). We could recover using the WAL
-			 * from the archive, even if pg_xlog is completely empty, but we'd
+			 * pg_wal, however (!fetch_ckpt). We could recover using the WAL
+			 * from the archive, even if pg_wal is completely empty, but we'd
 			 * have no idea how far we'd have to replay to reach consistency.
 			 * So err on the safe side and give up.
 			 */
@@ -4036,7 +4036,7 @@ ReadRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int emode,
 				!fetching_ckpt)
 			{
 				ereport(DEBUG1,
-						(errmsg_internal("reached end of WAL in pg_xlog, entering archive recovery")));
+						(errmsg_internal("reached end of WAL in pg_wal, entering archive recovery")));
 				InArchiveRecovery = true;
 				if (StandbyModeRequested)
 					StandbyMode = true;
@@ -4153,7 +4153,7 @@ rescanLatestTimeLine(void)
 
 	/*
 	 * As in StartupXLOG(), try to ensure we have all the history files
-	 * between the old target and new target in pg_xlog.
+	 * between the old target and new target in pg_wal.
 	 */
 	restoreTimeLineHistoryFiles(oldtarget + 1, newtarget);
 
@@ -5166,7 +5166,7 @@ readRecoveryCommandFile(void)
 			ereport(WARNING,
 					(errmsg("recovery command file \"%s\" specified neither primary_conninfo nor restore_command",
 							RECOVERY_COMMAND_FILE),
-					 errhint("The database server will regularly poll the pg_xlog subdirectory to check for files placed there.")));
+					 errhint("The database server will regularly poll the pg_wal subdirectory to check for files placed there.")));
 	}
 	else
 	{
@@ -5982,7 +5982,7 @@ StartupXLOG(void)
 #endif
 
 	/*
-	 * Verify that pg_xlog and pg_xlog/archive_status exist.  In cases where
+	 * Verify that pg_wal and pg_wal/archive_status exist.  In cases where
 	 * someone has performed a copy for PITR, these directories may have been
 	 * excluded and need to be re-created.
 	 */
@@ -6190,7 +6190,7 @@ StartupXLOG(void)
 		 * and put it into archive recovery by creating a recovery.conf file.
 		 *
 		 * Our strategy in that case is to perform crash recovery first,
-		 * replaying all the WAL present in pg_xlog, and only enter archive
+		 * replaying all the WAL present in pg_wal, and only enter archive
 		 * recovery after that.
 		 *
 		 * But usually we already know how far we need to replay the WAL (up
@@ -6394,7 +6394,7 @@ StartupXLOG(void)
 
 	/*
 	 * Copy any missing timeline history files between 'now' and the recovery
-	 * target timeline from archive to pg_xlog. While we don't need those
+	 * target timeline from archive to pg_wal. While we don't need those
 	 * files ourselves - the history file of the recovery target timeline
 	 * covers all the previous timelines in the history too - a cascading
 	 * standby server might be interested in them. Or, if you archive the WAL
@@ -7015,7 +7015,7 @@ StartupXLOG(void)
 	/*
 	 * We are now done reading the xlog from stream. Turn off streaming
 	 * recovery to force fetching the files (which would be required at end of
-	 * recovery, e.g., timeline history file) from archive or pg_xlog.
+	 * recovery, e.g., timeline history file) from archive or pg_wal.
 	 */
 	StandbyMode = false;
 
@@ -7297,7 +7297,7 @@ StartupXLOG(void)
 		 * As a compromise, we rename the last segment with the .partial
 		 * suffix, and archive it. Archive recovery will never try to read
 		 * .partial segments, so they will normally go unused. But in the odd
-		 * PITR case, the administrator can copy them manually to the pg_xlog
+		 * PITR case, the administrator can copy them manually to the pg_wal
 		 * directory (removing the suffix). They can be useful in debugging,
 		 * too.
 		 *
@@ -9862,7 +9862,7 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
 		 * first WAL segment containing the startup checkpoint has pages in
 		 * the beginning with the old timeline ID.  That can cause trouble at
 		 * recovery: we won't have a history file covering the old timeline if
-		 * pg_xlog directory was not included in the base backup and the WAL
+		 * pg_wal directory was not included in the base backup and the WAL
 		 * archive was cleared too before starting the backup.
 		 *
 		 * This also ensures that we have emitted a WAL page header that has
@@ -10509,7 +10509,7 @@ do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
 	 * archived before returning. If archiving isn't enabled, the required WAL
 	 * needs to be transported via streaming replication (hopefully with
 	 * wal_keep_segments set high enough), or some more exotic mechanism like
-	 * polling and copying files from pg_xlog with script. We have no
+	 * polling and copying files from pg_wal with script. We have no
 	 * knowledge of those mechanisms, so it's up to the user to ensure that he
 	 * gets all the required WAL.
 	 *
@@ -11099,9 +11099,9 @@ next_record_is_invalid:
  * Open the WAL segment containing WAL position 'RecPtr'.
  *
  * The segment can be fetched via restore_command, or via walreceiver having
- * streamed the record, or it can already be present in pg_xlog. Checking
- * pg_xlog is mainly for crash recovery, but it will be polled in standby mode
- * too, in case someone copies a new segment directly to pg_xlog. That is not
+ * streamed the record, or it can already be present in pg_wal. Checking
+ * pg_wal is mainly for crash recovery, but it will be polled in standby mode
+ * too, in case someone copies a new segment directly to pg_wal. That is not
  * documented or recommended, though.
  *
  * If 'fetching_ckpt' is true, we're fetching a checkpoint record, and should
@@ -11131,8 +11131,8 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 	/*-------
 	 * Standby mode is implemented by a state machine:
 	 *
-	 * 1. Read from either archive or pg_xlog (XLOG_FROM_ARCHIVE), or just
-	 *	  pg_xlog (XLOG_FROM_XLOG)
+	 * 1. Read from either archive or pg_wal (XLOG_FROM_ARCHIVE), or just
+	 *	  pg_wal (XLOG_FROM_PG_WAL)
 	 * 2. Check trigger file
 	 * 3. Read from primary server via walreceiver (XLOG_FROM_STREAM)
 	 * 4. Rescan timelines
@@ -11148,7 +11148,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 	 *-------
 	 */
 	if (!InArchiveRecovery)
-		currentSource = XLOG_FROM_PG_XLOG;
+		currentSource = XLOG_FROM_PG_WAL;
 	else if (currentSource == 0)
 		currentSource = XLOG_FROM_ARCHIVE;
 
@@ -11167,13 +11167,13 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 			switch (currentSource)
 			{
 				case XLOG_FROM_ARCHIVE:
-				case XLOG_FROM_PG_XLOG:
+				case XLOG_FROM_PG_WAL:
 
 					/*
 					 * Check to see if the trigger file exists. Note that we
 					 * do this only after failure, so when you create the
 					 * trigger file, we still finish replaying as much as we
-					 * can from archive and pg_xlog before failover.
+					 * can from archive and pg_wal before failover.
 					 */
 					if (StandbyMode && CheckForStandbyTrigger())
 					{
@@ -11183,7 +11183,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 
 					/*
 					 * Not in standby mode, and we've now tried the archive
-					 * and pg_xlog.
+					 * and pg_wal.
 					 */
 					if (!StandbyMode)
 						return false;
@@ -11243,7 +11243,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					 * little chance that the problem will just go away, but
 					 * PANIC is not good for availability either, especially
 					 * in hot standby mode. So, we treat that the same as
-					 * disconnection, and retry from archive/pg_xlog again.
+					 * disconnection, and retry from archive/pg_wal again.
 					 * The WAL in the archive should be identical to what was
 					 * streamed, so it's unlikely that it helps, but one can
 					 * hope...
@@ -11304,11 +11304,11 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					elog(ERROR, "unexpected WAL source %d", currentSource);
 			}
 		}
-		else if (currentSource == XLOG_FROM_PG_XLOG)
+		else if (currentSource == XLOG_FROM_PG_WAL)
 		{
 			/*
-			 * We just successfully read a file in pg_xlog. We prefer files in
-			 * the archive over ones in pg_xlog, so try the next file again
+			 * We just successfully read a file in pg_wal. We prefer files in
+			 * the archive over ones in pg_wal, so try the next file again
 			 * from the archive first.
 			 */
 			if (InArchiveRecovery)
@@ -11329,7 +11329,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 		switch (currentSource)
 		{
 			case XLOG_FROM_ARCHIVE:
-			case XLOG_FROM_PG_XLOG:
+			case XLOG_FROM_PG_WAL:
 				/* Close any old file we might have open. */
 				if (readFile >= 0)
 				{
@@ -11342,7 +11342,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 
 				/*
 				 * Try to restore the file from archive, or read an existing
-				 * file from pg_xlog.
+				 * file from pg_wal.
 				 */
 				readFile = XLogFileReadAnyTLI(readSegNo, DEBUG2,
 						 currentSource == XLOG_FROM_ARCHIVE ? XLOG_FROM_ANY :
@@ -11351,7 +11351,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					return true;	/* success! */
 
 				/*
-				 * Nope, not found in archive or pg_xlog.
+				 * Nope, not found in archive or pg_wal.
 				 */
 				lastSourceFailed = true;
 				break;
@@ -11407,7 +11407,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 						 * not open already.  Also read the timeline history
 						 * file if we haven't initialized timeline history
 						 * yet; it should be streamed over and present in
-						 * pg_xlog by now.  Use XLOG_FROM_STREAM so that
+						 * pg_wal by now.  Use XLOG_FROM_STREAM so that
 						 * source info is set correctly and XLogReceiptTime
 						 * isn't changed.
 						 */
@@ -11439,10 +11439,10 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 						/*
 						 * Note that we don't "return false" immediately here.
 						 * After being triggered, we still want to replay all
-						 * the WAL that was already streamed. It's in pg_xlog
+						 * the WAL that was already streamed. It's in pg_wal
 						 * now, so we just treat this as a failure, and the
 						 * state machine will move on to replay the streamed
-						 * WAL from pg_xlog, and then recheck the trigger and
+						 * WAL from pg_wal, and then recheck the trigger and
 						 * exit replay.
 						 */
 						lastSourceFailed = true;
@@ -11482,7 +11482,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
  * or legitimate end-of-WAL situation.   Generally, we use it as-is, but if
  * we're retrying the exact same record that we've tried previously, only
  * complain the first time to keep the noise down.  However, we only do when
- * reading from pg_xlog, because we don't expect any invalid records in archive
+ * reading from pg_wal, because we don't expect any invalid records in archive
  * or in records streamed from master. Files in the archive should be complete,
  * and we should never hit the end of WAL because we stop and wait for more WAL
  * to arrive before replaying it.
@@ -11497,7 +11497,7 @@ emode_for_corrupt_record(int emode, XLogRecPtr RecPtr)
 {
 	static XLogRecPtr lastComplaint = 0;
 
-	if (readSource == XLOG_FROM_PG_XLOG && emode == LOG)
+	if (readSource == XLOG_FROM_PG_WAL && emode == LOG)
 	{
 		if (RecPtr == lastComplaint)
 			emode = DEBUG1;
diff --git a/src/backend/access/transam/xlogarchive.c b/src/backend/access/transam/xlogarchive.c
index d153a44..b919164 100644
--- a/src/backend/access/transam/xlogarchive.c
+++ b/src/backend/access/transam/xlogarchive.c
@@ -421,7 +421,7 @@ ExecuteRecoveryCommand(char *command, char *commandName, bool failOnSignal)
 /*
  * A file was restored from the archive under a temporary filename (path),
  * and now we want to keep it. Rename it under the permanent filename in
- * in pg_xlog (xlogfname), replacing any existing file with the same name.
+ * in pg_wal (xlogfname), replacing any existing file with the same name.
  */
 void
 KeepFileRestoredFromArchive(char *path, char *xlogfname)
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 33383b4..01cbd90 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -128,7 +128,7 @@ pg_start_backup(PG_FUNCTION_ARGS)
  * pg_stop_backup: finish taking an on-line backup dump
  *
  * We write an end-of-backup WAL record, and remove the backup label file
- * created by pg_start_backup, creating a backup history file in pg_xlog
+ * created by pg_start_backup, creating a backup history file in pg_wal
  * instead (whence it will immediately be archived). The backup history file
  * contains the same info found in the label file, plus the backup-end time
  * and WAL location. Before 9.0, the backup-end time was read from the backup
diff --git a/src/backend/replication/README b/src/backend/replication/README
index ad4864d..0cbb990 100644
--- a/src/backend/replication/README
+++ b/src/backend/replication/README
@@ -54,7 +54,7 @@ and WalRcvData->slotname, and initializes the starting point in
 WalRcvData->receiveStart.
 
 As walreceiver receives WAL from the master server, and writes and flushes
-it to disk (in pg_xlog), it updates WalRcvData->receivedUpto and signals
+it to disk (in pg_wal), it updates WalRcvData->receivedUpto and signals
 the startup process to know how far WAL replay can advance.
 
 Walreceiver sends information about replication progress to the master server
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index da9b7a6..3ffc665 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -276,7 +276,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		TimeLineID	tli;
 
 		/*
-		 * I'd rather not worry about timelines here, so scan pg_xlog and
+		 * I'd rather not worry about timelines here, so scan pg_wal and
 		 * include all WAL files in the range between 'startptr' and 'endptr',
 		 * regardless of the timeline the file is stamped with. If there are
 		 * some spurious WAL files belonging to timelines that don't belong in
@@ -289,11 +289,11 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		XLByteToPrevSeg(endptr, endsegno);
 		XLogFileName(lastoff, ThisTimeLineID, endsegno);
 
-		dir = AllocateDir("pg_xlog");
+		dir = AllocateDir("pg_wal");
 		if (!dir)
 			ereport(ERROR,
-				 (errmsg("could not open directory \"%s\": %m", "pg_xlog")));
-		while ((de = ReadDir(dir, "pg_xlog")) != NULL)
+				 (errmsg("could not open directory \"%s\": %m", "pg_wal")));
+		while ((de = ReadDir(dir, "pg_wal")) != NULL)
 		{
 			/* Does it look like a WAL segment, and is it in the range? */
 			if (IsXLogFileName(de->d_name) &&
@@ -331,7 +331,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		qsort(walFiles, nWalFiles, sizeof(char *), compareWalFileNames);
 
 		/*
-		 * There must be at least one xlog file in the pg_xlog directory,
+		 * There must be at least one xlog file in the pg_wal directory,
 		 * since we are doing backup-including-xlog.
 		 */
 		if (nWalFiles < 1)
@@ -988,15 +988,15 @@ sendDir(char *path, int basepathlen, bool sizeonly, List *tablespaces,
 		}
 
 		/*
-		 * We can skip pg_xlog, the WAL segments need to be fetched from the
+		 * We can skip pg_wal, the WAL segments need to be fetched from the
 		 * WAL archive anyway. But include it as an empty directory anyway, so
 		 * we get permissions right.
 		 */
-		if (strcmp(pathbuf, "./pg_xlog") == 0)
+		if (strcmp(pathbuf, "./pg_wal") == 0)
 		{
 			if (!sizeonly)
 			{
-				/* If pg_xlog is a symlink, write it as a directory anyway */
+				/* If pg_wal is a symlink, write it as a directory anyway */
 #ifndef WIN32
 				if (S_ISLNK(statbuf.st_mode))
 #else
@@ -1012,10 +1012,10 @@ sendDir(char *path, int basepathlen, bool sizeonly, List *tablespaces,
 			 * statbuf from above ...).
 			 */
 			if (!sizeonly)
-				_tarWriteHeader("./pg_xlog/archive_status", NULL, &statbuf);
+				_tarWriteHeader("./pg_wal/archive_status", NULL, &statbuf);
 			size += 512;		/* Size of the header just added */
 
-			continue;			/* don't recurse into pg_xlog */
+			continue;			/* don't recurse into pg_wal */
 		}
 
 		/* Allow symbolic links in pg_tblspc only */
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 413ee3a..d40b5e9 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -18,7 +18,7 @@
  * If the primary server ends streaming, but doesn't disconnect, walreceiver
  * goes into "waiting" mode, and waits for the startup process to give new
  * instructions. The startup process will treat that the same as
- * disconnection, and will rescan the archive/pg_xlog directory. But when the
+ * disconnection, and will rescan the archive/pg_wal directory. But when the
  * startup process wants to try streaming replication again, it will just
  * nudge the existing walreceiver process that's waiting, instead of launching
  * a new one.
@@ -364,7 +364,7 @@ WalReceiverMain(void)
 		 * we've already reached the end of the old timeline, the server will
 		 * finish the streaming immediately, and we will go back to await
 		 * orders from the startup process. If recovery_target_timeline is
-		 * 'latest', the startup process will scan pg_xlog and find the new
+		 * 'latest', the startup process will scan pg_wal and find the new
 		 * history file, bump recovery target timeline, and ask us to restart
 		 * on the new timeline.
 		 */
@@ -739,7 +739,7 @@ WalRcvFetchTimeLineHistoryFiles(TimeLineID first, TimeLineID last)
 										 tli)));
 
 			/*
-			 * Write the file to pg_xlog.
+			 * Write the file to pg_wal.
 			 */
 			writeTimeLineHistoryFile(tli, content, len);
 
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 1ea2a5c..34e4dd0 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -586,7 +586,7 @@ StartReplication(StartReplicationCmd *cmd)
 			 * segment that contains switchpoint, but on the new timeline, so
 			 * that it doesn't end up with a partial segment. If you ask for a
 			 * too old starting point, you'll get an error later when we fail
-			 * to find the requested WAL segment in pg_xlog.
+			 * to find the requested WAL segment in pg_wal.
 			 *
 			 * XXX: we could be more strict here and only allow a startpoint
 			 * that's older than the switchpoint, if it's still in the same
@@ -2052,7 +2052,7 @@ retry:
 			 *
 			 * For example, imagine that this server is currently on timeline
 			 * 5, and we're streaming timeline 4. The switch from timeline 4
-			 * to 5 happened at 0/13002088. In pg_xlog, we have these files:
+			 * to 5 happened at 0/13002088. In pg_wal, we have these files:
 			 *
 			 * ...
 			 * 000000040000000000000012
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 03143f1..b7ff5ef 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -2787,7 +2787,7 @@ looks_like_temp_rel_name(const char *name)
  * Issue fsync recursively on PGDATA and all its contents.
  *
  * We fsync regular files and directories wherever they are, but we
- * follow symlinks only for pg_xlog and immediately under pg_tblspc.
+ * follow symlinks only for pg_wal and immediately under pg_tblspc.
  * Other symlinks are presumed to point at files we're not responsible
  * for fsyncing, and might not have privileges to write at all.
  *
@@ -2811,7 +2811,7 @@ SyncDataDirectory(void)
 		return;
 
 	/*
-	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * If pg_wal is a symlink, we'll need to recurse into it separately,
 	 * because the first walkdir below will ignore it.
 	 */
 	xlog_is_symlink = false;
@@ -2820,16 +2820,16 @@ SyncDataDirectory(void)
 	{
 		struct stat st;
 
-		if (lstat("pg_xlog", &st) < 0)
+		if (lstat("pg_wal", &st) < 0)
 			ereport(LOG,
 					(errcode_for_file_access(),
 					 errmsg("could not stat file \"%s\": %m",
-							"pg_xlog")));
+							"pg_wal")));
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
 #else
-	if (pgwin32_is_junction("pg_xlog"))
+	if (pgwin32_is_junction("pg_wal"))
 		xlog_is_symlink = true;
 #endif
 
@@ -2841,7 +2841,7 @@ SyncDataDirectory(void)
 #ifdef PG_FLUSH_DATA_WORKS
 	walkdir(".", pre_sync_fname, false, DEBUG1);
 	if (xlog_is_symlink)
-		walkdir("pg_xlog", pre_sync_fname, false, DEBUG1);
+		walkdir("pg_wal", pre_sync_fname, false, DEBUG1);
 	walkdir("pg_tblspc", pre_sync_fname, true, DEBUG1);
 #endif
 
@@ -2849,14 +2849,14 @@ SyncDataDirectory(void)
 	 * Now we do the fsync()s in the same order.
 	 *
 	 * The main call ignores symlinks, so in addition to specially processing
-	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * pg_wal if it's a symlink, pg_tblspc has to be visited separately with
 	 * process_symlinks = true.  Note that if there are any plain directories
 	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
 	 * so we don't worry about optimizing it.
 	 */
 	walkdir(".", datadir_fsync_fname, false, LOG);
 	if (xlog_is_symlink)
-		walkdir("pg_xlog", datadir_fsync_fname, false, LOG);
+		walkdir("pg_wal", datadir_fsync_fname, false, LOG);
 	walkdir("pg_tblspc", datadir_fsync_fname, true, LOG);
 }
 
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index ec06e34..08e7338 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -200,7 +200,7 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 
 static const char *const subdirs[] = {
 	"global",
-	"pg_xlog/archive_status",
+	"pg_wal/archive_status",
 	"pg_commit_ts",
 	"pg_dynshmem",
 	"pg_notify",
@@ -2281,7 +2281,7 @@ make_postgres(FILE *cmdfd)
  * Issue fsync recursively on PGDATA and all its contents.
  *
  * We fsync regular files and directories wherever they are, but we
- * follow symlinks only for pg_xlog and immediately under pg_tblspc.
+ * follow symlinks only for pg_wal and immediately under pg_tblspc.
  * Other symlinks are presumed to point at files we're not responsible
  * for fsyncing, and might not have privileges to write at all.
  *
@@ -2291,17 +2291,17 @@ static void
 fsync_pgdata(void)
 {
 	bool		xlog_is_symlink;
-	char		pg_xlog[MAXPGPATH];
+	char		pg_wal[MAXPGPATH];
 	char		pg_tblspc[MAXPGPATH];
 
 	fputs(_("syncing data to disk ... "), stdout);
 	fflush(stdout);
 
-	snprintf(pg_xlog, MAXPGPATH, "%s/pg_xlog", pg_data);
+	snprintf(pg_wal, MAXPGPATH, "%s/pg_wal", pg_data);
 	snprintf(pg_tblspc, MAXPGPATH, "%s/pg_tblspc", pg_data);
 
 	/*
-	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * If pg_wal is a symlink, we'll need to recurse into it separately,
 	 * because the first walkdir below will ignore it.
 	 */
 	xlog_is_symlink = false;
@@ -2310,14 +2310,14 @@ fsync_pgdata(void)
 	{
 		struct stat st;
 
-		if (lstat(pg_xlog, &st) < 0)
+		if (lstat(pg_wal, &st) < 0)
 			fprintf(stderr, _("%s: could not stat file \"%s\": %s\n"),
-					progname, pg_xlog, strerror(errno));
+					progname, pg_wal, strerror(errno));
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
 #else
-	if (pgwin32_is_junction(pg_xlog))
+	if (pgwin32_is_junction(pg_wal))
 		xlog_is_symlink = true;
 #endif
 
@@ -2328,7 +2328,7 @@ fsync_pgdata(void)
 #ifdef PG_FLUSH_DATA_WORKS
 	walkdir(pg_data, pre_sync_fname, false);
 	if (xlog_is_symlink)
-		walkdir(pg_xlog, pre_sync_fname, false);
+		walkdir(pg_wal, pre_sync_fname, false);
 	walkdir(pg_tblspc, pre_sync_fname, true);
 #endif
 
@@ -2336,14 +2336,14 @@ fsync_pgdata(void)
 	 * Now we do the fsync()s in the same order.
 	 *
 	 * The main call ignores symlinks, so in addition to specially processing
-	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * pg_wal if it's a symlink, pg_tblspc has to be visited separately with
 	 * process_symlinks = true.  Note that if there are any plain directories
 	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
 	 * so we don't worry about optimizing it.
 	 */
 	walkdir(pg_data, fsync_fname_ext, false);
 	if (xlog_is_symlink)
-		walkdir(pg_xlog, fsync_fname_ext, false);
+		walkdir(pg_wal, fsync_fname_ext, false);
 	walkdir(pg_tblspc, fsync_fname_ext, true);
 
 	check_ok();
@@ -3087,7 +3087,7 @@ create_xlog_or_symlink(void)
 	char	   *subdirloc;
 
 	/* form name of the place for the subdirectory or symlink */
-	subdirloc = psprintf("%s/pg_xlog", pg_data);
+	subdirloc = psprintf("%s/pg_wal", pg_data);
 
 	if (strcmp(xlog_dir, "") != 0)
 	{
@@ -3220,7 +3220,7 @@ initialize_data_directory(void)
 
 	create_xlog_or_symlink();
 
-	/* Create required subdirectories (other than pg_xlog) */
+	/* Create required subdirectories (other than pg_wal) */
 	printf(_("creating subdirectories ... "));
 	fflush(stdout);
 
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 351a420..74cdac5 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -445,14 +445,14 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 		/* Error message already written in GetConnection() */
 		exit(1);
 
-	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/pg_xlog", basedir);
+	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/pg_wal", basedir);
 
 	/*
-	 * Create pg_xlog/archive_status (and thus pg_xlog) so we can write to
-	 * basedir/pg_xlog as the directory entry in the tar file may arrive
+	 * Create pg_wal/archive_status (and thus pg_wal) so we can write to
+	 * basedir/pg_wal as the directory entry in the tar file may arrive
 	 * later.
 	 */
-	snprintf(statusdir, sizeof(statusdir), "%s/pg_xlog/archive_status",
+	snprintf(statusdir, sizeof(statusdir), "%s/pg_wal/archive_status",
 			 basedir);
 
 	if (pg_mkdir_p(statusdir, S_IRWXU) != 0 && errno != EEXIST)
@@ -1249,14 +1249,14 @@ ReceiveAndUnpackTarFile(PGconn *conn, PGresult *res, int rownum)
 					if (mkdir(filename, S_IRWXU) != 0)
 					{
 						/*
-						 * When streaming WAL, pg_xlog will have been created
+						 * When streaming WAL, pg_wal will have been created
 						 * by the wal receiver process. Also, when transaction
-						 * log directory location was specified, pg_xlog has
+						 * log directory location was specified, pg_wal has
 						 * already been created as a symbolic link before
 						 * starting the actual backup. So just ignore creation
 						 * failures on related directories.
 						 */
-						if (!((pg_str_endswith(filename, "/pg_xlog") ||
+						if (!((pg_str_endswith(filename, "/pg_wal") ||
 							 pg_str_endswith(filename, "/archive_status")) &&
 							  errno == EEXIST))
 						{
@@ -2180,7 +2180,7 @@ main(int argc, char **argv)
 		verify_dir_is_empty_or_create(xlog_dir);
 
 		/* form name of the place where the symlink must go */
-		linkloc = psprintf("%s/pg_xlog", basedir);
+		linkloc = psprintf("%s/pg_wal", basedir);
 
 #ifdef HAVE_SYMLINK
 		if (symlink(xlog_dir, linkloc) != 0)
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 6c33936..11642e4 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -52,7 +52,7 @@ $node->command_ok([ 'pg_basebackup', '-D', "$tempdir/backup" ],
 ok(-f "$tempdir/backup/PG_VERSION", 'backup was created');
 
 is_deeply(
-	[ sort(slurp_dir("$tempdir/backup/pg_xlog/")) ],
+	[ sort(slurp_dir("$tempdir/backup/pg_wal/")) ],
 	[ sort qw(. .. archive_status) ],
 	'no WAL files copied');
 
@@ -182,12 +182,12 @@ like(
 $node->command_ok(
 	[ 'pg_basebackup', '-D', "$tempdir/backupxf", '-X', 'fetch' ],
 	'pg_basebackup -X fetch runs');
-ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_xlog")),
+ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_wal")),
 	'WAL files copied');
 $node->command_ok(
 	[ 'pg_basebackup', '-D', "$tempdir/backupxs", '-X', 'stream' ],
 	'pg_basebackup -X stream runs');
-ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_xlog")),
+ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_wal")),
 	'WAL files copied');
 
 $node->command_fails(
diff --git a/src/bin/pg_resetxlog/pg_resetxlog.c b/src/bin/pg_resetxlog/pg_resetxlog.c
index 525b82ba..2b76f64 100644
--- a/src/bin/pg_resetxlog/pg_resetxlog.c
+++ b/src/bin/pg_resetxlog/pg_resetxlog.c
@@ -890,7 +890,7 @@ FindEndOfXLOG(void)
 	newXlogSegNo = ControlFile.checkPointCopy.redo / ControlFile.xlog_seg_size;
 
 	/*
-	 * Scan the pg_xlog directory to find existing WAL segment files. We
+	 * Scan the pg_wal directory to find existing WAL segment files. We
 	 * assume any present have been used; in most scenarios this should be
 	 * conservative, because of xlog.c's attempts to pre-create files.
 	 */
diff --git a/src/bin/pg_rewind/copy_fetch.c b/src/bin/pg_rewind/copy_fetch.c
index 327e7ef..d0c1586 100644
--- a/src/bin/pg_rewind/copy_fetch.c
+++ b/src/bin/pg_rewind/copy_fetch.c
@@ -131,10 +131,10 @@ recurse_dir(const char *datadir, const char *parentpath,
 			/*
 			 * If it's a symlink within pg_tblspc, we need to recurse into it,
 			 * to process all the tablespaces.  We also follow a symlink if
-			 * it's for pg_xlog.  Symlinks elsewhere are ignored.
+			 * it's for pg_wal.  Symlinks elsewhere are ignored.
 			 */
 			if ((parentpath && strcmp(parentpath, "pg_tblspc") == 0) ||
-				strcmp(path, "pg_xlog") == 0)
+				strcmp(path, "pg_wal") == 0)
 				recurse_dir(datadir, path, callback);
 #else
 			pg_fatal("\"%s\" is a symbolic link, but symbolic links are not supported on this platform\n",
diff --git a/src/bin/pg_rewind/filemap.c b/src/bin/pg_rewind/filemap.c
index 9b00dc1..3905a5d 100644
--- a/src/bin/pg_rewind/filemap.c
+++ b/src/bin/pg_rewind/filemap.c
@@ -79,11 +79,11 @@ process_source_file(const char *path, file_type_t type, size_t newsize,
 		return;
 
 	/*
-	 * Pretend that pg_xlog is a directory, even if it's really a symlink. We
+	 * Pretend that pg_wal is a directory, even if it's really a symlink. We
 	 * don't want to mess with the symlink itself, nor complain if it's a
 	 * symlink in source but not in target or vice versa.
 	 */
-	if (strcmp(path, "pg_xlog") == 0 && type == FILE_TYPE_SYMLINK)
+	if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK)
 		type = FILE_TYPE_DIRECTORY;
 
 	/*
@@ -120,7 +120,7 @@ process_source_file(const char *path, file_type_t type, size_t newsize,
 	switch (type)
 	{
 		case FILE_TYPE_DIRECTORY:
-			if (exists && !S_ISDIR(statbuf.st_mode) && strcmp(path, "pg_xlog") != 0)
+			if (exists && !S_ISDIR(statbuf.st_mode) && strcmp(path, "pg_wal") != 0)
 			{
 				/* it's a directory in source, but not in target. Strange.. */
 				pg_fatal("\"%s\" is not a directory\n", localpath);
@@ -296,7 +296,7 @@ process_target_file(const char *path, file_type_t type, size_t oldsize,
 	/*
 	 * Like in process_source_file, pretend that xlog is always a  directory.
 	 */
-	if (strcmp(path, "pg_xlog") == 0 && type == FILE_TYPE_SYMLINK)
+	if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK)
 		type = FILE_TYPE_DIRECTORY;
 
 	key.path = (char *) path;
diff --git a/src/bin/pg_rewind/parsexlog.c b/src/bin/pg_rewind/parsexlog.c
index b53591d..23ac4e7 100644
--- a/src/bin/pg_rewind/parsexlog.c
+++ b/src/bin/pg_rewind/parsexlog.c
@@ -54,7 +54,7 @@ static int SimpleXLogPageRead(XLogReaderState *xlogreader,
 				   TimeLineID *pageTLI);
 
 /*
- * Read WAL from the datadir/pg_xlog, starting from 'startpoint' on timeline
+ * Read WAL from the datadir/pg_wal, starting from 'startpoint' on timeline
  * index 'tliIndex' in target timeline history, until 'endpoint'. Make note of
  * the data blocks touched by the WAL records, and return them in a page map.
  */
diff --git a/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl b/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
index bdcab56..12950ea 100644
--- a/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
+++ b/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
@@ -1,5 +1,5 @@
 #
-# Test pg_rewind when the target's pg_xlog directory is a symlink.
+# Test pg_rewind when the target's pg_wal directory is a symlink.
 #
 use strict;
 use warnings;
@@ -30,10 +30,10 @@ sub run_test
 
 	my $test_master_datadir = $node_master->data_dir;
 
-	# turn pg_xlog into a symlink
-	print("moving $test_master_datadir/pg_xlog to $master_xlogdir\n");
-	move("$test_master_datadir/pg_xlog", $master_xlogdir) or die;
-	symlink($master_xlogdir, "$test_master_datadir/pg_xlog") or die;
+	# turn pg_wal into a symlink
+	print("moving $test_master_datadir/pg_wal to $master_xlogdir\n");
+	move("$test_master_datadir/pg_wal", $master_xlogdir) or die;
+	symlink($master_xlogdir, "$test_master_datadir/pg_wal") or die;
 
 	RewindTest::start_master();
 
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 5f6a6ea..9621d21 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -302,7 +302,12 @@ check_data_dir(ClusterInfo *cluster)
 	check_single_dir(pg_data, "pg_subtrans");
 	check_single_dir(pg_data, "pg_tblspc");
 	check_single_dir(pg_data, "pg_twophase");
-	check_single_dir(pg_data, "pg_xlog");
+
+	/* pg_xlog has been renamed to pg_wal in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_xlog");
+	else
+		check_single_dir(pg_data, "pg_wal");
 
 	/* pg_clog has been renamed to pg_trans in post-10 cluster */
 	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
diff --git a/src/bin/pg_xlogdump/pg_xlogdump.c b/src/bin/pg_xlogdump/pg_xlogdump.c
index 02575eb..abc6fb9 100644
--- a/src/bin/pg_xlogdump/pg_xlogdump.c
+++ b/src/bin/pg_xlogdump/pg_xlogdump.c
@@ -656,7 +656,7 @@ usage(void)
 	printf("  -f, --follow           keep retrying after reaching end of WAL\n");
 	printf("  -n, --limit=N          number of records to display\n");
 	printf("  -p, --path=PATH        directory in which to find log segment files\n");
-	printf("                         (default: ./pg_xlog)\n");
+	printf("                         (default: ./pg_wal)\n");
 	printf("  -r, --rmgr=RMGR        only show records generated by resource manager RMGR\n");
 	printf("                         use --rmgr=list to list valid resource manager names\n");
 	printf("  -s, --start=RECPTR     start reading at log position RECPTR\n");
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 0a595cc..ceb0462 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -128,7 +128,7 @@ typedef XLogLongPageHeaderData *XLogLongPageHeader;
 /*
  * The XLog directory and control file (relative to $PGDATA)
  */
-#define XLOGDIR				"pg_xlog"
+#define XLOGDIR				"pg_wal"
 #define XLOG_CONTROL_FILE	"global/pg_control"
 
 /*
diff --git a/src/include/postmaster/pgarch.h b/src/include/postmaster/pgarch.h
index f2cbfb3..6df73c9 100644
--- a/src/include/postmaster/pgarch.h
+++ b/src/include/postmaster/pgarch.h
@@ -16,7 +16,7 @@
 /* ----------
  * Archiver control info.
  *
- * We expect that archivable files within pg_xlog will have names between
+ * We expect that archivable files within pg_wal will have names between
  * MIN_XFN_CHARS and MAX_XFN_CHARS in length, consisting only of characters
  * appearing in VALID_XFN_CHARS.  The status files in archive_status have
  * corresponding names with ".ready" or ".done" appended.
-- 
2.9.3

From 9806c07cbb5bd31946b48274dde8b5db65aa6169 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@otacoo.com>
Date: Mon, 29 Aug 2016 15:05:46 +0900
Subject: [PATCH 2/2] Rename pg_clog to pg_trans

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml               |  4 ++--
 doc/src/sgml/catalogs.sgml             |  4 ++--
 doc/src/sgml/config.sgml               |  2 +-
 doc/src/sgml/func.sgml                 |  2 +-
 doc/src/sgml/maintenance.sgml          |  8 ++++----
 doc/src/sgml/ref/pg_resetxlog.sgml     |  4 ++--
 doc/src/sgml/ref/pg_rewind.sgml        |  2 +-
 doc/src/sgml/storage.sgml              | 10 +++++-----
 doc/src/sgml/wal.sgml                  |  2 +-
 src/backend/access/heap/heapam.c       |  4 ++--
 src/backend/access/transam/README      | 12 ++++++------
 src/backend/access/transam/clog.c      |  2 +-
 src/backend/access/transam/commit_ts.c |  2 +-
 src/backend/access/transam/multixact.c |  2 +-
 src/backend/access/transam/subtrans.c  |  4 ++--
 src/backend/access/transam/transam.c   |  2 +-
 src/backend/access/transam/twophase.c  |  4 ++--
 src/backend/access/transam/xact.c      | 18 +++++++++---------
 src/backend/access/transam/xlog.c      |  2 +-
 src/backend/commands/vacuum.c          | 10 +++++-----
 src/backend/postmaster/autovacuum.c    |  2 +-
 src/backend/storage/buffer/README      |  2 +-
 src/backend/storage/ipc/procarray.c    |  4 ++--
 src/backend/utils/time/tqual.c         |  6 +++---
 src/bin/initdb/initdb.c                |  2 +-
 src/bin/pg_upgrade/exec.c              |  6 ++++++
 src/bin/pg_upgrade/pg_upgrade.c        | 30 ++++++++++++++++++------------
 src/include/access/slru.h              |  4 ++--
 28 files changed, 84 insertions(+), 72 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 074a6b0..1fa4d0e 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -382,10 +382,10 @@ tar -cf backup.tar /usr/local/pgsql/data
       directories. This will <emphasis>not</> work because the
       information contained in these files is not usable without
       the commit log files,
-      <filename>pg_clog/*</filename>, which contain the commit status of
+      <filename>pg_trans/*</filename>, which contain the commit status of
       all transactions. A table file is only usable with this
       information. Of course it is also impossible to restore only a
-      table and the associated <filename>pg_clog</filename> data
+      table and the associated <filename>pg_trans</filename> data
       because that would render all other tables in the database
       cluster useless.  So file system backups only work for complete
       backup and restoration of an entire database cluster.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 4e09e06..783d49c 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1847,7 +1847,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this table.  This is used to track
        whether the table needs to be vacuumed in order to prevent transaction
-       ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
+       ID wraparound or to allow <literal>pg_trans</> to be shrunk.  Zero
        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
       </entry>
      </row>
@@ -2514,7 +2514,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this database.  This is used to
        track whether the database needs to be vacuumed in order to prevent
-       transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
+       transaction ID wraparound or to allow <literal>pg_trans</> to be shrunk.
        It is the minimum of the per-table
        <structname>pg_class</>.<structfield>relfrozenxid</> values.
       </entry>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 8e0bccc..dff2945 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5816,7 +5816,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
 
        <para>
         Vacuum also allows removal of old files from the
-        <filename>pg_clog</> subdirectory, which is why the default
+        <filename>pg_trans</> subdirectory, which is why the default
         is a relatively low 200 million transactions.
         This parameter can only be set at server start, but the setting
         can be reduced for individual tables by
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 79eace3..0fd06d6 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15312,7 +15312,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  postmaster.pid  |  9
  pg_ident.conf   | 10
  global          | 11
- pg_clog         | 12
+ pg_trans        | 12
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index 2713883..75f61cd 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -505,18 +505,18 @@
    <para>
     The sole disadvantage of increasing <varname>autovacuum_freeze_max_age</>
     (and <varname>vacuum_freeze_table_age</> along with it)
-    is that the <filename>pg_clog</> subdirectory of the database cluster
+    is that the <filename>pg_trans</> subdirectory of the database cluster
     will take more space, because it must store the commit status of all
     transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
     The commit status uses two bits per transaction, so if
     <varname>autovacuum_freeze_max_age</> is set to its maximum allowed
-    value of two billion, <filename>pg_clog</> can be expected to
+    value of two billion, <filename>pg_trans</> can be expected to
     grow to about half a gigabyte.  If this is trivial compared to your
     total database size, setting <varname>autovacuum_freeze_max_age</> to
     its maximum allowed value is recommended.  Otherwise, set it depending
-    on what you are willing to allow for <filename>pg_clog</> storage.
+    on what you are willing to allow for <filename>pg_trans</> storage.
     (The default, 200 million transactions, translates to about 50MB of
-    <filename>pg_clog</> storage.)
+    <filename>pg_trans</> storage.)
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index c949c5e..6226a33 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -256,12 +256,12 @@ PostgreSQL documentation
 
      <para>
       A safe value can be determined by looking for the numerically largest
-      file name in the directory <filename>pg_clog</> under the data directory,
+      file name in the directory <filename>pg_trans</> under the data directory,
       adding one,
       and then multiplying by 1048576 (0x100000).  Note that the file names are in
       hexadecimal.  It is usually easiest to specify the option value in
       hexadecimal too. For example, if <filename>0011</> is the largest entry
-      in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
+      in <filename>pg_trans</>, <literal>-x 0x1200000</> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 371c4a4..57ba80f 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -229,7 +229,7 @@ PostgreSQL documentation
     </step>
     <step>
      <para>
-      Copy all other files such as <filename>pg_clog</filename> and
+      Copy all other files such as <filename>pg_trans</filename> and
       configuration files from the source cluster to the target cluster
       (everything except the relation files).
      </para>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index fddb69b..000f3fd 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -72,11 +72,6 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_clog</></entry>
- <entry>Subdirectory containing transaction commit status data</entry>
-</row>
-
-<row>
  <entry><filename>pg_dynshmem</></entry>
  <entry>Subdirectory containing files used by the dynamic shared memory
   subsystem</entry>
@@ -136,6 +131,11 @@ Item
 </row>
 
 <row>
+ <entry><filename>pg_trans</></entry>
+ <entry>Subdirectory containing transaction commit status data</entry>
+</row>
+
+<row>
  <entry><filename>pg_twophase</></entry>
  <entry>Subdirectory containing state files for prepared transactions</entry>
 </row>
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index bfc9a02..79d9986 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_clog</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_trans</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 6a27ef4..39a3dc3 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -6751,8 +6751,8 @@ heap_prepare_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
  * Note: it might seem we could make the changes without exclusive lock, since
  * TransactionId read/write is assumed atomic anyway.  However there is a race
  * condition: someone who just fetched an old XID that we overwrite here could
- * conceivably not finish checking the XID against pg_clog before we finish
- * the VACUUM and perhaps truncate off the part of pg_clog he needs.  Getting
+ * conceivably not finish checking the XID against pg_trans before we finish
+ * the VACUUM and perhaps truncate off the part of pg_trans he needs.  Getting
  * exclusive lock ensures no other backend is in process of checking the
  * tuple status.  Also, getting exclusive lock makes it safe to adjust the
  * infomask bits.
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index 4ae4715..f941cfd 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -331,17 +331,17 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_clog and pg_subtrans
------------------------
+pg_trans and pg_subtrans
+------------------------
 
-pg_clog and pg_subtrans are permanent (on-disk) storage of transaction related
+pg_trans and pg_subtrans are permanent (on-disk) storage of transaction related
 information.  There is a limited number of pages of each kept in memory, so
 in many cases there is no need to actually read from disk.  However, if
 there's a long running transaction or a backend sitting idle with an open
 transaction, it may be necessary to be able to read and write this information
 from disk.  They also allow information to be permanent across server restarts.
 
-pg_clog records the commit status for each transaction that has been assigned
+pg_trans records the commit status for each transaction that has been assigned
 an XID.  A transaction can be in progress, committed, aborted, or
 "sub-committed".  This last state means that it's a subtransaction that's no
 longer running, but its parent has not updated its state yet.  It is not
@@ -381,9 +381,9 @@ each transaction we keep a "cache" of Xids that are known to be part of the
 transaction tree, so we can skip looking at pg_subtrans unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_clog and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_trans and pg_subtrans.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
-for pg_clog are implemented in transam.c, while the low-level functions are in
+for pg_trans are implemented in transam.c, while the low-level functions are in
 clog.c.  pg_subtrans is contained completely in subtrans.c.
 
 
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 2634476..a6bddd1 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -450,7 +450,7 @@ CLOGShmemInit(void)
 {
 	ClogCtl->PagePrecedes = CLOGPagePrecedes;
 	SimpleLruInit(ClogCtl, "clog", CLOGShmemBuffers(), CLOG_LSNS_PER_PAGE,
-				  CLogControlLock, "pg_clog", LWTRANCHE_CLOG_BUFFERS);
+				  CLogControlLock, "pg_trans", LWTRANCHE_CLOG_BUFFERS);
 }
 
 /*
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index e330105..08a0251 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -3,7 +3,7 @@
  * commit_ts.c
  *		PostgreSQL commit timestamp manager
  *
- * This module is a pg_clog-like system that stores the commit timestamp
+ * This module is a pg_trans-like system that stores the commit timestamp
  * for each transaction.
  *
  * XLOG interactions: this module generates an XLOG record whenever a new
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index e9588a7..303acf6 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3,7 +3,7 @@
  * multixact.c
  *		PostgreSQL multi-transaction-log manager
  *
- * The pg_multixact manager is a pg_clog-like manager that stores an array of
+ * The pg_multixact manager is a pg_trans-like manager that stores an array of
  * MultiXactMember for each MultiXactId.  It is a fundamental part of the
  * shared-row-lock implementation.  Each MultiXactMember is comprised of a
  * TransactionId and a set of flag bits.  The name is a bit historical:
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 908fe2d..8962c26 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,7 +3,7 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_clog-like manager that stores the parent
+ * The pg_subtrans manager is a pg_trans-like manager that stores the parent
  * transaction Id for each transaction.  It is a fundamental part of the
  * nested transactions implementation.  A main transaction has a parent
  * of InvalidTransactionId, and each subtransaction has its immediate parent.
@@ -11,7 +11,7 @@
  * opposite direction.
  *
  * This code is based on clog.c, but the robustness requirements
- * are completely different from pg_clog, because we only need to remember
+ * are completely different from pg_trans, because we only need to remember
  * pg_subtrans information for currently-open transactions.  Thus, there is
  * no need to preserve data over a crash and restart.
  *
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index 1eba49a..108c1da 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -224,7 +224,7 @@ TransactionIdDidAbort(TransactionId transactionId)
  *		True iff transaction associated with the identifier is currently
  *		known to have either committed or aborted.
  *
- * This does NOT look into pg_clog but merely probes our local cache
+ * This does NOT look into pg_trans but merely probes our local cache
  * (and so it's not named TransactionIdDidComplete, which would be the
  * appropriate name for a function that worked that way).  The intended
  * use is just to short-circuit TransactionIdIsInProgress calls when doing
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 9f55adc..2a51f67 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1379,7 +1379,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	/*
 	 * The order of operations here is critical: make the XLOG entry for
 	 * commit or abort, then mark the transaction committed or aborted in
-	 * pg_clog, then remove its PGPROC from the global ProcArray (which means
+	 * pg_trans, then remove its PGPROC from the global ProcArray (which means
 	 * TransactionIdIsInProgress will stop saying the prepared xact is in
 	 * progress), then run the post-commit or post-abort callbacks. The
 	 * callbacks will release the locks the transaction held.
@@ -2089,7 +2089,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	/* Flush XLOG to disk */
 	XLogFlush(recptr);
 
-	/* Mark the transaction committed in pg_clog */
+	/* Mark the transaction committed in pg_trans */
 	TransactionIdCommitTree(xid, nchildren, children);
 
 	/* Checkpoint can proceed now */
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index e11b229..2f5bf34 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1206,8 +1206,8 @@ RecordTransactionCommit(void)
 		/*
 		 * Mark ourselves as within our "commit critical section".  This
 		 * forces any concurrent checkpoint to wait until we've updated
-		 * pg_clog.  Without this, it is possible for the checkpoint to set
-		 * REDO after the XLOG record but fail to flush the pg_clog update to
+		 * pg_trans.  Without this, it is possible for the checkpoint to set
+		 * REDO after the XLOG record but fail to flush the pg_trans update to
 		 * disk, leading to loss of the transaction commit if the system
 		 * crashes a little later.
 		 *
@@ -2033,7 +2033,7 @@ CommitTransaction(void)
 	if (!is_parallel_worker)
 	{
 		/*
-		 * We need to mark our XIDs as committed in pg_clog.  This is where we
+		 * We need to mark our XIDs as committed in pg_trans.  This is where we
 		 * durably commit.
 		 */
 		latestXid = RecordTransactionCommit();
@@ -2539,7 +2539,7 @@ AbortTransaction(void)
 	AtAbort_Twophase();
 
 	/*
-	 * Advertise the fact that we aborted in pg_clog (assuming that we got as
+	 * Advertise the fact that we aborted in pg_trans (assuming that we got as
 	 * far as assigning an XID to advertise).  But if we're inside a parallel
 	 * worker, skip this; the user backend must be the one to write the abort
 	 * record.
@@ -4625,7 +4625,7 @@ AbortSubTransaction(void)
 								s->parent->subTransactionId);
 		AtSubAbort_Notify();
 
-		/* Advertise the fact that we aborted in pg_clog. */
+		/* Advertise the fact that we aborted in pg_trans. */
 		(void) RecordTransactionAbort(true);
 
 		/* Post-abort cleanup */
@@ -5371,7 +5371,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 	if (standbyState == STANDBY_DISABLED)
 	{
 		/*
-		 * Mark the transaction committed in pg_clog.
+		 * Mark the transaction committed in pg_trans.
 		 */
 		TransactionIdCommitTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
@@ -5389,7 +5389,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		RecordKnownAssignedTransactionIds(max_xid);
 
 		/*
-		 * Mark the transaction committed in pg_clog. We use async commit
+		 * Mark the transaction committed in pg_trans. We use async commit
 		 * protocol during recovery to provide information on database
 		 * consistency for when users try to set hint bits. It is important
 		 * that we do not set hint bits until the minRecoveryPoint is past
@@ -5526,7 +5526,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 
 	if (standbyState == STANDBY_DISABLED)
 	{
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_trans, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
 	else
@@ -5542,7 +5542,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 		 */
 		RecordKnownAssignedTransactionIds(max_xid);
 
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_trans, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 
 		/*
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 46dc15a..6946d4a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8392,7 +8392,7 @@ CreateCheckPoint(int flags)
 	 * that are currently in commit critical sections.  If an xact inserted
 	 * its commit record into XLOG just before the REDO point, then a crash
 	 * restart from the REDO point would not replay that record, which means
-	 * that our flushing had better include the xact's update of pg_clog.  So
+	 * that our flushing had better include the xact's update of pg_trans.  So
 	 * we wait till he's out of his commit critical section before proceeding.
 	 * See notes in RecordTransactionCommit().
 	 *
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 58bbf55..a5babef 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -356,7 +356,7 @@ vacuum(int options, RangeVar *relation, Oid relid, VacuumParams *params,
 	if ((options & VACOPT_VACUUM) && !IsAutoVacuumWorkerProcess())
 	{
 		/*
-		 * Update pg_database.datfrozenxid, and truncate pg_clog if possible.
+		 * Update pg_database.datfrozenxid, and truncate pg_trans if possible.
 		 * (autovacuum.c does this for itself.)
 		 */
 		vac_update_datfrozenxid();
@@ -880,7 +880,7 @@ vac_update_relstats(Relation relation,
  *		pg_class.relminmxid values.
  *
  *		If we are able to advance either pg_database value, also try to
- *		truncate pg_clog and pg_multixact.
+ *		truncate pg_trans and pg_multixact.
  *
  *		We violate transaction semantics here by overwriting the database's
  *		existing pg_database tuple with the new values.  This is reasonably
@@ -1026,7 +1026,7 @@ vac_update_datfrozenxid(void)
 
 	/*
 	 * If we were able to advance datfrozenxid or datminmxid, see if we can
-	 * truncate pg_clog and/or pg_multixact.  Also do it if the shared
+	 * truncate pg_trans and/or pg_multixact.  Also do it if the shared
 	 * XID-wrap-limit info is stale, since this action will update that too.
 	 */
 	if (dirty || ForceTransactionIdLimitUpdate())
@@ -1039,7 +1039,7 @@ vac_update_datfrozenxid(void)
  *	vac_truncate_clog() -- attempt to truncate the commit log
  *
  *		Scan pg_database to determine the system-wide oldest datfrozenxid,
- *		and use it to truncate the transaction commit log (pg_clog).
+ *		and use it to truncate the transaction commit log (pg_trans).
  *		Also update the XID wrap limit info maintained by varsup.c.
  *		Likewise for datminmxid.
  *
@@ -1086,7 +1086,7 @@ vac_truncate_clog(TransactionId frozenXID,
 	 * of the interlock against copying a DB containing an active backend.
 	 * Hence the new entry will not reduce the minimum.  Also, if two VACUUMs
 	 * concurrently modify the datfrozenxid's of different databases, the
-	 * worst possible outcome is that pg_clog is not truncated as aggressively
+	 * worst possible outcome is that pg_trans is not truncated as aggressively
 	 * as it could be.
 	 */
 	relation = heap_open(DatabaseRelationId, AccessShareLock);
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 1a92ca1..f77aa01 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2394,7 +2394,7 @@ deleted:
 	 */
 
 	/*
-	 * Update pg_database.datfrozenxid, and truncate pg_clog if possible. We
+	 * Update pg_database.datfrozenxid, and truncate pg_trans if possible. We
 	 * only need to do this once, not after each table.
 	 */
 	vac_update_datfrozenxid();
diff --git a/src/backend/storage/buffer/README b/src/backend/storage/buffer/README
index 248883f..e7dda01 100644
--- a/src/backend/storage/buffer/README
+++ b/src/backend/storage/buffer/README
@@ -63,7 +63,7 @@ at about the same time would OR the same bits into the field, so there
 is little or no risk of conflicting update; what's more, if there did
 manage to be a conflict it would merely mean that one bit-update would
 be lost and need to be done again later.  These four bits are only hints
-(they cache the results of transaction status lookups in pg_clog), so no
+(they cache the results of transaction status lookups in pg_trans), so no
 great harm is done if they get reset to zero by conflicting updates.
 Note, however, that a tuple is frozen by setting both HEAP_XMIN_INVALID
 and HEAP_XMIN_COMMITTED; this is a critical update and accordingly requires
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index e5d487d..5ce3a44 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -388,7 +388,7 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
  * ProcArrayEndTransaction -- mark a transaction as no longer running
  *
  * This is used interchangeably for commit and abort cases.  The transaction
- * commit/abort must already be reported to WAL and pg_clog.
+ * commit/abort must already be reported to WAL and pg_trans.
  *
  * proc is currently always MyProc, but we pass it explicitly for flexibility.
  * latestXid is the latest Xid among the transaction's main XID and
@@ -1180,7 +1180,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
 	 * subtransaction, we want to say "not running" even though its parent may
-	 * still be running.  So first, check pg_clog to see if it's been aborted.
+	 * still be running.  So first, check pg_trans to see if it's been aborted.
 	 */
 	xc_slow_answer_inc();
 
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 26a3be3..c4202e5 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -13,9 +13,9 @@
  * NOTE: When using a non-MVCC snapshot, we must check
  * TransactionIdIsInProgress (which looks in the PGXACT array)
  * before TransactionIdDidCommit/TransactionIdDidAbort (which look in
- * pg_clog).  Otherwise we have a race condition: we might decide that a
+ * pg_trans).  Otherwise we have a race condition: we might decide that a
  * just-committed transaction crashed, because none of the tests succeed.
- * xact.c is careful to record commit/abort in pg_clog before it unsets
+ * xact.c is careful to record commit/abort in pg_trans before it unsets
  * MyPgXact->xid in the PGXACT array.  That fixes that problem, but it
  * also means there is a window where TransactionIdIsInProgress and
  * TransactionIdDidCommit will both return true.  If we check only
@@ -29,7 +29,7 @@
  *
  * When using an MVCC snapshot, we rely on XidInMVCCSnapshot rather than
  * TransactionIdIsInProgress, but the logic is otherwise the same: do not
- * check pg_clog until after deciding that the xact is no longer in progress.
+ * check pg_trans until after deciding that the xact is no longer in progress.
  *
  *
  * Summary of visibility functions:
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 77b0760..08e7338 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -201,7 +201,6 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 static const char *const subdirs[] = {
 	"global",
 	"pg_wal/archive_status",
-	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
 	"pg_notify",
@@ -218,6 +217,7 @@ static const char *const subdirs[] = {
 	"pg_tblspc",
 	"pg_stat",
 	"pg_stat_tmp",
+	"pg_trans",
 	"pg_logical",
 	"pg_logical/snapshots",
 	"pg_logical/mappings"
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 16f9f09..55834b8 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -309,6 +309,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_xlog");
 	else
 		check_single_dir(pg_data, "pg_wal");
+
+	/* pg_clog has been renamed to pg_trans in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_clog");
+	else
+		check_single_dir(pg_data, "pg_trans");
 }
 
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index fa118e9..dd7a54b 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -47,7 +47,7 @@
 static void prepare_new_cluster(void);
 static void prepare_new_databases(void);
 static void create_new_objects(void);
-static void copy_clog_xlog_xid(void);
+static void copy_trans_xlog_xid(void);
 static void set_frozenxids(bool minmxid_only);
 static void setup(char *argv0, bool *live_check);
 static void cleanup(void);
@@ -113,7 +113,7 @@ main(int argc, char **argv)
 	 * Destructive Changes to New Cluster
 	 */
 
-	copy_clog_xlog_xid();
+	copy_trans_xlog_xid();
 
 	/* New now using xids of the old system */
 
@@ -374,17 +374,17 @@ remove_new_subdir(char *subdir, bool rmtopdir)
  * Copy the files from the old cluster into it
  */
 static void
-copy_subdir_files(char *subdir)
+copy_subdir_files(char *old_subdir, char *new_subdir)
 {
 	char		old_path[MAXPGPATH];
 	char		new_path[MAXPGPATH];
 
-	remove_new_subdir(subdir, true);
+	remove_new_subdir(new_subdir, true);
 
-	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, subdir);
-	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, subdir);
+	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, old_subdir);
+	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, new_subdir);
 
-	prep_status("Copying old %s to new server", subdir);
+	prep_status("Copying old %s to new server", old_subdir);
 
 	exec_prog(UTILITY_LOG_FILE, NULL, true,
 #ifndef WIN32
@@ -399,10 +399,16 @@ copy_subdir_files(char *subdir)
 }
 
 static void
-copy_clog_xlog_xid(void)
+copy_trans_xlog_xid(void)
 {
-	/* copy old commit logs to new data dir */
-	copy_subdir_files("pg_clog");
+	/*
+	 * Copy old commit logs to new data dir. pg_clog has been renamed to
+	 * pg_trans in post-10 clusters.
+	 */
+	copy_subdir_files(GET_MAJOR_VERSION(old_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_trans",
+					  GET_MAJOR_VERSION(new_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_trans");
 
 	/* set the next transaction id and epoch of the new cluster */
 	prep_status("Setting next transaction ID and epoch for new cluster");
@@ -432,8 +438,8 @@ copy_clog_xlog_xid(void)
 	if (old_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER &&
 		new_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER)
 	{
-		copy_subdir_files("pg_multixact/offsets");
-		copy_subdir_files("pg_multixact/members");
+		copy_subdir_files("pg_multixact/offsets", "pg_multixact/offsets");
+		copy_subdir_files("pg_multixact/members", "pg_multixact/members");
 
 		prep_status("Setting next multixact ID and offset for new cluster");
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 5fcebc5..e279d0d 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,7 +76,7 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_clog, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
+	 * for pg_trans, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
 	 * has lsn_groups_per_page entries per buffer slot, each containing the
 	 * highest LSN known for a contiguous group of SLRU entries on that slot's
 	 * page.
@@ -120,7 +120,7 @@ typedef struct SlruCtlData
 	SlruShared	shared;
 
 	/*
-	 * This flag tells whether to fsync writes (true for pg_clog and multixact
+	 * This flag tells whether to fsync writes (true for pg_trans and multixact
 	 * stuff, false for pg_subtrans and pg_notify).
 	 */
 	bool		do_fsync;
-- 
2.9.3

From 1bd7db0fbbc5822177e05fb6349a9586b36a732c Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@otacoo.com>
Date: Tue, 30 Aug 2016 10:53:00 +0900
Subject: [PATCH 1/2] Rename pg_xlog to pg_wal

Additional check handling is needed in pg_upgrade regarding the clusters
worked on, except that it is a very mechanical patch. As pg_basebackup
needs to support servers down to 9.1, special handling is needed depending
on the version of the target server as a consequence of this renaming:
- Soft links need to be generated using pg_xlog or pg_wal.
- stream mode needs to have its output in the correct place.
This has as direct consequence to need a connection to target server before
generating a soft link, which is a bit earlier than before this renaming.
---
 doc/src/sgml/backup.sgml                     |  28 ++++----
 doc/src/sgml/config.sgml                     |   6 +-
 doc/src/sgml/func.sgml                       |   2 +-
 doc/src/sgml/high-availability.sgml          |  14 ++--
 doc/src/sgml/perform.sgml                    |   2 +-
 doc/src/sgml/protocol.sgml                   |   6 +-
 doc/src/sgml/ref/pg_resetxlog.sgml           |  10 +--
 doc/src/sgml/ref/pg_rewind.sgml              |   4 +-
 doc/src/sgml/ref/pg_xlogdump.sgml            |   2 +-
 doc/src/sgml/ref/pgtestfsync.sgml            |   4 +-
 doc/src/sgml/ref/pgupgrade.sgml              |   4 +-
 doc/src/sgml/storage.sgml                    |   2 +-
 doc/src/sgml/wal.sgml                        |  10 +--
 src/backend/access/transam/timeline.c        |   4 +-
 src/backend/access/transam/xlog.c            | 100 +++++++++++++--------------
 src/backend/access/transam/xlogarchive.c     |   2 +-
 src/backend/access/transam/xlogfuncs.c       |   2 +-
 src/backend/replication/README               |   2 +-
 src/backend/replication/basebackup.c         |  20 +++---
 src/backend/replication/walreceiver.c        |   6 +-
 src/backend/replication/walsender.c          |   4 +-
 src/backend/storage/file/fd.c                |  16 ++---
 src/bin/initdb/initdb.c                      |  26 +++----
 src/bin/pg_basebackup/pg_basebackup.c        |  64 ++++++++++-------
 src/bin/pg_basebackup/t/010_pg_basebackup.pl |   6 +-
 src/bin/pg_resetxlog/pg_resetxlog.c          |   2 +-
 src/bin/pg_rewind/copy_fetch.c               |   4 +-
 src/bin/pg_rewind/filemap.c                  |   8 +--
 src/bin/pg_rewind/parsexlog.c                |   2 +-
 src/bin/pg_rewind/t/004_pg_xlog_symlink.pl   |  10 +--
 src/bin/pg_upgrade/exec.c                    |  79 +++++++++++++--------
 src/bin/pg_xlogdump/pg_xlogdump.c            |   2 +-
 src/include/access/xlog_internal.h           |   2 +-
 src/include/postmaster/pgarch.h              |   2 +-
 34 files changed, 245 insertions(+), 212 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 0f09d82..074a6b0 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -472,7 +472,7 @@ tar -cf backup.tar /usr/local/pgsql/data
 
   <para>
    At all times, <productname>PostgreSQL</> maintains a
-   <firstterm>write ahead log</> (WAL) in the <filename>pg_xlog/</>
+   <firstterm>write ahead log</> (WAL) in the <filename>pg_wal/</>
    subdirectory of the cluster's data directory. The log records
    every change made to the database's data files.  This log exists
    primarily for crash-safety purposes: if the system crashes, the
@@ -616,7 +616,7 @@ archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"'  # Windows
     <literal>%p</> and <literal>%f</> parameters have been replaced,
     the actual command executed might look like this:
 <programlisting>
-test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065
+test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_wal/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065
 </programlisting>
     A similar command will be generated for each new file to be archived.
    </para>
@@ -668,9 +668,9 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     fills, nothing further can be archived until the tape is swapped.
     You should ensure that any error condition or request to a human operator
     is reported appropriately so that the situation can be
-    resolved reasonably quickly. The <filename>pg_xlog/</> directory will
+    resolved reasonably quickly. The <filename>pg_wal/</> directory will
     continue to fill with WAL segment files until the situation is resolved.
-    (If the file system containing <filename>pg_xlog/</> fills up,
+    (If the file system containing <filename>pg_wal/</> fills up,
     <productname>PostgreSQL</> will do a PANIC shutdown.  No committed
     transactions will be lost, but the database will remain offline until
     you free some space.)
@@ -682,7 +682,7 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     operation continues even if the archiving process falls a little behind.
     If archiving falls significantly behind, this will increase the amount of
     data that would be lost in the event of a disaster. It will also mean that
-    the <filename>pg_xlog/</> directory will contain large numbers of
+    the <filename>pg_wal/</> directory will contain large numbers of
     not-yet-archived segment files, which could eventually exceed available
     disk space. You are advised to monitor the archiving process to ensure that
     it is working as you intend.
@@ -743,7 +743,7 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     configuration file reload.  If you wish to temporarily stop archiving,
     one way to do it is to set <varname>archive_command</> to the empty
     string (<literal>''</>).
-    This will cause WAL files to accumulate in <filename>pg_xlog/</> until a
+    This will cause WAL files to accumulate in <filename>pg_wal/</> until a
     working <varname>archive_command</> is re-established.
    </para>
   </sect2>
@@ -1062,10 +1062,10 @@ SELECT pg_stop_backup();
 
    <para>
     You should, however, omit from the backup the files within the
-    cluster's <filename>pg_xlog/</> subdirectory.  This
+    cluster's <filename>pg_wal/</> subdirectory.  This
     slight adjustment is worthwhile because it reduces the risk
     of mistakes when restoring.  This is easy to arrange if
-    <filename>pg_xlog/</> is a symbolic link pointing to someplace outside
+    <filename>pg_wal/</> is a symbolic link pointing to someplace outside
     the cluster directory, which is a common setup anyway for performance
     reasons.  You might also want to exclude <filename>postmaster.pid</>
     and <filename>postmaster.opts</>, which record information
@@ -1133,7 +1133,7 @@ SELECT pg_stop_backup();
      location in case you need them later. Note that this precaution will
      require that you have enough free space on your system to hold two
      copies of your existing database. If you do not have enough space,
-     you should at least save the contents of the cluster's <filename>pg_xlog</>
+     you should at least save the contents of the cluster's <filename>pg_wal</>
      subdirectory, as it might contain logs which
      were not archived before the system went down.
     </para>
@@ -1156,9 +1156,9 @@ SELECT pg_stop_backup();
    </listitem>
    <listitem>
     <para>
-     Remove any files present in <filename>pg_xlog/</>; these came from the
+     Remove any files present in <filename>pg_wal/</>; these came from the
      file system backup and are therefore probably obsolete rather than current.
-     If you didn't archive <filename>pg_xlog/</> at all, then recreate
+     If you didn't archive <filename>pg_wal/</> at all, then recreate
      it with proper permissions,
      being careful to ensure that you re-establish it as a symbolic link
      if you had it set up that way before.
@@ -1167,7 +1167,7 @@ SELECT pg_stop_backup();
    <listitem>
     <para>
      If you have unarchived WAL segment files that you saved in step 2,
-     copy them into <filename>pg_xlog/</>.  (It is best to copy them,
+     copy them into <filename>pg_wal/</>.  (It is best to copy them,
      not move them, so you still have the unmodified files if a
      problem occurs and you have to start over.)
     </para>
@@ -1249,9 +1249,9 @@ restore_command = 'cp /mnt/server/archivedir/%f %p'
 
    <para>
     WAL segments that cannot be found in the archive will be sought in
-    <filename>pg_xlog/</>; this allows use of recent un-archived segments.
+    <filename>pg_wal/</>; this allows use of recent un-archived segments.
     However, segments that are available from the archive will be used in
-    preference to files in <filename>pg_xlog/</>.
+    preference to files in <filename>pg_wal/</>.
    </para>
 
    <para>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7c483c6..8e0bccc 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2926,7 +2926,7 @@ include_dir 'conf.d'
        <listitem>
        <para>
         Specifies the minimum number of past log file segments kept in the
-        <filename>pg_xlog</>
+        <filename>pg_wal</>
         directory, in case a standby server needs to fetch them for streaming
         replication. Each segment is normally 16 megabytes. If a standby
         server connected to the sending server falls behind by more than
@@ -2940,7 +2940,7 @@ include_dir 'conf.d'
 
        <para>
         This sets only the minimum number of segments retained in
-        <filename>pg_xlog</>; the system might need to retain more segments
+        <filename>pg_wal</>; the system might need to retain more segments
         for WAL archival or to recover from a checkpoint. If
         <varname>wal_keep_segments</> is zero (the default), the system
         doesn't keep any extra segments for standby purposes, so the number
@@ -3316,7 +3316,7 @@ include_dir 'conf.d'
        <para>
         Specify how long the standby server should wait when WAL data is not
         available from any sources (streaming replication,
-        local <filename>pg_xlog</> or WAL archive) before retrying to
+        local <filename>pg_wal</> or WAL archive) before retrying to
         retrieve WAL data.  This parameter can only be set in the
         <filename>postgresql.conf</> file or on the server command line.
         The default value is 5 seconds. Units are milliseconds if not specified.
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 5148095..79eace3 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15316,7 +15316,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
- pg_xlog         | 16
+ pg_wal          | 16
  pg_hba.conf     | 17
  pg_stat_tmp     | 18
  pg_subtrans     | 19
diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index 06f49db..5bedaf2 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -594,24 +594,24 @@ protocol to make nodes agree on a serializable transactional order.
     (see <xref linkend="restore-command">) or directly from the master
     over a TCP connection (streaming replication). The standby server will
     also attempt to restore any WAL found in the standby cluster's
-    <filename>pg_xlog</> directory. That typically happens after a server
+    <filename>pg_wal</> directory. That typically happens after a server
     restart, when the standby replays again WAL that was streamed from the
     master before the restart, but you can also manually copy files to
-    <filename>pg_xlog</> at any time to have them replayed.
+    <filename>pg_wal</> at any time to have them replayed.
    </para>
 
    <para>
     At startup, the standby begins by restoring all WAL available in the
     archive location, calling <varname>restore_command</>. Once it
     reaches the end of WAL available there and <varname>restore_command</>
-    fails, it tries to restore any WAL available in the <filename>pg_xlog</> directory.
+    fails, it tries to restore any WAL available in the <filename>pg_wal</> directory.
     If that fails, and streaming replication has been configured, the
     standby tries to connect to the primary server and start streaming WAL
-    from the last valid record found in archive or <filename>pg_xlog</>. If that fails
+    from the last valid record found in archive or <filename>pg_wal</>. If that fails
     or streaming replication is not configured, or if the connection is
     later disconnected, the standby goes back to step 1 and tries to
     restore the file from the archive again. This loop of retries from the
-    archive, <filename>pg_xlog</>, and via streaming replication goes on until the server
+    archive, <filename>pg_wal</>, and via streaming replication goes on until the server
     is stopped or failover is triggered by a trigger file.
    </para>
 
@@ -619,7 +619,7 @@ protocol to make nodes agree on a serializable transactional order.
     Standby mode is exited and the server switches to normal operation
     when <command>pg_ctl promote</> is run or a trigger file is found
     (<varname>trigger_file</>). Before failover,
-    any WAL immediately available in the archive or in <filename>pg_xlog</> will be
+    any WAL immediately available in the archive or in <filename>pg_wal</> will be
     restored, but no attempt is made to connect to the master.
    </para>
   </sect2>
@@ -895,7 +895,7 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass'
     However, these methods often result in retaining more WAL segments than
     required, whereas replication slots retain only the number of segments
     known to be needed.  An advantage of these methods is that they bound
-    the space requirement for <literal>pg_xlog</>; there is currently no way
+    the space requirement for <literal>pg_wal</>; there is currently no way
     to do this using replication slots.
    </para>
    <para>
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml
index 7bcbfa7..8d30fd1 100644
--- a/doc/src/sgml/perform.sgml
+++ b/doc/src/sgml/perform.sgml
@@ -1612,7 +1612,7 @@ SELECT * FROM x, y, a, b, c WHERE something AND somethingelse;
        Increase <xref linkend="guc-max-wal-size"> and <xref
        linkend="guc-checkpoint-timeout"> ; this reduces the frequency
        of checkpoints, but increases the storage requirements of
-       <filename>/pg_xlog</>.
+       <filename>/pg_wal</>.
       </para>
      </listitem>
 
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 68b0941..800e39d 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -1947,7 +1947,7 @@ The commands accepted in walsender mode are:
          <para>
           Include the necessary WAL segments in the backup. This will include
           all the files between start and stop backup in the
-          <filename>pg_xlog</filename> directory of the base directory tar
+          <filename>pg_wal</filename> directory of the base directory tar
           file.
          </para>
         </listitem>
@@ -2074,8 +2074,8 @@ The commands accepted in walsender mode are:
        </listitem>
        <listitem>
         <para>
-         <filename>pg_xlog</>, including subdirectories. If the backup is run
-         with WAL files included, a synthesized version of <filename>pg_xlog</filename> will be
+         <filename>pg_wal</>, including subdirectories. If the backup is run
+         with WAL files included, a synthesized version of <filename>pg_wal</filename> will be
          included, but it will only contain the files necessary for the
          backup to work, not the rest of the contents.
         </para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index fd9d0be..c949c5e 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -173,22 +173,22 @@ PostgreSQL documentation
      <para>
       The WAL starting address should be
       larger than any WAL segment file name currently existing in
-      the directory <filename>pg_xlog</> under the data directory.
+      the directory <filename>pg_wal</> under the data directory.
       These names are also in hexadecimal and have three parts.  The first
       part is the <quote>timeline ID</> and should usually be kept the same.
       For example, if <filename>00000001000000320000004A</> is the
-      largest entry in <filename>pg_xlog</>, use <literal>-l 00000001000000320000004B</> or higher.
+      largest entry in <filename>pg_wal</>, use <literal>-l 00000001000000320000004B</> or higher.
      </para>
 
      <note>
       <para>
        <command>pg_resetxlog</command> itself looks at the files in
-       <filename>pg_xlog</> and chooses a default <option>-l</> setting
+       <filename>pg_wal</> and chooses a default <option>-l</> setting
        beyond the last existing file name.  Therefore, manual adjustment of
        <option>-l</> should only be needed if you are aware of WAL segment
-       files that are not currently present in <filename>pg_xlog</>, such as
+       files that are not currently present in <filename>pg_wal</>, such as
        entries in an offline archive; or if the contents of
-       <filename>pg_xlog</> have been lost entirely.
+       <filename>pg_wal</> have been lost entirely.
       </para>
      </note>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 42ebfbf..371c4a4 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -61,14 +61,14 @@ PostgreSQL documentation
   <para>
    <application>pg_rewind</> examines the timeline histories of the source
    and target clusters to determine the point where they diverged, and
-   expects to find WAL in the target cluster's <filename>pg_xlog</> directory
+   expects to find WAL in the target cluster's <filename>pg_wal</> directory
    reaching all the way back to the point of divergence. The point of divergence
    can be found either on the target timeline, the source timeline, or their common
    ancestor. In the typical failover scenario where the target cluster was
    shut down soon after the divergence, this is not a problem, but if the
    target cluster ran for a long time after the divergence, the old WAL
    files might no longer be present. In that case, they can be manually
-   copied from the WAL archive to the <filename>pg_xlog</> directory, or
+   copied from the WAL archive to the <filename>pg_wal</> directory, or
    fetched on startup by configuring <filename>recovery.conf</>.  The use of
    <application>pg_rewind</> is not limited to failover, e.g.  a standby
    server can be promoted, run some write transactions, and then rewinded
diff --git a/doc/src/sgml/ref/pg_xlogdump.sgml b/doc/src/sgml/ref/pg_xlogdump.sgml
index 177caab..cfb6d87 100644
--- a/doc/src/sgml/ref/pg_xlogdump.sgml
+++ b/doc/src/sgml/ref/pg_xlogdump.sgml
@@ -118,7 +118,7 @@ PostgreSQL documentation
       <listitem>
        <para>
         Directory in which to find log segment files.  The default is to search
-        for them in the <literal>pg_xlog</literal> subdirectory of the current
+        for them in the <literal>pg_wal</literal> subdirectory of the current
         directory.
        </para>
       </listitem>
diff --git a/doc/src/sgml/ref/pgtestfsync.sgml b/doc/src/sgml/ref/pgtestfsync.sgml
index 6e134c7..5856356 100644
--- a/doc/src/sgml/ref/pgtestfsync.sgml
+++ b/doc/src/sgml/ref/pgtestfsync.sgml
@@ -57,8 +57,8 @@
        <para>
         Specifies the file name to write test data in.
         This file should be in the same file system that the
-        <filename>pg_xlog</> directory is or will be placed in.
-        (<filename>pg_xlog</> contains the <acronym>WAL</> files.)
+        <filename>pg_wal</> directory is or will be placed in.
+        (<filename>pg_wal</> contains the <acronym>WAL</> files.)
         The default is <filename>pg_test_fsync.out</> in the current
         directory.
        </para>
diff --git a/doc/src/sgml/ref/pgupgrade.sgml b/doc/src/sgml/ref/pgupgrade.sgml
index 9685193..4b9aab2 100644
--- a/doc/src/sgml/ref/pgupgrade.sgml
+++ b/doc/src/sgml/ref/pgupgrade.sgml
@@ -345,7 +345,7 @@ NET STOP postgresql-9.0
      your old cluster
      once you start the new cluster after the upgrade.  Link mode also
      requires that the old and new cluster data directories be in the
-     same file system.  (Tablespaces and <filename>pg_xlog</> can be on
+     same file system.  (Tablespaces and <filename>pg_wal</> can be on
      different file systems.)  See <literal>pg_upgrade --help</> for a full
      list of options.
     </para>
@@ -508,7 +508,7 @@ rsync --archive --delete --hard-links --size-only old_pgdata new_pgdata remote_d
       <para>
        If you have tablespaces, you will need to run a similar
        <application>rsync</> command for each tablespace directory.  If you
-       have relocated <filename>pg_xlog</> outside the data directories,
+       have relocated <filename>pg_wal</> outside the data directories,
        <application>rsync</> must be run on those directories too.
       </para>
      </step>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 1b812bd..fddb69b 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -141,7 +141,7 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_xlog</></entry>
+ <entry><filename>pg_wal</></entry>
  <entry>Subdirectory containing WAL (Write Ahead Log) files</entry>
 </row>
 
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 503ea8a..bfc9a02 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -557,7 +557,7 @@
   </para>
 
   <para>
-   The number of WAL segment files in <filename>pg_xlog</> directory depends on
+   The number of WAL segment files in <filename>pg_wal</> directory depends on
    <varname>min_wal_size</>, <varname>max_wal_size</> and
    the amount of WAL generated in previous checkpoint cycles. When old log
    segment files are no longer needed, they are removed or recycled (that is,
@@ -582,7 +582,7 @@
    kept at all times. Also, if WAL archiving is used, old segments can not be
    removed or recycled until they are archived. If WAL archiving cannot keep up
    with the pace that WAL is generated, or if <varname>archive_command</varname>
-   fails repeatedly, old WAL files will accumulate in <filename>pg_xlog</>
+   fails repeatedly, old WAL files will accumulate in <filename>pg_wal</>
    until the situation is resolved. A slow or failed standby server that
    uses a replication slot will have the same effect (see
    <xref linkend="streaming-replication-slots">).
@@ -594,7 +594,7 @@
    which are similar to checkpoints in normal operation: the server forces
    all its state to disk, updates the <filename>pg_control</> file to
    indicate that the already-processed WAL data need not be scanned again,
-   and then recycles any old log segment files in the <filename>pg_xlog</>
+   and then recycles any old log segment files in the <filename>pg_wal</>
    directory.
    Restartpoints can't be performed more frequently than checkpoints in the
    master because restartpoints can only be performed at checkpoint records.
@@ -734,7 +734,7 @@
 
   <para>
    <acronym>WAL</acronym> logs are stored in the directory
-   <filename>pg_xlog</filename> under the data directory, as a set of
+   <filename>pg_wal</filename> under the data directory, as a set of
    segment files, normally each 16 MB in size (but the size can be changed
    by altering the <option>--with-wal-segsize</> configure option when
    building the server).  Each segment is divided into pages, normally
@@ -751,7 +751,7 @@
   <para>
    It is advantageous if the log is located on a different disk from the
    main database files.  This can be achieved by moving the
-   <filename>pg_xlog</filename> directory to another location (while the server
+   <filename>pg_wal</filename> directory to another location (while the server
    is shut down, of course) and creating a symbolic link from the
    original location in the main data directory to the new location.
   </para>
diff --git a/src/backend/access/transam/timeline.c b/src/backend/access/transam/timeline.c
index bd91573..43436a9 100644
--- a/src/backend/access/transam/timeline.c
+++ b/src/backend/access/transam/timeline.c
@@ -43,7 +43,7 @@
 
 /*
  * Copies all timeline history files with id's between 'begin' and 'end'
- * from archive to pg_xlog.
+ * from archive to pg_wal.
  */
 void
 restoreTimeLineHistoryFiles(TimeLineID begin, TimeLineID end)
@@ -191,7 +191,7 @@ readTimeLineHistory(TimeLineID targetTLI)
 	result = lcons(entry, result);
 
 	/*
-	 * If the history file was fetched from archive, save it in pg_xlog for
+	 * If the history file was fetched from archive, save it in pg_wal for
 	 * future reference.
 	 */
 	if (fromArchive)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index acd95aa..46dc15a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -234,9 +234,9 @@ static int	LocalXLogInsertAllowed = -1;
  * valid in the startup process.
  *
  * When ArchiveRecoveryRequested is true, but InArchiveRecovery is false, we're
- * currently performing crash recovery using only XLOG files in pg_xlog, but
+ * currently performing crash recovery using only XLOG files in pg_wal, but
  * will switch to using offline XLOG archives as soon as we reach the end of
- * WAL in pg_xlog.
+ * WAL in pg_wal.
 */
 bool		ArchiveRecoveryRequested = false;
 bool		InArchiveRecovery = false;
@@ -697,12 +697,12 @@ typedef enum
 {
 	XLOG_FROM_ANY = 0,			/* request to read WAL from any source */
 	XLOG_FROM_ARCHIVE,			/* restored using restore_command */
-	XLOG_FROM_PG_XLOG,			/* existing file in pg_xlog */
+	XLOG_FROM_PG_WAL,			/* existing file in pg_wal */
 	XLOG_FROM_STREAM			/* streamed from master */
 } XLogSource;
 
 /* human-readable names for XLogSources, for debugging output */
-static const char *xlogSourceNames[] = {"any", "archive", "pg_xlog", "stream"};
+static const char *xlogSourceNames[] = {"any", "archive", "pg_wal", "stream"};
 
 /*
  * openLogFile is -1 or a kernel FD for an open log file segment.
@@ -3342,7 +3342,7 @@ XLogFileOpen(XLogSegNo segno)
  * Open a logfile segment for reading (during recovery).
  *
  * If source == XLOG_FROM_ARCHIVE, the segment is retrieved from archive.
- * Otherwise, it's assumed to be already available in pg_xlog.
+ * Otherwise, it's assumed to be already available in pg_wal.
  */
 static int
 XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
@@ -3371,7 +3371,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 				return -1;
 			break;
 
-		case XLOG_FROM_PG_XLOG:
+		case XLOG_FROM_PG_WAL:
 		case XLOG_FROM_STREAM:
 			XLogFilePath(path, tli, segno);
 			restoredFromArchive = false;
@@ -3390,7 +3390,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 		KeepFileRestoredFromArchive(path, xlogfname);
 
 		/*
-		 * Set path to point at the new file in pg_xlog.
+		 * Set path to point at the new file in pg_wal.
 		 */
 		snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlogfname);
 	}
@@ -3478,10 +3478,10 @@ XLogFileReadAnyTLI(XLogSegNo segno, int emode, int source)
 			}
 		}
 
-		if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_XLOG)
+		if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_WAL)
 		{
 			fd = XLogFileRead(segno, emode, tli,
-							  XLOG_FROM_PG_XLOG, true);
+							  XLOG_FROM_PG_WAL, true);
 			if (fd != -1)
 			{
 				if (!expectedTLEs)
@@ -3690,10 +3690,10 @@ RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
  *
  * This is called during recovery, whenever we switch to follow a new
  * timeline, and at the end of recovery when we create a new timeline. We
- * wouldn't otherwise care about extra WAL files lying in pg_xlog, but they
+ * wouldn't otherwise care about extra WAL files lying in pg_wal, but they
  * might be leftover pre-allocated or recycled WAL segments on the old timeline
  * that we haven't used yet, and contain garbage. If we just leave them in
- * pg_xlog, they will eventually be archived, and we can't let that happen.
+ * pg_wal, they will eventually be archived, and we can't let that happen.
  * Files that belong to our timeline history are valid, because we have
  * successfully replayed them, but from others we can't be sure.
  *
@@ -3850,15 +3850,15 @@ RemoveXlogFile(const char *segname, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
 }
 
 /*
- * Verify whether pg_xlog and pg_xlog/archive_status exist.
+ * Verify whether pg_wal and pg_wal/archive_status exist.
  * If the latter does not exist, recreate it.
  *
  * It is not the goal of this function to verify the contents of these
  * directories, but to help in cases where someone has performed a cluster
- * copy for PITR purposes but omitted pg_xlog from the copy.
+ * copy for PITR purposes but omitted pg_wal from the copy.
  *
- * We could also recreate pg_xlog if it doesn't exist, but a deliberate
- * policy decision was made not to.  It is fairly common for pg_xlog to be
+ * We could also recreate pg_wal if it doesn't exist, but a deliberate
+ * policy decision was made not to.  It is fairly common for pg_wal to be
  * a symlink, and if that was the DBA's intent then automatically making a
  * plain directory would result in degraded performance with no notice.
  */
@@ -3868,7 +3868,7 @@ ValidateXLOGDirectoryStructure(void)
 	char		path[MAXPGPATH];
 	struct stat stat_buf;
 
-	/* Check for pg_xlog; if it doesn't exist, error out */
+	/* Check for pg_wal; if it doesn't exist, error out */
 	if (stat(XLOGDIR, &stat_buf) != 0 ||
 		!S_ISDIR(stat_buf.st_mode))
 		ereport(FATAL,
@@ -4024,11 +4024,11 @@ ReadRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int emode,
 			 * If archive recovery was requested, but we were still doing
 			 * crash recovery, switch to archive recovery and retry using the
 			 * offline archive. We have now replayed all the valid WAL in
-			 * pg_xlog, so we are presumably now consistent.
+			 * pg_wal, so we are presumably now consistent.
 			 *
 			 * We require that there's at least some valid WAL present in
-			 * pg_xlog, however (!fetch_ckpt). We could recover using the WAL
-			 * from the archive, even if pg_xlog is completely empty, but we'd
+			 * pg_wal, however (!fetch_ckpt). We could recover using the WAL
+			 * from the archive, even if pg_wal is completely empty, but we'd
 			 * have no idea how far we'd have to replay to reach consistency.
 			 * So err on the safe side and give up.
 			 */
@@ -4036,7 +4036,7 @@ ReadRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int emode,
 				!fetching_ckpt)
 			{
 				ereport(DEBUG1,
-						(errmsg_internal("reached end of WAL in pg_xlog, entering archive recovery")));
+						(errmsg_internal("reached end of WAL in pg_wal, entering archive recovery")));
 				InArchiveRecovery = true;
 				if (StandbyModeRequested)
 					StandbyMode = true;
@@ -4153,7 +4153,7 @@ rescanLatestTimeLine(void)
 
 	/*
 	 * As in StartupXLOG(), try to ensure we have all the history files
-	 * between the old target and new target in pg_xlog.
+	 * between the old target and new target in pg_wal.
 	 */
 	restoreTimeLineHistoryFiles(oldtarget + 1, newtarget);
 
@@ -5166,7 +5166,7 @@ readRecoveryCommandFile(void)
 			ereport(WARNING,
 					(errmsg("recovery command file \"%s\" specified neither primary_conninfo nor restore_command",
 							RECOVERY_COMMAND_FILE),
-					 errhint("The database server will regularly poll the pg_xlog subdirectory to check for files placed there.")));
+					 errhint("The database server will regularly poll the pg_wal subdirectory to check for files placed there.")));
 	}
 	else
 	{
@@ -5982,7 +5982,7 @@ StartupXLOG(void)
 #endif
 
 	/*
-	 * Verify that pg_xlog and pg_xlog/archive_status exist.  In cases where
+	 * Verify that pg_wal and pg_wal/archive_status exist.  In cases where
 	 * someone has performed a copy for PITR, these directories may have been
 	 * excluded and need to be re-created.
 	 */
@@ -6190,7 +6190,7 @@ StartupXLOG(void)
 		 * and put it into archive recovery by creating a recovery.conf file.
 		 *
 		 * Our strategy in that case is to perform crash recovery first,
-		 * replaying all the WAL present in pg_xlog, and only enter archive
+		 * replaying all the WAL present in pg_wal, and only enter archive
 		 * recovery after that.
 		 *
 		 * But usually we already know how far we need to replay the WAL (up
@@ -6394,7 +6394,7 @@ StartupXLOG(void)
 
 	/*
 	 * Copy any missing timeline history files between 'now' and the recovery
-	 * target timeline from archive to pg_xlog. While we don't need those
+	 * target timeline from archive to pg_wal. While we don't need those
 	 * files ourselves - the history file of the recovery target timeline
 	 * covers all the previous timelines in the history too - a cascading
 	 * standby server might be interested in them. Or, if you archive the WAL
@@ -7015,7 +7015,7 @@ StartupXLOG(void)
 	/*
 	 * We are now done reading the xlog from stream. Turn off streaming
 	 * recovery to force fetching the files (which would be required at end of
-	 * recovery, e.g., timeline history file) from archive or pg_xlog.
+	 * recovery, e.g., timeline history file) from archive or pg_wal.
 	 */
 	StandbyMode = false;
 
@@ -7297,7 +7297,7 @@ StartupXLOG(void)
 		 * As a compromise, we rename the last segment with the .partial
 		 * suffix, and archive it. Archive recovery will never try to read
 		 * .partial segments, so they will normally go unused. But in the odd
-		 * PITR case, the administrator can copy them manually to the pg_xlog
+		 * PITR case, the administrator can copy them manually to the pg_wal
 		 * directory (removing the suffix). They can be useful in debugging,
 		 * too.
 		 *
@@ -9862,7 +9862,7 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
 		 * first WAL segment containing the startup checkpoint has pages in
 		 * the beginning with the old timeline ID.  That can cause trouble at
 		 * recovery: we won't have a history file covering the old timeline if
-		 * pg_xlog directory was not included in the base backup and the WAL
+		 * pg_wal directory was not included in the base backup and the WAL
 		 * archive was cleared too before starting the backup.
 		 *
 		 * This also ensures that we have emitted a WAL page header that has
@@ -10509,7 +10509,7 @@ do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
 	 * archived before returning. If archiving isn't enabled, the required WAL
 	 * needs to be transported via streaming replication (hopefully with
 	 * wal_keep_segments set high enough), or some more exotic mechanism like
-	 * polling and copying files from pg_xlog with script. We have no
+	 * polling and copying files from pg_wal with script. We have no
 	 * knowledge of those mechanisms, so it's up to the user to ensure that he
 	 * gets all the required WAL.
 	 *
@@ -11099,9 +11099,9 @@ next_record_is_invalid:
  * Open the WAL segment containing WAL position 'RecPtr'.
  *
  * The segment can be fetched via restore_command, or via walreceiver having
- * streamed the record, or it can already be present in pg_xlog. Checking
- * pg_xlog is mainly for crash recovery, but it will be polled in standby mode
- * too, in case someone copies a new segment directly to pg_xlog. That is not
+ * streamed the record, or it can already be present in pg_wal. Checking
+ * pg_wal is mainly for crash recovery, but it will be polled in standby mode
+ * too, in case someone copies a new segment directly to pg_wal. That is not
  * documented or recommended, though.
  *
  * If 'fetching_ckpt' is true, we're fetching a checkpoint record, and should
@@ -11131,8 +11131,8 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 	/*-------
 	 * Standby mode is implemented by a state machine:
 	 *
-	 * 1. Read from either archive or pg_xlog (XLOG_FROM_ARCHIVE), or just
-	 *	  pg_xlog (XLOG_FROM_XLOG)
+	 * 1. Read from either archive or pg_wal (XLOG_FROM_ARCHIVE), or just
+	 *	  pg_wal (XLOG_FROM_PG_WAL)
 	 * 2. Check trigger file
 	 * 3. Read from primary server via walreceiver (XLOG_FROM_STREAM)
 	 * 4. Rescan timelines
@@ -11148,7 +11148,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 	 *-------
 	 */
 	if (!InArchiveRecovery)
-		currentSource = XLOG_FROM_PG_XLOG;
+		currentSource = XLOG_FROM_PG_WAL;
 	else if (currentSource == 0)
 		currentSource = XLOG_FROM_ARCHIVE;
 
@@ -11167,13 +11167,13 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 			switch (currentSource)
 			{
 				case XLOG_FROM_ARCHIVE:
-				case XLOG_FROM_PG_XLOG:
+				case XLOG_FROM_PG_WAL:
 
 					/*
 					 * Check to see if the trigger file exists. Note that we
 					 * do this only after failure, so when you create the
 					 * trigger file, we still finish replaying as much as we
-					 * can from archive and pg_xlog before failover.
+					 * can from archive and pg_wal before failover.
 					 */
 					if (StandbyMode && CheckForStandbyTrigger())
 					{
@@ -11183,7 +11183,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 
 					/*
 					 * Not in standby mode, and we've now tried the archive
-					 * and pg_xlog.
+					 * and pg_wal.
 					 */
 					if (!StandbyMode)
 						return false;
@@ -11243,7 +11243,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					 * little chance that the problem will just go away, but
 					 * PANIC is not good for availability either, especially
 					 * in hot standby mode. So, we treat that the same as
-					 * disconnection, and retry from archive/pg_xlog again.
+					 * disconnection, and retry from archive/pg_wal again.
 					 * The WAL in the archive should be identical to what was
 					 * streamed, so it's unlikely that it helps, but one can
 					 * hope...
@@ -11304,11 +11304,11 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					elog(ERROR, "unexpected WAL source %d", currentSource);
 			}
 		}
-		else if (currentSource == XLOG_FROM_PG_XLOG)
+		else if (currentSource == XLOG_FROM_PG_WAL)
 		{
 			/*
-			 * We just successfully read a file in pg_xlog. We prefer files in
-			 * the archive over ones in pg_xlog, so try the next file again
+			 * We just successfully read a file in pg_wal. We prefer files in
+			 * the archive over ones in pg_wal, so try the next file again
 			 * from the archive first.
 			 */
 			if (InArchiveRecovery)
@@ -11329,7 +11329,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 		switch (currentSource)
 		{
 			case XLOG_FROM_ARCHIVE:
-			case XLOG_FROM_PG_XLOG:
+			case XLOG_FROM_PG_WAL:
 				/* Close any old file we might have open. */
 				if (readFile >= 0)
 				{
@@ -11342,7 +11342,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 
 				/*
 				 * Try to restore the file from archive, or read an existing
-				 * file from pg_xlog.
+				 * file from pg_wal.
 				 */
 				readFile = XLogFileReadAnyTLI(readSegNo, DEBUG2,
 						 currentSource == XLOG_FROM_ARCHIVE ? XLOG_FROM_ANY :
@@ -11351,7 +11351,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					return true;	/* success! */
 
 				/*
-				 * Nope, not found in archive or pg_xlog.
+				 * Nope, not found in archive or pg_wal.
 				 */
 				lastSourceFailed = true;
 				break;
@@ -11407,7 +11407,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 						 * not open already.  Also read the timeline history
 						 * file if we haven't initialized timeline history
 						 * yet; it should be streamed over and present in
-						 * pg_xlog by now.  Use XLOG_FROM_STREAM so that
+						 * pg_wal by now.  Use XLOG_FROM_STREAM so that
 						 * source info is set correctly and XLogReceiptTime
 						 * isn't changed.
 						 */
@@ -11439,10 +11439,10 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 						/*
 						 * Note that we don't "return false" immediately here.
 						 * After being triggered, we still want to replay all
-						 * the WAL that was already streamed. It's in pg_xlog
+						 * the WAL that was already streamed. It's in pg_wal
 						 * now, so we just treat this as a failure, and the
 						 * state machine will move on to replay the streamed
-						 * WAL from pg_xlog, and then recheck the trigger and
+						 * WAL from pg_wal, and then recheck the trigger and
 						 * exit replay.
 						 */
 						lastSourceFailed = true;
@@ -11482,7 +11482,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
  * or legitimate end-of-WAL situation.   Generally, we use it as-is, but if
  * we're retrying the exact same record that we've tried previously, only
  * complain the first time to keep the noise down.  However, we only do when
- * reading from pg_xlog, because we don't expect any invalid records in archive
+ * reading from pg_wal, because we don't expect any invalid records in archive
  * or in records streamed from master. Files in the archive should be complete,
  * and we should never hit the end of WAL because we stop and wait for more WAL
  * to arrive before replaying it.
@@ -11497,7 +11497,7 @@ emode_for_corrupt_record(int emode, XLogRecPtr RecPtr)
 {
 	static XLogRecPtr lastComplaint = 0;
 
-	if (readSource == XLOG_FROM_PG_XLOG && emode == LOG)
+	if (readSource == XLOG_FROM_PG_WAL && emode == LOG)
 	{
 		if (RecPtr == lastComplaint)
 			emode = DEBUG1;
diff --git a/src/backend/access/transam/xlogarchive.c b/src/backend/access/transam/xlogarchive.c
index d153a44..b919164 100644
--- a/src/backend/access/transam/xlogarchive.c
+++ b/src/backend/access/transam/xlogarchive.c
@@ -421,7 +421,7 @@ ExecuteRecoveryCommand(char *command, char *commandName, bool failOnSignal)
 /*
  * A file was restored from the archive under a temporary filename (path),
  * and now we want to keep it. Rename it under the permanent filename in
- * in pg_xlog (xlogfname), replacing any existing file with the same name.
+ * in pg_wal (xlogfname), replacing any existing file with the same name.
  */
 void
 KeepFileRestoredFromArchive(char *path, char *xlogfname)
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 33383b4..01cbd90 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -128,7 +128,7 @@ pg_start_backup(PG_FUNCTION_ARGS)
  * pg_stop_backup: finish taking an on-line backup dump
  *
  * We write an end-of-backup WAL record, and remove the backup label file
- * created by pg_start_backup, creating a backup history file in pg_xlog
+ * created by pg_start_backup, creating a backup history file in pg_wal
  * instead (whence it will immediately be archived). The backup history file
  * contains the same info found in the label file, plus the backup-end time
  * and WAL location. Before 9.0, the backup-end time was read from the backup
diff --git a/src/backend/replication/README b/src/backend/replication/README
index ad4864d..0cbb990 100644
--- a/src/backend/replication/README
+++ b/src/backend/replication/README
@@ -54,7 +54,7 @@ and WalRcvData->slotname, and initializes the starting point in
 WalRcvData->receiveStart.
 
 As walreceiver receives WAL from the master server, and writes and flushes
-it to disk (in pg_xlog), it updates WalRcvData->receivedUpto and signals
+it to disk (in pg_wal), it updates WalRcvData->receivedUpto and signals
 the startup process to know how far WAL replay can advance.
 
 Walreceiver sends information about replication progress to the master server
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index da9b7a6..3ffc665 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -276,7 +276,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		TimeLineID	tli;
 
 		/*
-		 * I'd rather not worry about timelines here, so scan pg_xlog and
+		 * I'd rather not worry about timelines here, so scan pg_wal and
 		 * include all WAL files in the range between 'startptr' and 'endptr',
 		 * regardless of the timeline the file is stamped with. If there are
 		 * some spurious WAL files belonging to timelines that don't belong in
@@ -289,11 +289,11 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		XLByteToPrevSeg(endptr, endsegno);
 		XLogFileName(lastoff, ThisTimeLineID, endsegno);
 
-		dir = AllocateDir("pg_xlog");
+		dir = AllocateDir("pg_wal");
 		if (!dir)
 			ereport(ERROR,
-				 (errmsg("could not open directory \"%s\": %m", "pg_xlog")));
-		while ((de = ReadDir(dir, "pg_xlog")) != NULL)
+				 (errmsg("could not open directory \"%s\": %m", "pg_wal")));
+		while ((de = ReadDir(dir, "pg_wal")) != NULL)
 		{
 			/* Does it look like a WAL segment, and is it in the range? */
 			if (IsXLogFileName(de->d_name) &&
@@ -331,7 +331,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		qsort(walFiles, nWalFiles, sizeof(char *), compareWalFileNames);
 
 		/*
-		 * There must be at least one xlog file in the pg_xlog directory,
+		 * There must be at least one xlog file in the pg_wal directory,
 		 * since we are doing backup-including-xlog.
 		 */
 		if (nWalFiles < 1)
@@ -988,15 +988,15 @@ sendDir(char *path, int basepathlen, bool sizeonly, List *tablespaces,
 		}
 
 		/*
-		 * We can skip pg_xlog, the WAL segments need to be fetched from the
+		 * We can skip pg_wal, the WAL segments need to be fetched from the
 		 * WAL archive anyway. But include it as an empty directory anyway, so
 		 * we get permissions right.
 		 */
-		if (strcmp(pathbuf, "./pg_xlog") == 0)
+		if (strcmp(pathbuf, "./pg_wal") == 0)
 		{
 			if (!sizeonly)
 			{
-				/* If pg_xlog is a symlink, write it as a directory anyway */
+				/* If pg_wal is a symlink, write it as a directory anyway */
 #ifndef WIN32
 				if (S_ISLNK(statbuf.st_mode))
 #else
@@ -1012,10 +1012,10 @@ sendDir(char *path, int basepathlen, bool sizeonly, List *tablespaces,
 			 * statbuf from above ...).
 			 */
 			if (!sizeonly)
-				_tarWriteHeader("./pg_xlog/archive_status", NULL, &statbuf);
+				_tarWriteHeader("./pg_wal/archive_status", NULL, &statbuf);
 			size += 512;		/* Size of the header just added */
 
-			continue;			/* don't recurse into pg_xlog */
+			continue;			/* don't recurse into pg_wal */
 		}
 
 		/* Allow symbolic links in pg_tblspc only */
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 413ee3a..d40b5e9 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -18,7 +18,7 @@
  * If the primary server ends streaming, but doesn't disconnect, walreceiver
  * goes into "waiting" mode, and waits for the startup process to give new
  * instructions. The startup process will treat that the same as
- * disconnection, and will rescan the archive/pg_xlog directory. But when the
+ * disconnection, and will rescan the archive/pg_wal directory. But when the
  * startup process wants to try streaming replication again, it will just
  * nudge the existing walreceiver process that's waiting, instead of launching
  * a new one.
@@ -364,7 +364,7 @@ WalReceiverMain(void)
 		 * we've already reached the end of the old timeline, the server will
 		 * finish the streaming immediately, and we will go back to await
 		 * orders from the startup process. If recovery_target_timeline is
-		 * 'latest', the startup process will scan pg_xlog and find the new
+		 * 'latest', the startup process will scan pg_wal and find the new
 		 * history file, bump recovery target timeline, and ask us to restart
 		 * on the new timeline.
 		 */
@@ -739,7 +739,7 @@ WalRcvFetchTimeLineHistoryFiles(TimeLineID first, TimeLineID last)
 										 tli)));
 
 			/*
-			 * Write the file to pg_xlog.
+			 * Write the file to pg_wal.
 			 */
 			writeTimeLineHistoryFile(tli, content, len);
 
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 1ea2a5c..34e4dd0 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -586,7 +586,7 @@ StartReplication(StartReplicationCmd *cmd)
 			 * segment that contains switchpoint, but on the new timeline, so
 			 * that it doesn't end up with a partial segment. If you ask for a
 			 * too old starting point, you'll get an error later when we fail
-			 * to find the requested WAL segment in pg_xlog.
+			 * to find the requested WAL segment in pg_wal.
 			 *
 			 * XXX: we could be more strict here and only allow a startpoint
 			 * that's older than the switchpoint, if it's still in the same
@@ -2052,7 +2052,7 @@ retry:
 			 *
 			 * For example, imagine that this server is currently on timeline
 			 * 5, and we're streaming timeline 4. The switch from timeline 4
-			 * to 5 happened at 0/13002088. In pg_xlog, we have these files:
+			 * to 5 happened at 0/13002088. In pg_wal, we have these files:
 			 *
 			 * ...
 			 * 000000040000000000000012
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 03143f1..b7ff5ef 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -2787,7 +2787,7 @@ looks_like_temp_rel_name(const char *name)
  * Issue fsync recursively on PGDATA and all its contents.
  *
  * We fsync regular files and directories wherever they are, but we
- * follow symlinks only for pg_xlog and immediately under pg_tblspc.
+ * follow symlinks only for pg_wal and immediately under pg_tblspc.
  * Other symlinks are presumed to point at files we're not responsible
  * for fsyncing, and might not have privileges to write at all.
  *
@@ -2811,7 +2811,7 @@ SyncDataDirectory(void)
 		return;
 
 	/*
-	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * If pg_wal is a symlink, we'll need to recurse into it separately,
 	 * because the first walkdir below will ignore it.
 	 */
 	xlog_is_symlink = false;
@@ -2820,16 +2820,16 @@ SyncDataDirectory(void)
 	{
 		struct stat st;
 
-		if (lstat("pg_xlog", &st) < 0)
+		if (lstat("pg_wal", &st) < 0)
 			ereport(LOG,
 					(errcode_for_file_access(),
 					 errmsg("could not stat file \"%s\": %m",
-							"pg_xlog")));
+							"pg_wal")));
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
 #else
-	if (pgwin32_is_junction("pg_xlog"))
+	if (pgwin32_is_junction("pg_wal"))
 		xlog_is_symlink = true;
 #endif
 
@@ -2841,7 +2841,7 @@ SyncDataDirectory(void)
 #ifdef PG_FLUSH_DATA_WORKS
 	walkdir(".", pre_sync_fname, false, DEBUG1);
 	if (xlog_is_symlink)
-		walkdir("pg_xlog", pre_sync_fname, false, DEBUG1);
+		walkdir("pg_wal", pre_sync_fname, false, DEBUG1);
 	walkdir("pg_tblspc", pre_sync_fname, true, DEBUG1);
 #endif
 
@@ -2849,14 +2849,14 @@ SyncDataDirectory(void)
 	 * Now we do the fsync()s in the same order.
 	 *
 	 * The main call ignores symlinks, so in addition to specially processing
-	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * pg_wal if it's a symlink, pg_tblspc has to be visited separately with
 	 * process_symlinks = true.  Note that if there are any plain directories
 	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
 	 * so we don't worry about optimizing it.
 	 */
 	walkdir(".", datadir_fsync_fname, false, LOG);
 	if (xlog_is_symlink)
-		walkdir("pg_xlog", datadir_fsync_fname, false, LOG);
+		walkdir("pg_wal", datadir_fsync_fname, false, LOG);
 	walkdir("pg_tblspc", datadir_fsync_fname, true, LOG);
 }
 
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index aad6ba5..77b0760 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -200,7 +200,7 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 
 static const char *const subdirs[] = {
 	"global",
-	"pg_xlog/archive_status",
+	"pg_wal/archive_status",
 	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
@@ -2281,7 +2281,7 @@ make_postgres(FILE *cmdfd)
  * Issue fsync recursively on PGDATA and all its contents.
  *
  * We fsync regular files and directories wherever they are, but we
- * follow symlinks only for pg_xlog and immediately under pg_tblspc.
+ * follow symlinks only for pg_wal and immediately under pg_tblspc.
  * Other symlinks are presumed to point at files we're not responsible
  * for fsyncing, and might not have privileges to write at all.
  *
@@ -2291,17 +2291,17 @@ static void
 fsync_pgdata(void)
 {
 	bool		xlog_is_symlink;
-	char		pg_xlog[MAXPGPATH];
+	char		pg_wal[MAXPGPATH];
 	char		pg_tblspc[MAXPGPATH];
 
 	fputs(_("syncing data to disk ... "), stdout);
 	fflush(stdout);
 
-	snprintf(pg_xlog, MAXPGPATH, "%s/pg_xlog", pg_data);
+	snprintf(pg_wal, MAXPGPATH, "%s/pg_wal", pg_data);
 	snprintf(pg_tblspc, MAXPGPATH, "%s/pg_tblspc", pg_data);
 
 	/*
-	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * If pg_wal is a symlink, we'll need to recurse into it separately,
 	 * because the first walkdir below will ignore it.
 	 */
 	xlog_is_symlink = false;
@@ -2310,14 +2310,14 @@ fsync_pgdata(void)
 	{
 		struct stat st;
 
-		if (lstat(pg_xlog, &st) < 0)
+		if (lstat(pg_wal, &st) < 0)
 			fprintf(stderr, _("%s: could not stat file \"%s\": %s\n"),
-					progname, pg_xlog, strerror(errno));
+					progname, pg_wal, strerror(errno));
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
 #else
-	if (pgwin32_is_junction(pg_xlog))
+	if (pgwin32_is_junction(pg_wal))
 		xlog_is_symlink = true;
 #endif
 
@@ -2328,7 +2328,7 @@ fsync_pgdata(void)
 #ifdef PG_FLUSH_DATA_WORKS
 	walkdir(pg_data, pre_sync_fname, false);
 	if (xlog_is_symlink)
-		walkdir(pg_xlog, pre_sync_fname, false);
+		walkdir(pg_wal, pre_sync_fname, false);
 	walkdir(pg_tblspc, pre_sync_fname, true);
 #endif
 
@@ -2336,14 +2336,14 @@ fsync_pgdata(void)
 	 * Now we do the fsync()s in the same order.
 	 *
 	 * The main call ignores symlinks, so in addition to specially processing
-	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * pg_wal if it's a symlink, pg_tblspc has to be visited separately with
 	 * process_symlinks = true.  Note that if there are any plain directories
 	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
 	 * so we don't worry about optimizing it.
 	 */
 	walkdir(pg_data, fsync_fname_ext, false);
 	if (xlog_is_symlink)
-		walkdir(pg_xlog, fsync_fname_ext, false);
+		walkdir(pg_wal, fsync_fname_ext, false);
 	walkdir(pg_tblspc, fsync_fname_ext, true);
 
 	check_ok();
@@ -3087,7 +3087,7 @@ create_xlog_or_symlink(void)
 	char	   *subdirloc;
 
 	/* form name of the place for the subdirectory or symlink */
-	subdirloc = psprintf("%s/pg_xlog", pg_data);
+	subdirloc = psprintf("%s/pg_wal", pg_data);
 
 	if (strcmp(xlog_dir, "") != 0)
 	{
@@ -3220,7 +3220,7 @@ initialize_data_directory(void)
 
 	create_xlog_or_symlink();
 
-	/* Create required subdirectories (other than pg_xlog) */
+	/* Create required subdirectories (other than pg_wal) */
 	printf(_("creating subdirectories ... "));
 	fflush(stdout);
 
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 351a420..9401a9f 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -411,6 +411,7 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 	uint32		hi,
 				lo;
 	char		statusdir[MAXPGPATH];
+	int			serverMajor;
 
 	param = pg_malloc0(sizeof(logstreamer_param));
 	param->timeline = timeline;
@@ -445,15 +446,21 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 		/* Error message already written in GetConnection() */
 		exit(1);
 
-	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/pg_xlog", basedir);
+	serverMajor = PQserverVersion(conn) / 100;
+
+	/* In post-10 cluster, pg_xlog has been renamed to pg_wal */
+	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/%s",
+			 basedir, serverMajor < 1000 ? "pg_xlog" : "pg_wal");
 
 	/*
-	 * Create pg_xlog/archive_status (and thus pg_xlog) so we can write to
-	 * basedir/pg_xlog as the directory entry in the tar file may arrive
-	 * later.
+	 * Create pg_wal/archive_status or pg_xlog/archive_status (and thus
+	 * pg_wal or pg_xlog) depending on the target server so we can write to
+	 * basedir/pg_wal or basedir/pg_xlog as the directory entry in the tar
+	 * file may arrive later.
 	 */
-	snprintf(statusdir, sizeof(statusdir), "%s/pg_xlog/archive_status",
-			 basedir);
+	snprintf(statusdir, sizeof(statusdir), "%s/%s/archive_status",
+			 basedir,
+			 serverMajor < 1000 ? "pg_xlog" : "pg_wal");
 
 	if (pg_mkdir_p(statusdir, S_IRWXU) != 0 && errno != EEXIST)
 	{
@@ -1249,15 +1256,17 @@ ReceiveAndUnpackTarFile(PGconn *conn, PGresult *res, int rownum)
 					if (mkdir(filename, S_IRWXU) != 0)
 					{
 						/*
-						 * When streaming WAL, pg_xlog will have been created
-						 * by the wal receiver process. Also, when transaction
-						 * log directory location was specified, pg_xlog has
-						 * already been created as a symbolic link before
-						 * starting the actual backup. So just ignore creation
-						 * failures on related directories.
+						 * When streaming WAL, pg_wal (or pg_xlog for pre-9.6
+						 * clusters) will have been created by the wal receiver
+						 * process. Also, when transaction log directory location
+						 * was specified, pg_wal (or pg_xlog) has already been
+						 * created as a symbolic link before starting the actual
+						 * backup. So just ignore creation failures on related
+						 * directories.
 						 */
-						if (!((pg_str_endswith(filename, "/pg_xlog") ||
-							 pg_str_endswith(filename, "/archive_status")) &&
+						if (!((pg_str_endswith(filename, "/pg_wal") ||
+							   pg_str_endswith(filename, "/pg_xlog")||
+							   pg_str_endswith(filename, "/archive_status")) &&
 							  errno == EEXIST))
 						{
 							fprintf(stderr,
@@ -1542,13 +1551,7 @@ BaseBackup(void)
 				maxServerMajor;
 	int			serverMajor;
 
-	/*
-	 * Connect in replication mode to the server
-	 */
-	conn = GetConnection();
-	if (!conn)
-		/* Error message already written in GetConnection() */
-		exit(1);
+	Assert(conn != NULL);
 
 	/*
 	 * Check server version. BASE_BACKUP command was introduced in 9.1, so we
@@ -2172,26 +2175,37 @@ main(int argc, char **argv)
 	if (format == 'p' || strcmp(basedir, "-") != 0)
 		verify_dir_is_empty_or_create(basedir);
 
+	/* connection in replication mode to server */
+	conn = GetConnection();
+	if (!conn)
+		/* Error message already written in GetConnection() */
+		exit(1);
+
 	/* Create transaction log symlink, if required */
 	if (strcmp(xlog_dir, "") != 0)
 	{
 		char	   *linkloc;
+		int			serverMajor = PQserverVersion(conn) / 100;
 
 		verify_dir_is_empty_or_create(xlog_dir);
 
-		/* form name of the place where the symlink must go */
-		linkloc = psprintf("%s/pg_xlog", basedir);
+		/*
+		 * Form name of the place where the symlink must go. pg_xlog has
+		 * been renamed to pg_wal in post-10 clusters.
+		 */
+		linkloc = psprintf("%s/%s", basedir,
+						   serverMajor < 1000 ? "pg_xlog" : "pg_wal");
 
 #ifdef HAVE_SYMLINK
 		if (symlink(xlog_dir, linkloc) != 0)
 		{
 			fprintf(stderr, _("%s: could not create symbolic link \"%s\": %s\n"),
 					progname, linkloc, strerror(errno));
-			exit(1);
+			disconnect_and_exit(1);
 		}
 #else
 		fprintf(stderr, _("%s: symlinks are not supported on this platform\n"));
-		exit(1);
+		disconnect_and_exit(1);
 #endif
 		free(linkloc);
 	}
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 6c33936..11642e4 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -52,7 +52,7 @@ $node->command_ok([ 'pg_basebackup', '-D', "$tempdir/backup" ],
 ok(-f "$tempdir/backup/PG_VERSION", 'backup was created');
 
 is_deeply(
-	[ sort(slurp_dir("$tempdir/backup/pg_xlog/")) ],
+	[ sort(slurp_dir("$tempdir/backup/pg_wal/")) ],
 	[ sort qw(. .. archive_status) ],
 	'no WAL files copied');
 
@@ -182,12 +182,12 @@ like(
 $node->command_ok(
 	[ 'pg_basebackup', '-D', "$tempdir/backupxf", '-X', 'fetch' ],
 	'pg_basebackup -X fetch runs');
-ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_xlog")),
+ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_wal")),
 	'WAL files copied');
 $node->command_ok(
 	[ 'pg_basebackup', '-D', "$tempdir/backupxs", '-X', 'stream' ],
 	'pg_basebackup -X stream runs');
-ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_xlog")),
+ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_wal")),
 	'WAL files copied');
 
 $node->command_fails(
diff --git a/src/bin/pg_resetxlog/pg_resetxlog.c b/src/bin/pg_resetxlog/pg_resetxlog.c
index 525b82ba..2b76f64 100644
--- a/src/bin/pg_resetxlog/pg_resetxlog.c
+++ b/src/bin/pg_resetxlog/pg_resetxlog.c
@@ -890,7 +890,7 @@ FindEndOfXLOG(void)
 	newXlogSegNo = ControlFile.checkPointCopy.redo / ControlFile.xlog_seg_size;
 
 	/*
-	 * Scan the pg_xlog directory to find existing WAL segment files. We
+	 * Scan the pg_wal directory to find existing WAL segment files. We
 	 * assume any present have been used; in most scenarios this should be
 	 * conservative, because of xlog.c's attempts to pre-create files.
 	 */
diff --git a/src/bin/pg_rewind/copy_fetch.c b/src/bin/pg_rewind/copy_fetch.c
index 327e7ef..d0c1586 100644
--- a/src/bin/pg_rewind/copy_fetch.c
+++ b/src/bin/pg_rewind/copy_fetch.c
@@ -131,10 +131,10 @@ recurse_dir(const char *datadir, const char *parentpath,
 			/*
 			 * If it's a symlink within pg_tblspc, we need to recurse into it,
 			 * to process all the tablespaces.  We also follow a symlink if
-			 * it's for pg_xlog.  Symlinks elsewhere are ignored.
+			 * it's for pg_wal.  Symlinks elsewhere are ignored.
 			 */
 			if ((parentpath && strcmp(parentpath, "pg_tblspc") == 0) ||
-				strcmp(path, "pg_xlog") == 0)
+				strcmp(path, "pg_wal") == 0)
 				recurse_dir(datadir, path, callback);
 #else
 			pg_fatal("\"%s\" is a symbolic link, but symbolic links are not supported on this platform\n",
diff --git a/src/bin/pg_rewind/filemap.c b/src/bin/pg_rewind/filemap.c
index 9b00dc1..3905a5d 100644
--- a/src/bin/pg_rewind/filemap.c
+++ b/src/bin/pg_rewind/filemap.c
@@ -79,11 +79,11 @@ process_source_file(const char *path, file_type_t type, size_t newsize,
 		return;
 
 	/*
-	 * Pretend that pg_xlog is a directory, even if it's really a symlink. We
+	 * Pretend that pg_wal is a directory, even if it's really a symlink. We
 	 * don't want to mess with the symlink itself, nor complain if it's a
 	 * symlink in source but not in target or vice versa.
 	 */
-	if (strcmp(path, "pg_xlog") == 0 && type == FILE_TYPE_SYMLINK)
+	if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK)
 		type = FILE_TYPE_DIRECTORY;
 
 	/*
@@ -120,7 +120,7 @@ process_source_file(const char *path, file_type_t type, size_t newsize,
 	switch (type)
 	{
 		case FILE_TYPE_DIRECTORY:
-			if (exists && !S_ISDIR(statbuf.st_mode) && strcmp(path, "pg_xlog") != 0)
+			if (exists && !S_ISDIR(statbuf.st_mode) && strcmp(path, "pg_wal") != 0)
 			{
 				/* it's a directory in source, but not in target. Strange.. */
 				pg_fatal("\"%s\" is not a directory\n", localpath);
@@ -296,7 +296,7 @@ process_target_file(const char *path, file_type_t type, size_t oldsize,
 	/*
 	 * Like in process_source_file, pretend that xlog is always a  directory.
 	 */
-	if (strcmp(path, "pg_xlog") == 0 && type == FILE_TYPE_SYMLINK)
+	if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK)
 		type = FILE_TYPE_DIRECTORY;
 
 	key.path = (char *) path;
diff --git a/src/bin/pg_rewind/parsexlog.c b/src/bin/pg_rewind/parsexlog.c
index b53591d..23ac4e7 100644
--- a/src/bin/pg_rewind/parsexlog.c
+++ b/src/bin/pg_rewind/parsexlog.c
@@ -54,7 +54,7 @@ static int SimpleXLogPageRead(XLogReaderState *xlogreader,
 				   TimeLineID *pageTLI);
 
 /*
- * Read WAL from the datadir/pg_xlog, starting from 'startpoint' on timeline
+ * Read WAL from the datadir/pg_wal, starting from 'startpoint' on timeline
  * index 'tliIndex' in target timeline history, until 'endpoint'. Make note of
  * the data blocks touched by the WAL records, and return them in a page map.
  */
diff --git a/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl b/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
index bdcab56..12950ea 100644
--- a/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
+++ b/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
@@ -1,5 +1,5 @@
 #
-# Test pg_rewind when the target's pg_xlog directory is a symlink.
+# Test pg_rewind when the target's pg_wal directory is a symlink.
 #
 use strict;
 use warnings;
@@ -30,10 +30,10 @@ sub run_test
 
 	my $test_master_datadir = $node_master->data_dir;
 
-	# turn pg_xlog into a symlink
-	print("moving $test_master_datadir/pg_xlog to $master_xlogdir\n");
-	move("$test_master_datadir/pg_xlog", $master_xlogdir) or die;
-	symlink($master_xlogdir, "$test_master_datadir/pg_xlog") or die;
+	# turn pg_wal into a symlink
+	print("moving $test_master_datadir/pg_wal to $master_xlogdir\n");
+	move("$test_master_datadir/pg_wal", $master_xlogdir) or die;
+	symlink($master_xlogdir, "$test_master_datadir/pg_wal") or die;
 
 	RewindTest::start_master();
 
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index dd30952..16f9f09 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -14,7 +14,7 @@
 #include <fcntl.h>
 #include <sys/types.h>
 
-static void check_data_dir(const char *pg_data);
+static void check_data_dir(ClusterInfo *cluster);
 static void check_bin_dir(ClusterInfo *cluster);
 static void validate_exec(const char *dir, const char *cmdName);
 
@@ -220,9 +220,9 @@ verify_directories(void)
 		pg_fatal("You must have read and write access in the current directory.\n");
 
 	check_bin_dir(&old_cluster);
-	check_data_dir(old_cluster.pgdata);
+	check_data_dir(&old_cluster);
 	check_bin_dir(&new_cluster);
-	check_data_dir(new_cluster.pgdata);
+	check_data_dir(&new_cluster);
 }
 
 
@@ -253,6 +253,32 @@ win32_check_directory_write_permissions(void)
 
 
 /*
+ * check_single_dir()
+ *
+ *  Check for the presence of a single directory in PGDATA, and fail if
+ * is it missing or not accessible.
+ */
+static void
+check_single_dir(const char *pg_data, const char *subdir)
+{
+	struct stat statBuf;
+	char		subDirName[MAXPGPATH];
+
+	snprintf(subDirName, sizeof(subDirName), "%s%s%s", pg_data,
+			 /* Win32 can't stat() a directory with a trailing slash. */
+			 *subdir ? "/" : "",
+			 subdir);
+
+	if (stat(subDirName, &statBuf) != 0)
+		report_status(PG_FATAL, "check for \"%s\" failed: %s\n",
+					  subDirName, getErrorText());
+	else if (!S_ISDIR(statBuf.st_mode))
+		report_status(PG_FATAL, "%s is not a directory\n",
+					  subDirName);
+}
+
+
+/*
  * check_data_dir()
  *
  *	This function validates the given cluster directory - we search for a
@@ -262,34 +288,27 @@ win32_check_directory_write_permissions(void)
  *
  */
 static void
-check_data_dir(const char *pg_data)
+check_data_dir(ClusterInfo *cluster)
 {
-	char		subDirName[MAXPGPATH];
-	int			subdirnum;
-
-	/* start check with top-most directory */
-	const char *requiredSubdirs[] = {"", "base", "global", "pg_clog",
-		"pg_multixact", "pg_subtrans", "pg_tblspc", "pg_twophase",
-	"pg_xlog"};
-
-	for (subdirnum = 0;
-		 subdirnum < sizeof(requiredSubdirs) / sizeof(requiredSubdirs[0]);
-		 ++subdirnum)
-	{
-		struct stat statBuf;
-
-		snprintf(subDirName, sizeof(subDirName), "%s%s%s", pg_data,
-		/* Win32 can't stat() a directory with a trailing slash. */
-				 *requiredSubdirs[subdirnum] ? "/" : "",
-				 requiredSubdirs[subdirnum]);
-
-		if (stat(subDirName, &statBuf) != 0)
-			report_status(PG_FATAL, "check for \"%s\" failed: %s\n",
-						  subDirName, getErrorText());
-		else if (!S_ISDIR(statBuf.st_mode))
-			report_status(PG_FATAL, "%s is not a directory\n",
-						  subDirName);
-	}
+	const char *pg_data = cluster->pgdata;
+
+	/* get old and new cluster versions */
+	old_cluster.major_version = get_major_server_version(&old_cluster);
+	new_cluster.major_version = get_major_server_version(&new_cluster);
+
+	check_single_dir(pg_data, "");
+	check_single_dir(pg_data, "base");
+	check_single_dir(pg_data, "global");
+	check_single_dir(pg_data, "pg_multixact");
+	check_single_dir(pg_data, "pg_subtrans");
+	check_single_dir(pg_data, "pg_tblspc");
+	check_single_dir(pg_data, "pg_twophase");
+
+	/* pg_xlog has been renamed to pg_wal in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_xlog");
+	else
+		check_single_dir(pg_data, "pg_wal");
 }
 
 
diff --git a/src/bin/pg_xlogdump/pg_xlogdump.c b/src/bin/pg_xlogdump/pg_xlogdump.c
index 02575eb..abc6fb9 100644
--- a/src/bin/pg_xlogdump/pg_xlogdump.c
+++ b/src/bin/pg_xlogdump/pg_xlogdump.c
@@ -656,7 +656,7 @@ usage(void)
 	printf("  -f, --follow           keep retrying after reaching end of WAL\n");
 	printf("  -n, --limit=N          number of records to display\n");
 	printf("  -p, --path=PATH        directory in which to find log segment files\n");
-	printf("                         (default: ./pg_xlog)\n");
+	printf("                         (default: ./pg_wal)\n");
 	printf("  -r, --rmgr=RMGR        only show records generated by resource manager RMGR\n");
 	printf("                         use --rmgr=list to list valid resource manager names\n");
 	printf("  -s, --start=RECPTR     start reading at log position RECPTR\n");
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 0a595cc..ceb0462 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -128,7 +128,7 @@ typedef XLogLongPageHeaderData *XLogLongPageHeader;
 /*
  * The XLog directory and control file (relative to $PGDATA)
  */
-#define XLOGDIR				"pg_xlog"
+#define XLOGDIR				"pg_wal"
 #define XLOG_CONTROL_FILE	"global/pg_control"
 
 /*
diff --git a/src/include/postmaster/pgarch.h b/src/include/postmaster/pgarch.h
index f2cbfb3..6df73c9 100644
--- a/src/include/postmaster/pgarch.h
+++ b/src/include/postmaster/pgarch.h
@@ -16,7 +16,7 @@
 /* ----------
  * Archiver control info.
  *
- * We expect that archivable files within pg_xlog will have names between
+ * We expect that archivable files within pg_wal will have names between
  * MIN_XFN_CHARS and MAX_XFN_CHARS in length, consisting only of characters
  * appearing in VALID_XFN_CHARS.  The status files in archive_status have
  * corresponding names with ".ready" or ".done" appended.
-- 
2.9.3

From 0a7ae9826184ffa2d4d599a855d6b0caffc069ae Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Fri, 30 Sep 2016 14:22:32 +0900
Subject: [PATCH 1/2] Rename pg_xlog to pg_wal

Additional check handling is needed in pg_upgrade regarding the clusters
worked on, except that it is a very mechanical patch. As pg_basebackup
needs to support servers down to 9.1, special handling is needed depending
on the version of the target server as a consequence of this renaming:
- Soft links need to be generated using pg_xlog or pg_wal.
- stream mode needs to have its output in the correct place.
This has as direct consequence to need a connection to target server before
generating a soft link, which is a bit earlier than before this renaming.
---
 doc/src/sgml/backup.sgml                     |  28 ++++----
 doc/src/sgml/config.sgml                     |   6 +-
 doc/src/sgml/func.sgml                       |   2 +-
 doc/src/sgml/high-availability.sgml          |  14 ++--
 doc/src/sgml/perform.sgml                    |   2 +-
 doc/src/sgml/protocol.sgml                   |   6 +-
 doc/src/sgml/ref/pg_resetxlog.sgml           |  10 +--
 doc/src/sgml/ref/pg_rewind.sgml              |   4 +-
 doc/src/sgml/ref/pg_xlogdump.sgml            |   2 +-
 doc/src/sgml/ref/pgtestfsync.sgml            |   4 +-
 doc/src/sgml/ref/pgupgrade.sgml              |   4 +-
 doc/src/sgml/storage.sgml                    |   2 +-
 doc/src/sgml/wal.sgml                        |  10 +--
 src/backend/access/transam/timeline.c        |   4 +-
 src/backend/access/transam/xlog.c            | 100 +++++++++++++--------------
 src/backend/access/transam/xlogarchive.c     |   2 +-
 src/backend/access/transam/xlogfuncs.c       |   2 +-
 src/backend/replication/README               |   2 +-
 src/backend/replication/basebackup.c         |  20 +++---
 src/backend/replication/walreceiver.c        |   6 +-
 src/backend/replication/walsender.c          |   4 +-
 src/backend/storage/file/fd.c                |  16 ++---
 src/bin/initdb/initdb.c                      |   8 +--
 src/bin/pg_basebackup/pg_basebackup.c        |  64 ++++++++++-------
 src/bin/pg_basebackup/t/010_pg_basebackup.pl |   8 +--
 src/bin/pg_resetxlog/pg_resetxlog.c          |   2 +-
 src/bin/pg_rewind/copy_fetch.c               |   4 +-
 src/bin/pg_rewind/filemap.c                  |   8 +--
 src/bin/pg_rewind/parsexlog.c                |   2 +-
 src/bin/pg_rewind/t/004_pg_xlog_symlink.pl   |  10 +--
 src/bin/pg_upgrade/exec.c                    |  79 +++++++++++++--------
 src/bin/pg_xlogdump/pg_xlogdump.c            |   2 +-
 src/common/file_utils.c                      |  20 +++---
 src/include/access/xlog_internal.h           |   2 +-
 src/include/postmaster/pgarch.h              |   2 +-
 35 files changed, 246 insertions(+), 215 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 95d0ff3..6eaed1e 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -472,7 +472,7 @@ tar -cf backup.tar /usr/local/pgsql/data
 
   <para>
    At all times, <productname>PostgreSQL</> maintains a
-   <firstterm>write ahead log</> (WAL) in the <filename>pg_xlog/</>
+   <firstterm>write ahead log</> (WAL) in the <filename>pg_wal/</>
    subdirectory of the cluster's data directory. The log records
    every change made to the database's data files.  This log exists
    primarily for crash-safety purposes: if the system crashes, the
@@ -616,7 +616,7 @@ archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"'  # Windows
     <literal>%p</> and <literal>%f</> parameters have been replaced,
     the actual command executed might look like this:
 <programlisting>
-test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065
+test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_wal/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065
 </programlisting>
     A similar command will be generated for each new file to be archived.
    </para>
@@ -668,9 +668,9 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     fills, nothing further can be archived until the tape is swapped.
     You should ensure that any error condition or request to a human operator
     is reported appropriately so that the situation can be
-    resolved reasonably quickly. The <filename>pg_xlog/</> directory will
+    resolved reasonably quickly. The <filename>pg_wal/</> directory will
     continue to fill with WAL segment files until the situation is resolved.
-    (If the file system containing <filename>pg_xlog/</> fills up,
+    (If the file system containing <filename>pg_wal/</> fills up,
     <productname>PostgreSQL</> will do a PANIC shutdown.  No committed
     transactions will be lost, but the database will remain offline until
     you free some space.)
@@ -682,7 +682,7 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     operation continues even if the archiving process falls a little behind.
     If archiving falls significantly behind, this will increase the amount of
     data that would be lost in the event of a disaster. It will also mean that
-    the <filename>pg_xlog/</> directory will contain large numbers of
+    the <filename>pg_wal/</> directory will contain large numbers of
     not-yet-archived segment files, which could eventually exceed available
     disk space. You are advised to monitor the archiving process to ensure that
     it is working as you intend.
@@ -743,7 +743,7 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     configuration file reload.  If you wish to temporarily stop archiving,
     one way to do it is to set <varname>archive_command</> to the empty
     string (<literal>''</>).
-    This will cause WAL files to accumulate in <filename>pg_xlog/</> until a
+    This will cause WAL files to accumulate in <filename>pg_wal/</> until a
     working <varname>archive_command</> is re-established.
    </para>
   </sect2>
@@ -1062,10 +1062,10 @@ SELECT pg_stop_backup();
 
    <para>
     You should, however, omit from the backup the files within the
-    cluster's <filename>pg_xlog/</> subdirectory.  This
+    cluster's <filename>pg_wal/</> subdirectory.  This
     slight adjustment is worthwhile because it reduces the risk
     of mistakes when restoring.  This is easy to arrange if
-    <filename>pg_xlog/</> is a symbolic link pointing to someplace outside
+    <filename>pg_wal/</> is a symbolic link pointing to someplace outside
     the cluster directory, which is a common setup anyway for performance
     reasons.  You might also want to exclude <filename>postmaster.pid</>
     and <filename>postmaster.opts</>, which record information
@@ -1149,7 +1149,7 @@ SELECT pg_stop_backup();
      location in case you need them later. Note that this precaution will
      require that you have enough free space on your system to hold two
      copies of your existing database. If you do not have enough space,
-     you should at least save the contents of the cluster's <filename>pg_xlog</>
+     you should at least save the contents of the cluster's <filename>pg_wal</>
      subdirectory, as it might contain logs which
      were not archived before the system went down.
     </para>
@@ -1172,9 +1172,9 @@ SELECT pg_stop_backup();
    </listitem>
    <listitem>
     <para>
-     Remove any files present in <filename>pg_xlog/</>; these came from the
+     Remove any files present in <filename>pg_wal/</>; these came from the
      file system backup and are therefore probably obsolete rather than current.
-     If you didn't archive <filename>pg_xlog/</> at all, then recreate
+     If you didn't archive <filename>pg_wal/</> at all, then recreate
      it with proper permissions,
      being careful to ensure that you re-establish it as a symbolic link
      if you had it set up that way before.
@@ -1183,7 +1183,7 @@ SELECT pg_stop_backup();
    <listitem>
     <para>
      If you have unarchived WAL segment files that you saved in step 2,
-     copy them into <filename>pg_xlog/</>.  (It is best to copy them,
+     copy them into <filename>pg_wal/</>.  (It is best to copy them,
      not move them, so you still have the unmodified files if a
      problem occurs and you have to start over.)
     </para>
@@ -1265,9 +1265,9 @@ restore_command = 'cp /mnt/server/archivedir/%f %p'
 
    <para>
     WAL segments that cannot be found in the archive will be sought in
-    <filename>pg_xlog/</>; this allows use of recent un-archived segments.
+    <filename>pg_wal/</>; this allows use of recent un-archived segments.
     However, segments that are available from the archive will be used in
-    preference to files in <filename>pg_xlog/</>.
+    preference to files in <filename>pg_wal/</>.
    </para>
 
    <para>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index e826c19..1bb501c 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2932,7 +2932,7 @@ include_dir 'conf.d'
        <listitem>
        <para>
         Specifies the minimum number of past log file segments kept in the
-        <filename>pg_xlog</>
+        <filename>pg_wal</>
         directory, in case a standby server needs to fetch them for streaming
         replication. Each segment is normally 16 megabytes. If a standby
         server connected to the sending server falls behind by more than
@@ -2946,7 +2946,7 @@ include_dir 'conf.d'
 
        <para>
         This sets only the minimum number of segments retained in
-        <filename>pg_xlog</>; the system might need to retain more segments
+        <filename>pg_wal</>; the system might need to retain more segments
         for WAL archival or to recover from a checkpoint. If
         <varname>wal_keep_segments</> is zero (the default), the system
         doesn't keep any extra segments for standby purposes, so the number
@@ -3322,7 +3322,7 @@ include_dir 'conf.d'
        <para>
         Specify how long the standby server should wait when WAL data is not
         available from any sources (streaming replication,
-        local <filename>pg_xlog</> or WAL archive) before retrying to
+        local <filename>pg_wal</> or WAL archive) before retrying to
         retrieve WAL data.  This parameter can only be set in the
         <filename>postgresql.conf</> file or on the server command line.
         The default value is 5 seconds. Units are milliseconds if not specified.
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index a588350..2e64cc4 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15327,7 +15327,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
- pg_xlog         | 16
+ pg_wal          | 16
  pg_hba.conf     | 17
  pg_stat_tmp     | 18
  pg_subtrans     | 19
diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index 06f49db..5bedaf2 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -594,24 +594,24 @@ protocol to make nodes agree on a serializable transactional order.
     (see <xref linkend="restore-command">) or directly from the master
     over a TCP connection (streaming replication). The standby server will
     also attempt to restore any WAL found in the standby cluster's
-    <filename>pg_xlog</> directory. That typically happens after a server
+    <filename>pg_wal</> directory. That typically happens after a server
     restart, when the standby replays again WAL that was streamed from the
     master before the restart, but you can also manually copy files to
-    <filename>pg_xlog</> at any time to have them replayed.
+    <filename>pg_wal</> at any time to have them replayed.
    </para>
 
    <para>
     At startup, the standby begins by restoring all WAL available in the
     archive location, calling <varname>restore_command</>. Once it
     reaches the end of WAL available there and <varname>restore_command</>
-    fails, it tries to restore any WAL available in the <filename>pg_xlog</> directory.
+    fails, it tries to restore any WAL available in the <filename>pg_wal</> directory.
     If that fails, and streaming replication has been configured, the
     standby tries to connect to the primary server and start streaming WAL
-    from the last valid record found in archive or <filename>pg_xlog</>. If that fails
+    from the last valid record found in archive or <filename>pg_wal</>. If that fails
     or streaming replication is not configured, or if the connection is
     later disconnected, the standby goes back to step 1 and tries to
     restore the file from the archive again. This loop of retries from the
-    archive, <filename>pg_xlog</>, and via streaming replication goes on until the server
+    archive, <filename>pg_wal</>, and via streaming replication goes on until the server
     is stopped or failover is triggered by a trigger file.
    </para>
 
@@ -619,7 +619,7 @@ protocol to make nodes agree on a serializable transactional order.
     Standby mode is exited and the server switches to normal operation
     when <command>pg_ctl promote</> is run or a trigger file is found
     (<varname>trigger_file</>). Before failover,
-    any WAL immediately available in the archive or in <filename>pg_xlog</> will be
+    any WAL immediately available in the archive or in <filename>pg_wal</> will be
     restored, but no attempt is made to connect to the master.
    </para>
   </sect2>
@@ -895,7 +895,7 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass'
     However, these methods often result in retaining more WAL segments than
     required, whereas replication slots retain only the number of segments
     known to be needed.  An advantage of these methods is that they bound
-    the space requirement for <literal>pg_xlog</>; there is currently no way
+    the space requirement for <literal>pg_wal</>; there is currently no way
     to do this using replication slots.
    </para>
    <para>
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml
index 7bcbfa7..8d30fd1 100644
--- a/doc/src/sgml/perform.sgml
+++ b/doc/src/sgml/perform.sgml
@@ -1612,7 +1612,7 @@ SELECT * FROM x, y, a, b, c WHERE something AND somethingelse;
        Increase <xref linkend="guc-max-wal-size"> and <xref
        linkend="guc-checkpoint-timeout"> ; this reduces the frequency
        of checkpoints, but increases the storage requirements of
-       <filename>/pg_xlog</>.
+       <filename>/pg_wal</>.
       </para>
      </listitem>
 
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 3384e73..50cf527 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -1947,7 +1947,7 @@ The commands accepted in walsender mode are:
          <para>
           Include the necessary WAL segments in the backup. This will include
           all the files between start and stop backup in the
-          <filename>pg_xlog</filename> directory of the base directory tar
+          <filename>pg_wal</filename> directory of the base directory tar
           file.
          </para>
         </listitem>
@@ -2076,8 +2076,8 @@ The commands accepted in walsender mode are:
        </listitem>
        <listitem>
         <para>
-         <filename>pg_xlog</>, including subdirectories. If the backup is run
-         with WAL files included, a synthesized version of <filename>pg_xlog</filename> will be
+         <filename>pg_wal</>, including subdirectories. If the backup is run
+         with WAL files included, a synthesized version of <filename>pg_wal</filename> will be
          included, but it will only contain the files necessary for the
          backup to work, not the rest of the contents.
         </para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index fd9d0be..c949c5e 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -173,22 +173,22 @@ PostgreSQL documentation
      <para>
       The WAL starting address should be
       larger than any WAL segment file name currently existing in
-      the directory <filename>pg_xlog</> under the data directory.
+      the directory <filename>pg_wal</> under the data directory.
       These names are also in hexadecimal and have three parts.  The first
       part is the <quote>timeline ID</> and should usually be kept the same.
       For example, if <filename>00000001000000320000004A</> is the
-      largest entry in <filename>pg_xlog</>, use <literal>-l 00000001000000320000004B</> or higher.
+      largest entry in <filename>pg_wal</>, use <literal>-l 00000001000000320000004B</> or higher.
      </para>
 
      <note>
       <para>
        <command>pg_resetxlog</command> itself looks at the files in
-       <filename>pg_xlog</> and chooses a default <option>-l</> setting
+       <filename>pg_wal</> and chooses a default <option>-l</> setting
        beyond the last existing file name.  Therefore, manual adjustment of
        <option>-l</> should only be needed if you are aware of WAL segment
-       files that are not currently present in <filename>pg_xlog</>, such as
+       files that are not currently present in <filename>pg_wal</>, such as
        entries in an offline archive; or if the contents of
-       <filename>pg_xlog</> have been lost entirely.
+       <filename>pg_wal</> have been lost entirely.
       </para>
      </note>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 42ebfbf..371c4a4 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -61,14 +61,14 @@ PostgreSQL documentation
   <para>
    <application>pg_rewind</> examines the timeline histories of the source
    and target clusters to determine the point where they diverged, and
-   expects to find WAL in the target cluster's <filename>pg_xlog</> directory
+   expects to find WAL in the target cluster's <filename>pg_wal</> directory
    reaching all the way back to the point of divergence. The point of divergence
    can be found either on the target timeline, the source timeline, or their common
    ancestor. In the typical failover scenario where the target cluster was
    shut down soon after the divergence, this is not a problem, but if the
    target cluster ran for a long time after the divergence, the old WAL
    files might no longer be present. In that case, they can be manually
-   copied from the WAL archive to the <filename>pg_xlog</> directory, or
+   copied from the WAL archive to the <filename>pg_wal</> directory, or
    fetched on startup by configuring <filename>recovery.conf</>.  The use of
    <application>pg_rewind</> is not limited to failover, e.g.  a standby
    server can be promoted, run some write transactions, and then rewinded
diff --git a/doc/src/sgml/ref/pg_xlogdump.sgml b/doc/src/sgml/ref/pg_xlogdump.sgml
index 177caab..cfb6d87 100644
--- a/doc/src/sgml/ref/pg_xlogdump.sgml
+++ b/doc/src/sgml/ref/pg_xlogdump.sgml
@@ -118,7 +118,7 @@ PostgreSQL documentation
       <listitem>
        <para>
         Directory in which to find log segment files.  The default is to search
-        for them in the <literal>pg_xlog</literal> subdirectory of the current
+        for them in the <literal>pg_wal</literal> subdirectory of the current
         directory.
        </para>
       </listitem>
diff --git a/doc/src/sgml/ref/pgtestfsync.sgml b/doc/src/sgml/ref/pgtestfsync.sgml
index 6e134c7..5856356 100644
--- a/doc/src/sgml/ref/pgtestfsync.sgml
+++ b/doc/src/sgml/ref/pgtestfsync.sgml
@@ -57,8 +57,8 @@
        <para>
         Specifies the file name to write test data in.
         This file should be in the same file system that the
-        <filename>pg_xlog</> directory is or will be placed in.
-        (<filename>pg_xlog</> contains the <acronym>WAL</> files.)
+        <filename>pg_wal</> directory is or will be placed in.
+        (<filename>pg_wal</> contains the <acronym>WAL</> files.)
         The default is <filename>pg_test_fsync.out</> in the current
         directory.
        </para>
diff --git a/doc/src/sgml/ref/pgupgrade.sgml b/doc/src/sgml/ref/pgupgrade.sgml
index 9685193..4b9aab2 100644
--- a/doc/src/sgml/ref/pgupgrade.sgml
+++ b/doc/src/sgml/ref/pgupgrade.sgml
@@ -345,7 +345,7 @@ NET STOP postgresql-9.0
      your old cluster
      once you start the new cluster after the upgrade.  Link mode also
      requires that the old and new cluster data directories be in the
-     same file system.  (Tablespaces and <filename>pg_xlog</> can be on
+     same file system.  (Tablespaces and <filename>pg_wal</> can be on
      different file systems.)  See <literal>pg_upgrade --help</> for a full
      list of options.
     </para>
@@ -508,7 +508,7 @@ rsync --archive --delete --hard-links --size-only old_pgdata new_pgdata remote_d
       <para>
        If you have tablespaces, you will need to run a similar
        <application>rsync</> command for each tablespace directory.  If you
-       have relocated <filename>pg_xlog</> outside the data directories,
+       have relocated <filename>pg_wal</> outside the data directories,
        <application>rsync</> must be run on those directories too.
       </para>
      </step>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 1b812bd..fddb69b 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -141,7 +141,7 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_xlog</></entry>
+ <entry><filename>pg_wal</></entry>
  <entry>Subdirectory containing WAL (Write Ahead Log) files</entry>
 </row>
 
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index fe3b588..346aa76 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -557,7 +557,7 @@
   </para>
 
   <para>
-   The number of WAL segment files in <filename>pg_xlog</> directory depends on
+   The number of WAL segment files in <filename>pg_wal</> directory depends on
    <varname>min_wal_size</>, <varname>max_wal_size</> and
    the amount of WAL generated in previous checkpoint cycles. When old log
    segment files are no longer needed, they are removed or recycled (that is,
@@ -582,7 +582,7 @@
    kept at all times. Also, if WAL archiving is used, old segments can not be
    removed or recycled until they are archived. If WAL archiving cannot keep up
    with the pace that WAL is generated, or if <varname>archive_command</varname>
-   fails repeatedly, old WAL files will accumulate in <filename>pg_xlog</>
+   fails repeatedly, old WAL files will accumulate in <filename>pg_wal</>
    until the situation is resolved. A slow or failed standby server that
    uses a replication slot will have the same effect (see
    <xref linkend="streaming-replication-slots">).
@@ -594,7 +594,7 @@
    which are similar to checkpoints in normal operation: the server forces
    all its state to disk, updates the <filename>pg_control</> file to
    indicate that the already-processed WAL data need not be scanned again,
-   and then recycles any old log segment files in the <filename>pg_xlog</>
+   and then recycles any old log segment files in the <filename>pg_wal</>
    directory.
    Restartpoints can't be performed more frequently than checkpoints in the
    master because restartpoints can only be performed at checkpoint records.
@@ -750,7 +750,7 @@
 
   <para>
    <acronym>WAL</acronym> logs are stored in the directory
-   <filename>pg_xlog</filename> under the data directory, as a set of
+   <filename>pg_wal</filename> under the data directory, as a set of
    segment files, normally each 16 MB in size (but the size can be changed
    by altering the <option>--with-wal-segsize</> configure option when
    building the server).  Each segment is divided into pages, normally
@@ -767,7 +767,7 @@
   <para>
    It is advantageous if the log is located on a different disk from the
    main database files.  This can be achieved by moving the
-   <filename>pg_xlog</filename> directory to another location (while the server
+   <filename>pg_wal</filename> directory to another location (while the server
    is shut down, of course) and creating a symbolic link from the
    original location in the main data directory to the new location.
   </para>
diff --git a/src/backend/access/transam/timeline.c b/src/backend/access/transam/timeline.c
index bd91573..43436a9 100644
--- a/src/backend/access/transam/timeline.c
+++ b/src/backend/access/transam/timeline.c
@@ -43,7 +43,7 @@
 
 /*
  * Copies all timeline history files with id's between 'begin' and 'end'
- * from archive to pg_xlog.
+ * from archive to pg_wal.
  */
 void
 restoreTimeLineHistoryFiles(TimeLineID begin, TimeLineID end)
@@ -191,7 +191,7 @@ readTimeLineHistory(TimeLineID targetTLI)
 	result = lcons(entry, result);
 
 	/*
-	 * If the history file was fetched from archive, save it in pg_xlog for
+	 * If the history file was fetched from archive, save it in pg_wal for
 	 * future reference.
 	 */
 	if (fromArchive)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index c1b9a97..48c18e8 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -235,9 +235,9 @@ static int	LocalXLogInsertAllowed = -1;
  * valid in the startup process.
  *
  * When ArchiveRecoveryRequested is true, but InArchiveRecovery is false, we're
- * currently performing crash recovery using only XLOG files in pg_xlog, but
+ * currently performing crash recovery using only XLOG files in pg_wal, but
  * will switch to using offline XLOG archives as soon as we reach the end of
- * WAL in pg_xlog.
+ * WAL in pg_wal.
 */
 bool		ArchiveRecoveryRequested = false;
 bool		InArchiveRecovery = false;
@@ -700,12 +700,12 @@ typedef enum
 {
 	XLOG_FROM_ANY = 0,			/* request to read WAL from any source */
 	XLOG_FROM_ARCHIVE,			/* restored using restore_command */
-	XLOG_FROM_PG_XLOG,			/* existing file in pg_xlog */
+	XLOG_FROM_PG_WAL,			/* existing file in pg_wal */
 	XLOG_FROM_STREAM			/* streamed from master */
 } XLogSource;
 
 /* human-readable names for XLogSources, for debugging output */
-static const char *xlogSourceNames[] = {"any", "archive", "pg_xlog", "stream"};
+static const char *xlogSourceNames[] = {"any", "archive", "pg_wal", "stream"};
 
 /*
  * openLogFile is -1 or a kernel FD for an open log file segment.
@@ -3345,7 +3345,7 @@ XLogFileOpen(XLogSegNo segno)
  * Open a logfile segment for reading (during recovery).
  *
  * If source == XLOG_FROM_ARCHIVE, the segment is retrieved from archive.
- * Otherwise, it's assumed to be already available in pg_xlog.
+ * Otherwise, it's assumed to be already available in pg_wal.
  */
 static int
 XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
@@ -3374,7 +3374,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 				return -1;
 			break;
 
-		case XLOG_FROM_PG_XLOG:
+		case XLOG_FROM_PG_WAL:
 		case XLOG_FROM_STREAM:
 			XLogFilePath(path, tli, segno);
 			restoredFromArchive = false;
@@ -3393,7 +3393,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 		KeepFileRestoredFromArchive(path, xlogfname);
 
 		/*
-		 * Set path to point at the new file in pg_xlog.
+		 * Set path to point at the new file in pg_wal.
 		 */
 		snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlogfname);
 	}
@@ -3481,10 +3481,10 @@ XLogFileReadAnyTLI(XLogSegNo segno, int emode, int source)
 			}
 		}
 
-		if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_XLOG)
+		if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_WAL)
 		{
 			fd = XLogFileRead(segno, emode, tli,
-							  XLOG_FROM_PG_XLOG, true);
+							  XLOG_FROM_PG_WAL, true);
 			if (fd != -1)
 			{
 				if (!expectedTLEs)
@@ -3693,10 +3693,10 @@ RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
  *
  * This is called during recovery, whenever we switch to follow a new
  * timeline, and at the end of recovery when we create a new timeline. We
- * wouldn't otherwise care about extra WAL files lying in pg_xlog, but they
+ * wouldn't otherwise care about extra WAL files lying in pg_wal, but they
  * might be leftover pre-allocated or recycled WAL segments on the old timeline
  * that we haven't used yet, and contain garbage. If we just leave them in
- * pg_xlog, they will eventually be archived, and we can't let that happen.
+ * pg_wal, they will eventually be archived, and we can't let that happen.
  * Files that belong to our timeline history are valid, because we have
  * successfully replayed them, but from others we can't be sure.
  *
@@ -3853,15 +3853,15 @@ RemoveXlogFile(const char *segname, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
 }
 
 /*
- * Verify whether pg_xlog and pg_xlog/archive_status exist.
+ * Verify whether pg_wal and pg_wal/archive_status exist.
  * If the latter does not exist, recreate it.
  *
  * It is not the goal of this function to verify the contents of these
  * directories, but to help in cases where someone has performed a cluster
- * copy for PITR purposes but omitted pg_xlog from the copy.
+ * copy for PITR purposes but omitted pg_wal from the copy.
  *
- * We could also recreate pg_xlog if it doesn't exist, but a deliberate
- * policy decision was made not to.  It is fairly common for pg_xlog to be
+ * We could also recreate pg_wal if it doesn't exist, but a deliberate
+ * policy decision was made not to.  It is fairly common for pg_wal to be
  * a symlink, and if that was the DBA's intent then automatically making a
  * plain directory would result in degraded performance with no notice.
  */
@@ -3871,7 +3871,7 @@ ValidateXLOGDirectoryStructure(void)
 	char		path[MAXPGPATH];
 	struct stat stat_buf;
 
-	/* Check for pg_xlog; if it doesn't exist, error out */
+	/* Check for pg_wal; if it doesn't exist, error out */
 	if (stat(XLOGDIR, &stat_buf) != 0 ||
 		!S_ISDIR(stat_buf.st_mode))
 		ereport(FATAL,
@@ -4027,11 +4027,11 @@ ReadRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int emode,
 			 * If archive recovery was requested, but we were still doing
 			 * crash recovery, switch to archive recovery and retry using the
 			 * offline archive. We have now replayed all the valid WAL in
-			 * pg_xlog, so we are presumably now consistent.
+			 * pg_wal, so we are presumably now consistent.
 			 *
 			 * We require that there's at least some valid WAL present in
-			 * pg_xlog, however (!fetch_ckpt). We could recover using the WAL
-			 * from the archive, even if pg_xlog is completely empty, but we'd
+			 * pg_wal, however (!fetch_ckpt). We could recover using the WAL
+			 * from the archive, even if pg_wal is completely empty, but we'd
 			 * have no idea how far we'd have to replay to reach consistency.
 			 * So err on the safe side and give up.
 			 */
@@ -4039,7 +4039,7 @@ ReadRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int emode,
 				!fetching_ckpt)
 			{
 				ereport(DEBUG1,
-						(errmsg_internal("reached end of WAL in pg_xlog, entering archive recovery")));
+						(errmsg_internal("reached end of WAL in pg_wal, entering archive recovery")));
 				InArchiveRecovery = true;
 				if (StandbyModeRequested)
 					StandbyMode = true;
@@ -4156,7 +4156,7 @@ rescanLatestTimeLine(void)
 
 	/*
 	 * As in StartupXLOG(), try to ensure we have all the history files
-	 * between the old target and new target in pg_xlog.
+	 * between the old target and new target in pg_wal.
 	 */
 	restoreTimeLineHistoryFiles(oldtarget + 1, newtarget);
 
@@ -5189,7 +5189,7 @@ readRecoveryCommandFile(void)
 			ereport(WARNING,
 					(errmsg("recovery command file \"%s\" specified neither primary_conninfo nor restore_command",
 							RECOVERY_COMMAND_FILE),
-					 errhint("The database server will regularly poll the pg_xlog subdirectory to check for files placed there.")));
+					 errhint("The database server will regularly poll the pg_wal subdirectory to check for files placed there.")));
 	}
 	else
 	{
@@ -6055,7 +6055,7 @@ StartupXLOG(void)
 #endif
 
 	/*
-	 * Verify that pg_xlog and pg_xlog/archive_status exist.  In cases where
+	 * Verify that pg_wal and pg_wal/archive_status exist.  In cases where
 	 * someone has performed a copy for PITR, these directories may have been
 	 * excluded and need to be re-created.
 	 */
@@ -6268,7 +6268,7 @@ StartupXLOG(void)
 		 * and put it into archive recovery by creating a recovery.conf file.
 		 *
 		 * Our strategy in that case is to perform crash recovery first,
-		 * replaying all the WAL present in pg_xlog, and only enter archive
+		 * replaying all the WAL present in pg_wal, and only enter archive
 		 * recovery after that.
 		 *
 		 * But usually we already know how far we need to replay the WAL (up
@@ -6472,7 +6472,7 @@ StartupXLOG(void)
 
 	/*
 	 * Copy any missing timeline history files between 'now' and the recovery
-	 * target timeline from archive to pg_xlog. While we don't need those
+	 * target timeline from archive to pg_wal. While we don't need those
 	 * files ourselves - the history file of the recovery target timeline
 	 * covers all the previous timelines in the history too - a cascading
 	 * standby server might be interested in them. Or, if you archive the WAL
@@ -7093,7 +7093,7 @@ StartupXLOG(void)
 	/*
 	 * We are now done reading the xlog from stream. Turn off streaming
 	 * recovery to force fetching the files (which would be required at end of
-	 * recovery, e.g., timeline history file) from archive or pg_xlog.
+	 * recovery, e.g., timeline history file) from archive or pg_wal.
 	 */
 	StandbyMode = false;
 
@@ -7381,7 +7381,7 @@ StartupXLOG(void)
 		 * As a compromise, we rename the last segment with the .partial
 		 * suffix, and archive it. Archive recovery will never try to read
 		 * .partial segments, so they will normally go unused. But in the odd
-		 * PITR case, the administrator can copy them manually to the pg_xlog
+		 * PITR case, the administrator can copy them manually to the pg_wal
 		 * directory (removing the suffix). They can be useful in debugging,
 		 * too.
 		 *
@@ -9957,7 +9957,7 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
 		 * first WAL segment containing the startup checkpoint has pages in
 		 * the beginning with the old timeline ID.  That can cause trouble at
 		 * recovery: we won't have a history file covering the old timeline if
-		 * pg_xlog directory was not included in the base backup and the WAL
+		 * pg_wal directory was not included in the base backup and the WAL
 		 * archive was cleared too before starting the backup.
 		 *
 		 * This also ensures that we have emitted a WAL page header that has
@@ -10604,7 +10604,7 @@ do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
 	 * archived before returning. If archiving isn't enabled, the required WAL
 	 * needs to be transported via streaming replication (hopefully with
 	 * wal_keep_segments set high enough), or some more exotic mechanism like
-	 * polling and copying files from pg_xlog with script. We have no
+	 * polling and copying files from pg_wal with script. We have no
 	 * knowledge of those mechanisms, so it's up to the user to ensure that he
 	 * gets all the required WAL.
 	 *
@@ -11194,9 +11194,9 @@ next_record_is_invalid:
  * Open the WAL segment containing WAL position 'RecPtr'.
  *
  * The segment can be fetched via restore_command, or via walreceiver having
- * streamed the record, or it can already be present in pg_xlog. Checking
- * pg_xlog is mainly for crash recovery, but it will be polled in standby mode
- * too, in case someone copies a new segment directly to pg_xlog. That is not
+ * streamed the record, or it can already be present in pg_wal. Checking
+ * pg_wal is mainly for crash recovery, but it will be polled in standby mode
+ * too, in case someone copies a new segment directly to pg_wal. That is not
  * documented or recommended, though.
  *
  * If 'fetching_ckpt' is true, we're fetching a checkpoint record, and should
@@ -11226,8 +11226,8 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 	/*-------
 	 * Standby mode is implemented by a state machine:
 	 *
-	 * 1. Read from either archive or pg_xlog (XLOG_FROM_ARCHIVE), or just
-	 *	  pg_xlog (XLOG_FROM_XLOG)
+	 * 1. Read from either archive or pg_wal (XLOG_FROM_ARCHIVE), or just
+	 *	  pg_wal (XLOG_FROM_PG_WAL)
 	 * 2. Check trigger file
 	 * 3. Read from primary server via walreceiver (XLOG_FROM_STREAM)
 	 * 4. Rescan timelines
@@ -11243,7 +11243,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 	 *-------
 	 */
 	if (!InArchiveRecovery)
-		currentSource = XLOG_FROM_PG_XLOG;
+		currentSource = XLOG_FROM_PG_WAL;
 	else if (currentSource == 0)
 		currentSource = XLOG_FROM_ARCHIVE;
 
@@ -11262,13 +11262,13 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 			switch (currentSource)
 			{
 				case XLOG_FROM_ARCHIVE:
-				case XLOG_FROM_PG_XLOG:
+				case XLOG_FROM_PG_WAL:
 
 					/*
 					 * Check to see if the trigger file exists. Note that we
 					 * do this only after failure, so when you create the
 					 * trigger file, we still finish replaying as much as we
-					 * can from archive and pg_xlog before failover.
+					 * can from archive and pg_wal before failover.
 					 */
 					if (StandbyMode && CheckForStandbyTrigger())
 					{
@@ -11278,7 +11278,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 
 					/*
 					 * Not in standby mode, and we've now tried the archive
-					 * and pg_xlog.
+					 * and pg_wal.
 					 */
 					if (!StandbyMode)
 						return false;
@@ -11338,7 +11338,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					 * little chance that the problem will just go away, but
 					 * PANIC is not good for availability either, especially
 					 * in hot standby mode. So, we treat that the same as
-					 * disconnection, and retry from archive/pg_xlog again.
+					 * disconnection, and retry from archive/pg_wal again.
 					 * The WAL in the archive should be identical to what was
 					 * streamed, so it's unlikely that it helps, but one can
 					 * hope...
@@ -11399,11 +11399,11 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					elog(ERROR, "unexpected WAL source %d", currentSource);
 			}
 		}
-		else if (currentSource == XLOG_FROM_PG_XLOG)
+		else if (currentSource == XLOG_FROM_PG_WAL)
 		{
 			/*
-			 * We just successfully read a file in pg_xlog. We prefer files in
-			 * the archive over ones in pg_xlog, so try the next file again
+			 * We just successfully read a file in pg_wal. We prefer files in
+			 * the archive over ones in pg_wal, so try the next file again
 			 * from the archive first.
 			 */
 			if (InArchiveRecovery)
@@ -11424,7 +11424,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 		switch (currentSource)
 		{
 			case XLOG_FROM_ARCHIVE:
-			case XLOG_FROM_PG_XLOG:
+			case XLOG_FROM_PG_WAL:
 				/* Close any old file we might have open. */
 				if (readFile >= 0)
 				{
@@ -11437,7 +11437,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 
 				/*
 				 * Try to restore the file from archive, or read an existing
-				 * file from pg_xlog.
+				 * file from pg_wal.
 				 */
 				readFile = XLogFileReadAnyTLI(readSegNo, DEBUG2,
 						 currentSource == XLOG_FROM_ARCHIVE ? XLOG_FROM_ANY :
@@ -11446,7 +11446,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					return true;	/* success! */
 
 				/*
-				 * Nope, not found in archive or pg_xlog.
+				 * Nope, not found in archive or pg_wal.
 				 */
 				lastSourceFailed = true;
 				break;
@@ -11502,7 +11502,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 						 * not open already.  Also read the timeline history
 						 * file if we haven't initialized timeline history
 						 * yet; it should be streamed over and present in
-						 * pg_xlog by now.  Use XLOG_FROM_STREAM so that
+						 * pg_wal by now.  Use XLOG_FROM_STREAM so that
 						 * source info is set correctly and XLogReceiptTime
 						 * isn't changed.
 						 */
@@ -11534,10 +11534,10 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 						/*
 						 * Note that we don't "return false" immediately here.
 						 * After being triggered, we still want to replay all
-						 * the WAL that was already streamed. It's in pg_xlog
+						 * the WAL that was already streamed. It's in pg_wal
 						 * now, so we just treat this as a failure, and the
 						 * state machine will move on to replay the streamed
-						 * WAL from pg_xlog, and then recheck the trigger and
+						 * WAL from pg_wal, and then recheck the trigger and
 						 * exit replay.
 						 */
 						lastSourceFailed = true;
@@ -11577,7 +11577,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
  * or legitimate end-of-WAL situation.   Generally, we use it as-is, but if
  * we're retrying the exact same record that we've tried previously, only
  * complain the first time to keep the noise down.  However, we only do when
- * reading from pg_xlog, because we don't expect any invalid records in archive
+ * reading from pg_wal, because we don't expect any invalid records in archive
  * or in records streamed from master. Files in the archive should be complete,
  * and we should never hit the end of WAL because we stop and wait for more WAL
  * to arrive before replaying it.
@@ -11592,7 +11592,7 @@ emode_for_corrupt_record(int emode, XLogRecPtr RecPtr)
 {
 	static XLogRecPtr lastComplaint = 0;
 
-	if (readSource == XLOG_FROM_PG_XLOG && emode == LOG)
+	if (readSource == XLOG_FROM_PG_WAL && emode == LOG)
 	{
 		if (RecPtr == lastComplaint)
 			emode = DEBUG1;
diff --git a/src/backend/access/transam/xlogarchive.c b/src/backend/access/transam/xlogarchive.c
index d153a44..b919164 100644
--- a/src/backend/access/transam/xlogarchive.c
+++ b/src/backend/access/transam/xlogarchive.c
@@ -421,7 +421,7 @@ ExecuteRecoveryCommand(char *command, char *commandName, bool failOnSignal)
 /*
  * A file was restored from the archive under a temporary filename (path),
  * and now we want to keep it. Rename it under the permanent filename in
- * in pg_xlog (xlogfname), replacing any existing file with the same name.
+ * in pg_wal (xlogfname), replacing any existing file with the same name.
  */
 void
 KeepFileRestoredFromArchive(char *path, char *xlogfname)
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 33383b4..01cbd90 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -128,7 +128,7 @@ pg_start_backup(PG_FUNCTION_ARGS)
  * pg_stop_backup: finish taking an on-line backup dump
  *
  * We write an end-of-backup WAL record, and remove the backup label file
- * created by pg_start_backup, creating a backup history file in pg_xlog
+ * created by pg_start_backup, creating a backup history file in pg_wal
  * instead (whence it will immediately be archived). The backup history file
  * contains the same info found in the label file, plus the backup-end time
  * and WAL location. Before 9.0, the backup-end time was read from the backup
diff --git a/src/backend/replication/README b/src/backend/replication/README
index ad4864d..0cbb990 100644
--- a/src/backend/replication/README
+++ b/src/backend/replication/README
@@ -54,7 +54,7 @@ and WalRcvData->slotname, and initializes the starting point in
 WalRcvData->receiveStart.
 
 As walreceiver receives WAL from the master server, and writes and flushes
-it to disk (in pg_xlog), it updates WalRcvData->receivedUpto and signals
+it to disk (in pg_wal), it updates WalRcvData->receivedUpto and signals
 the startup process to know how far WAL replay can advance.
 
 Walreceiver sends information about replication progress to the master server
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 1eabaef..6dd47ce 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -346,7 +346,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		TimeLineID	tli;
 
 		/*
-		 * I'd rather not worry about timelines here, so scan pg_xlog and
+		 * I'd rather not worry about timelines here, so scan pg_wal and
 		 * include all WAL files in the range between 'startptr' and 'endptr',
 		 * regardless of the timeline the file is stamped with. If there are
 		 * some spurious WAL files belonging to timelines that don't belong in
@@ -359,11 +359,11 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		XLByteToPrevSeg(endptr, endsegno);
 		XLogFileName(lastoff, ThisTimeLineID, endsegno);
 
-		dir = AllocateDir("pg_xlog");
+		dir = AllocateDir("pg_wal");
 		if (!dir)
 			ereport(ERROR,
-				 (errmsg("could not open directory \"%s\": %m", "pg_xlog")));
-		while ((de = ReadDir(dir, "pg_xlog")) != NULL)
+				 (errmsg("could not open directory \"%s\": %m", "pg_wal")));
+		while ((de = ReadDir(dir, "pg_wal")) != NULL)
 		{
 			/* Does it look like a WAL segment, and is it in the range? */
 			if (IsXLogFileName(de->d_name) &&
@@ -401,7 +401,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		qsort(walFiles, nWalFiles, sizeof(char *), compareWalFileNames);
 
 		/*
-		 * There must be at least one xlog file in the pg_xlog directory,
+		 * There must be at least one xlog file in the pg_wal directory,
 		 * since we are doing backup-including-xlog.
 		 */
 		if (nWalFiles < 1)
@@ -1054,23 +1054,23 @@ sendDir(char *path, int basepathlen, bool sizeonly, List *tablespaces,
 		}
 
 		/*
-		 * We can skip pg_xlog, the WAL segments need to be fetched from the
+		 * We can skip pg_wal, the WAL segments need to be fetched from the
 		 * WAL archive anyway. But include it as an empty directory anyway, so
 		 * we get permissions right.
 		 */
-		if (strcmp(pathbuf, "./pg_xlog") == 0)
+		if (strcmp(pathbuf, "./pg_wal") == 0)
 		{
-			/* If pg_xlog is a symlink, write it as a directory anyway */
+			/* If pg_wal is a symlink, write it as a directory anyway */
 			size += _tarWriteDir(pathbuf, basepathlen, &statbuf, sizeonly);
 
 			/*
 			 * Also send archive_status directory (by hackishly reusing
 			 * statbuf from above ...).
 			 */
-			size += _tarWriteHeader("./pg_xlog/archive_status", NULL, &statbuf,
+			size += _tarWriteHeader("./pg_wal/archive_status", NULL, &statbuf,
 									sizeonly);
 
-			continue;			/* don't recurse into pg_xlog */
+			continue;			/* don't recurse into pg_wal */
 		}
 
 		/* Allow symbolic links in pg_tblspc only */
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 413ee3a..d40b5e9 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -18,7 +18,7 @@
  * If the primary server ends streaming, but doesn't disconnect, walreceiver
  * goes into "waiting" mode, and waits for the startup process to give new
  * instructions. The startup process will treat that the same as
- * disconnection, and will rescan the archive/pg_xlog directory. But when the
+ * disconnection, and will rescan the archive/pg_wal directory. But when the
  * startup process wants to try streaming replication again, it will just
  * nudge the existing walreceiver process that's waiting, instead of launching
  * a new one.
@@ -364,7 +364,7 @@ WalReceiverMain(void)
 		 * we've already reached the end of the old timeline, the server will
 		 * finish the streaming immediately, and we will go back to await
 		 * orders from the startup process. If recovery_target_timeline is
-		 * 'latest', the startup process will scan pg_xlog and find the new
+		 * 'latest', the startup process will scan pg_wal and find the new
 		 * history file, bump recovery target timeline, and ask us to restart
 		 * on the new timeline.
 		 */
@@ -739,7 +739,7 @@ WalRcvFetchTimeLineHistoryFiles(TimeLineID first, TimeLineID last)
 										 tli)));
 
 			/*
-			 * Write the file to pg_xlog.
+			 * Write the file to pg_wal.
 			 */
 			writeTimeLineHistoryFile(tli, content, len);
 
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index c7743da..dcbb289 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -586,7 +586,7 @@ StartReplication(StartReplicationCmd *cmd)
 			 * segment that contains switchpoint, but on the new timeline, so
 			 * that it doesn't end up with a partial segment. If you ask for a
 			 * too old starting point, you'll get an error later when we fail
-			 * to find the requested WAL segment in pg_xlog.
+			 * to find the requested WAL segment in pg_wal.
 			 *
 			 * XXX: we could be more strict here and only allow a startpoint
 			 * that's older than the switchpoint, if it's still in the same
@@ -2055,7 +2055,7 @@ retry:
 			 *
 			 * For example, imagine that this server is currently on timeline
 			 * 5, and we're streaming timeline 4. The switch from timeline 4
-			 * to 5 happened at 0/13002088. In pg_xlog, we have these files:
+			 * to 5 happened at 0/13002088. In pg_wal, we have these files:
 			 *
 			 * ...
 			 * 000000040000000000000012
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 03143f1..b7ff5ef 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -2787,7 +2787,7 @@ looks_like_temp_rel_name(const char *name)
  * Issue fsync recursively on PGDATA and all its contents.
  *
  * We fsync regular files and directories wherever they are, but we
- * follow symlinks only for pg_xlog and immediately under pg_tblspc.
+ * follow symlinks only for pg_wal and immediately under pg_tblspc.
  * Other symlinks are presumed to point at files we're not responsible
  * for fsyncing, and might not have privileges to write at all.
  *
@@ -2811,7 +2811,7 @@ SyncDataDirectory(void)
 		return;
 
 	/*
-	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * If pg_wal is a symlink, we'll need to recurse into it separately,
 	 * because the first walkdir below will ignore it.
 	 */
 	xlog_is_symlink = false;
@@ -2820,16 +2820,16 @@ SyncDataDirectory(void)
 	{
 		struct stat st;
 
-		if (lstat("pg_xlog", &st) < 0)
+		if (lstat("pg_wal", &st) < 0)
 			ereport(LOG,
 					(errcode_for_file_access(),
 					 errmsg("could not stat file \"%s\": %m",
-							"pg_xlog")));
+							"pg_wal")));
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
 #else
-	if (pgwin32_is_junction("pg_xlog"))
+	if (pgwin32_is_junction("pg_wal"))
 		xlog_is_symlink = true;
 #endif
 
@@ -2841,7 +2841,7 @@ SyncDataDirectory(void)
 #ifdef PG_FLUSH_DATA_WORKS
 	walkdir(".", pre_sync_fname, false, DEBUG1);
 	if (xlog_is_symlink)
-		walkdir("pg_xlog", pre_sync_fname, false, DEBUG1);
+		walkdir("pg_wal", pre_sync_fname, false, DEBUG1);
 	walkdir("pg_tblspc", pre_sync_fname, true, DEBUG1);
 #endif
 
@@ -2849,14 +2849,14 @@ SyncDataDirectory(void)
 	 * Now we do the fsync()s in the same order.
 	 *
 	 * The main call ignores symlinks, so in addition to specially processing
-	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * pg_wal if it's a symlink, pg_tblspc has to be visited separately with
 	 * process_symlinks = true.  Note that if there are any plain directories
 	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
 	 * so we don't worry about optimizing it.
 	 */
 	walkdir(".", datadir_fsync_fname, false, LOG);
 	if (xlog_is_symlink)
-		walkdir("pg_xlog", datadir_fsync_fname, false, LOG);
+		walkdir("pg_wal", datadir_fsync_fname, false, LOG);
 	walkdir("pg_tblspc", datadir_fsync_fname, true, LOG);
 }
 
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index e52e67d..e256bcb 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -195,7 +195,7 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 
 static const char *const subdirs[] = {
 	"global",
-	"pg_xlog/archive_status",
+	"pg_wal/archive_status",
 	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
@@ -2091,8 +2091,6 @@ make_postgres(FILE *cmdfd)
 		PG_CMD_PUTS(*line);
 }
 
-
-
 /*
  * signal handler in case we are interrupted.
  *
@@ -2830,7 +2828,7 @@ create_xlog_or_symlink(void)
 	char	   *subdirloc;
 
 	/* form name of the place for the subdirectory or symlink */
-	subdirloc = psprintf("%s/pg_xlog", pg_data);
+	subdirloc = psprintf("%s/pg_wal", pg_data);
 
 	if (strcmp(xlog_dir, "") != 0)
 	{
@@ -2963,7 +2961,7 @@ initialize_data_directory(void)
 
 	create_xlog_or_symlink();
 
-	/* Create required subdirectories (other than pg_xlog) */
+	/* Create required subdirectories (other than pg_wal) */
 	printf(_("creating subdirectories ... "));
 	fflush(stdout);
 
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 0f5d9d6..229f558 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -492,6 +492,7 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 	uint32		hi,
 				lo;
 	char		statusdir[MAXPGPATH];
+	int			serverMajor;
 
 	param = pg_malloc0(sizeof(logstreamer_param));
 	param->timeline = timeline;
@@ -526,15 +527,21 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 		/* Error message already written in GetConnection() */
 		exit(1);
 
-	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/pg_xlog", basedir);
+	serverMajor = PQserverVersion(conn) / 100;
+
+	/* In post-10 cluster, pg_xlog has been renamed to pg_wal */
+	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/%s",
+			 basedir, serverMajor < 1000 ? "pg_xlog" : "pg_wal");
 
 	/*
-	 * Create pg_xlog/archive_status (and thus pg_xlog) so we can write to
-	 * basedir/pg_xlog as the directory entry in the tar file may arrive
-	 * later.
+	 * Create pg_wal/archive_status or pg_xlog/archive_status (and thus
+	 * pg_wal or pg_xlog) depending on the target server so we can write to
+	 * basedir/pg_wal or basedir/pg_xlog as the directory entry in the tar
+	 * file may arrive later.
 	 */
-	snprintf(statusdir, sizeof(statusdir), "%s/pg_xlog/archive_status",
-			 basedir);
+	snprintf(statusdir, sizeof(statusdir), "%s/%s/archive_status",
+			 basedir,
+			 serverMajor < 1000 ? "pg_xlog" : "pg_wal");
 
 	if (pg_mkdir_p(statusdir, S_IRWXU) != 0 && errno != EEXIST)
 	{
@@ -1338,15 +1345,17 @@ ReceiveAndUnpackTarFile(PGconn *conn, PGresult *res, int rownum)
 					if (mkdir(filename, S_IRWXU) != 0)
 					{
 						/*
-						 * When streaming WAL, pg_xlog will have been created
-						 * by the wal receiver process. Also, when transaction
-						 * log directory location was specified, pg_xlog has
-						 * already been created as a symbolic link before
-						 * starting the actual backup. So just ignore creation
-						 * failures on related directories.
+						 * When streaming WAL, pg_wal (or pg_xlog for pre-9.6
+						 * clusters) will have been created by the wal receiver
+						 * process. Also, when transaction log directory location
+						 * was specified, pg_wal (or pg_xlog) has already been
+						 * created as a symbolic link before starting the actual
+						 * backup. So just ignore creation failures on related
+						 * directories.
 						 */
-						if (!((pg_str_endswith(filename, "/pg_xlog") ||
-							 pg_str_endswith(filename, "/archive_status")) &&
+						if (!((pg_str_endswith(filename, "/pg_wal") ||
+							   pg_str_endswith(filename, "/pg_xlog")||
+							   pg_str_endswith(filename, "/archive_status")) &&
 							  errno == EEXIST))
 						{
 							fprintf(stderr,
@@ -1636,13 +1645,7 @@ BaseBackup(void)
 				maxServerMajor;
 	int			serverMajor;
 
-	/*
-	 * Connect in replication mode to the server
-	 */
-	conn = GetConnection();
-	if (!conn)
-		/* Error message already written in GetConnection() */
-		exit(1);
+	Assert(conn != NULL);
 
 	/*
 	 * Check server version. BASE_BACKUP command was introduced in 9.1, so we
@@ -2296,26 +2299,37 @@ main(int argc, char **argv)
 	if (format == 'p' || strcmp(basedir, "-") != 0)
 		verify_dir_is_empty_or_create(basedir, &made_new_pgdata, &found_existing_pgdata);
 
+	/* connection in replication mode to server */
+	conn = GetConnection();
+	if (!conn)
+		/* Error message already written in GetConnection() */
+		exit(1);
+
 	/* Create transaction log symlink, if required */
 	if (strcmp(xlog_dir, "") != 0)
 	{
 		char	   *linkloc;
+		int			serverMajor = PQserverVersion(conn) / 100;
 
 		verify_dir_is_empty_or_create(xlog_dir, &made_new_xlogdir, &found_existing_xlogdir);
 
-		/* form name of the place where the symlink must go */
-		linkloc = psprintf("%s/pg_xlog", basedir);
+		/*
+		 * Form name of the place where the symlink must go. pg_xlog has
+		 * been renamed to pg_wal in post-10 clusters.
+		 */
+		linkloc = psprintf("%s/%s", basedir,
+						   serverMajor < 1000 ? "pg_xlog" : "pg_wal");
 
 #ifdef HAVE_SYMLINK
 		if (symlink(xlog_dir, linkloc) != 0)
 		{
 			fprintf(stderr, _("%s: could not create symbolic link \"%s\": %s\n"),
 					progname, linkloc, strerror(errno));
-			exit(1);
+			disconnect_and_exit(1);
 		}
 #else
 		fprintf(stderr, _("%s: symlinks are not supported on this platform\n"));
-		exit(1);
+		disconnect_and_exit(1);
 #endif
 		free(linkloc);
 	}
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index a52bd4e..c8abbeb 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -67,9 +67,9 @@ $node->command_ok([ 'pg_basebackup', '-D', "$tempdir/backup" ],
 	'pg_basebackup runs');
 ok(-f "$tempdir/backup/PG_VERSION", 'backup was created');
 
-# Only archive_status directory should be copied in pg_xlog/.
+# Only archive_status directory should be copied in pg_wal/.
 is_deeply(
-	[ sort(slurp_dir("$tempdir/backup/pg_xlog/")) ],
+	[ sort(slurp_dir("$tempdir/backup/pg_wal/")) ],
 	[ sort qw(. .. archive_status) ],
 	'no WAL files copied');
 
@@ -230,12 +230,12 @@ like(
 $node->command_ok(
 	[ 'pg_basebackup', '-D', "$tempdir/backupxf", '-X', 'fetch' ],
 	'pg_basebackup -X fetch runs');
-ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_xlog")),
+ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_wal")),
 	'WAL files copied');
 $node->command_ok(
 	[ 'pg_basebackup', '-D', "$tempdir/backupxs", '-X', 'stream' ],
 	'pg_basebackup -X stream runs');
-ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_xlog")),
+ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_wal")),
 	'WAL files copied');
 
 $node->command_fails(
diff --git a/src/bin/pg_resetxlog/pg_resetxlog.c b/src/bin/pg_resetxlog/pg_resetxlog.c
index 525b82ba..2b76f64 100644
--- a/src/bin/pg_resetxlog/pg_resetxlog.c
+++ b/src/bin/pg_resetxlog/pg_resetxlog.c
@@ -890,7 +890,7 @@ FindEndOfXLOG(void)
 	newXlogSegNo = ControlFile.checkPointCopy.redo / ControlFile.xlog_seg_size;
 
 	/*
-	 * Scan the pg_xlog directory to find existing WAL segment files. We
+	 * Scan the pg_wal directory to find existing WAL segment files. We
 	 * assume any present have been used; in most scenarios this should be
 	 * conservative, because of xlog.c's attempts to pre-create files.
 	 */
diff --git a/src/bin/pg_rewind/copy_fetch.c b/src/bin/pg_rewind/copy_fetch.c
index 327e7ef..d0c1586 100644
--- a/src/bin/pg_rewind/copy_fetch.c
+++ b/src/bin/pg_rewind/copy_fetch.c
@@ -131,10 +131,10 @@ recurse_dir(const char *datadir, const char *parentpath,
 			/*
 			 * If it's a symlink within pg_tblspc, we need to recurse into it,
 			 * to process all the tablespaces.  We also follow a symlink if
-			 * it's for pg_xlog.  Symlinks elsewhere are ignored.
+			 * it's for pg_wal.  Symlinks elsewhere are ignored.
 			 */
 			if ((parentpath && strcmp(parentpath, "pg_tblspc") == 0) ||
-				strcmp(path, "pg_xlog") == 0)
+				strcmp(path, "pg_wal") == 0)
 				recurse_dir(datadir, path, callback);
 #else
 			pg_fatal("\"%s\" is a symbolic link, but symbolic links are not supported on this platform\n",
diff --git a/src/bin/pg_rewind/filemap.c b/src/bin/pg_rewind/filemap.c
index 9b00dc1..3905a5d 100644
--- a/src/bin/pg_rewind/filemap.c
+++ b/src/bin/pg_rewind/filemap.c
@@ -79,11 +79,11 @@ process_source_file(const char *path, file_type_t type, size_t newsize,
 		return;
 
 	/*
-	 * Pretend that pg_xlog is a directory, even if it's really a symlink. We
+	 * Pretend that pg_wal is a directory, even if it's really a symlink. We
 	 * don't want to mess with the symlink itself, nor complain if it's a
 	 * symlink in source but not in target or vice versa.
 	 */
-	if (strcmp(path, "pg_xlog") == 0 && type == FILE_TYPE_SYMLINK)
+	if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK)
 		type = FILE_TYPE_DIRECTORY;
 
 	/*
@@ -120,7 +120,7 @@ process_source_file(const char *path, file_type_t type, size_t newsize,
 	switch (type)
 	{
 		case FILE_TYPE_DIRECTORY:
-			if (exists && !S_ISDIR(statbuf.st_mode) && strcmp(path, "pg_xlog") != 0)
+			if (exists && !S_ISDIR(statbuf.st_mode) && strcmp(path, "pg_wal") != 0)
 			{
 				/* it's a directory in source, but not in target. Strange.. */
 				pg_fatal("\"%s\" is not a directory\n", localpath);
@@ -296,7 +296,7 @@ process_target_file(const char *path, file_type_t type, size_t oldsize,
 	/*
 	 * Like in process_source_file, pretend that xlog is always a  directory.
 	 */
-	if (strcmp(path, "pg_xlog") == 0 && type == FILE_TYPE_SYMLINK)
+	if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK)
 		type = FILE_TYPE_DIRECTORY;
 
 	key.path = (char *) path;
diff --git a/src/bin/pg_rewind/parsexlog.c b/src/bin/pg_rewind/parsexlog.c
index b53591d..23ac4e7 100644
--- a/src/bin/pg_rewind/parsexlog.c
+++ b/src/bin/pg_rewind/parsexlog.c
@@ -54,7 +54,7 @@ static int SimpleXLogPageRead(XLogReaderState *xlogreader,
 				   TimeLineID *pageTLI);
 
 /*
- * Read WAL from the datadir/pg_xlog, starting from 'startpoint' on timeline
+ * Read WAL from the datadir/pg_wal, starting from 'startpoint' on timeline
  * index 'tliIndex' in target timeline history, until 'endpoint'. Make note of
  * the data blocks touched by the WAL records, and return them in a page map.
  */
diff --git a/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl b/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
index bdcab56..12950ea 100644
--- a/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
+++ b/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
@@ -1,5 +1,5 @@
 #
-# Test pg_rewind when the target's pg_xlog directory is a symlink.
+# Test pg_rewind when the target's pg_wal directory is a symlink.
 #
 use strict;
 use warnings;
@@ -30,10 +30,10 @@ sub run_test
 
 	my $test_master_datadir = $node_master->data_dir;
 
-	# turn pg_xlog into a symlink
-	print("moving $test_master_datadir/pg_xlog to $master_xlogdir\n");
-	move("$test_master_datadir/pg_xlog", $master_xlogdir) or die;
-	symlink($master_xlogdir, "$test_master_datadir/pg_xlog") or die;
+	# turn pg_wal into a symlink
+	print("moving $test_master_datadir/pg_wal to $master_xlogdir\n");
+	move("$test_master_datadir/pg_wal", $master_xlogdir) or die;
+	symlink($master_xlogdir, "$test_master_datadir/pg_wal") or die;
 
 	RewindTest::start_master();
 
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index dd30952..16f9f09 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -14,7 +14,7 @@
 #include <fcntl.h>
 #include <sys/types.h>
 
-static void check_data_dir(const char *pg_data);
+static void check_data_dir(ClusterInfo *cluster);
 static void check_bin_dir(ClusterInfo *cluster);
 static void validate_exec(const char *dir, const char *cmdName);
 
@@ -220,9 +220,9 @@ verify_directories(void)
 		pg_fatal("You must have read and write access in the current directory.\n");
 
 	check_bin_dir(&old_cluster);
-	check_data_dir(old_cluster.pgdata);
+	check_data_dir(&old_cluster);
 	check_bin_dir(&new_cluster);
-	check_data_dir(new_cluster.pgdata);
+	check_data_dir(&new_cluster);
 }
 
 
@@ -253,6 +253,32 @@ win32_check_directory_write_permissions(void)
 
 
 /*
+ * check_single_dir()
+ *
+ *  Check for the presence of a single directory in PGDATA, and fail if
+ * is it missing or not accessible.
+ */
+static void
+check_single_dir(const char *pg_data, const char *subdir)
+{
+	struct stat statBuf;
+	char		subDirName[MAXPGPATH];
+
+	snprintf(subDirName, sizeof(subDirName), "%s%s%s", pg_data,
+			 /* Win32 can't stat() a directory with a trailing slash. */
+			 *subdir ? "/" : "",
+			 subdir);
+
+	if (stat(subDirName, &statBuf) != 0)
+		report_status(PG_FATAL, "check for \"%s\" failed: %s\n",
+					  subDirName, getErrorText());
+	else if (!S_ISDIR(statBuf.st_mode))
+		report_status(PG_FATAL, "%s is not a directory\n",
+					  subDirName);
+}
+
+
+/*
  * check_data_dir()
  *
  *	This function validates the given cluster directory - we search for a
@@ -262,34 +288,27 @@ win32_check_directory_write_permissions(void)
  *
  */
 static void
-check_data_dir(const char *pg_data)
+check_data_dir(ClusterInfo *cluster)
 {
-	char		subDirName[MAXPGPATH];
-	int			subdirnum;
-
-	/* start check with top-most directory */
-	const char *requiredSubdirs[] = {"", "base", "global", "pg_clog",
-		"pg_multixact", "pg_subtrans", "pg_tblspc", "pg_twophase",
-	"pg_xlog"};
-
-	for (subdirnum = 0;
-		 subdirnum < sizeof(requiredSubdirs) / sizeof(requiredSubdirs[0]);
-		 ++subdirnum)
-	{
-		struct stat statBuf;
-
-		snprintf(subDirName, sizeof(subDirName), "%s%s%s", pg_data,
-		/* Win32 can't stat() a directory with a trailing slash. */
-				 *requiredSubdirs[subdirnum] ? "/" : "",
-				 requiredSubdirs[subdirnum]);
-
-		if (stat(subDirName, &statBuf) != 0)
-			report_status(PG_FATAL, "check for \"%s\" failed: %s\n",
-						  subDirName, getErrorText());
-		else if (!S_ISDIR(statBuf.st_mode))
-			report_status(PG_FATAL, "%s is not a directory\n",
-						  subDirName);
-	}
+	const char *pg_data = cluster->pgdata;
+
+	/* get old and new cluster versions */
+	old_cluster.major_version = get_major_server_version(&old_cluster);
+	new_cluster.major_version = get_major_server_version(&new_cluster);
+
+	check_single_dir(pg_data, "");
+	check_single_dir(pg_data, "base");
+	check_single_dir(pg_data, "global");
+	check_single_dir(pg_data, "pg_multixact");
+	check_single_dir(pg_data, "pg_subtrans");
+	check_single_dir(pg_data, "pg_tblspc");
+	check_single_dir(pg_data, "pg_twophase");
+
+	/* pg_xlog has been renamed to pg_wal in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_xlog");
+	else
+		check_single_dir(pg_data, "pg_wal");
 }
 
 
diff --git a/src/bin/pg_xlogdump/pg_xlogdump.c b/src/bin/pg_xlogdump/pg_xlogdump.c
index 02575eb..abc6fb9 100644
--- a/src/bin/pg_xlogdump/pg_xlogdump.c
+++ b/src/bin/pg_xlogdump/pg_xlogdump.c
@@ -656,7 +656,7 @@ usage(void)
 	printf("  -f, --follow           keep retrying after reaching end of WAL\n");
 	printf("  -n, --limit=N          number of records to display\n");
 	printf("  -p, --path=PATH        directory in which to find log segment files\n");
-	printf("                         (default: ./pg_xlog)\n");
+	printf("                         (default: ./pg_wal)\n");
 	printf("  -r, --rmgr=RMGR        only show records generated by resource manager RMGR\n");
 	printf("                         use --rmgr=list to list valid resource manager names\n");
 	printf("  -s, --start=RECPTR     start reading at log position RECPTR\n");
diff --git a/src/common/file_utils.c b/src/common/file_utils.c
index 1d85564..fe2d238 100644
--- a/src/common/file_utils.c
+++ b/src/common/file_utils.c
@@ -41,7 +41,7 @@ static void walkdir(const char *path,
  * Issue fsync recursively on PGDATA and all its contents.
  *
  * We fsync regular files and directories wherever they are, but we
- * follow symlinks only for pg_xlog and immediately under pg_tblspc.
+ * follow symlinks only for pg_wal and immediately under pg_tblspc.
  * Other symlinks are presumed to point at files we're not responsible
  * for fsyncing, and might not have privileges to write at all.
  *
@@ -51,14 +51,14 @@ void
 fsync_pgdata(const char *pg_data, const char *progname)
 {
 	bool		xlog_is_symlink;
-	char		pg_xlog[MAXPGPATH];
+	char		pg_wal[MAXPGPATH];
 	char		pg_tblspc[MAXPGPATH];
 
-	snprintf(pg_xlog, MAXPGPATH, "%s/pg_xlog", pg_data);
+	snprintf(pg_wal, MAXPGPATH, "%s/pg_wal", pg_data);
 	snprintf(pg_tblspc, MAXPGPATH, "%s/pg_tblspc", pg_data);
 
 	/*
-	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * If pg_wal is a symlink, we'll need to recurse into it separately,
 	 * because the first walkdir below will ignore it.
 	 */
 	xlog_is_symlink = false;
@@ -67,14 +67,14 @@ fsync_pgdata(const char *pg_data, const char *progname)
 	{
 		struct stat st;
 
-		if (lstat(pg_xlog, &st) < 0)
+		if (lstat(pg_wal, &st) < 0)
 			fprintf(stderr, _("%s: could not stat file \"%s\": %s\n"),
-					progname, pg_xlog, strerror(errno));
+					progname, pg_wal, strerror(errno));
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
 #else
-	if (pgwin32_is_junction(pg_xlog))
+	if (pgwin32_is_junction(pg_wal))
 		xlog_is_symlink = true;
 #endif
 
@@ -85,7 +85,7 @@ fsync_pgdata(const char *pg_data, const char *progname)
 #ifdef PG_FLUSH_DATA_WORKS
 	walkdir(pg_data, pre_sync_fname, false, progname);
 	if (xlog_is_symlink)
-		walkdir(pg_xlog, pre_sync_fname, false, progname);
+		walkdir(pg_wal, pre_sync_fname, false, progname);
 	walkdir(pg_tblspc, pre_sync_fname, true, progname);
 #endif
 
@@ -93,14 +93,14 @@ fsync_pgdata(const char *pg_data, const char *progname)
 	 * Now we do the fsync()s in the same order.
 	 *
 	 * The main call ignores symlinks, so in addition to specially processing
-	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * pg_wal if it's a symlink, pg_tblspc has to be visited separately with
 	 * process_symlinks = true.  Note that if there are any plain directories
 	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
 	 * so we don't worry about optimizing it.
 	 */
 	walkdir(pg_data, fsync_fname, false, progname);
 	if (xlog_is_symlink)
-		walkdir(pg_xlog, fsync_fname, false, progname);
+		walkdir(pg_wal, fsync_fname, false, progname);
 	walkdir(pg_tblspc, fsync_fname, true, progname);
 }
 
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 0a595cc..ceb0462 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -128,7 +128,7 @@ typedef XLogLongPageHeaderData *XLogLongPageHeader;
 /*
  * The XLog directory and control file (relative to $PGDATA)
  */
-#define XLOGDIR				"pg_xlog"
+#define XLOGDIR				"pg_wal"
 #define XLOG_CONTROL_FILE	"global/pg_control"
 
 /*
diff --git a/src/include/postmaster/pgarch.h b/src/include/postmaster/pgarch.h
index f2cbfb3..6df73c9 100644
--- a/src/include/postmaster/pgarch.h
+++ b/src/include/postmaster/pgarch.h
@@ -16,7 +16,7 @@
 /* ----------
  * Archiver control info.
  *
- * We expect that archivable files within pg_xlog will have names between
+ * We expect that archivable files within pg_wal will have names between
  * MIN_XFN_CHARS and MAX_XFN_CHARS in length, consisting only of characters
  * appearing in VALID_XFN_CHARS.  The status files in archive_status have
  * corresponding names with ".ready" or ".done" appended.
-- 
2.10.0

From 448bc915890b215a07ac70afd4b037594feabe41 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Fri, 30 Sep 2016 14:42:27 +0900
Subject: [PATCH 2/2] Rename pg_clog to pg_transaction

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml               |  6 +++---
 doc/src/sgml/catalogs.sgml             |  6 +++---
 doc/src/sgml/config.sgml               |  2 +-
 doc/src/sgml/func.sgml                 |  2 +-
 doc/src/sgml/maintenance.sgml          | 12 +++++------
 doc/src/sgml/ref/pg_resetxlog.sgml     |  6 +++---
 doc/src/sgml/ref/pg_rewind.sgml        |  2 +-
 doc/src/sgml/storage.sgml              | 10 ++++-----
 doc/src/sgml/wal.sgml                  |  2 +-
 src/backend/access/heap/heapam.c       | 10 ++++-----
 src/backend/access/transam/README      | 20 +++++++++---------
 src/backend/access/transam/clog.c      |  2 +-
 src/backend/access/transam/commit_ts.c |  4 ++--
 src/backend/access/transam/multixact.c |  8 +++----
 src/backend/access/transam/subtrans.c  | 18 ++++++++--------
 src/backend/access/transam/transam.c   |  2 +-
 src/backend/access/transam/twophase.c  |  6 +++---
 src/backend/access/transam/xact.c      | 38 ++++++++++++++++++++--------------
 src/backend/access/transam/xlog.c      |  6 +++---
 src/backend/commands/vacuum.c          | 14 ++++++-------
 src/backend/postmaster/autovacuum.c    |  4 ++--
 src/backend/storage/buffer/README      |  4 ++--
 src/backend/storage/ipc/procarray.c    |  5 +++--
 src/backend/utils/time/tqual.c         | 29 +++++++++++++-------------
 src/bin/initdb/initdb.c                |  2 +-
 src/bin/pg_upgrade/exec.c              |  6 ++++++
 src/bin/pg_upgrade/pg_upgrade.c        | 30 ++++++++++++++++-----------
 src/include/access/slru.h              | 12 +++++------
 28 files changed, 144 insertions(+), 124 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 6eaed1e..eb4f962 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -382,10 +382,10 @@ tar -cf backup.tar /usr/local/pgsql/data
       directories. This will <emphasis>not</> work because the
       information contained in these files is not usable without
       the commit log files,
-      <filename>pg_clog/*</filename>, which contain the commit status of
-      all transactions. A table file is only usable with this
+      <filename>pg_transaction/*</filename>, which contain the commit status
+      of all transactions. A table file is only usable with this
       information. Of course it is also impossible to restore only a
-      table and the associated <filename>pg_clog</filename> data
+      table and the associated <filename>pg_transaction</filename> data
       because that would render all other tables in the database
       cluster useless.  So file system backups only work for complete
       backup and restoration of an entire database cluster.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 29738b0..77b395e 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1847,7 +1847,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this table.  This is used to track
        whether the table needs to be vacuumed in order to prevent transaction
-       ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
+       ID wraparound or to allow <literal>pg_transaction</> to be shrunk.  Zero
        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
       </entry>
      </row>
@@ -2514,8 +2514,8 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this database.  This is used to
        track whether the database needs to be vacuumed in order to prevent
-       transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
-       It is the minimum of the per-table
+       transaction ID wraparound or to allow <literal>pg_transaction</> to be
+       shrunk.  It is the minimum of the per-table
        <structname>pg_class</>.<structfield>relfrozenxid</> values.
       </entry>
      </row>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 1bb501c..b0b7215 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5822,7 +5822,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
 
        <para>
         Vacuum also allows removal of old files from the
-        <filename>pg_clog</> subdirectory, which is why the default
+        <filename>pg_transaction</> subdirectory, which is why the default
         is a relatively low 200 million transactions.
         This parameter can only be set at server start, but the setting
         can be reduced for individual tables by
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 2e64cc4..a9d2ec4 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15323,7 +15323,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  postmaster.pid  |  9
  pg_ident.conf   | 10
  global          | 11
- pg_clog         | 12
+ pg_transaction  | 12
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index f87f3e0..c741a9b 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -527,18 +527,18 @@
    <para>
     The sole disadvantage of increasing <varname>autovacuum_freeze_max_age</>
     (and <varname>vacuum_freeze_table_age</> along with it)
-    is that the <filename>pg_clog</> subdirectory of the database cluster
-    will take more space, because it must store the commit status of all
-    transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
+    is that the <filename>pg_transaction</> subdirectory of the database
+    cluster will take more space, because it must store the commit status of
+    all transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
     The commit status uses two bits per transaction, so if
     <varname>autovacuum_freeze_max_age</> is set to its maximum allowed
-    value of two billion, <filename>pg_clog</> can be expected to
+    value of two billion, <filename>pg_transaction</> can be expected to
     grow to about half a gigabyte.  If this is trivial compared to your
     total database size, setting <varname>autovacuum_freeze_max_age</> to
     its maximum allowed value is recommended.  Otherwise, set it depending
-    on what you are willing to allow for <filename>pg_clog</> storage.
+    on what you are willing to allow for <filename>pg_transaction</> storage.
     (The default, 200 million transactions, translates to about 50MB of
-    <filename>pg_clog</> storage.)
+    <filename>pg_transaction</> storage.)
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index c949c5e..67b048b 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -256,12 +256,12 @@ PostgreSQL documentation
 
      <para>
       A safe value can be determined by looking for the numerically largest
-      file name in the directory <filename>pg_clog</> under the data directory,
-      adding one,
+      file name in the directory <filename>pg_transaction</> under the data
+      directory, adding one,
       and then multiplying by 1048576 (0x100000).  Note that the file names are in
       hexadecimal.  It is usually easiest to specify the option value in
       hexadecimal too. For example, if <filename>0011</> is the largest entry
-      in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
+      in <filename>pg_transaction</>, <literal>-x 0x1200000</> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 371c4a4..34ef4f1 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -229,7 +229,7 @@ PostgreSQL documentation
     </step>
     <step>
      <para>
-      Copy all other files such as <filename>pg_clog</filename> and
+      Copy all other files such as <filename>pg_transaction</filename> and
       configuration files from the source cluster to the target cluster
       (everything except the relation files).
      </para>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index fddb69b..61d15d4 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -72,11 +72,6 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_clog</></entry>
- <entry>Subdirectory containing transaction commit status data</entry>
-</row>
-
-<row>
  <entry><filename>pg_dynshmem</></entry>
  <entry>Subdirectory containing files used by the dynamic shared memory
   subsystem</entry>
@@ -136,6 +131,11 @@ Item
 </row>
 
 <row>
+ <entry><filename>pg_transaction</></entry>
+ <entry>Subdirectory containing transaction commit status data</entry>
+</row>
+
+<row>
  <entry><filename>pg_twophase</></entry>
  <entry>Subdirectory containing state files for prepared transactions</entry>
 </row>
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 346aa76..aac0a8d 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_clog</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_transaction</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index b019bc1..075d06a 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -6762,11 +6762,11 @@ heap_prepare_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
  * Note: it might seem we could make the changes without exclusive lock, since
  * TransactionId read/write is assumed atomic anyway.  However there is a race
  * condition: someone who just fetched an old XID that we overwrite here could
- * conceivably not finish checking the XID against pg_clog before we finish
- * the VACUUM and perhaps truncate off the part of pg_clog he needs.  Getting
- * exclusive lock ensures no other backend is in process of checking the
- * tuple status.  Also, getting exclusive lock makes it safe to adjust the
- * infomask bits.
+ * conceivably not finish checking the XID against pg_transaction before we
+ * finish the VACUUM and perhaps truncate off the part of pg_transaction he
+ * needs.  Getting exclusive lock ensures no other backend is in process of
+ * checking the tuple status.  Also, getting exclusive lock makes it safe to
+ * adjust the infomask bits.
  *
  * NB: All code in here must be safe to execute during crash recovery!
  */
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index 4ae4715..4a41263 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -331,17 +331,17 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_clog and pg_subtrans
------------------------
+pg_transaction and pg_subtrans
+------------------------------
 
-pg_clog and pg_subtrans are permanent (on-disk) storage of transaction related
-information.  There is a limited number of pages of each kept in memory, so
-in many cases there is no need to actually read from disk.  However, if
-there's a long running transaction or a backend sitting idle with an open
+pg_transaction and pg_subtrans are permanent (on-disk) storage of transaction
+related information.  There is a limited number of pages of each kept in
+memory, so in many cases there is no need to actually read from disk.  However,
+if there's a long running transaction or a backend sitting idle with an open
 transaction, it may be necessary to be able to read and write this information
 from disk.  They also allow information to be permanent across server restarts.
 
-pg_clog records the commit status for each transaction that has been assigned
+pg_trans records the commit status for each transaction that has been assigned
 an XID.  A transaction can be in progress, committed, aborted, or
 "sub-committed".  This last state means that it's a subtransaction that's no
 longer running, but its parent has not updated its state yet.  It is not
@@ -381,10 +381,10 @@ each transaction we keep a "cache" of Xids that are known to be part of the
 transaction tree, so we can skip looking at pg_subtrans unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_clog and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_transaction and pg_subtrans.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
-for pg_clog are implemented in transam.c, while the low-level functions are in
-clog.c.  pg_subtrans is contained completely in subtrans.c.
+for pg_transaction are implemented in transam.c, while the low-level functions
+are in clog.c.  pg_subtrans is contained completely in subtrans.c.
 
 
 Write-Ahead Log Coding
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 2634476..c7a3cbb 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -450,7 +450,7 @@ CLOGShmemInit(void)
 {
 	ClogCtl->PagePrecedes = CLOGPagePrecedes;
 	SimpleLruInit(ClogCtl, "clog", CLOGShmemBuffers(), CLOG_LSNS_PER_PAGE,
-				  CLogControlLock, "pg_clog", LWTRANCHE_CLOG_BUFFERS);
+				  CLogControlLock, "pg_transaction", LWTRANCHE_CLOG_BUFFERS);
 }
 
 /*
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index a8d275f..4a48f76 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -3,8 +3,8 @@
  * commit_ts.c
  *		PostgreSQL commit timestamp manager
  *
- * This module is a pg_clog-like system that stores the commit timestamp
- * for each transaction.
+ * This module is a pg_transaction-like system that stores the commit
+ * timestamp for each transaction.
  *
  * XLOG interactions: this module generates an XLOG record whenever a new
  * CommitTs page is initialized to zeroes.  Also, one XLOG record is
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index e9588a7..aa8e07e 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3,10 +3,10 @@
  * multixact.c
  *		PostgreSQL multi-transaction-log manager
  *
- * The pg_multixact manager is a pg_clog-like manager that stores an array of
- * MultiXactMember for each MultiXactId.  It is a fundamental part of the
- * shared-row-lock implementation.  Each MultiXactMember is comprised of a
- * TransactionId and a set of flag bits.  The name is a bit historical:
+ * The pg_multixact manager is a pg_transaction-like manager that stores an
+ * array of MultiXactMember for each MultiXactId.  It is a fundamental part
+ * of the shared-row-lock implementation.  Each MultiXactMember is comprised
+ * of a TransactionId and a set of flag bits.  The name is a bit historical:
  * originally, a MultiXactId consisted of more than one TransactionId (except
  * in rare corner cases), hence "multi".  Nowadays, however, it's perfectly
  * legitimate to have MultiXactIds that only include a single Xid.
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 908fe2d..d96a487 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,17 +3,17 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_clog-like manager that stores the parent
- * transaction Id for each transaction.  It is a fundamental part of the
- * nested transactions implementation.  A main transaction has a parent
- * of InvalidTransactionId, and each subtransaction has its immediate parent.
- * The tree can easily be walked from child to parent, but not in the
- * opposite direction.
+ * The pg_subtrans manager is a pg_transaction-like manager that stores
+ * the parent transaction Id for each transaction.  It is a fundamental
+ * part of the nested transactions implementation.  A main transaction has
+ * a parent of InvalidTransactionId, and each subtransaction has its
+ * immediate parent.  The tree can easily be walked from child to parent,
+ * but not in the opposite direction.
  *
  * This code is based on clog.c, but the robustness requirements
- * are completely different from pg_clog, because we only need to remember
- * pg_subtrans information for currently-open transactions.  Thus, there is
- * no need to preserve data over a crash and restart.
+ * are completely different from pg_transaction, because we only need to
+ * remember pg_subtrans information for currently-open transactions.  Thus,
+ * there is no need to preserve data over a crash and restart.
  *
  * There are no XLOG interactions since we do not care about preserving
  * data across crashes.  During database startup, we simply force the
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index 1eba49a..8a41c7f 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -224,7 +224,7 @@ TransactionIdDidAbort(TransactionId transactionId)
  *		True iff transaction associated with the identifier is currently
  *		known to have either committed or aborted.
  *
- * This does NOT look into pg_clog but merely probes our local cache
+ * This does NOT look into pg_transaction but merely probes our local cache
  * (and so it's not named TransactionIdDidComplete, which would be the
  * appropriate name for a function that worked that way).  The intended
  * use is just to short-circuit TransactionIdIsInProgress calls when doing
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 5415604..52de336 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1379,8 +1379,8 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	/*
 	 * The order of operations here is critical: make the XLOG entry for
 	 * commit or abort, then mark the transaction committed or aborted in
-	 * pg_clog, then remove its PGPROC from the global ProcArray (which means
-	 * TransactionIdIsInProgress will stop saying the prepared xact is in
+	 * pg_transaction, then remove its PGPROC from the global ProcArray (which
+	 * means TransactionIdIsInProgress will stop saying the prepared xact is in
 	 * progress), then run the post-commit or post-abort callbacks. The
 	 * callbacks will release the locks the transaction held.
 	 */
@@ -2093,7 +2093,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	/* Flush XLOG to disk */
 	XLogFlush(recptr);
 
-	/* Mark the transaction committed in pg_clog */
+	/* Mark the transaction committed in pg_transaction */
 	TransactionIdCommitTree(xid, nchildren, children);
 
 	/* Checkpoint can proceed now */
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index e11b229..817b323 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1206,10 +1206,10 @@ RecordTransactionCommit(void)
 		/*
 		 * Mark ourselves as within our "commit critical section".  This
 		 * forces any concurrent checkpoint to wait until we've updated
-		 * pg_clog.  Without this, it is possible for the checkpoint to set
-		 * REDO after the XLOG record but fail to flush the pg_clog update to
-		 * disk, leading to loss of the transaction commit if the system
-		 * crashes a little later.
+		 * pg_transaction.  Without this, it is possible for the checkpoint
+		 * to set REDO after the XLOG record but fail to flush the pg_trans
+		 * update to disk, leading to loss of the transaction commit if the
+		 * system crashes a little later.
 		 *
 		 * Note: we could, but don't bother to, set this flag in
 		 * RecordTransactionAbort.  That's because loss of a transaction abort
@@ -2033,8 +2033,8 @@ CommitTransaction(void)
 	if (!is_parallel_worker)
 	{
 		/*
-		 * We need to mark our XIDs as committed in pg_clog.  This is where we
-		 * durably commit.
+		 * We need to mark our XIDs as committed in pg_transaction.  This is
+		 * where we durably commit.
 		 */
 		latestXid = RecordTransactionCommit();
 	}
@@ -2539,10 +2539,10 @@ AbortTransaction(void)
 	AtAbort_Twophase();
 
 	/*
-	 * Advertise the fact that we aborted in pg_clog (assuming that we got as
-	 * far as assigning an XID to advertise).  But if we're inside a parallel
-	 * worker, skip this; the user backend must be the one to write the abort
-	 * record.
+	 * Advertise the fact that we aborted in pg_transaction (assuming that we
+	 * got as far as assigning an XID to advertise).  But if we're inside a
+	 * parallel worker, skip this; the user backend must be the one to write
+	 * the abort record.
 	 */
 	if (!is_parallel_worker)
 		latestXid = RecordTransactionAbort(false);
@@ -4625,7 +4625,7 @@ AbortSubTransaction(void)
 								s->parent->subTransactionId);
 		AtSubAbort_Notify();
 
-		/* Advertise the fact that we aborted in pg_clog. */
+		/* Advertise the fact that we aborted in pg_transaction. */
 		(void) RecordTransactionAbort(true);
 
 		/* Post-abort cleanup */
@@ -5371,7 +5371,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 	if (standbyState == STANDBY_DISABLED)
 	{
 		/*
-		 * Mark the transaction committed in pg_clog.
+		 * Mark the transaction committed in pg_transaction.
 		 */
 		TransactionIdCommitTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
@@ -5389,8 +5389,8 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		RecordKnownAssignedTransactionIds(max_xid);
 
 		/*
-		 * Mark the transaction committed in pg_clog. We use async commit
-		 * protocol during recovery to provide information on database
+		 * Mark the transaction committed in pg_transaction. We use async
+		 * commit protocol during recovery to provide information on database
 		 * consistency for when users try to set hint bits. It is important
 		 * that we do not set hint bits until the minRecoveryPoint is past
 		 * this commit record. This ensures that if we crash we don't see hint
@@ -5526,7 +5526,10 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 
 	if (standbyState == STANDBY_DISABLED)
 	{
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/*
+		 * Mark the transaction aborted in pg_transaction, no need for async
+		 * stuff.
+		 */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
 	else
@@ -5542,7 +5545,10 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 		 */
 		RecordKnownAssignedTransactionIds(max_xid);
 
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/*
+		 * Mark the transaction aborted in pg_transaction, no need for async
+		 * stuff.
+		 */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 
 		/*
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 48c18e8..2262ae0 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8487,9 +8487,9 @@ CreateCheckPoint(int flags)
 	 * that are currently in commit critical sections.  If an xact inserted
 	 * its commit record into XLOG just before the REDO point, then a crash
 	 * restart from the REDO point would not replay that record, which means
-	 * that our flushing had better include the xact's update of pg_clog.  So
-	 * we wait till he's out of his commit critical section before proceeding.
-	 * See notes in RecordTransactionCommit().
+	 * that our flushing had better include the xact's update of
+	 * pg_transaction.  So we wait till he's out of his commit critical
+	 * section before proceeding.  See notes in RecordTransactionCommit().
 	 *
 	 * Because we've already released the insertion locks, this test is a bit
 	 * fuzzy: it is possible that we will wait for xacts we didn't really need
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 58bbf55..5c61d1a 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -356,8 +356,8 @@ vacuum(int options, RangeVar *relation, Oid relid, VacuumParams *params,
 	if ((options & VACOPT_VACUUM) && !IsAutoVacuumWorkerProcess())
 	{
 		/*
-		 * Update pg_database.datfrozenxid, and truncate pg_clog if possible.
-		 * (autovacuum.c does this for itself.)
+		 * Update pg_database.datfrozenxid, and truncate pg_transaction if
+		 * possible. (autovacuum.c does this for itself.)
 		 */
 		vac_update_datfrozenxid();
 	}
@@ -880,7 +880,7 @@ vac_update_relstats(Relation relation,
  *		pg_class.relminmxid values.
  *
  *		If we are able to advance either pg_database value, also try to
- *		truncate pg_clog and pg_multixact.
+ *		truncate pg_transaction and pg_multixact.
  *
  *		We violate transaction semantics here by overwriting the database's
  *		existing pg_database tuple with the new values.  This is reasonably
@@ -1026,7 +1026,7 @@ vac_update_datfrozenxid(void)
 
 	/*
 	 * If we were able to advance datfrozenxid or datminmxid, see if we can
-	 * truncate pg_clog and/or pg_multixact.  Also do it if the shared
+	 * truncate pg_transaction and/or pg_multixact.  Also do it if the shared
 	 * XID-wrap-limit info is stale, since this action will update that too.
 	 */
 	if (dirty || ForceTransactionIdLimitUpdate())
@@ -1039,7 +1039,7 @@ vac_update_datfrozenxid(void)
  *	vac_truncate_clog() -- attempt to truncate the commit log
  *
  *		Scan pg_database to determine the system-wide oldest datfrozenxid,
- *		and use it to truncate the transaction commit log (pg_clog).
+ *		and use it to truncate the transaction commit log (pg_transaction).
  *		Also update the XID wrap limit info maintained by varsup.c.
  *		Likewise for datminmxid.
  *
@@ -1086,8 +1086,8 @@ vac_truncate_clog(TransactionId frozenXID,
 	 * of the interlock against copying a DB containing an active backend.
 	 * Hence the new entry will not reduce the minimum.  Also, if two VACUUMs
 	 * concurrently modify the datfrozenxid's of different databases, the
-	 * worst possible outcome is that pg_clog is not truncated as aggressively
-	 * as it could be.
+	 * worst possible outcome is that pg_transaction is not truncated as
+	 * aggressively as it could be.
 	 */
 	relation = heap_open(DatabaseRelationId, AccessShareLock);
 
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 1a92ca1..31fcd51 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2394,8 +2394,8 @@ deleted:
 	 */
 
 	/*
-	 * Update pg_database.datfrozenxid, and truncate pg_clog if possible. We
-	 * only need to do this once, not after each table.
+	 * Update pg_database.datfrozenxid, and truncate pg_transaction if
+	 * possible. We only need to do this once, not after each table.
 	 */
 	vac_update_datfrozenxid();
 
diff --git a/src/backend/storage/buffer/README b/src/backend/storage/buffer/README
index 248883f..94da258 100644
--- a/src/backend/storage/buffer/README
+++ b/src/backend/storage/buffer/README
@@ -63,8 +63,8 @@ at about the same time would OR the same bits into the field, so there
 is little or no risk of conflicting update; what's more, if there did
 manage to be a conflict it would merely mean that one bit-update would
 be lost and need to be done again later.  These four bits are only hints
-(they cache the results of transaction status lookups in pg_clog), so no
-great harm is done if they get reset to zero by conflicting updates.
+(they cache the results of transaction status lookups in pg_transaction),
+so no great harm is done if they get reset to zero by conflicting updates.
 Note, however, that a tuple is frozen by setting both HEAP_XMIN_INVALID
 and HEAP_XMIN_COMMITTED; this is a critical update and accordingly requires
 an exclusive buffer lock (and it must also be WAL-logged).
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index e5d487d..dd5c79a 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -388,7 +388,7 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
  * ProcArrayEndTransaction -- mark a transaction as no longer running
  *
  * This is used interchangeably for commit and abort cases.  The transaction
- * commit/abort must already be reported to WAL and pg_clog.
+ * commit/abort must already be reported to WAL and pg_transaction.
  *
  * proc is currently always MyProc, but we pass it explicitly for flexibility.
  * latestXid is the latest Xid among the transaction's main XID and
@@ -1180,7 +1180,8 @@ TransactionIdIsInProgress(TransactionId xid)
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
 	 * subtransaction, we want to say "not running" even though its parent may
-	 * still be running.  So first, check pg_clog to see if it's been aborted.
+	 * still be running.  So first, check pg_transaction to see if it's been
+	 * aborted.
 	 */
 	xc_slow_answer_inc();
 
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 26a3be3..fbf9c6c 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -13,23 +13,24 @@
  * NOTE: When using a non-MVCC snapshot, we must check
  * TransactionIdIsInProgress (which looks in the PGXACT array)
  * before TransactionIdDidCommit/TransactionIdDidAbort (which look in
- * pg_clog).  Otherwise we have a race condition: we might decide that a
- * just-committed transaction crashed, because none of the tests succeed.
- * xact.c is careful to record commit/abort in pg_clog before it unsets
- * MyPgXact->xid in the PGXACT array.  That fixes that problem, but it
- * also means there is a window where TransactionIdIsInProgress and
- * TransactionIdDidCommit will both return true.  If we check only
- * TransactionIdDidCommit, we could consider a tuple committed when a
- * later GetSnapshotData call will still think the originating transaction
- * is in progress, which leads to application-level inconsistency.  The
- * upshot is that we gotta check TransactionIdIsInProgress first in all
- * code paths, except for a few cases where we are looking at
- * subtransactions of our own main transaction and so there can't be any
- * race condition.
+ * pg_transaction).  Otherwise we have a race condition: we might decide
+ * that a just-committed transaction crashed, because none of the tests
+ * succeed.  xact.c is careful to record commit/abort in pg_transaction
+ * before it unsets MyPgXact->xid in the PGXACT array.  That fixes that
+ * problem, but it also means there is a window where
+ * TransactionIdIsInProgress and TransactionIdDidCommit will both return
+ * true.  If we check only TransactionIdDidCommit, we could consider a
+ * tuple committed when a later GetSnapshotData call will still think
+ * the originating transaction is in progress, which leads to
+ * application-level inconsistency.  The upshot is that we gotta check
+ * TransactionIdIsInProgress first in all code paths, except for a few
+ * cases where we are looking at subtransactions of our own main
+ * transaction and so there can't be any race condition.
  *
  * When using an MVCC snapshot, we rely on XidInMVCCSnapshot rather than
  * TransactionIdIsInProgress, but the logic is otherwise the same: do not
- * check pg_clog until after deciding that the xact is no longer in progress.
+ * check pg_transaction until after deciding that the xact is no longer
+ * in progress.
  *
  *
  * Summary of visibility functions:
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index e256bcb..b724c2d 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -196,7 +196,6 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 static const char *const subdirs[] = {
 	"global",
 	"pg_wal/archive_status",
-	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
 	"pg_notify",
@@ -213,6 +212,7 @@ static const char *const subdirs[] = {
 	"pg_tblspc",
 	"pg_stat",
 	"pg_stat_tmp",
+	"pg_transaction",
 	"pg_logical",
 	"pg_logical/snapshots",
 	"pg_logical/mappings"
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 16f9f09..fe63edb 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -309,6 +309,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_xlog");
 	else
 		check_single_dir(pg_data, "pg_wal");
+
+	/* pg_clog has been renamed to pg_transaction in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_clog");
+	else
+		check_single_dir(pg_data, "pg_transaction");
 }
 
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index fa118e9..1c67f10 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -47,7 +47,7 @@
 static void prepare_new_cluster(void);
 static void prepare_new_databases(void);
 static void create_new_objects(void);
-static void copy_clog_xlog_xid(void);
+static void copy_trans_xlog_xid(void);
 static void set_frozenxids(bool minmxid_only);
 static void setup(char *argv0, bool *live_check);
 static void cleanup(void);
@@ -113,7 +113,7 @@ main(int argc, char **argv)
 	 * Destructive Changes to New Cluster
 	 */
 
-	copy_clog_xlog_xid();
+	copy_trans_xlog_xid();
 
 	/* New now using xids of the old system */
 
@@ -374,17 +374,17 @@ remove_new_subdir(char *subdir, bool rmtopdir)
  * Copy the files from the old cluster into it
  */
 static void
-copy_subdir_files(char *subdir)
+copy_subdir_files(char *old_subdir, char *new_subdir)
 {
 	char		old_path[MAXPGPATH];
 	char		new_path[MAXPGPATH];
 
-	remove_new_subdir(subdir, true);
+	remove_new_subdir(new_subdir, true);
 
-	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, subdir);
-	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, subdir);
+	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, old_subdir);
+	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, new_subdir);
 
-	prep_status("Copying old %s to new server", subdir);
+	prep_status("Copying old %s to new server", old_subdir);
 
 	exec_prog(UTILITY_LOG_FILE, NULL, true,
 #ifndef WIN32
@@ -399,10 +399,16 @@ copy_subdir_files(char *subdir)
 }
 
 static void
-copy_clog_xlog_xid(void)
+copy_trans_xlog_xid(void)
 {
-	/* copy old commit logs to new data dir */
-	copy_subdir_files("pg_clog");
+	/*
+	 * Copy old commit logs to new data dir. pg_clog has been renamed to
+	 * pg_trans in post-10 clusters.
+	 */
+	copy_subdir_files(GET_MAJOR_VERSION(old_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_transaction",
+					  GET_MAJOR_VERSION(new_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_transaction");
 
 	/* set the next transaction id and epoch of the new cluster */
 	prep_status("Setting next transaction ID and epoch for new cluster");
@@ -432,8 +438,8 @@ copy_clog_xlog_xid(void)
 	if (old_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER &&
 		new_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER)
 	{
-		copy_subdir_files("pg_multixact/offsets");
-		copy_subdir_files("pg_multixact/members");
+		copy_subdir_files("pg_multixact/offsets", "pg_multixact/offsets");
+		copy_subdir_files("pg_multixact/members", "pg_multixact/members");
 
 		prep_status("Setting next multixact ID and offset for new cluster");
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 5fcebc5..001817f 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,10 +76,10 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_clog, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
-	 * has lsn_groups_per_page entries per buffer slot, each containing the
-	 * highest LSN known for a contiguous group of SLRU entries on that slot's
-	 * page.
+	 * for pg_transaction, false for multixact, pg_subtrans, pg_notify).
+	 * group_lsn[] has lsn_groups_per_page entries per buffer slot, each
+	 * containing the highest LSN known for a contiguous group of SLRU entries
+	 * on that slot's page.
 	 */
 	XLogRecPtr *group_lsn;
 	int			lsn_groups_per_page;
@@ -120,8 +120,8 @@ typedef struct SlruCtlData
 	SlruShared	shared;
 
 	/*
-	 * This flag tells whether to fsync writes (true for pg_clog and multixact
-	 * stuff, false for pg_subtrans and pg_notify).
+	 * This flag tells whether to fsync writes (true for pg_transaction and
+	 * multixact stuff, false for pg_subtrans and pg_notify).
 	 */
 	bool		do_fsync;
 
-- 
2.10.0

From fda247ab502f4163217d44997d2c7acd5c0c2208 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 4 Oct 2016 14:38:05 +0900
Subject: [PATCH 1/2] Rename pg_xlog to pg_wal

Additional check handling is needed in pg_upgrade regarding the clusters
worked on, except that it is a very mechanical patch. As pg_basebackup
needs to support servers down to 9.1, special handling is needed depending
on the version of the target server as a consequence of this renaming:
- Soft links need to be generated using pg_xlog or pg_wal.
- stream mode needs to have its output in the correct place.
This has as direct consequence to need a connection to target server before
generating a soft link, which is a bit earlier than before this renaming.
---
 doc/src/sgml/backup.sgml                     |  28 ++++----
 doc/src/sgml/config.sgml                     |   6 +-
 doc/src/sgml/func.sgml                       |   2 +-
 doc/src/sgml/high-availability.sgml          |  14 ++--
 doc/src/sgml/perform.sgml                    |   2 +-
 doc/src/sgml/protocol.sgml                   |   6 +-
 doc/src/sgml/ref/pg_resetxlog.sgml           |  10 +--
 doc/src/sgml/ref/pg_rewind.sgml              |   4 +-
 doc/src/sgml/ref/pg_xlogdump.sgml            |   2 +-
 doc/src/sgml/ref/pgtestfsync.sgml            |   4 +-
 doc/src/sgml/ref/pgupgrade.sgml              |   4 +-
 doc/src/sgml/storage.sgml                    |   2 +-
 doc/src/sgml/wal.sgml                        |  10 +--
 src/backend/access/transam/timeline.c        |   4 +-
 src/backend/access/transam/xlog.c            | 100 +++++++++++++--------------
 src/backend/access/transam/xlogarchive.c     |   2 +-
 src/backend/access/transam/xlogfuncs.c       |   2 +-
 src/backend/replication/README               |   2 +-
 src/backend/replication/basebackup.c         |  20 +++---
 src/backend/replication/walreceiver.c        |   6 +-
 src/backend/replication/walsender.c          |   4 +-
 src/backend/storage/file/fd.c                |  16 ++---
 src/bin/initdb/initdb.c                      |  12 ++--
 src/bin/pg_basebackup/pg_basebackup.c        |  80 +++++++++++++--------
 src/bin/pg_basebackup/t/010_pg_basebackup.pl |   8 +--
 src/bin/pg_resetxlog/pg_resetxlog.c          |   2 +-
 src/bin/pg_rewind/copy_fetch.c               |   4 +-
 src/bin/pg_rewind/filemap.c                  |   8 +--
 src/bin/pg_rewind/parsexlog.c                |   2 +-
 src/bin/pg_rewind/t/004_pg_xlog_symlink.pl   |  10 +--
 src/bin/pg_upgrade/exec.c                    |  79 +++++++++++++--------
 src/bin/pg_xlogdump/pg_xlogdump.c            |   2 +-
 src/common/file_utils.c                      |  39 +++++++----
 src/include/access/xlog_internal.h           |   2 +-
 src/include/common/file_utils.h              |   3 +-
 src/include/postmaster/pgarch.h              |   2 +-
 36 files changed, 278 insertions(+), 225 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 95d0ff3..6eaed1e 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -472,7 +472,7 @@ tar -cf backup.tar /usr/local/pgsql/data
 
   <para>
    At all times, <productname>PostgreSQL</> maintains a
-   <firstterm>write ahead log</> (WAL) in the <filename>pg_xlog/</>
+   <firstterm>write ahead log</> (WAL) in the <filename>pg_wal/</>
    subdirectory of the cluster's data directory. The log records
    every change made to the database's data files.  This log exists
    primarily for crash-safety purposes: if the system crashes, the
@@ -616,7 +616,7 @@ archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"'  # Windows
     <literal>%p</> and <literal>%f</> parameters have been replaced,
     the actual command executed might look like this:
 <programlisting>
-test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065
+test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_wal/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065
 </programlisting>
     A similar command will be generated for each new file to be archived.
    </para>
@@ -668,9 +668,9 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     fills, nothing further can be archived until the tape is swapped.
     You should ensure that any error condition or request to a human operator
     is reported appropriately so that the situation can be
-    resolved reasonably quickly. The <filename>pg_xlog/</> directory will
+    resolved reasonably quickly. The <filename>pg_wal/</> directory will
     continue to fill with WAL segment files until the situation is resolved.
-    (If the file system containing <filename>pg_xlog/</> fills up,
+    (If the file system containing <filename>pg_wal/</> fills up,
     <productname>PostgreSQL</> will do a PANIC shutdown.  No committed
     transactions will be lost, but the database will remain offline until
     you free some space.)
@@ -682,7 +682,7 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     operation continues even if the archiving process falls a little behind.
     If archiving falls significantly behind, this will increase the amount of
     data that would be lost in the event of a disaster. It will also mean that
-    the <filename>pg_xlog/</> directory will contain large numbers of
+    the <filename>pg_wal/</> directory will contain large numbers of
     not-yet-archived segment files, which could eventually exceed available
     disk space. You are advised to monitor the archiving process to ensure that
     it is working as you intend.
@@ -743,7 +743,7 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     configuration file reload.  If you wish to temporarily stop archiving,
     one way to do it is to set <varname>archive_command</> to the empty
     string (<literal>''</>).
-    This will cause WAL files to accumulate in <filename>pg_xlog/</> until a
+    This will cause WAL files to accumulate in <filename>pg_wal/</> until a
     working <varname>archive_command</> is re-established.
    </para>
   </sect2>
@@ -1062,10 +1062,10 @@ SELECT pg_stop_backup();
 
    <para>
     You should, however, omit from the backup the files within the
-    cluster's <filename>pg_xlog/</> subdirectory.  This
+    cluster's <filename>pg_wal/</> subdirectory.  This
     slight adjustment is worthwhile because it reduces the risk
     of mistakes when restoring.  This is easy to arrange if
-    <filename>pg_xlog/</> is a symbolic link pointing to someplace outside
+    <filename>pg_wal/</> is a symbolic link pointing to someplace outside
     the cluster directory, which is a common setup anyway for performance
     reasons.  You might also want to exclude <filename>postmaster.pid</>
     and <filename>postmaster.opts</>, which record information
@@ -1149,7 +1149,7 @@ SELECT pg_stop_backup();
      location in case you need them later. Note that this precaution will
      require that you have enough free space on your system to hold two
      copies of your existing database. If you do not have enough space,
-     you should at least save the contents of the cluster's <filename>pg_xlog</>
+     you should at least save the contents of the cluster's <filename>pg_wal</>
      subdirectory, as it might contain logs which
      were not archived before the system went down.
     </para>
@@ -1172,9 +1172,9 @@ SELECT pg_stop_backup();
    </listitem>
    <listitem>
     <para>
-     Remove any files present in <filename>pg_xlog/</>; these came from the
+     Remove any files present in <filename>pg_wal/</>; these came from the
      file system backup and are therefore probably obsolete rather than current.
-     If you didn't archive <filename>pg_xlog/</> at all, then recreate
+     If you didn't archive <filename>pg_wal/</> at all, then recreate
      it with proper permissions,
      being careful to ensure that you re-establish it as a symbolic link
      if you had it set up that way before.
@@ -1183,7 +1183,7 @@ SELECT pg_stop_backup();
    <listitem>
     <para>
      If you have unarchived WAL segment files that you saved in step 2,
-     copy them into <filename>pg_xlog/</>.  (It is best to copy them,
+     copy them into <filename>pg_wal/</>.  (It is best to copy them,
      not move them, so you still have the unmodified files if a
      problem occurs and you have to start over.)
     </para>
@@ -1265,9 +1265,9 @@ restore_command = 'cp /mnt/server/archivedir/%f %p'
 
    <para>
     WAL segments that cannot be found in the archive will be sought in
-    <filename>pg_xlog/</>; this allows use of recent un-archived segments.
+    <filename>pg_wal/</>; this allows use of recent un-archived segments.
     However, segments that are available from the archive will be used in
-    preference to files in <filename>pg_xlog/</>.
+    preference to files in <filename>pg_wal/</>.
    </para>
 
    <para>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index e826c19..1bb501c 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2932,7 +2932,7 @@ include_dir 'conf.d'
        <listitem>
        <para>
         Specifies the minimum number of past log file segments kept in the
-        <filename>pg_xlog</>
+        <filename>pg_wal</>
         directory, in case a standby server needs to fetch them for streaming
         replication. Each segment is normally 16 megabytes. If a standby
         server connected to the sending server falls behind by more than
@@ -2946,7 +2946,7 @@ include_dir 'conf.d'
 
        <para>
         This sets only the minimum number of segments retained in
-        <filename>pg_xlog</>; the system might need to retain more segments
+        <filename>pg_wal</>; the system might need to retain more segments
         for WAL archival or to recover from a checkpoint. If
         <varname>wal_keep_segments</> is zero (the default), the system
         doesn't keep any extra segments for standby purposes, so the number
@@ -3322,7 +3322,7 @@ include_dir 'conf.d'
        <para>
         Specify how long the standby server should wait when WAL data is not
         available from any sources (streaming replication,
-        local <filename>pg_xlog</> or WAL archive) before retrying to
+        local <filename>pg_wal</> or WAL archive) before retrying to
         retrieve WAL data.  This parameter can only be set in the
         <filename>postgresql.conf</> file or on the server command line.
         The default value is 5 seconds. Units are milliseconds if not specified.
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index a588350..2e64cc4 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15327,7 +15327,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
- pg_xlog         | 16
+ pg_wal          | 16
  pg_hba.conf     | 17
  pg_stat_tmp     | 18
  pg_subtrans     | 19
diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index 06f49db..5bedaf2 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -594,24 +594,24 @@ protocol to make nodes agree on a serializable transactional order.
     (see <xref linkend="restore-command">) or directly from the master
     over a TCP connection (streaming replication). The standby server will
     also attempt to restore any WAL found in the standby cluster's
-    <filename>pg_xlog</> directory. That typically happens after a server
+    <filename>pg_wal</> directory. That typically happens after a server
     restart, when the standby replays again WAL that was streamed from the
     master before the restart, but you can also manually copy files to
-    <filename>pg_xlog</> at any time to have them replayed.
+    <filename>pg_wal</> at any time to have them replayed.
    </para>
 
    <para>
     At startup, the standby begins by restoring all WAL available in the
     archive location, calling <varname>restore_command</>. Once it
     reaches the end of WAL available there and <varname>restore_command</>
-    fails, it tries to restore any WAL available in the <filename>pg_xlog</> directory.
+    fails, it tries to restore any WAL available in the <filename>pg_wal</> directory.
     If that fails, and streaming replication has been configured, the
     standby tries to connect to the primary server and start streaming WAL
-    from the last valid record found in archive or <filename>pg_xlog</>. If that fails
+    from the last valid record found in archive or <filename>pg_wal</>. If that fails
     or streaming replication is not configured, or if the connection is
     later disconnected, the standby goes back to step 1 and tries to
     restore the file from the archive again. This loop of retries from the
-    archive, <filename>pg_xlog</>, and via streaming replication goes on until the server
+    archive, <filename>pg_wal</>, and via streaming replication goes on until the server
     is stopped or failover is triggered by a trigger file.
    </para>
 
@@ -619,7 +619,7 @@ protocol to make nodes agree on a serializable transactional order.
     Standby mode is exited and the server switches to normal operation
     when <command>pg_ctl promote</> is run or a trigger file is found
     (<varname>trigger_file</>). Before failover,
-    any WAL immediately available in the archive or in <filename>pg_xlog</> will be
+    any WAL immediately available in the archive or in <filename>pg_wal</> will be
     restored, but no attempt is made to connect to the master.
    </para>
   </sect2>
@@ -895,7 +895,7 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass'
     However, these methods often result in retaining more WAL segments than
     required, whereas replication slots retain only the number of segments
     known to be needed.  An advantage of these methods is that they bound
-    the space requirement for <literal>pg_xlog</>; there is currently no way
+    the space requirement for <literal>pg_wal</>; there is currently no way
     to do this using replication slots.
    </para>
    <para>
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml
index 7bcbfa7..8d30fd1 100644
--- a/doc/src/sgml/perform.sgml
+++ b/doc/src/sgml/perform.sgml
@@ -1612,7 +1612,7 @@ SELECT * FROM x, y, a, b, c WHERE something AND somethingelse;
        Increase <xref linkend="guc-max-wal-size"> and <xref
        linkend="guc-checkpoint-timeout"> ; this reduces the frequency
        of checkpoints, but increases the storage requirements of
-       <filename>/pg_xlog</>.
+       <filename>/pg_wal</>.
       </para>
      </listitem>
 
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 3384e73..50cf527 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -1947,7 +1947,7 @@ The commands accepted in walsender mode are:
          <para>
           Include the necessary WAL segments in the backup. This will include
           all the files between start and stop backup in the
-          <filename>pg_xlog</filename> directory of the base directory tar
+          <filename>pg_wal</filename> directory of the base directory tar
           file.
          </para>
         </listitem>
@@ -2076,8 +2076,8 @@ The commands accepted in walsender mode are:
        </listitem>
        <listitem>
         <para>
-         <filename>pg_xlog</>, including subdirectories. If the backup is run
-         with WAL files included, a synthesized version of <filename>pg_xlog</filename> will be
+         <filename>pg_wal</>, including subdirectories. If the backup is run
+         with WAL files included, a synthesized version of <filename>pg_wal</filename> will be
          included, but it will only contain the files necessary for the
          backup to work, not the rest of the contents.
         </para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index fd9d0be..c949c5e 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -173,22 +173,22 @@ PostgreSQL documentation
      <para>
       The WAL starting address should be
       larger than any WAL segment file name currently existing in
-      the directory <filename>pg_xlog</> under the data directory.
+      the directory <filename>pg_wal</> under the data directory.
       These names are also in hexadecimal and have three parts.  The first
       part is the <quote>timeline ID</> and should usually be kept the same.
       For example, if <filename>00000001000000320000004A</> is the
-      largest entry in <filename>pg_xlog</>, use <literal>-l 00000001000000320000004B</> or higher.
+      largest entry in <filename>pg_wal</>, use <literal>-l 00000001000000320000004B</> or higher.
      </para>
 
      <note>
       <para>
        <command>pg_resetxlog</command> itself looks at the files in
-       <filename>pg_xlog</> and chooses a default <option>-l</> setting
+       <filename>pg_wal</> and chooses a default <option>-l</> setting
        beyond the last existing file name.  Therefore, manual adjustment of
        <option>-l</> should only be needed if you are aware of WAL segment
-       files that are not currently present in <filename>pg_xlog</>, such as
+       files that are not currently present in <filename>pg_wal</>, such as
        entries in an offline archive; or if the contents of
-       <filename>pg_xlog</> have been lost entirely.
+       <filename>pg_wal</> have been lost entirely.
       </para>
      </note>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 42ebfbf..371c4a4 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -61,14 +61,14 @@ PostgreSQL documentation
   <para>
    <application>pg_rewind</> examines the timeline histories of the source
    and target clusters to determine the point where they diverged, and
-   expects to find WAL in the target cluster's <filename>pg_xlog</> directory
+   expects to find WAL in the target cluster's <filename>pg_wal</> directory
    reaching all the way back to the point of divergence. The point of divergence
    can be found either on the target timeline, the source timeline, or their common
    ancestor. In the typical failover scenario where the target cluster was
    shut down soon after the divergence, this is not a problem, but if the
    target cluster ran for a long time after the divergence, the old WAL
    files might no longer be present. In that case, they can be manually
-   copied from the WAL archive to the <filename>pg_xlog</> directory, or
+   copied from the WAL archive to the <filename>pg_wal</> directory, or
    fetched on startup by configuring <filename>recovery.conf</>.  The use of
    <application>pg_rewind</> is not limited to failover, e.g.  a standby
    server can be promoted, run some write transactions, and then rewinded
diff --git a/doc/src/sgml/ref/pg_xlogdump.sgml b/doc/src/sgml/ref/pg_xlogdump.sgml
index 177caab..cfb6d87 100644
--- a/doc/src/sgml/ref/pg_xlogdump.sgml
+++ b/doc/src/sgml/ref/pg_xlogdump.sgml
@@ -118,7 +118,7 @@ PostgreSQL documentation
       <listitem>
        <para>
         Directory in which to find log segment files.  The default is to search
-        for them in the <literal>pg_xlog</literal> subdirectory of the current
+        for them in the <literal>pg_wal</literal> subdirectory of the current
         directory.
        </para>
       </listitem>
diff --git a/doc/src/sgml/ref/pgtestfsync.sgml b/doc/src/sgml/ref/pgtestfsync.sgml
index 6e134c7..5856356 100644
--- a/doc/src/sgml/ref/pgtestfsync.sgml
+++ b/doc/src/sgml/ref/pgtestfsync.sgml
@@ -57,8 +57,8 @@
        <para>
         Specifies the file name to write test data in.
         This file should be in the same file system that the
-        <filename>pg_xlog</> directory is or will be placed in.
-        (<filename>pg_xlog</> contains the <acronym>WAL</> files.)
+        <filename>pg_wal</> directory is or will be placed in.
+        (<filename>pg_wal</> contains the <acronym>WAL</> files.)
         The default is <filename>pg_test_fsync.out</> in the current
         directory.
        </para>
diff --git a/doc/src/sgml/ref/pgupgrade.sgml b/doc/src/sgml/ref/pgupgrade.sgml
index 9685193..4b9aab2 100644
--- a/doc/src/sgml/ref/pgupgrade.sgml
+++ b/doc/src/sgml/ref/pgupgrade.sgml
@@ -345,7 +345,7 @@ NET STOP postgresql-9.0
      your old cluster
      once you start the new cluster after the upgrade.  Link mode also
      requires that the old and new cluster data directories be in the
-     same file system.  (Tablespaces and <filename>pg_xlog</> can be on
+     same file system.  (Tablespaces and <filename>pg_wal</> can be on
      different file systems.)  See <literal>pg_upgrade --help</> for a full
      list of options.
     </para>
@@ -508,7 +508,7 @@ rsync --archive --delete --hard-links --size-only old_pgdata new_pgdata remote_d
       <para>
        If you have tablespaces, you will need to run a similar
        <application>rsync</> command for each tablespace directory.  If you
-       have relocated <filename>pg_xlog</> outside the data directories,
+       have relocated <filename>pg_wal</> outside the data directories,
        <application>rsync</> must be run on those directories too.
       </para>
      </step>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 1b812bd..fddb69b 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -141,7 +141,7 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_xlog</></entry>
+ <entry><filename>pg_wal</></entry>
  <entry>Subdirectory containing WAL (Write Ahead Log) files</entry>
 </row>
 
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index fe3b588..346aa76 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -557,7 +557,7 @@
   </para>
 
   <para>
-   The number of WAL segment files in <filename>pg_xlog</> directory depends on
+   The number of WAL segment files in <filename>pg_wal</> directory depends on
    <varname>min_wal_size</>, <varname>max_wal_size</> and
    the amount of WAL generated in previous checkpoint cycles. When old log
    segment files are no longer needed, they are removed or recycled (that is,
@@ -582,7 +582,7 @@
    kept at all times. Also, if WAL archiving is used, old segments can not be
    removed or recycled until they are archived. If WAL archiving cannot keep up
    with the pace that WAL is generated, or if <varname>archive_command</varname>
-   fails repeatedly, old WAL files will accumulate in <filename>pg_xlog</>
+   fails repeatedly, old WAL files will accumulate in <filename>pg_wal</>
    until the situation is resolved. A slow or failed standby server that
    uses a replication slot will have the same effect (see
    <xref linkend="streaming-replication-slots">).
@@ -594,7 +594,7 @@
    which are similar to checkpoints in normal operation: the server forces
    all its state to disk, updates the <filename>pg_control</> file to
    indicate that the already-processed WAL data need not be scanned again,
-   and then recycles any old log segment files in the <filename>pg_xlog</>
+   and then recycles any old log segment files in the <filename>pg_wal</>
    directory.
    Restartpoints can't be performed more frequently than checkpoints in the
    master because restartpoints can only be performed at checkpoint records.
@@ -750,7 +750,7 @@
 
   <para>
    <acronym>WAL</acronym> logs are stored in the directory
-   <filename>pg_xlog</filename> under the data directory, as a set of
+   <filename>pg_wal</filename> under the data directory, as a set of
    segment files, normally each 16 MB in size (but the size can be changed
    by altering the <option>--with-wal-segsize</> configure option when
    building the server).  Each segment is divided into pages, normally
@@ -767,7 +767,7 @@
   <para>
    It is advantageous if the log is located on a different disk from the
    main database files.  This can be achieved by moving the
-   <filename>pg_xlog</filename> directory to another location (while the server
+   <filename>pg_wal</filename> directory to another location (while the server
    is shut down, of course) and creating a symbolic link from the
    original location in the main data directory to the new location.
   </para>
diff --git a/src/backend/access/transam/timeline.c b/src/backend/access/transam/timeline.c
index bd91573..43436a9 100644
--- a/src/backend/access/transam/timeline.c
+++ b/src/backend/access/transam/timeline.c
@@ -43,7 +43,7 @@
 
 /*
  * Copies all timeline history files with id's between 'begin' and 'end'
- * from archive to pg_xlog.
+ * from archive to pg_wal.
  */
 void
 restoreTimeLineHistoryFiles(TimeLineID begin, TimeLineID end)
@@ -191,7 +191,7 @@ readTimeLineHistory(TimeLineID targetTLI)
 	result = lcons(entry, result);
 
 	/*
-	 * If the history file was fetched from archive, save it in pg_xlog for
+	 * If the history file was fetched from archive, save it in pg_wal for
 	 * future reference.
 	 */
 	if (fromArchive)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index c1b9a97..48c18e8 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -235,9 +235,9 @@ static int	LocalXLogInsertAllowed = -1;
  * valid in the startup process.
  *
  * When ArchiveRecoveryRequested is true, but InArchiveRecovery is false, we're
- * currently performing crash recovery using only XLOG files in pg_xlog, but
+ * currently performing crash recovery using only XLOG files in pg_wal, but
  * will switch to using offline XLOG archives as soon as we reach the end of
- * WAL in pg_xlog.
+ * WAL in pg_wal.
 */
 bool		ArchiveRecoveryRequested = false;
 bool		InArchiveRecovery = false;
@@ -700,12 +700,12 @@ typedef enum
 {
 	XLOG_FROM_ANY = 0,			/* request to read WAL from any source */
 	XLOG_FROM_ARCHIVE,			/* restored using restore_command */
-	XLOG_FROM_PG_XLOG,			/* existing file in pg_xlog */
+	XLOG_FROM_PG_WAL,			/* existing file in pg_wal */
 	XLOG_FROM_STREAM			/* streamed from master */
 } XLogSource;
 
 /* human-readable names for XLogSources, for debugging output */
-static const char *xlogSourceNames[] = {"any", "archive", "pg_xlog", "stream"};
+static const char *xlogSourceNames[] = {"any", "archive", "pg_wal", "stream"};
 
 /*
  * openLogFile is -1 or a kernel FD for an open log file segment.
@@ -3345,7 +3345,7 @@ XLogFileOpen(XLogSegNo segno)
  * Open a logfile segment for reading (during recovery).
  *
  * If source == XLOG_FROM_ARCHIVE, the segment is retrieved from archive.
- * Otherwise, it's assumed to be already available in pg_xlog.
+ * Otherwise, it's assumed to be already available in pg_wal.
  */
 static int
 XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
@@ -3374,7 +3374,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 				return -1;
 			break;
 
-		case XLOG_FROM_PG_XLOG:
+		case XLOG_FROM_PG_WAL:
 		case XLOG_FROM_STREAM:
 			XLogFilePath(path, tli, segno);
 			restoredFromArchive = false;
@@ -3393,7 +3393,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 		KeepFileRestoredFromArchive(path, xlogfname);
 
 		/*
-		 * Set path to point at the new file in pg_xlog.
+		 * Set path to point at the new file in pg_wal.
 		 */
 		snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlogfname);
 	}
@@ -3481,10 +3481,10 @@ XLogFileReadAnyTLI(XLogSegNo segno, int emode, int source)
 			}
 		}
 
-		if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_XLOG)
+		if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_WAL)
 		{
 			fd = XLogFileRead(segno, emode, tli,
-							  XLOG_FROM_PG_XLOG, true);
+							  XLOG_FROM_PG_WAL, true);
 			if (fd != -1)
 			{
 				if (!expectedTLEs)
@@ -3693,10 +3693,10 @@ RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
  *
  * This is called during recovery, whenever we switch to follow a new
  * timeline, and at the end of recovery when we create a new timeline. We
- * wouldn't otherwise care about extra WAL files lying in pg_xlog, but they
+ * wouldn't otherwise care about extra WAL files lying in pg_wal, but they
  * might be leftover pre-allocated or recycled WAL segments on the old timeline
  * that we haven't used yet, and contain garbage. If we just leave them in
- * pg_xlog, they will eventually be archived, and we can't let that happen.
+ * pg_wal, they will eventually be archived, and we can't let that happen.
  * Files that belong to our timeline history are valid, because we have
  * successfully replayed them, but from others we can't be sure.
  *
@@ -3853,15 +3853,15 @@ RemoveXlogFile(const char *segname, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
 }
 
 /*
- * Verify whether pg_xlog and pg_xlog/archive_status exist.
+ * Verify whether pg_wal and pg_wal/archive_status exist.
  * If the latter does not exist, recreate it.
  *
  * It is not the goal of this function to verify the contents of these
  * directories, but to help in cases where someone has performed a cluster
- * copy for PITR purposes but omitted pg_xlog from the copy.
+ * copy for PITR purposes but omitted pg_wal from the copy.
  *
- * We could also recreate pg_xlog if it doesn't exist, but a deliberate
- * policy decision was made not to.  It is fairly common for pg_xlog to be
+ * We could also recreate pg_wal if it doesn't exist, but a deliberate
+ * policy decision was made not to.  It is fairly common for pg_wal to be
  * a symlink, and if that was the DBA's intent then automatically making a
  * plain directory would result in degraded performance with no notice.
  */
@@ -3871,7 +3871,7 @@ ValidateXLOGDirectoryStructure(void)
 	char		path[MAXPGPATH];
 	struct stat stat_buf;
 
-	/* Check for pg_xlog; if it doesn't exist, error out */
+	/* Check for pg_wal; if it doesn't exist, error out */
 	if (stat(XLOGDIR, &stat_buf) != 0 ||
 		!S_ISDIR(stat_buf.st_mode))
 		ereport(FATAL,
@@ -4027,11 +4027,11 @@ ReadRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int emode,
 			 * If archive recovery was requested, but we were still doing
 			 * crash recovery, switch to archive recovery and retry using the
 			 * offline archive. We have now replayed all the valid WAL in
-			 * pg_xlog, so we are presumably now consistent.
+			 * pg_wal, so we are presumably now consistent.
 			 *
 			 * We require that there's at least some valid WAL present in
-			 * pg_xlog, however (!fetch_ckpt). We could recover using the WAL
-			 * from the archive, even if pg_xlog is completely empty, but we'd
+			 * pg_wal, however (!fetch_ckpt). We could recover using the WAL
+			 * from the archive, even if pg_wal is completely empty, but we'd
 			 * have no idea how far we'd have to replay to reach consistency.
 			 * So err on the safe side and give up.
 			 */
@@ -4039,7 +4039,7 @@ ReadRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int emode,
 				!fetching_ckpt)
 			{
 				ereport(DEBUG1,
-						(errmsg_internal("reached end of WAL in pg_xlog, entering archive recovery")));
+						(errmsg_internal("reached end of WAL in pg_wal, entering archive recovery")));
 				InArchiveRecovery = true;
 				if (StandbyModeRequested)
 					StandbyMode = true;
@@ -4156,7 +4156,7 @@ rescanLatestTimeLine(void)
 
 	/*
 	 * As in StartupXLOG(), try to ensure we have all the history files
-	 * between the old target and new target in pg_xlog.
+	 * between the old target and new target in pg_wal.
 	 */
 	restoreTimeLineHistoryFiles(oldtarget + 1, newtarget);
 
@@ -5189,7 +5189,7 @@ readRecoveryCommandFile(void)
 			ereport(WARNING,
 					(errmsg("recovery command file \"%s\" specified neither primary_conninfo nor restore_command",
 							RECOVERY_COMMAND_FILE),
-					 errhint("The database server will regularly poll the pg_xlog subdirectory to check for files placed there.")));
+					 errhint("The database server will regularly poll the pg_wal subdirectory to check for files placed there.")));
 	}
 	else
 	{
@@ -6055,7 +6055,7 @@ StartupXLOG(void)
 #endif
 
 	/*
-	 * Verify that pg_xlog and pg_xlog/archive_status exist.  In cases where
+	 * Verify that pg_wal and pg_wal/archive_status exist.  In cases where
 	 * someone has performed a copy for PITR, these directories may have been
 	 * excluded and need to be re-created.
 	 */
@@ -6268,7 +6268,7 @@ StartupXLOG(void)
 		 * and put it into archive recovery by creating a recovery.conf file.
 		 *
 		 * Our strategy in that case is to perform crash recovery first,
-		 * replaying all the WAL present in pg_xlog, and only enter archive
+		 * replaying all the WAL present in pg_wal, and only enter archive
 		 * recovery after that.
 		 *
 		 * But usually we already know how far we need to replay the WAL (up
@@ -6472,7 +6472,7 @@ StartupXLOG(void)
 
 	/*
 	 * Copy any missing timeline history files between 'now' and the recovery
-	 * target timeline from archive to pg_xlog. While we don't need those
+	 * target timeline from archive to pg_wal. While we don't need those
 	 * files ourselves - the history file of the recovery target timeline
 	 * covers all the previous timelines in the history too - a cascading
 	 * standby server might be interested in them. Or, if you archive the WAL
@@ -7093,7 +7093,7 @@ StartupXLOG(void)
 	/*
 	 * We are now done reading the xlog from stream. Turn off streaming
 	 * recovery to force fetching the files (which would be required at end of
-	 * recovery, e.g., timeline history file) from archive or pg_xlog.
+	 * recovery, e.g., timeline history file) from archive or pg_wal.
 	 */
 	StandbyMode = false;
 
@@ -7381,7 +7381,7 @@ StartupXLOG(void)
 		 * As a compromise, we rename the last segment with the .partial
 		 * suffix, and archive it. Archive recovery will never try to read
 		 * .partial segments, so they will normally go unused. But in the odd
-		 * PITR case, the administrator can copy them manually to the pg_xlog
+		 * PITR case, the administrator can copy them manually to the pg_wal
 		 * directory (removing the suffix). They can be useful in debugging,
 		 * too.
 		 *
@@ -9957,7 +9957,7 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
 		 * first WAL segment containing the startup checkpoint has pages in
 		 * the beginning with the old timeline ID.  That can cause trouble at
 		 * recovery: we won't have a history file covering the old timeline if
-		 * pg_xlog directory was not included in the base backup and the WAL
+		 * pg_wal directory was not included in the base backup and the WAL
 		 * archive was cleared too before starting the backup.
 		 *
 		 * This also ensures that we have emitted a WAL page header that has
@@ -10604,7 +10604,7 @@ do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
 	 * archived before returning. If archiving isn't enabled, the required WAL
 	 * needs to be transported via streaming replication (hopefully with
 	 * wal_keep_segments set high enough), or some more exotic mechanism like
-	 * polling and copying files from pg_xlog with script. We have no
+	 * polling and copying files from pg_wal with script. We have no
 	 * knowledge of those mechanisms, so it's up to the user to ensure that he
 	 * gets all the required WAL.
 	 *
@@ -11194,9 +11194,9 @@ next_record_is_invalid:
  * Open the WAL segment containing WAL position 'RecPtr'.
  *
  * The segment can be fetched via restore_command, or via walreceiver having
- * streamed the record, or it can already be present in pg_xlog. Checking
- * pg_xlog is mainly for crash recovery, but it will be polled in standby mode
- * too, in case someone copies a new segment directly to pg_xlog. That is not
+ * streamed the record, or it can already be present in pg_wal. Checking
+ * pg_wal is mainly for crash recovery, but it will be polled in standby mode
+ * too, in case someone copies a new segment directly to pg_wal. That is not
  * documented or recommended, though.
  *
  * If 'fetching_ckpt' is true, we're fetching a checkpoint record, and should
@@ -11226,8 +11226,8 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 	/*-------
 	 * Standby mode is implemented by a state machine:
 	 *
-	 * 1. Read from either archive or pg_xlog (XLOG_FROM_ARCHIVE), or just
-	 *	  pg_xlog (XLOG_FROM_XLOG)
+	 * 1. Read from either archive or pg_wal (XLOG_FROM_ARCHIVE), or just
+	 *	  pg_wal (XLOG_FROM_PG_WAL)
 	 * 2. Check trigger file
 	 * 3. Read from primary server via walreceiver (XLOG_FROM_STREAM)
 	 * 4. Rescan timelines
@@ -11243,7 +11243,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 	 *-------
 	 */
 	if (!InArchiveRecovery)
-		currentSource = XLOG_FROM_PG_XLOG;
+		currentSource = XLOG_FROM_PG_WAL;
 	else if (currentSource == 0)
 		currentSource = XLOG_FROM_ARCHIVE;
 
@@ -11262,13 +11262,13 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 			switch (currentSource)
 			{
 				case XLOG_FROM_ARCHIVE:
-				case XLOG_FROM_PG_XLOG:
+				case XLOG_FROM_PG_WAL:
 
 					/*
 					 * Check to see if the trigger file exists. Note that we
 					 * do this only after failure, so when you create the
 					 * trigger file, we still finish replaying as much as we
-					 * can from archive and pg_xlog before failover.
+					 * can from archive and pg_wal before failover.
 					 */
 					if (StandbyMode && CheckForStandbyTrigger())
 					{
@@ -11278,7 +11278,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 
 					/*
 					 * Not in standby mode, and we've now tried the archive
-					 * and pg_xlog.
+					 * and pg_wal.
 					 */
 					if (!StandbyMode)
 						return false;
@@ -11338,7 +11338,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					 * little chance that the problem will just go away, but
 					 * PANIC is not good for availability either, especially
 					 * in hot standby mode. So, we treat that the same as
-					 * disconnection, and retry from archive/pg_xlog again.
+					 * disconnection, and retry from archive/pg_wal again.
 					 * The WAL in the archive should be identical to what was
 					 * streamed, so it's unlikely that it helps, but one can
 					 * hope...
@@ -11399,11 +11399,11 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					elog(ERROR, "unexpected WAL source %d", currentSource);
 			}
 		}
-		else if (currentSource == XLOG_FROM_PG_XLOG)
+		else if (currentSource == XLOG_FROM_PG_WAL)
 		{
 			/*
-			 * We just successfully read a file in pg_xlog. We prefer files in
-			 * the archive over ones in pg_xlog, so try the next file again
+			 * We just successfully read a file in pg_wal. We prefer files in
+			 * the archive over ones in pg_wal, so try the next file again
 			 * from the archive first.
 			 */
 			if (InArchiveRecovery)
@@ -11424,7 +11424,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 		switch (currentSource)
 		{
 			case XLOG_FROM_ARCHIVE:
-			case XLOG_FROM_PG_XLOG:
+			case XLOG_FROM_PG_WAL:
 				/* Close any old file we might have open. */
 				if (readFile >= 0)
 				{
@@ -11437,7 +11437,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 
 				/*
 				 * Try to restore the file from archive, or read an existing
-				 * file from pg_xlog.
+				 * file from pg_wal.
 				 */
 				readFile = XLogFileReadAnyTLI(readSegNo, DEBUG2,
 						 currentSource == XLOG_FROM_ARCHIVE ? XLOG_FROM_ANY :
@@ -11446,7 +11446,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					return true;	/* success! */
 
 				/*
-				 * Nope, not found in archive or pg_xlog.
+				 * Nope, not found in archive or pg_wal.
 				 */
 				lastSourceFailed = true;
 				break;
@@ -11502,7 +11502,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 						 * not open already.  Also read the timeline history
 						 * file if we haven't initialized timeline history
 						 * yet; it should be streamed over and present in
-						 * pg_xlog by now.  Use XLOG_FROM_STREAM so that
+						 * pg_wal by now.  Use XLOG_FROM_STREAM so that
 						 * source info is set correctly and XLogReceiptTime
 						 * isn't changed.
 						 */
@@ -11534,10 +11534,10 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 						/*
 						 * Note that we don't "return false" immediately here.
 						 * After being triggered, we still want to replay all
-						 * the WAL that was already streamed. It's in pg_xlog
+						 * the WAL that was already streamed. It's in pg_wal
 						 * now, so we just treat this as a failure, and the
 						 * state machine will move on to replay the streamed
-						 * WAL from pg_xlog, and then recheck the trigger and
+						 * WAL from pg_wal, and then recheck the trigger and
 						 * exit replay.
 						 */
 						lastSourceFailed = true;
@@ -11577,7 +11577,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
  * or legitimate end-of-WAL situation.   Generally, we use it as-is, but if
  * we're retrying the exact same record that we've tried previously, only
  * complain the first time to keep the noise down.  However, we only do when
- * reading from pg_xlog, because we don't expect any invalid records in archive
+ * reading from pg_wal, because we don't expect any invalid records in archive
  * or in records streamed from master. Files in the archive should be complete,
  * and we should never hit the end of WAL because we stop and wait for more WAL
  * to arrive before replaying it.
@@ -11592,7 +11592,7 @@ emode_for_corrupt_record(int emode, XLogRecPtr RecPtr)
 {
 	static XLogRecPtr lastComplaint = 0;
 
-	if (readSource == XLOG_FROM_PG_XLOG && emode == LOG)
+	if (readSource == XLOG_FROM_PG_WAL && emode == LOG)
 	{
 		if (RecPtr == lastComplaint)
 			emode = DEBUG1;
diff --git a/src/backend/access/transam/xlogarchive.c b/src/backend/access/transam/xlogarchive.c
index d153a44..b919164 100644
--- a/src/backend/access/transam/xlogarchive.c
+++ b/src/backend/access/transam/xlogarchive.c
@@ -421,7 +421,7 @@ ExecuteRecoveryCommand(char *command, char *commandName, bool failOnSignal)
 /*
  * A file was restored from the archive under a temporary filename (path),
  * and now we want to keep it. Rename it under the permanent filename in
- * in pg_xlog (xlogfname), replacing any existing file with the same name.
+ * in pg_wal (xlogfname), replacing any existing file with the same name.
  */
 void
 KeepFileRestoredFromArchive(char *path, char *xlogfname)
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 33383b4..01cbd90 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -128,7 +128,7 @@ pg_start_backup(PG_FUNCTION_ARGS)
  * pg_stop_backup: finish taking an on-line backup dump
  *
  * We write an end-of-backup WAL record, and remove the backup label file
- * created by pg_start_backup, creating a backup history file in pg_xlog
+ * created by pg_start_backup, creating a backup history file in pg_wal
  * instead (whence it will immediately be archived). The backup history file
  * contains the same info found in the label file, plus the backup-end time
  * and WAL location. Before 9.0, the backup-end time was read from the backup
diff --git a/src/backend/replication/README b/src/backend/replication/README
index ad4864d..0cbb990 100644
--- a/src/backend/replication/README
+++ b/src/backend/replication/README
@@ -54,7 +54,7 @@ and WalRcvData->slotname, and initializes the starting point in
 WalRcvData->receiveStart.
 
 As walreceiver receives WAL from the master server, and writes and flushes
-it to disk (in pg_xlog), it updates WalRcvData->receivedUpto and signals
+it to disk (in pg_wal), it updates WalRcvData->receivedUpto and signals
 the startup process to know how far WAL replay can advance.
 
 Walreceiver sends information about replication progress to the master server
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 1eabaef..6dd47ce 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -346,7 +346,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		TimeLineID	tli;
 
 		/*
-		 * I'd rather not worry about timelines here, so scan pg_xlog and
+		 * I'd rather not worry about timelines here, so scan pg_wal and
 		 * include all WAL files in the range between 'startptr' and 'endptr',
 		 * regardless of the timeline the file is stamped with. If there are
 		 * some spurious WAL files belonging to timelines that don't belong in
@@ -359,11 +359,11 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		XLByteToPrevSeg(endptr, endsegno);
 		XLogFileName(lastoff, ThisTimeLineID, endsegno);
 
-		dir = AllocateDir("pg_xlog");
+		dir = AllocateDir("pg_wal");
 		if (!dir)
 			ereport(ERROR,
-				 (errmsg("could not open directory \"%s\": %m", "pg_xlog")));
-		while ((de = ReadDir(dir, "pg_xlog")) != NULL)
+				 (errmsg("could not open directory \"%s\": %m", "pg_wal")));
+		while ((de = ReadDir(dir, "pg_wal")) != NULL)
 		{
 			/* Does it look like a WAL segment, and is it in the range? */
 			if (IsXLogFileName(de->d_name) &&
@@ -401,7 +401,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		qsort(walFiles, nWalFiles, sizeof(char *), compareWalFileNames);
 
 		/*
-		 * There must be at least one xlog file in the pg_xlog directory,
+		 * There must be at least one xlog file in the pg_wal directory,
 		 * since we are doing backup-including-xlog.
 		 */
 		if (nWalFiles < 1)
@@ -1054,23 +1054,23 @@ sendDir(char *path, int basepathlen, bool sizeonly, List *tablespaces,
 		}
 
 		/*
-		 * We can skip pg_xlog, the WAL segments need to be fetched from the
+		 * We can skip pg_wal, the WAL segments need to be fetched from the
 		 * WAL archive anyway. But include it as an empty directory anyway, so
 		 * we get permissions right.
 		 */
-		if (strcmp(pathbuf, "./pg_xlog") == 0)
+		if (strcmp(pathbuf, "./pg_wal") == 0)
 		{
-			/* If pg_xlog is a symlink, write it as a directory anyway */
+			/* If pg_wal is a symlink, write it as a directory anyway */
 			size += _tarWriteDir(pathbuf, basepathlen, &statbuf, sizeonly);
 
 			/*
 			 * Also send archive_status directory (by hackishly reusing
 			 * statbuf from above ...).
 			 */
-			size += _tarWriteHeader("./pg_xlog/archive_status", NULL, &statbuf,
+			size += _tarWriteHeader("./pg_wal/archive_status", NULL, &statbuf,
 									sizeonly);
 
-			continue;			/* don't recurse into pg_xlog */
+			continue;			/* don't recurse into pg_wal */
 		}
 
 		/* Allow symbolic links in pg_tblspc only */
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 413ee3a..d40b5e9 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -18,7 +18,7 @@
  * If the primary server ends streaming, but doesn't disconnect, walreceiver
  * goes into "waiting" mode, and waits for the startup process to give new
  * instructions. The startup process will treat that the same as
- * disconnection, and will rescan the archive/pg_xlog directory. But when the
+ * disconnection, and will rescan the archive/pg_wal directory. But when the
  * startup process wants to try streaming replication again, it will just
  * nudge the existing walreceiver process that's waiting, instead of launching
  * a new one.
@@ -364,7 +364,7 @@ WalReceiverMain(void)
 		 * we've already reached the end of the old timeline, the server will
 		 * finish the streaming immediately, and we will go back to await
 		 * orders from the startup process. If recovery_target_timeline is
-		 * 'latest', the startup process will scan pg_xlog and find the new
+		 * 'latest', the startup process will scan pg_wal and find the new
 		 * history file, bump recovery target timeline, and ask us to restart
 		 * on the new timeline.
 		 */
@@ -739,7 +739,7 @@ WalRcvFetchTimeLineHistoryFiles(TimeLineID first, TimeLineID last)
 										 tli)));
 
 			/*
-			 * Write the file to pg_xlog.
+			 * Write the file to pg_wal.
 			 */
 			writeTimeLineHistoryFile(tli, content, len);
 
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index c7743da..dcbb289 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -586,7 +586,7 @@ StartReplication(StartReplicationCmd *cmd)
 			 * segment that contains switchpoint, but on the new timeline, so
 			 * that it doesn't end up with a partial segment. If you ask for a
 			 * too old starting point, you'll get an error later when we fail
-			 * to find the requested WAL segment in pg_xlog.
+			 * to find the requested WAL segment in pg_wal.
 			 *
 			 * XXX: we could be more strict here and only allow a startpoint
 			 * that's older than the switchpoint, if it's still in the same
@@ -2055,7 +2055,7 @@ retry:
 			 *
 			 * For example, imagine that this server is currently on timeline
 			 * 5, and we're streaming timeline 4. The switch from timeline 4
-			 * to 5 happened at 0/13002088. In pg_xlog, we have these files:
+			 * to 5 happened at 0/13002088. In pg_wal, we have these files:
 			 *
 			 * ...
 			 * 000000040000000000000012
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 03143f1..b7ff5ef 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -2787,7 +2787,7 @@ looks_like_temp_rel_name(const char *name)
  * Issue fsync recursively on PGDATA and all its contents.
  *
  * We fsync regular files and directories wherever they are, but we
- * follow symlinks only for pg_xlog and immediately under pg_tblspc.
+ * follow symlinks only for pg_wal and immediately under pg_tblspc.
  * Other symlinks are presumed to point at files we're not responsible
  * for fsyncing, and might not have privileges to write at all.
  *
@@ -2811,7 +2811,7 @@ SyncDataDirectory(void)
 		return;
 
 	/*
-	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * If pg_wal is a symlink, we'll need to recurse into it separately,
 	 * because the first walkdir below will ignore it.
 	 */
 	xlog_is_symlink = false;
@@ -2820,16 +2820,16 @@ SyncDataDirectory(void)
 	{
 		struct stat st;
 
-		if (lstat("pg_xlog", &st) < 0)
+		if (lstat("pg_wal", &st) < 0)
 			ereport(LOG,
 					(errcode_for_file_access(),
 					 errmsg("could not stat file \"%s\": %m",
-							"pg_xlog")));
+							"pg_wal")));
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
 #else
-	if (pgwin32_is_junction("pg_xlog"))
+	if (pgwin32_is_junction("pg_wal"))
 		xlog_is_symlink = true;
 #endif
 
@@ -2841,7 +2841,7 @@ SyncDataDirectory(void)
 #ifdef PG_FLUSH_DATA_WORKS
 	walkdir(".", pre_sync_fname, false, DEBUG1);
 	if (xlog_is_symlink)
-		walkdir("pg_xlog", pre_sync_fname, false, DEBUG1);
+		walkdir("pg_wal", pre_sync_fname, false, DEBUG1);
 	walkdir("pg_tblspc", pre_sync_fname, true, DEBUG1);
 #endif
 
@@ -2849,14 +2849,14 @@ SyncDataDirectory(void)
 	 * Now we do the fsync()s in the same order.
 	 *
 	 * The main call ignores symlinks, so in addition to specially processing
-	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * pg_wal if it's a symlink, pg_tblspc has to be visited separately with
 	 * process_symlinks = true.  Note that if there are any plain directories
 	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
 	 * so we don't worry about optimizing it.
 	 */
 	walkdir(".", datadir_fsync_fname, false, LOG);
 	if (xlog_is_symlink)
-		walkdir("pg_xlog", datadir_fsync_fname, false, LOG);
+		walkdir("pg_wal", datadir_fsync_fname, false, LOG);
 	walkdir("pg_tblspc", datadir_fsync_fname, true, LOG);
 }
 
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index e52e67d..385e808 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -195,7 +195,7 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 
 static const char *const subdirs[] = {
 	"global",
-	"pg_xlog/archive_status",
+	"pg_wal/archive_status",
 	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
@@ -2091,8 +2091,6 @@ make_postgres(FILE *cmdfd)
 		PG_CMD_PUTS(*line);
 }
 
-
-
 /*
  * signal handler in case we are interrupted.
  *
@@ -2830,7 +2828,7 @@ create_xlog_or_symlink(void)
 	char	   *subdirloc;
 
 	/* form name of the place for the subdirectory or symlink */
-	subdirloc = psprintf("%s/pg_xlog", pg_data);
+	subdirloc = psprintf("%s/pg_wal", pg_data);
 
 	if (strcmp(xlog_dir, "") != 0)
 	{
@@ -2963,7 +2961,7 @@ initialize_data_directory(void)
 
 	create_xlog_or_symlink();
 
-	/* Create required subdirectories (other than pg_xlog) */
+	/* Create required subdirectories (other than pg_wal) */
 	printf(_("creating subdirectories ... "));
 	fflush(stdout);
 
@@ -3258,7 +3256,7 @@ main(int argc, char *argv[])
 
 		fputs(_("syncing data to disk ... "), stdout);
 		fflush(stdout);
-		fsync_pgdata(pg_data, progname);
+		fsync_pgdata(pg_data, progname, PG_VERSION_NUM);
 		check_ok();
 		return 0;
 	}
@@ -3324,7 +3322,7 @@ main(int argc, char *argv[])
 	{
 		fputs(_("syncing data to disk ... "), stdout);
 		fflush(stdout);
-		fsync_pgdata(pg_data, progname);
+		fsync_pgdata(pg_data, progname, PG_VERSION_NUM);
 		check_ok();
 	}
 	else
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 0f5d9d6..6b2a01f 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -55,6 +55,12 @@ typedef struct TablespaceList
 	TablespaceListCell *tail;
 } TablespaceList;
 
+/*
+ * pg_xlog has been renamed to pg_wal in version 10.  This version number
+ * should be compared with PQserverVersion().
+ */
+#define MINIMUM_VERSION_FOR_PG_WAL	100000
+
 /* Global options */
 static char *basedir = NULL;
 static TablespaceList tablespace_dirs = {NULL, NULL};
@@ -526,15 +532,22 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 		/* Error message already written in GetConnection() */
 		exit(1);
 
-	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/pg_xlog", basedir);
+	/* In post-10 cluster, pg_xlog has been renamed to pg_wal */
+	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/%s",
+			 basedir,
+			 PQserverVersion(conn) < MINIMUM_VERSION_FOR_PG_WAL ?
+				"pg_xlog" : "pg_wal");
 
 	/*
-	 * Create pg_xlog/archive_status (and thus pg_xlog) so we can write to
-	 * basedir/pg_xlog as the directory entry in the tar file may arrive
-	 * later.
+	 * Create pg_wal/archive_status or pg_xlog/archive_status (and thus
+	 * pg_wal or pg_xlog) depending on the target server so we can write to
+	 * basedir/pg_wal or basedir/pg_xlog as the directory entry in the tar
+	 * file may arrive later.
 	 */
-	snprintf(statusdir, sizeof(statusdir), "%s/pg_xlog/archive_status",
-			 basedir);
+	snprintf(statusdir, sizeof(statusdir), "%s/%s/archive_status",
+			 basedir,
+			 PQserverVersion(conn) < MINIMUM_VERSION_FOR_PG_WAL ?
+				"pg_xlog" : "pg_wal");
 
 	if (pg_mkdir_p(statusdir, S_IRWXU) != 0 && errno != EEXIST)
 	{
@@ -1338,15 +1351,17 @@ ReceiveAndUnpackTarFile(PGconn *conn, PGresult *res, int rownum)
 					if (mkdir(filename, S_IRWXU) != 0)
 					{
 						/*
-						 * When streaming WAL, pg_xlog will have been created
-						 * by the wal receiver process. Also, when transaction
-						 * log directory location was specified, pg_xlog has
-						 * already been created as a symbolic link before
-						 * starting the actual backup. So just ignore creation
-						 * failures on related directories.
+						 * When streaming WAL, pg_wal (or pg_xlog for pre-9.6
+						 * clusters) will have been created by the wal receiver
+						 * process. Also, when transaction log directory location
+						 * was specified, pg_wal (or pg_xlog) has already been
+						 * created as a symbolic link before starting the actual
+						 * backup. So just ignore creation failures on related
+						 * directories.
 						 */
-						if (!((pg_str_endswith(filename, "/pg_xlog") ||
-							 pg_str_endswith(filename, "/archive_status")) &&
+						if (!((pg_str_endswith(filename, "/pg_wal") ||
+							   pg_str_endswith(filename, "/pg_xlog")||
+							   pg_str_endswith(filename, "/archive_status")) &&
 							  errno == EEXIST))
 						{
 							fprintf(stderr,
@@ -1634,15 +1649,10 @@ BaseBackup(void)
 	char		xlogend[64];
 	int			minServerMajor,
 				maxServerMajor;
-	int			serverMajor;
+	int			serverVersion,
+				serverMajor;
 
-	/*
-	 * Connect in replication mode to the server
-	 */
-	conn = GetConnection();
-	if (!conn)
-		/* Error message already written in GetConnection() */
-		exit(1);
+	Assert(conn != NULL);
 
 	/*
 	 * Check server version. BASE_BACKUP command was introduced in 9.1, so we
@@ -1650,7 +1660,8 @@ BaseBackup(void)
 	 */
 	minServerMajor = 901;
 	maxServerMajor = PG_VERSION_NUM / 100;
-	serverMajor = PQserverVersion(conn) / 100;
+	serverVersion = PQserverVersion(conn);
+	serverMajor = serverVersion / 100;
 	if (serverMajor < minServerMajor || serverMajor > maxServerMajor)
 	{
 		const char *serverver = PQparameterStatus(conn, "server_version");
@@ -1979,7 +1990,7 @@ BaseBackup(void)
 		}
 		else
 		{
-			(void) fsync_pgdata(basedir, progname);
+			(void) fsync_pgdata(basedir, progname, serverVersion);
 		}
 	}
 
@@ -2296,6 +2307,14 @@ main(int argc, char **argv)
 	if (format == 'p' || strcmp(basedir, "-") != 0)
 		verify_dir_is_empty_or_create(basedir, &made_new_pgdata, &found_existing_pgdata);
 
+	/* connection in replication mode to server */
+	conn = GetConnection();
+	if (!conn)
+	{
+		/* Error message already written in GetConnection() */
+		exit(1);
+	}
+
 	/* Create transaction log symlink, if required */
 	if (strcmp(xlog_dir, "") != 0)
 	{
@@ -2303,19 +2322,24 @@ main(int argc, char **argv)
 
 		verify_dir_is_empty_or_create(xlog_dir, &made_new_xlogdir, &found_existing_xlogdir);
 
-		/* form name of the place where the symlink must go */
-		linkloc = psprintf("%s/pg_xlog", basedir);
+		/*
+		 * Form name of the place where the symlink must go. pg_xlog has
+		 * been renamed to pg_wal in post-10 clusters.
+		 */
+		linkloc = psprintf("%s/%s", basedir,
+						   PQserverVersion(conn) < MINIMUM_VERSION_FOR_PG_WAL ?
+								"pg_xlog" : "pg_wal");
 
 #ifdef HAVE_SYMLINK
 		if (symlink(xlog_dir, linkloc) != 0)
 		{
 			fprintf(stderr, _("%s: could not create symbolic link \"%s\": %s\n"),
 					progname, linkloc, strerror(errno));
-			exit(1);
+			disconnect_and_exit(1);
 		}
 #else
 		fprintf(stderr, _("%s: symlinks are not supported on this platform\n"));
-		exit(1);
+		disconnect_and_exit(1);
 #endif
 		free(linkloc);
 	}
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index a52bd4e..c8abbeb 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -67,9 +67,9 @@ $node->command_ok([ 'pg_basebackup', '-D', "$tempdir/backup" ],
 	'pg_basebackup runs');
 ok(-f "$tempdir/backup/PG_VERSION", 'backup was created');
 
-# Only archive_status directory should be copied in pg_xlog/.
+# Only archive_status directory should be copied in pg_wal/.
 is_deeply(
-	[ sort(slurp_dir("$tempdir/backup/pg_xlog/")) ],
+	[ sort(slurp_dir("$tempdir/backup/pg_wal/")) ],
 	[ sort qw(. .. archive_status) ],
 	'no WAL files copied');
 
@@ -230,12 +230,12 @@ like(
 $node->command_ok(
 	[ 'pg_basebackup', '-D', "$tempdir/backupxf", '-X', 'fetch' ],
 	'pg_basebackup -X fetch runs');
-ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_xlog")),
+ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_wal")),
 	'WAL files copied');
 $node->command_ok(
 	[ 'pg_basebackup', '-D', "$tempdir/backupxs", '-X', 'stream' ],
 	'pg_basebackup -X stream runs');
-ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_xlog")),
+ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_wal")),
 	'WAL files copied');
 
 $node->command_fails(
diff --git a/src/bin/pg_resetxlog/pg_resetxlog.c b/src/bin/pg_resetxlog/pg_resetxlog.c
index 525b82ba..2b76f64 100644
--- a/src/bin/pg_resetxlog/pg_resetxlog.c
+++ b/src/bin/pg_resetxlog/pg_resetxlog.c
@@ -890,7 +890,7 @@ FindEndOfXLOG(void)
 	newXlogSegNo = ControlFile.checkPointCopy.redo / ControlFile.xlog_seg_size;
 
 	/*
-	 * Scan the pg_xlog directory to find existing WAL segment files. We
+	 * Scan the pg_wal directory to find existing WAL segment files. We
 	 * assume any present have been used; in most scenarios this should be
 	 * conservative, because of xlog.c's attempts to pre-create files.
 	 */
diff --git a/src/bin/pg_rewind/copy_fetch.c b/src/bin/pg_rewind/copy_fetch.c
index 327e7ef..d0c1586 100644
--- a/src/bin/pg_rewind/copy_fetch.c
+++ b/src/bin/pg_rewind/copy_fetch.c
@@ -131,10 +131,10 @@ recurse_dir(const char *datadir, const char *parentpath,
 			/*
 			 * If it's a symlink within pg_tblspc, we need to recurse into it,
 			 * to process all the tablespaces.  We also follow a symlink if
-			 * it's for pg_xlog.  Symlinks elsewhere are ignored.
+			 * it's for pg_wal.  Symlinks elsewhere are ignored.
 			 */
 			if ((parentpath && strcmp(parentpath, "pg_tblspc") == 0) ||
-				strcmp(path, "pg_xlog") == 0)
+				strcmp(path, "pg_wal") == 0)
 				recurse_dir(datadir, path, callback);
 #else
 			pg_fatal("\"%s\" is a symbolic link, but symbolic links are not supported on this platform\n",
diff --git a/src/bin/pg_rewind/filemap.c b/src/bin/pg_rewind/filemap.c
index 9b00dc1..3905a5d 100644
--- a/src/bin/pg_rewind/filemap.c
+++ b/src/bin/pg_rewind/filemap.c
@@ -79,11 +79,11 @@ process_source_file(const char *path, file_type_t type, size_t newsize,
 		return;
 
 	/*
-	 * Pretend that pg_xlog is a directory, even if it's really a symlink. We
+	 * Pretend that pg_wal is a directory, even if it's really a symlink. We
 	 * don't want to mess with the symlink itself, nor complain if it's a
 	 * symlink in source but not in target or vice versa.
 	 */
-	if (strcmp(path, "pg_xlog") == 0 && type == FILE_TYPE_SYMLINK)
+	if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK)
 		type = FILE_TYPE_DIRECTORY;
 
 	/*
@@ -120,7 +120,7 @@ process_source_file(const char *path, file_type_t type, size_t newsize,
 	switch (type)
 	{
 		case FILE_TYPE_DIRECTORY:
-			if (exists && !S_ISDIR(statbuf.st_mode) && strcmp(path, "pg_xlog") != 0)
+			if (exists && !S_ISDIR(statbuf.st_mode) && strcmp(path, "pg_wal") != 0)
 			{
 				/* it's a directory in source, but not in target. Strange.. */
 				pg_fatal("\"%s\" is not a directory\n", localpath);
@@ -296,7 +296,7 @@ process_target_file(const char *path, file_type_t type, size_t oldsize,
 	/*
 	 * Like in process_source_file, pretend that xlog is always a  directory.
 	 */
-	if (strcmp(path, "pg_xlog") == 0 && type == FILE_TYPE_SYMLINK)
+	if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK)
 		type = FILE_TYPE_DIRECTORY;
 
 	key.path = (char *) path;
diff --git a/src/bin/pg_rewind/parsexlog.c b/src/bin/pg_rewind/parsexlog.c
index b53591d..23ac4e7 100644
--- a/src/bin/pg_rewind/parsexlog.c
+++ b/src/bin/pg_rewind/parsexlog.c
@@ -54,7 +54,7 @@ static int SimpleXLogPageRead(XLogReaderState *xlogreader,
 				   TimeLineID *pageTLI);
 
 /*
- * Read WAL from the datadir/pg_xlog, starting from 'startpoint' on timeline
+ * Read WAL from the datadir/pg_wal, starting from 'startpoint' on timeline
  * index 'tliIndex' in target timeline history, until 'endpoint'. Make note of
  * the data blocks touched by the WAL records, and return them in a page map.
  */
diff --git a/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl b/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
index bdcab56..12950ea 100644
--- a/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
+++ b/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
@@ -1,5 +1,5 @@
 #
-# Test pg_rewind when the target's pg_xlog directory is a symlink.
+# Test pg_rewind when the target's pg_wal directory is a symlink.
 #
 use strict;
 use warnings;
@@ -30,10 +30,10 @@ sub run_test
 
 	my $test_master_datadir = $node_master->data_dir;
 
-	# turn pg_xlog into a symlink
-	print("moving $test_master_datadir/pg_xlog to $master_xlogdir\n");
-	move("$test_master_datadir/pg_xlog", $master_xlogdir) or die;
-	symlink($master_xlogdir, "$test_master_datadir/pg_xlog") or die;
+	# turn pg_wal into a symlink
+	print("moving $test_master_datadir/pg_wal to $master_xlogdir\n");
+	move("$test_master_datadir/pg_wal", $master_xlogdir) or die;
+	symlink($master_xlogdir, "$test_master_datadir/pg_wal") or die;
 
 	RewindTest::start_master();
 
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 6d04e56..55a6f0d 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -14,7 +14,7 @@
 #include <fcntl.h>
 #include <sys/types.h>
 
-static void check_data_dir(const char *pg_data);
+static void check_data_dir(ClusterInfo *cluster);
 static void check_bin_dir(ClusterInfo *cluster);
 static void validate_exec(const char *dir, const char *cmdName);
 
@@ -220,9 +220,9 @@ verify_directories(void)
 		pg_fatal("You must have read and write access in the current directory.\n");
 
 	check_bin_dir(&old_cluster);
-	check_data_dir(old_cluster.pgdata);
+	check_data_dir(&old_cluster);
 	check_bin_dir(&new_cluster);
-	check_data_dir(new_cluster.pgdata);
+	check_data_dir(&new_cluster);
 }
 
 
@@ -253,6 +253,32 @@ win32_check_directory_write_permissions(void)
 
 
 /*
+ * check_single_dir()
+ *
+ *  Check for the presence of a single directory in PGDATA, and fail if
+ * is it missing or not accessible.
+ */
+static void
+check_single_dir(const char *pg_data, const char *subdir)
+{
+	struct stat statBuf;
+	char		subDirName[MAXPGPATH];
+
+	snprintf(subDirName, sizeof(subDirName), "%s%s%s", pg_data,
+			 /* Win32 can't stat() a directory with a trailing slash. */
+			 *subdir ? "/" : "",
+			 subdir);
+
+	if (stat(subDirName, &statBuf) != 0)
+		report_status(PG_FATAL, "check for \"%s\" failed: %s\n",
+					  subDirName, strerror(errno));
+	else if (!S_ISDIR(statBuf.st_mode))
+		report_status(PG_FATAL, "%s is not a directory\n",
+					  subDirName);
+}
+
+
+/*
  * check_data_dir()
  *
  *	This function validates the given cluster directory - we search for a
@@ -262,34 +288,27 @@ win32_check_directory_write_permissions(void)
  *
  */
 static void
-check_data_dir(const char *pg_data)
+check_data_dir(ClusterInfo *cluster)
 {
-	char		subDirName[MAXPGPATH];
-	int			subdirnum;
-
-	/* start check with top-most directory */
-	const char *requiredSubdirs[] = {"", "base", "global", "pg_clog",
-		"pg_multixact", "pg_subtrans", "pg_tblspc", "pg_twophase",
-	"pg_xlog"};
-
-	for (subdirnum = 0;
-		 subdirnum < sizeof(requiredSubdirs) / sizeof(requiredSubdirs[0]);
-		 ++subdirnum)
-	{
-		struct stat statBuf;
-
-		snprintf(subDirName, sizeof(subDirName), "%s%s%s", pg_data,
-		/* Win32 can't stat() a directory with a trailing slash. */
-				 *requiredSubdirs[subdirnum] ? "/" : "",
-				 requiredSubdirs[subdirnum]);
-
-		if (stat(subDirName, &statBuf) != 0)
-			report_status(PG_FATAL, "check for \"%s\" failed: %s\n",
-						  subDirName, strerror(errno));
-		else if (!S_ISDIR(statBuf.st_mode))
-			report_status(PG_FATAL, "%s is not a directory\n",
-						  subDirName);
-	}
+	const char *pg_data = cluster->pgdata;
+
+	/* get old and new cluster versions */
+	old_cluster.major_version = get_major_server_version(&old_cluster);
+	new_cluster.major_version = get_major_server_version(&new_cluster);
+
+	check_single_dir(pg_data, "");
+	check_single_dir(pg_data, "base");
+	check_single_dir(pg_data, "global");
+	check_single_dir(pg_data, "pg_multixact");
+	check_single_dir(pg_data, "pg_subtrans");
+	check_single_dir(pg_data, "pg_tblspc");
+	check_single_dir(pg_data, "pg_twophase");
+
+	/* pg_xlog has been renamed to pg_wal in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_xlog");
+	else
+		check_single_dir(pg_data, "pg_wal");
 }
 
 
diff --git a/src/bin/pg_xlogdump/pg_xlogdump.c b/src/bin/pg_xlogdump/pg_xlogdump.c
index 9ad9321..7490398 100644
--- a/src/bin/pg_xlogdump/pg_xlogdump.c
+++ b/src/bin/pg_xlogdump/pg_xlogdump.c
@@ -680,7 +680,7 @@ usage(void)
 	printf("  -f, --follow           keep retrying after reaching end of WAL\n");
 	printf("  -n, --limit=N          number of records to display\n");
 	printf("  -p, --path=PATH        directory in which to find log segment files\n");
-	printf("                         (default: ./pg_xlog)\n");
+	printf("                         (default: ./pg_wal)\n");
 	printf("  -r, --rmgr=RMGR        only show records generated by resource manager RMGR\n");
 	printf("                         use --rmgr=list to list valid resource manager names\n");
 	printf("  -s, --start=RECPTR     start reading at log position RECPTR\n");
diff --git a/src/common/file_utils.c b/src/common/file_utils.c
index 1855e23..2fdb469 100644
--- a/src/common/file_utils.c
+++ b/src/common/file_utils.c
@@ -29,6 +29,11 @@
 #define PG_FLUSH_DATA_WORKS 1
 #endif
 
+/*
+ * pg_xlog has been renamed to pg_wal in version 10.
+ */
+#define MINIMUM_VERSION_FOR_PG_WAL  100000
+
 #ifdef PG_FLUSH_DATA_WORKS
 static int pre_sync_fname(const char *fname, bool isdir,
 						   const char *progname);
@@ -40,25 +45,31 @@ static void walkdir(const char *path,
 /*
  * Issue fsync recursively on PGDATA and all its contents.
  *
- * We fsync regular files and directories wherever they are, but we
- * follow symlinks only for pg_xlog and immediately under pg_tblspc.
- * Other symlinks are presumed to point at files we're not responsible
- * for fsyncing, and might not have privileges to write at all.
+ * We fsync regular files and directories wherever they are, but we follow
+ * symlinks only for pg_wal (or pg_xlog) and immediately under pg_tblspc.
+ * Other symlinks are presumed to point at files we're not responsible for
+ * fsyncing, and might not have privileges to write at all.
+ *
+ * serverVersion indicates the version of the server to be fsync'd.
  *
  * Errors are reported but not considered fatal.
  */
 void
-fsync_pgdata(const char *pg_data, const char *progname)
+fsync_pgdata(const char *pg_data,
+			 const char *progname,
+			 int serverVersion)
 {
 	bool		xlog_is_symlink;
-	char		pg_xlog[MAXPGPATH];
+	char		pg_wal[MAXPGPATH];
 	char		pg_tblspc[MAXPGPATH];
 
-	snprintf(pg_xlog, MAXPGPATH, "%s/pg_xlog", pg_data);
+	/* handle renaming of pg_xlog to pg_wal in post-10 clusters */
+	snprintf(pg_wal, MAXPGPATH, "%s/%s", pg_data,
+		serverVersion < MINIMUM_VERSION_FOR_PG_WAL ? "pg_xlog" : "pg_wal");
 	snprintf(pg_tblspc, MAXPGPATH, "%s/pg_tblspc", pg_data);
 
 	/*
-	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * If pg_wal is a symlink, we'll need to recurse into it separately,
 	 * because the first walkdir below will ignore it.
 	 */
 	xlog_is_symlink = false;
@@ -67,14 +78,14 @@ fsync_pgdata(const char *pg_data, const char *progname)
 	{
 		struct stat st;
 
-		if (lstat(pg_xlog, &st) < 0)
+		if (lstat(pg_wal, &st) < 0)
 			fprintf(stderr, _("%s: could not stat file \"%s\": %s\n"),
-					progname, pg_xlog, strerror(errno));
+					progname, pg_wal, strerror(errno));
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
 #else
-	if (pgwin32_is_junction(pg_xlog))
+	if (pgwin32_is_junction(pg_wal))
 		xlog_is_symlink = true;
 #endif
 
@@ -85,7 +96,7 @@ fsync_pgdata(const char *pg_data, const char *progname)
 #ifdef PG_FLUSH_DATA_WORKS
 	walkdir(pg_data, pre_sync_fname, false, progname);
 	if (xlog_is_symlink)
-		walkdir(pg_xlog, pre_sync_fname, false, progname);
+		walkdir(pg_wal, pre_sync_fname, false, progname);
 	walkdir(pg_tblspc, pre_sync_fname, true, progname);
 #endif
 
@@ -93,14 +104,14 @@ fsync_pgdata(const char *pg_data, const char *progname)
 	 * Now we do the fsync()s in the same order.
 	 *
 	 * The main call ignores symlinks, so in addition to specially processing
-	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * pg_wal if it's a symlink, pg_tblspc has to be visited separately with
 	 * process_symlinks = true.  Note that if there are any plain directories
 	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
 	 * so we don't worry about optimizing it.
 	 */
 	walkdir(pg_data, fsync_fname, false, progname);
 	if (xlog_is_symlink)
-		walkdir(pg_xlog, fsync_fname, false, progname);
+		walkdir(pg_wal, fsync_fname, false, progname);
 	walkdir(pg_tblspc, fsync_fname, true, progname);
 }
 
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 0a595cc..ceb0462 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -128,7 +128,7 @@ typedef XLogLongPageHeaderData *XLogLongPageHeader;
 /*
  * The XLog directory and control file (relative to $PGDATA)
  */
-#define XLOGDIR				"pg_xlog"
+#define XLOGDIR				"pg_wal"
 #define XLOG_CONTROL_FILE	"global/pg_control"
 
 /*
diff --git a/src/include/common/file_utils.h b/src/include/common/file_utils.h
index 1cb263d..b83c398 100644
--- a/src/include/common/file_utils.h
+++ b/src/include/common/file_utils.h
@@ -17,7 +17,8 @@
 
 extern int fsync_fname(const char *fname, bool isdir,
 					   const char *progname);
-extern void fsync_pgdata(const char *pg_data, const char *progname);
+extern void fsync_pgdata(const char *pg_data, const char *progname,
+						 int serverVersion);
 extern int durable_rename(const char *oldfile, const char *newfile,
 						  const char *progname);
 extern int fsync_parent_path(const char *fname, const char *progname);
diff --git a/src/include/postmaster/pgarch.h b/src/include/postmaster/pgarch.h
index f2cbfb3..6df73c9 100644
--- a/src/include/postmaster/pgarch.h
+++ b/src/include/postmaster/pgarch.h
@@ -16,7 +16,7 @@
 /* ----------
  * Archiver control info.
  *
- * We expect that archivable files within pg_xlog will have names between
+ * We expect that archivable files within pg_wal will have names between
  * MIN_XFN_CHARS and MAX_XFN_CHARS in length, consisting only of characters
  * appearing in VALID_XFN_CHARS.  The status files in archive_status have
  * corresponding names with ".ready" or ".done" appended.
-- 
2.10.0

From 0d30ef662a52b6b02496a6618c0457d6d6773992 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 4 Oct 2016 14:41:15 +0900
Subject: [PATCH 2/2] Rename pg_clog to pg_transaction

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml               |  6 +++---
 doc/src/sgml/catalogs.sgml             |  6 +++---
 doc/src/sgml/config.sgml               |  2 +-
 doc/src/sgml/func.sgml                 |  2 +-
 doc/src/sgml/maintenance.sgml          | 12 +++++------
 doc/src/sgml/ref/pg_resetxlog.sgml     |  6 +++---
 doc/src/sgml/ref/pg_rewind.sgml        |  2 +-
 doc/src/sgml/storage.sgml              | 10 ++++-----
 doc/src/sgml/wal.sgml                  |  2 +-
 src/backend/access/heap/heapam.c       | 10 ++++-----
 src/backend/access/transam/README      | 22 ++++++++++----------
 src/backend/access/transam/clog.c      |  2 +-
 src/backend/access/transam/commit_ts.c |  4 ++--
 src/backend/access/transam/multixact.c |  8 +++----
 src/backend/access/transam/subtrans.c  | 18 ++++++++--------
 src/backend/access/transam/transam.c   |  2 +-
 src/backend/access/transam/twophase.c  |  6 +++---
 src/backend/access/transam/xact.c      | 38 ++++++++++++++++++++--------------
 src/backend/access/transam/xlog.c      |  6 +++---
 src/backend/commands/vacuum.c          | 14 ++++++-------
 src/backend/postmaster/autovacuum.c    |  4 ++--
 src/backend/storage/buffer/README      |  4 ++--
 src/backend/storage/ipc/procarray.c    |  5 +++--
 src/backend/utils/time/tqual.c         | 29 +++++++++++++-------------
 src/bin/initdb/initdb.c                |  2 +-
 src/bin/pg_upgrade/exec.c              |  6 ++++++
 src/bin/pg_upgrade/pg_upgrade.c        | 30 ++++++++++++++++-----------
 src/include/access/slru.h              | 12 +++++------
 28 files changed, 145 insertions(+), 125 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 6eaed1e..eb4f962 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -382,10 +382,10 @@ tar -cf backup.tar /usr/local/pgsql/data
       directories. This will <emphasis>not</> work because the
       information contained in these files is not usable without
       the commit log files,
-      <filename>pg_clog/*</filename>, which contain the commit status of
-      all transactions. A table file is only usable with this
+      <filename>pg_transaction/*</filename>, which contain the commit status
+      of all transactions. A table file is only usable with this
       information. Of course it is also impossible to restore only a
-      table and the associated <filename>pg_clog</filename> data
+      table and the associated <filename>pg_transaction</filename> data
       because that would render all other tables in the database
       cluster useless.  So file system backups only work for complete
       backup and restoration of an entire database cluster.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 29738b0..77b395e 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1847,7 +1847,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this table.  This is used to track
        whether the table needs to be vacuumed in order to prevent transaction
-       ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
+       ID wraparound or to allow <literal>pg_transaction</> to be shrunk.  Zero
        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
       </entry>
      </row>
@@ -2514,8 +2514,8 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this database.  This is used to
        track whether the database needs to be vacuumed in order to prevent
-       transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
-       It is the minimum of the per-table
+       transaction ID wraparound or to allow <literal>pg_transaction</> to be
+       shrunk.  It is the minimum of the per-table
        <structname>pg_class</>.<structfield>relfrozenxid</> values.
       </entry>
      </row>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 1bb501c..b0b7215 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5822,7 +5822,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
 
        <para>
         Vacuum also allows removal of old files from the
-        <filename>pg_clog</> subdirectory, which is why the default
+        <filename>pg_transaction</> subdirectory, which is why the default
         is a relatively low 200 million transactions.
         This parameter can only be set at server start, but the setting
         can be reduced for individual tables by
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 2e64cc4..a9d2ec4 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15323,7 +15323,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  postmaster.pid  |  9
  pg_ident.conf   | 10
  global          | 11
- pg_clog         | 12
+ pg_transaction  | 12
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index f87f3e0..c741a9b 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -527,18 +527,18 @@
    <para>
     The sole disadvantage of increasing <varname>autovacuum_freeze_max_age</>
     (and <varname>vacuum_freeze_table_age</> along with it)
-    is that the <filename>pg_clog</> subdirectory of the database cluster
-    will take more space, because it must store the commit status of all
-    transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
+    is that the <filename>pg_transaction</> subdirectory of the database
+    cluster will take more space, because it must store the commit status of
+    all transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
     The commit status uses two bits per transaction, so if
     <varname>autovacuum_freeze_max_age</> is set to its maximum allowed
-    value of two billion, <filename>pg_clog</> can be expected to
+    value of two billion, <filename>pg_transaction</> can be expected to
     grow to about half a gigabyte.  If this is trivial compared to your
     total database size, setting <varname>autovacuum_freeze_max_age</> to
     its maximum allowed value is recommended.  Otherwise, set it depending
-    on what you are willing to allow for <filename>pg_clog</> storage.
+    on what you are willing to allow for <filename>pg_transaction</> storage.
     (The default, 200 million transactions, translates to about 50MB of
-    <filename>pg_clog</> storage.)
+    <filename>pg_transaction</> storage.)
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index c949c5e..67b048b 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -256,12 +256,12 @@ PostgreSQL documentation
 
      <para>
       A safe value can be determined by looking for the numerically largest
-      file name in the directory <filename>pg_clog</> under the data directory,
-      adding one,
+      file name in the directory <filename>pg_transaction</> under the data
+      directory, adding one,
       and then multiplying by 1048576 (0x100000).  Note that the file names are in
       hexadecimal.  It is usually easiest to specify the option value in
       hexadecimal too. For example, if <filename>0011</> is the largest entry
-      in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
+      in <filename>pg_transaction</>, <literal>-x 0x1200000</> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 371c4a4..34ef4f1 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -229,7 +229,7 @@ PostgreSQL documentation
     </step>
     <step>
      <para>
-      Copy all other files such as <filename>pg_clog</filename> and
+      Copy all other files such as <filename>pg_transaction</filename> and
       configuration files from the source cluster to the target cluster
       (everything except the relation files).
      </para>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index fddb69b..61d15d4 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -72,11 +72,6 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_clog</></entry>
- <entry>Subdirectory containing transaction commit status data</entry>
-</row>
-
-<row>
  <entry><filename>pg_dynshmem</></entry>
  <entry>Subdirectory containing files used by the dynamic shared memory
   subsystem</entry>
@@ -136,6 +131,11 @@ Item
 </row>
 
 <row>
+ <entry><filename>pg_transaction</></entry>
+ <entry>Subdirectory containing transaction commit status data</entry>
+</row>
+
+<row>
  <entry><filename>pg_twophase</></entry>
  <entry>Subdirectory containing state files for prepared transactions</entry>
 </row>
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 346aa76..aac0a8d 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_clog</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_transaction</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index b019bc1..075d06a 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -6762,11 +6762,11 @@ heap_prepare_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
  * Note: it might seem we could make the changes without exclusive lock, since
  * TransactionId read/write is assumed atomic anyway.  However there is a race
  * condition: someone who just fetched an old XID that we overwrite here could
- * conceivably not finish checking the XID against pg_clog before we finish
- * the VACUUM and perhaps truncate off the part of pg_clog he needs.  Getting
- * exclusive lock ensures no other backend is in process of checking the
- * tuple status.  Also, getting exclusive lock makes it safe to adjust the
- * infomask bits.
+ * conceivably not finish checking the XID against pg_transaction before we
+ * finish the VACUUM and perhaps truncate off the part of pg_transaction he
+ * needs.  Getting exclusive lock ensures no other backend is in process of
+ * checking the tuple status.  Also, getting exclusive lock makes it safe to
+ * adjust the infomask bits.
  *
  * NB: All code in here must be safe to execute during crash recovery!
  */
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index 4ae4715..36bcde9 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -331,18 +331,18 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_clog and pg_subtrans
------------------------
+pg_transaction and pg_subtrans
+------------------------------
 
-pg_clog and pg_subtrans are permanent (on-disk) storage of transaction related
-information.  There is a limited number of pages of each kept in memory, so
-in many cases there is no need to actually read from disk.  However, if
-there's a long running transaction or a backend sitting idle with an open
+pg_transaction and pg_subtrans are permanent (on-disk) storage of transaction
+related information.  There is a limited number of pages of each kept in
+memory, so in many cases there is no need to actually read from disk.  However,
+if there's a long running transaction or a backend sitting idle with an open
 transaction, it may be necessary to be able to read and write this information
 from disk.  They also allow information to be permanent across server restarts.
 
-pg_clog records the commit status for each transaction that has been assigned
-an XID.  A transaction can be in progress, committed, aborted, or
+pg_transaction records the commit status for each transaction that has been
+assigned an XID.  A transaction can be in progress, committed, aborted, or
 "sub-committed".  This last state means that it's a subtransaction that's no
 longer running, but its parent has not updated its state yet.  It is not
 necessary to update a subtransaction's transaction status to subcommit, so we
@@ -381,10 +381,10 @@ each transaction we keep a "cache" of Xids that are known to be part of the
 transaction tree, so we can skip looking at pg_subtrans unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_clog and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_transaction and pg_subtrans.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
-for pg_clog are implemented in transam.c, while the low-level functions are in
-clog.c.  pg_subtrans is contained completely in subtrans.c.
+for pg_transaction are implemented in transam.c, while the low-level functions
+are in clog.c.  pg_subtrans is contained completely in subtrans.c.
 
 
 Write-Ahead Log Coding
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 2634476..c7a3cbb 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -450,7 +450,7 @@ CLOGShmemInit(void)
 {
 	ClogCtl->PagePrecedes = CLOGPagePrecedes;
 	SimpleLruInit(ClogCtl, "clog", CLOGShmemBuffers(), CLOG_LSNS_PER_PAGE,
-				  CLogControlLock, "pg_clog", LWTRANCHE_CLOG_BUFFERS);
+				  CLogControlLock, "pg_transaction", LWTRANCHE_CLOG_BUFFERS);
 }
 
 /*
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index a8d275f..4a48f76 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -3,8 +3,8 @@
  * commit_ts.c
  *		PostgreSQL commit timestamp manager
  *
- * This module is a pg_clog-like system that stores the commit timestamp
- * for each transaction.
+ * This module is a pg_transaction-like system that stores the commit
+ * timestamp for each transaction.
  *
  * XLOG interactions: this module generates an XLOG record whenever a new
  * CommitTs page is initialized to zeroes.  Also, one XLOG record is
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index e9588a7..aa8e07e 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3,10 +3,10 @@
  * multixact.c
  *		PostgreSQL multi-transaction-log manager
  *
- * The pg_multixact manager is a pg_clog-like manager that stores an array of
- * MultiXactMember for each MultiXactId.  It is a fundamental part of the
- * shared-row-lock implementation.  Each MultiXactMember is comprised of a
- * TransactionId and a set of flag bits.  The name is a bit historical:
+ * The pg_multixact manager is a pg_transaction-like manager that stores an
+ * array of MultiXactMember for each MultiXactId.  It is a fundamental part
+ * of the shared-row-lock implementation.  Each MultiXactMember is comprised
+ * of a TransactionId and a set of flag bits.  The name is a bit historical:
  * originally, a MultiXactId consisted of more than one TransactionId (except
  * in rare corner cases), hence "multi".  Nowadays, however, it's perfectly
  * legitimate to have MultiXactIds that only include a single Xid.
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 908fe2d..d96a487 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,17 +3,17 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_clog-like manager that stores the parent
- * transaction Id for each transaction.  It is a fundamental part of the
- * nested transactions implementation.  A main transaction has a parent
- * of InvalidTransactionId, and each subtransaction has its immediate parent.
- * The tree can easily be walked from child to parent, but not in the
- * opposite direction.
+ * The pg_subtrans manager is a pg_transaction-like manager that stores
+ * the parent transaction Id for each transaction.  It is a fundamental
+ * part of the nested transactions implementation.  A main transaction has
+ * a parent of InvalidTransactionId, and each subtransaction has its
+ * immediate parent.  The tree can easily be walked from child to parent,
+ * but not in the opposite direction.
  *
  * This code is based on clog.c, but the robustness requirements
- * are completely different from pg_clog, because we only need to remember
- * pg_subtrans information for currently-open transactions.  Thus, there is
- * no need to preserve data over a crash and restart.
+ * are completely different from pg_transaction, because we only need to
+ * remember pg_subtrans information for currently-open transactions.  Thus,
+ * there is no need to preserve data over a crash and restart.
  *
  * There are no XLOG interactions since we do not care about preserving
  * data across crashes.  During database startup, we simply force the
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index 1eba49a..8a41c7f 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -224,7 +224,7 @@ TransactionIdDidAbort(TransactionId transactionId)
  *		True iff transaction associated with the identifier is currently
  *		known to have either committed or aborted.
  *
- * This does NOT look into pg_clog but merely probes our local cache
+ * This does NOT look into pg_transaction but merely probes our local cache
  * (and so it's not named TransactionIdDidComplete, which would be the
  * appropriate name for a function that worked that way).  The intended
  * use is just to short-circuit TransactionIdIsInProgress calls when doing
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 5415604..52de336 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1379,8 +1379,8 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	/*
 	 * The order of operations here is critical: make the XLOG entry for
 	 * commit or abort, then mark the transaction committed or aborted in
-	 * pg_clog, then remove its PGPROC from the global ProcArray (which means
-	 * TransactionIdIsInProgress will stop saying the prepared xact is in
+	 * pg_transaction, then remove its PGPROC from the global ProcArray (which
+	 * means TransactionIdIsInProgress will stop saying the prepared xact is in
 	 * progress), then run the post-commit or post-abort callbacks. The
 	 * callbacks will release the locks the transaction held.
 	 */
@@ -2093,7 +2093,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	/* Flush XLOG to disk */
 	XLogFlush(recptr);
 
-	/* Mark the transaction committed in pg_clog */
+	/* Mark the transaction committed in pg_transaction */
 	TransactionIdCommitTree(xid, nchildren, children);
 
 	/* Checkpoint can proceed now */
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index e11b229..817b323 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1206,10 +1206,10 @@ RecordTransactionCommit(void)
 		/*
 		 * Mark ourselves as within our "commit critical section".  This
 		 * forces any concurrent checkpoint to wait until we've updated
-		 * pg_clog.  Without this, it is possible for the checkpoint to set
-		 * REDO after the XLOG record but fail to flush the pg_clog update to
-		 * disk, leading to loss of the transaction commit if the system
-		 * crashes a little later.
+		 * pg_transaction.  Without this, it is possible for the checkpoint
+		 * to set REDO after the XLOG record but fail to flush the pg_trans
+		 * update to disk, leading to loss of the transaction commit if the
+		 * system crashes a little later.
 		 *
 		 * Note: we could, but don't bother to, set this flag in
 		 * RecordTransactionAbort.  That's because loss of a transaction abort
@@ -2033,8 +2033,8 @@ CommitTransaction(void)
 	if (!is_parallel_worker)
 	{
 		/*
-		 * We need to mark our XIDs as committed in pg_clog.  This is where we
-		 * durably commit.
+		 * We need to mark our XIDs as committed in pg_transaction.  This is
+		 * where we durably commit.
 		 */
 		latestXid = RecordTransactionCommit();
 	}
@@ -2539,10 +2539,10 @@ AbortTransaction(void)
 	AtAbort_Twophase();
 
 	/*
-	 * Advertise the fact that we aborted in pg_clog (assuming that we got as
-	 * far as assigning an XID to advertise).  But if we're inside a parallel
-	 * worker, skip this; the user backend must be the one to write the abort
-	 * record.
+	 * Advertise the fact that we aborted in pg_transaction (assuming that we
+	 * got as far as assigning an XID to advertise).  But if we're inside a
+	 * parallel worker, skip this; the user backend must be the one to write
+	 * the abort record.
 	 */
 	if (!is_parallel_worker)
 		latestXid = RecordTransactionAbort(false);
@@ -4625,7 +4625,7 @@ AbortSubTransaction(void)
 								s->parent->subTransactionId);
 		AtSubAbort_Notify();
 
-		/* Advertise the fact that we aborted in pg_clog. */
+		/* Advertise the fact that we aborted in pg_transaction. */
 		(void) RecordTransactionAbort(true);
 
 		/* Post-abort cleanup */
@@ -5371,7 +5371,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 	if (standbyState == STANDBY_DISABLED)
 	{
 		/*
-		 * Mark the transaction committed in pg_clog.
+		 * Mark the transaction committed in pg_transaction.
 		 */
 		TransactionIdCommitTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
@@ -5389,8 +5389,8 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		RecordKnownAssignedTransactionIds(max_xid);
 
 		/*
-		 * Mark the transaction committed in pg_clog. We use async commit
-		 * protocol during recovery to provide information on database
+		 * Mark the transaction committed in pg_transaction. We use async
+		 * commit protocol during recovery to provide information on database
 		 * consistency for when users try to set hint bits. It is important
 		 * that we do not set hint bits until the minRecoveryPoint is past
 		 * this commit record. This ensures that if we crash we don't see hint
@@ -5526,7 +5526,10 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 
 	if (standbyState == STANDBY_DISABLED)
 	{
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/*
+		 * Mark the transaction aborted in pg_transaction, no need for async
+		 * stuff.
+		 */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
 	else
@@ -5542,7 +5545,10 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 		 */
 		RecordKnownAssignedTransactionIds(max_xid);
 
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/*
+		 * Mark the transaction aborted in pg_transaction, no need for async
+		 * stuff.
+		 */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 
 		/*
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 48c18e8..2262ae0 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8487,9 +8487,9 @@ CreateCheckPoint(int flags)
 	 * that are currently in commit critical sections.  If an xact inserted
 	 * its commit record into XLOG just before the REDO point, then a crash
 	 * restart from the REDO point would not replay that record, which means
-	 * that our flushing had better include the xact's update of pg_clog.  So
-	 * we wait till he's out of his commit critical section before proceeding.
-	 * See notes in RecordTransactionCommit().
+	 * that our flushing had better include the xact's update of
+	 * pg_transaction.  So we wait till he's out of his commit critical
+	 * section before proceeding.  See notes in RecordTransactionCommit().
 	 *
 	 * Because we've already released the insertion locks, this test is a bit
 	 * fuzzy: it is possible that we will wait for xacts we didn't really need
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 58bbf55..5c61d1a 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -356,8 +356,8 @@ vacuum(int options, RangeVar *relation, Oid relid, VacuumParams *params,
 	if ((options & VACOPT_VACUUM) && !IsAutoVacuumWorkerProcess())
 	{
 		/*
-		 * Update pg_database.datfrozenxid, and truncate pg_clog if possible.
-		 * (autovacuum.c does this for itself.)
+		 * Update pg_database.datfrozenxid, and truncate pg_transaction if
+		 * possible. (autovacuum.c does this for itself.)
 		 */
 		vac_update_datfrozenxid();
 	}
@@ -880,7 +880,7 @@ vac_update_relstats(Relation relation,
  *		pg_class.relminmxid values.
  *
  *		If we are able to advance either pg_database value, also try to
- *		truncate pg_clog and pg_multixact.
+ *		truncate pg_transaction and pg_multixact.
  *
  *		We violate transaction semantics here by overwriting the database's
  *		existing pg_database tuple with the new values.  This is reasonably
@@ -1026,7 +1026,7 @@ vac_update_datfrozenxid(void)
 
 	/*
 	 * If we were able to advance datfrozenxid or datminmxid, see if we can
-	 * truncate pg_clog and/or pg_multixact.  Also do it if the shared
+	 * truncate pg_transaction and/or pg_multixact.  Also do it if the shared
 	 * XID-wrap-limit info is stale, since this action will update that too.
 	 */
 	if (dirty || ForceTransactionIdLimitUpdate())
@@ -1039,7 +1039,7 @@ vac_update_datfrozenxid(void)
  *	vac_truncate_clog() -- attempt to truncate the commit log
  *
  *		Scan pg_database to determine the system-wide oldest datfrozenxid,
- *		and use it to truncate the transaction commit log (pg_clog).
+ *		and use it to truncate the transaction commit log (pg_transaction).
  *		Also update the XID wrap limit info maintained by varsup.c.
  *		Likewise for datminmxid.
  *
@@ -1086,8 +1086,8 @@ vac_truncate_clog(TransactionId frozenXID,
 	 * of the interlock against copying a DB containing an active backend.
 	 * Hence the new entry will not reduce the minimum.  Also, if two VACUUMs
 	 * concurrently modify the datfrozenxid's of different databases, the
-	 * worst possible outcome is that pg_clog is not truncated as aggressively
-	 * as it could be.
+	 * worst possible outcome is that pg_transaction is not truncated as
+	 * aggressively as it could be.
 	 */
 	relation = heap_open(DatabaseRelationId, AccessShareLock);
 
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 1a92ca1..31fcd51 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2394,8 +2394,8 @@ deleted:
 	 */
 
 	/*
-	 * Update pg_database.datfrozenxid, and truncate pg_clog if possible. We
-	 * only need to do this once, not after each table.
+	 * Update pg_database.datfrozenxid, and truncate pg_transaction if
+	 * possible. We only need to do this once, not after each table.
 	 */
 	vac_update_datfrozenxid();
 
diff --git a/src/backend/storage/buffer/README b/src/backend/storage/buffer/README
index 248883f..94da258 100644
--- a/src/backend/storage/buffer/README
+++ b/src/backend/storage/buffer/README
@@ -63,8 +63,8 @@ at about the same time would OR the same bits into the field, so there
 is little or no risk of conflicting update; what's more, if there did
 manage to be a conflict it would merely mean that one bit-update would
 be lost and need to be done again later.  These four bits are only hints
-(they cache the results of transaction status lookups in pg_clog), so no
-great harm is done if they get reset to zero by conflicting updates.
+(they cache the results of transaction status lookups in pg_transaction),
+so no great harm is done if they get reset to zero by conflicting updates.
 Note, however, that a tuple is frozen by setting both HEAP_XMIN_INVALID
 and HEAP_XMIN_COMMITTED; this is a critical update and accordingly requires
 an exclusive buffer lock (and it must also be WAL-logged).
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index e5d487d..dd5c79a 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -388,7 +388,7 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
  * ProcArrayEndTransaction -- mark a transaction as no longer running
  *
  * This is used interchangeably for commit and abort cases.  The transaction
- * commit/abort must already be reported to WAL and pg_clog.
+ * commit/abort must already be reported to WAL and pg_transaction.
  *
  * proc is currently always MyProc, but we pass it explicitly for flexibility.
  * latestXid is the latest Xid among the transaction's main XID and
@@ -1180,7 +1180,8 @@ TransactionIdIsInProgress(TransactionId xid)
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
 	 * subtransaction, we want to say "not running" even though its parent may
-	 * still be running.  So first, check pg_clog to see if it's been aborted.
+	 * still be running.  So first, check pg_transaction to see if it's been
+	 * aborted.
 	 */
 	xc_slow_answer_inc();
 
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 26a3be3..fbf9c6c 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -13,23 +13,24 @@
  * NOTE: When using a non-MVCC snapshot, we must check
  * TransactionIdIsInProgress (which looks in the PGXACT array)
  * before TransactionIdDidCommit/TransactionIdDidAbort (which look in
- * pg_clog).  Otherwise we have a race condition: we might decide that a
- * just-committed transaction crashed, because none of the tests succeed.
- * xact.c is careful to record commit/abort in pg_clog before it unsets
- * MyPgXact->xid in the PGXACT array.  That fixes that problem, but it
- * also means there is a window where TransactionIdIsInProgress and
- * TransactionIdDidCommit will both return true.  If we check only
- * TransactionIdDidCommit, we could consider a tuple committed when a
- * later GetSnapshotData call will still think the originating transaction
- * is in progress, which leads to application-level inconsistency.  The
- * upshot is that we gotta check TransactionIdIsInProgress first in all
- * code paths, except for a few cases where we are looking at
- * subtransactions of our own main transaction and so there can't be any
- * race condition.
+ * pg_transaction).  Otherwise we have a race condition: we might decide
+ * that a just-committed transaction crashed, because none of the tests
+ * succeed.  xact.c is careful to record commit/abort in pg_transaction
+ * before it unsets MyPgXact->xid in the PGXACT array.  That fixes that
+ * problem, but it also means there is a window where
+ * TransactionIdIsInProgress and TransactionIdDidCommit will both return
+ * true.  If we check only TransactionIdDidCommit, we could consider a
+ * tuple committed when a later GetSnapshotData call will still think
+ * the originating transaction is in progress, which leads to
+ * application-level inconsistency.  The upshot is that we gotta check
+ * TransactionIdIsInProgress first in all code paths, except for a few
+ * cases where we are looking at subtransactions of our own main
+ * transaction and so there can't be any race condition.
  *
  * When using an MVCC snapshot, we rely on XidInMVCCSnapshot rather than
  * TransactionIdIsInProgress, but the logic is otherwise the same: do not
- * check pg_clog until after deciding that the xact is no longer in progress.
+ * check pg_transaction until after deciding that the xact is no longer
+ * in progress.
  *
  *
  * Summary of visibility functions:
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 385e808..974f11a 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -196,7 +196,6 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 static const char *const subdirs[] = {
 	"global",
 	"pg_wal/archive_status",
-	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
 	"pg_notify",
@@ -213,6 +212,7 @@ static const char *const subdirs[] = {
 	"pg_tblspc",
 	"pg_stat",
 	"pg_stat_tmp",
+	"pg_transaction",
 	"pg_logical",
 	"pg_logical/snapshots",
 	"pg_logical/mappings"
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 55a6f0d..a3a0a0f 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -309,6 +309,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_xlog");
 	else
 		check_single_dir(pg_data, "pg_wal");
+
+	/* pg_clog has been renamed to pg_transaction in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_clog");
+	else
+		check_single_dir(pg_data, "pg_transaction");
 }
 
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 90c0720..04704c2 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -47,7 +47,7 @@
 static void prepare_new_cluster(void);
 static void prepare_new_databases(void);
 static void create_new_objects(void);
-static void copy_clog_xlog_xid(void);
+static void copy_trans_xlog_xid(void);
 static void set_frozenxids(bool minmxid_only);
 static void setup(char *argv0, bool *live_check);
 static void cleanup(void);
@@ -113,7 +113,7 @@ main(int argc, char **argv)
 	 * Destructive Changes to New Cluster
 	 */
 
-	copy_clog_xlog_xid();
+	copy_trans_xlog_xid();
 
 	/* New now using xids of the old system */
 
@@ -374,17 +374,17 @@ remove_new_subdir(char *subdir, bool rmtopdir)
  * Copy the files from the old cluster into it
  */
 static void
-copy_subdir_files(char *subdir)
+copy_subdir_files(char *old_subdir, char *new_subdir)
 {
 	char		old_path[MAXPGPATH];
 	char		new_path[MAXPGPATH];
 
-	remove_new_subdir(subdir, true);
+	remove_new_subdir(new_subdir, true);
 
-	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, subdir);
-	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, subdir);
+	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, old_subdir);
+	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, new_subdir);
 
-	prep_status("Copying old %s to new server", subdir);
+	prep_status("Copying old %s to new server", old_subdir);
 
 	exec_prog(UTILITY_LOG_FILE, NULL, true,
 #ifndef WIN32
@@ -399,10 +399,16 @@ copy_subdir_files(char *subdir)
 }
 
 static void
-copy_clog_xlog_xid(void)
+copy_trans_xlog_xid(void)
 {
-	/* copy old commit logs to new data dir */
-	copy_subdir_files("pg_clog");
+	/*
+	 * Copy old commit logs to new data dir. pg_clog has been renamed to
+	 * pg_transaction in post-10 clusters.
+	 */
+	copy_subdir_files(GET_MAJOR_VERSION(old_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_transaction",
+					  GET_MAJOR_VERSION(new_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_transaction");
 
 	/* set the next transaction id and epoch of the new cluster */
 	prep_status("Setting next transaction ID and epoch for new cluster");
@@ -432,8 +438,8 @@ copy_clog_xlog_xid(void)
 	if (old_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER &&
 		new_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER)
 	{
-		copy_subdir_files("pg_multixact/offsets");
-		copy_subdir_files("pg_multixact/members");
+		copy_subdir_files("pg_multixact/offsets", "pg_multixact/offsets");
+		copy_subdir_files("pg_multixact/members", "pg_multixact/members");
 
 		prep_status("Setting next multixact ID and offset for new cluster");
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 5fcebc5..001817f 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,10 +76,10 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_clog, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
-	 * has lsn_groups_per_page entries per buffer slot, each containing the
-	 * highest LSN known for a contiguous group of SLRU entries on that slot's
-	 * page.
+	 * for pg_transaction, false for multixact, pg_subtrans, pg_notify).
+	 * group_lsn[] has lsn_groups_per_page entries per buffer slot, each
+	 * containing the highest LSN known for a contiguous group of SLRU entries
+	 * on that slot's page.
 	 */
 	XLogRecPtr *group_lsn;
 	int			lsn_groups_per_page;
@@ -120,8 +120,8 @@ typedef struct SlruCtlData
 	SlruShared	shared;
 
 	/*
-	 * This flag tells whether to fsync writes (true for pg_clog and multixact
-	 * stuff, false for pg_subtrans and pg_notify).
+	 * This flag tells whether to fsync writes (true for pg_transaction and
+	 * multixact stuff, false for pg_subtrans and pg_notify).
 	 */
 	bool		do_fsync;
 
-- 
2.10.0

From 79d665f1bda7944cae7631b9aeb6870fe1df67cd Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 4 Oct 2016 14:38:05 +0900
Subject: [PATCH 1/2] Rename pg_xlog to pg_wal

Additional check handling is needed in pg_upgrade regarding the clusters
worked on, except that it is a very mechanical patch. As pg_basebackup
needs to support servers down to 9.1, special handling is needed depending
on the version of the target server as a consequence of this renaming:
- Soft links need to be generated using pg_xlog or pg_wal.
- stream mode needs to have its output in the correct place.
This has as direct consequence to need a connection to target server before
generating a soft link, which is a bit earlier than before this renaming.
---
 doc/src/sgml/backup.sgml                     |  28 ++++----
 doc/src/sgml/config.sgml                     |   6 +-
 doc/src/sgml/func.sgml                       |   2 +-
 doc/src/sgml/high-availability.sgml          |  14 ++--
 doc/src/sgml/perform.sgml                    |   2 +-
 doc/src/sgml/protocol.sgml                   |   6 +-
 doc/src/sgml/ref/pg_resetxlog.sgml           |  10 +--
 doc/src/sgml/ref/pg_rewind.sgml              |   4 +-
 doc/src/sgml/ref/pg_xlogdump.sgml            |   2 +-
 doc/src/sgml/ref/pgtestfsync.sgml            |   4 +-
 doc/src/sgml/ref/pgupgrade.sgml              |   4 +-
 doc/src/sgml/storage.sgml                    |   2 +-
 doc/src/sgml/wal.sgml                        |  10 +--
 src/backend/access/transam/timeline.c        |   4 +-
 src/backend/access/transam/xlog.c            | 100 +++++++++++++--------------
 src/backend/access/transam/xlogarchive.c     |   2 +-
 src/backend/access/transam/xlogfuncs.c       |   2 +-
 src/backend/replication/README               |   2 +-
 src/backend/replication/basebackup.c         |  20 +++---
 src/backend/replication/walreceiver.c        |   6 +-
 src/backend/replication/walsender.c          |   4 +-
 src/backend/storage/file/fd.c                |  16 ++---
 src/bin/initdb/initdb.c                      |  12 ++--
 src/bin/pg_basebackup/pg_basebackup.c        |  80 +++++++++++++--------
 src/bin/pg_basebackup/t/010_pg_basebackup.pl |   8 +--
 src/bin/pg_resetxlog/pg_resetxlog.c          |   2 +-
 src/bin/pg_rewind/copy_fetch.c               |   4 +-
 src/bin/pg_rewind/filemap.c                  |   8 +--
 src/bin/pg_rewind/parsexlog.c                |   2 +-
 src/bin/pg_rewind/t/004_pg_xlog_symlink.pl   |  10 +--
 src/bin/pg_upgrade/exec.c                    |  79 +++++++++++++--------
 src/bin/pg_xlogdump/pg_xlogdump.c            |   2 +-
 src/common/file_utils.c                      |  39 +++++++----
 src/include/access/xlog_internal.h           |   2 +-
 src/include/common/file_utils.h              |   3 +-
 src/include/postmaster/pgarch.h              |   2 +-
 36 files changed, 278 insertions(+), 225 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 95d0ff3..6eaed1e 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -472,7 +472,7 @@ tar -cf backup.tar /usr/local/pgsql/data
 
   <para>
    At all times, <productname>PostgreSQL</> maintains a
-   <firstterm>write ahead log</> (WAL) in the <filename>pg_xlog/</>
+   <firstterm>write ahead log</> (WAL) in the <filename>pg_wal/</>
    subdirectory of the cluster's data directory. The log records
    every change made to the database's data files.  This log exists
    primarily for crash-safety purposes: if the system crashes, the
@@ -616,7 +616,7 @@ archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"'  # Windows
     <literal>%p</> and <literal>%f</> parameters have been replaced,
     the actual command executed might look like this:
 <programlisting>
-test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065
+test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_wal/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065
 </programlisting>
     A similar command will be generated for each new file to be archived.
    </para>
@@ -668,9 +668,9 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     fills, nothing further can be archived until the tape is swapped.
     You should ensure that any error condition or request to a human operator
     is reported appropriately so that the situation can be
-    resolved reasonably quickly. The <filename>pg_xlog/</> directory will
+    resolved reasonably quickly. The <filename>pg_wal/</> directory will
     continue to fill with WAL segment files until the situation is resolved.
-    (If the file system containing <filename>pg_xlog/</> fills up,
+    (If the file system containing <filename>pg_wal/</> fills up,
     <productname>PostgreSQL</> will do a PANIC shutdown.  No committed
     transactions will be lost, but the database will remain offline until
     you free some space.)
@@ -682,7 +682,7 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     operation continues even if the archiving process falls a little behind.
     If archiving falls significantly behind, this will increase the amount of
     data that would be lost in the event of a disaster. It will also mean that
-    the <filename>pg_xlog/</> directory will contain large numbers of
+    the <filename>pg_wal/</> directory will contain large numbers of
     not-yet-archived segment files, which could eventually exceed available
     disk space. You are advised to monitor the archiving process to ensure that
     it is working as you intend.
@@ -743,7 +743,7 @@ test ! -f /mnt/server/archivedir/00000001000000A900000065 &amp;&amp; cp pg_xlog/
     configuration file reload.  If you wish to temporarily stop archiving,
     one way to do it is to set <varname>archive_command</> to the empty
     string (<literal>''</>).
-    This will cause WAL files to accumulate in <filename>pg_xlog/</> until a
+    This will cause WAL files to accumulate in <filename>pg_wal/</> until a
     working <varname>archive_command</> is re-established.
    </para>
   </sect2>
@@ -1062,10 +1062,10 @@ SELECT pg_stop_backup();
 
    <para>
     You should, however, omit from the backup the files within the
-    cluster's <filename>pg_xlog/</> subdirectory.  This
+    cluster's <filename>pg_wal/</> subdirectory.  This
     slight adjustment is worthwhile because it reduces the risk
     of mistakes when restoring.  This is easy to arrange if
-    <filename>pg_xlog/</> is a symbolic link pointing to someplace outside
+    <filename>pg_wal/</> is a symbolic link pointing to someplace outside
     the cluster directory, which is a common setup anyway for performance
     reasons.  You might also want to exclude <filename>postmaster.pid</>
     and <filename>postmaster.opts</>, which record information
@@ -1149,7 +1149,7 @@ SELECT pg_stop_backup();
      location in case you need them later. Note that this precaution will
      require that you have enough free space on your system to hold two
      copies of your existing database. If you do not have enough space,
-     you should at least save the contents of the cluster's <filename>pg_xlog</>
+     you should at least save the contents of the cluster's <filename>pg_wal</>
      subdirectory, as it might contain logs which
      were not archived before the system went down.
     </para>
@@ -1172,9 +1172,9 @@ SELECT pg_stop_backup();
    </listitem>
    <listitem>
     <para>
-     Remove any files present in <filename>pg_xlog/</>; these came from the
+     Remove any files present in <filename>pg_wal/</>; these came from the
      file system backup and are therefore probably obsolete rather than current.
-     If you didn't archive <filename>pg_xlog/</> at all, then recreate
+     If you didn't archive <filename>pg_wal/</> at all, then recreate
      it with proper permissions,
      being careful to ensure that you re-establish it as a symbolic link
      if you had it set up that way before.
@@ -1183,7 +1183,7 @@ SELECT pg_stop_backup();
    <listitem>
     <para>
      If you have unarchived WAL segment files that you saved in step 2,
-     copy them into <filename>pg_xlog/</>.  (It is best to copy them,
+     copy them into <filename>pg_wal/</>.  (It is best to copy them,
      not move them, so you still have the unmodified files if a
      problem occurs and you have to start over.)
     </para>
@@ -1265,9 +1265,9 @@ restore_command = 'cp /mnt/server/archivedir/%f %p'
 
    <para>
     WAL segments that cannot be found in the archive will be sought in
-    <filename>pg_xlog/</>; this allows use of recent un-archived segments.
+    <filename>pg_wal/</>; this allows use of recent un-archived segments.
     However, segments that are available from the archive will be used in
-    preference to files in <filename>pg_xlog/</>.
+    preference to files in <filename>pg_wal/</>.
    </para>
 
    <para>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index e826c19..1bb501c 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2932,7 +2932,7 @@ include_dir 'conf.d'
        <listitem>
        <para>
         Specifies the minimum number of past log file segments kept in the
-        <filename>pg_xlog</>
+        <filename>pg_wal</>
         directory, in case a standby server needs to fetch them for streaming
         replication. Each segment is normally 16 megabytes. If a standby
         server connected to the sending server falls behind by more than
@@ -2946,7 +2946,7 @@ include_dir 'conf.d'
 
        <para>
         This sets only the minimum number of segments retained in
-        <filename>pg_xlog</>; the system might need to retain more segments
+        <filename>pg_wal</>; the system might need to retain more segments
         for WAL archival or to recover from a checkpoint. If
         <varname>wal_keep_segments</> is zero (the default), the system
         doesn't keep any extra segments for standby purposes, so the number
@@ -3322,7 +3322,7 @@ include_dir 'conf.d'
        <para>
         Specify how long the standby server should wait when WAL data is not
         available from any sources (streaming replication,
-        local <filename>pg_xlog</> or WAL archive) before retrying to
+        local <filename>pg_wal</> or WAL archive) before retrying to
         retrieve WAL data.  This parameter can only be set in the
         <filename>postgresql.conf</> file or on the server command line.
         The default value is 5 seconds. Units are milliseconds if not specified.
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index a588350..2e64cc4 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15327,7 +15327,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
- pg_xlog         | 16
+ pg_wal          | 16
  pg_hba.conf     | 17
  pg_stat_tmp     | 18
  pg_subtrans     | 19
diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index 06f49db..5bedaf2 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -594,24 +594,24 @@ protocol to make nodes agree on a serializable transactional order.
     (see <xref linkend="restore-command">) or directly from the master
     over a TCP connection (streaming replication). The standby server will
     also attempt to restore any WAL found in the standby cluster's
-    <filename>pg_xlog</> directory. That typically happens after a server
+    <filename>pg_wal</> directory. That typically happens after a server
     restart, when the standby replays again WAL that was streamed from the
     master before the restart, but you can also manually copy files to
-    <filename>pg_xlog</> at any time to have them replayed.
+    <filename>pg_wal</> at any time to have them replayed.
    </para>
 
    <para>
     At startup, the standby begins by restoring all WAL available in the
     archive location, calling <varname>restore_command</>. Once it
     reaches the end of WAL available there and <varname>restore_command</>
-    fails, it tries to restore any WAL available in the <filename>pg_xlog</> directory.
+    fails, it tries to restore any WAL available in the <filename>pg_wal</> directory.
     If that fails, and streaming replication has been configured, the
     standby tries to connect to the primary server and start streaming WAL
-    from the last valid record found in archive or <filename>pg_xlog</>. If that fails
+    from the last valid record found in archive or <filename>pg_wal</>. If that fails
     or streaming replication is not configured, or if the connection is
     later disconnected, the standby goes back to step 1 and tries to
     restore the file from the archive again. This loop of retries from the
-    archive, <filename>pg_xlog</>, and via streaming replication goes on until the server
+    archive, <filename>pg_wal</>, and via streaming replication goes on until the server
     is stopped or failover is triggered by a trigger file.
    </para>
 
@@ -619,7 +619,7 @@ protocol to make nodes agree on a serializable transactional order.
     Standby mode is exited and the server switches to normal operation
     when <command>pg_ctl promote</> is run or a trigger file is found
     (<varname>trigger_file</>). Before failover,
-    any WAL immediately available in the archive or in <filename>pg_xlog</> will be
+    any WAL immediately available in the archive or in <filename>pg_wal</> will be
     restored, but no attempt is made to connect to the master.
    </para>
   </sect2>
@@ -895,7 +895,7 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass'
     However, these methods often result in retaining more WAL segments than
     required, whereas replication slots retain only the number of segments
     known to be needed.  An advantage of these methods is that they bound
-    the space requirement for <literal>pg_xlog</>; there is currently no way
+    the space requirement for <literal>pg_wal</>; there is currently no way
     to do this using replication slots.
    </para>
    <para>
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml
index 7bcbfa7..8d30fd1 100644
--- a/doc/src/sgml/perform.sgml
+++ b/doc/src/sgml/perform.sgml
@@ -1612,7 +1612,7 @@ SELECT * FROM x, y, a, b, c WHERE something AND somethingelse;
        Increase <xref linkend="guc-max-wal-size"> and <xref
        linkend="guc-checkpoint-timeout"> ; this reduces the frequency
        of checkpoints, but increases the storage requirements of
-       <filename>/pg_xlog</>.
+       <filename>/pg_wal</>.
       </para>
      </listitem>
 
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 3384e73..50cf527 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -1947,7 +1947,7 @@ The commands accepted in walsender mode are:
          <para>
           Include the necessary WAL segments in the backup. This will include
           all the files between start and stop backup in the
-          <filename>pg_xlog</filename> directory of the base directory tar
+          <filename>pg_wal</filename> directory of the base directory tar
           file.
          </para>
         </listitem>
@@ -2076,8 +2076,8 @@ The commands accepted in walsender mode are:
        </listitem>
        <listitem>
         <para>
-         <filename>pg_xlog</>, including subdirectories. If the backup is run
-         with WAL files included, a synthesized version of <filename>pg_xlog</filename> will be
+         <filename>pg_wal</>, including subdirectories. If the backup is run
+         with WAL files included, a synthesized version of <filename>pg_wal</filename> will be
          included, but it will only contain the files necessary for the
          backup to work, not the rest of the contents.
         </para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index fd9d0be..c949c5e 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -173,22 +173,22 @@ PostgreSQL documentation
      <para>
       The WAL starting address should be
       larger than any WAL segment file name currently existing in
-      the directory <filename>pg_xlog</> under the data directory.
+      the directory <filename>pg_wal</> under the data directory.
       These names are also in hexadecimal and have three parts.  The first
       part is the <quote>timeline ID</> and should usually be kept the same.
       For example, if <filename>00000001000000320000004A</> is the
-      largest entry in <filename>pg_xlog</>, use <literal>-l 00000001000000320000004B</> or higher.
+      largest entry in <filename>pg_wal</>, use <literal>-l 00000001000000320000004B</> or higher.
      </para>
 
      <note>
       <para>
        <command>pg_resetxlog</command> itself looks at the files in
-       <filename>pg_xlog</> and chooses a default <option>-l</> setting
+       <filename>pg_wal</> and chooses a default <option>-l</> setting
        beyond the last existing file name.  Therefore, manual adjustment of
        <option>-l</> should only be needed if you are aware of WAL segment
-       files that are not currently present in <filename>pg_xlog</>, such as
+       files that are not currently present in <filename>pg_wal</>, such as
        entries in an offline archive; or if the contents of
-       <filename>pg_xlog</> have been lost entirely.
+       <filename>pg_wal</> have been lost entirely.
       </para>
      </note>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 42ebfbf..371c4a4 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -61,14 +61,14 @@ PostgreSQL documentation
   <para>
    <application>pg_rewind</> examines the timeline histories of the source
    and target clusters to determine the point where they diverged, and
-   expects to find WAL in the target cluster's <filename>pg_xlog</> directory
+   expects to find WAL in the target cluster's <filename>pg_wal</> directory
    reaching all the way back to the point of divergence. The point of divergence
    can be found either on the target timeline, the source timeline, or their common
    ancestor. In the typical failover scenario where the target cluster was
    shut down soon after the divergence, this is not a problem, but if the
    target cluster ran for a long time after the divergence, the old WAL
    files might no longer be present. In that case, they can be manually
-   copied from the WAL archive to the <filename>pg_xlog</> directory, or
+   copied from the WAL archive to the <filename>pg_wal</> directory, or
    fetched on startup by configuring <filename>recovery.conf</>.  The use of
    <application>pg_rewind</> is not limited to failover, e.g.  a standby
    server can be promoted, run some write transactions, and then rewinded
diff --git a/doc/src/sgml/ref/pg_xlogdump.sgml b/doc/src/sgml/ref/pg_xlogdump.sgml
index 177caab..cfb6d87 100644
--- a/doc/src/sgml/ref/pg_xlogdump.sgml
+++ b/doc/src/sgml/ref/pg_xlogdump.sgml
@@ -118,7 +118,7 @@ PostgreSQL documentation
       <listitem>
        <para>
         Directory in which to find log segment files.  The default is to search
-        for them in the <literal>pg_xlog</literal> subdirectory of the current
+        for them in the <literal>pg_wal</literal> subdirectory of the current
         directory.
        </para>
       </listitem>
diff --git a/doc/src/sgml/ref/pgtestfsync.sgml b/doc/src/sgml/ref/pgtestfsync.sgml
index 6e134c7..5856356 100644
--- a/doc/src/sgml/ref/pgtestfsync.sgml
+++ b/doc/src/sgml/ref/pgtestfsync.sgml
@@ -57,8 +57,8 @@
        <para>
         Specifies the file name to write test data in.
         This file should be in the same file system that the
-        <filename>pg_xlog</> directory is or will be placed in.
-        (<filename>pg_xlog</> contains the <acronym>WAL</> files.)
+        <filename>pg_wal</> directory is or will be placed in.
+        (<filename>pg_wal</> contains the <acronym>WAL</> files.)
         The default is <filename>pg_test_fsync.out</> in the current
         directory.
        </para>
diff --git a/doc/src/sgml/ref/pgupgrade.sgml b/doc/src/sgml/ref/pgupgrade.sgml
index 9685193..4b9aab2 100644
--- a/doc/src/sgml/ref/pgupgrade.sgml
+++ b/doc/src/sgml/ref/pgupgrade.sgml
@@ -345,7 +345,7 @@ NET STOP postgresql-9.0
      your old cluster
      once you start the new cluster after the upgrade.  Link mode also
      requires that the old and new cluster data directories be in the
-     same file system.  (Tablespaces and <filename>pg_xlog</> can be on
+     same file system.  (Tablespaces and <filename>pg_wal</> can be on
      different file systems.)  See <literal>pg_upgrade --help</> for a full
      list of options.
     </para>
@@ -508,7 +508,7 @@ rsync --archive --delete --hard-links --size-only old_pgdata new_pgdata remote_d
       <para>
        If you have tablespaces, you will need to run a similar
        <application>rsync</> command for each tablespace directory.  If you
-       have relocated <filename>pg_xlog</> outside the data directories,
+       have relocated <filename>pg_wal</> outside the data directories,
        <application>rsync</> must be run on those directories too.
       </para>
      </step>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 1b812bd..fddb69b 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -141,7 +141,7 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_xlog</></entry>
+ <entry><filename>pg_wal</></entry>
  <entry>Subdirectory containing WAL (Write Ahead Log) files</entry>
 </row>
 
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index fe3b588..346aa76 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -557,7 +557,7 @@
   </para>
 
   <para>
-   The number of WAL segment files in <filename>pg_xlog</> directory depends on
+   The number of WAL segment files in <filename>pg_wal</> directory depends on
    <varname>min_wal_size</>, <varname>max_wal_size</> and
    the amount of WAL generated in previous checkpoint cycles. When old log
    segment files are no longer needed, they are removed or recycled (that is,
@@ -582,7 +582,7 @@
    kept at all times. Also, if WAL archiving is used, old segments can not be
    removed or recycled until they are archived. If WAL archiving cannot keep up
    with the pace that WAL is generated, or if <varname>archive_command</varname>
-   fails repeatedly, old WAL files will accumulate in <filename>pg_xlog</>
+   fails repeatedly, old WAL files will accumulate in <filename>pg_wal</>
    until the situation is resolved. A slow or failed standby server that
    uses a replication slot will have the same effect (see
    <xref linkend="streaming-replication-slots">).
@@ -594,7 +594,7 @@
    which are similar to checkpoints in normal operation: the server forces
    all its state to disk, updates the <filename>pg_control</> file to
    indicate that the already-processed WAL data need not be scanned again,
-   and then recycles any old log segment files in the <filename>pg_xlog</>
+   and then recycles any old log segment files in the <filename>pg_wal</>
    directory.
    Restartpoints can't be performed more frequently than checkpoints in the
    master because restartpoints can only be performed at checkpoint records.
@@ -750,7 +750,7 @@
 
   <para>
    <acronym>WAL</acronym> logs are stored in the directory
-   <filename>pg_xlog</filename> under the data directory, as a set of
+   <filename>pg_wal</filename> under the data directory, as a set of
    segment files, normally each 16 MB in size (but the size can be changed
    by altering the <option>--with-wal-segsize</> configure option when
    building the server).  Each segment is divided into pages, normally
@@ -767,7 +767,7 @@
   <para>
    It is advantageous if the log is located on a different disk from the
    main database files.  This can be achieved by moving the
-   <filename>pg_xlog</filename> directory to another location (while the server
+   <filename>pg_wal</filename> directory to another location (while the server
    is shut down, of course) and creating a symbolic link from the
    original location in the main data directory to the new location.
   </para>
diff --git a/src/backend/access/transam/timeline.c b/src/backend/access/transam/timeline.c
index bd91573..43436a9 100644
--- a/src/backend/access/transam/timeline.c
+++ b/src/backend/access/transam/timeline.c
@@ -43,7 +43,7 @@
 
 /*
  * Copies all timeline history files with id's between 'begin' and 'end'
- * from archive to pg_xlog.
+ * from archive to pg_wal.
  */
 void
 restoreTimeLineHistoryFiles(TimeLineID begin, TimeLineID end)
@@ -191,7 +191,7 @@ readTimeLineHistory(TimeLineID targetTLI)
 	result = lcons(entry, result);
 
 	/*
-	 * If the history file was fetched from archive, save it in pg_xlog for
+	 * If the history file was fetched from archive, save it in pg_wal for
 	 * future reference.
 	 */
 	if (fromArchive)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 08c87f9..4fda179 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -235,9 +235,9 @@ static int	LocalXLogInsertAllowed = -1;
  * valid in the startup process.
  *
  * When ArchiveRecoveryRequested is true, but InArchiveRecovery is false, we're
- * currently performing crash recovery using only XLOG files in pg_xlog, but
+ * currently performing crash recovery using only XLOG files in pg_wal, but
  * will switch to using offline XLOG archives as soon as we reach the end of
- * WAL in pg_xlog.
+ * WAL in pg_wal.
 */
 bool		ArchiveRecoveryRequested = false;
 bool		InArchiveRecovery = false;
@@ -700,12 +700,12 @@ typedef enum
 {
 	XLOG_FROM_ANY = 0,			/* request to read WAL from any source */
 	XLOG_FROM_ARCHIVE,			/* restored using restore_command */
-	XLOG_FROM_PG_XLOG,			/* existing file in pg_xlog */
+	XLOG_FROM_PG_WAL,			/* existing file in pg_wal */
 	XLOG_FROM_STREAM			/* streamed from master */
 } XLogSource;
 
 /* human-readable names for XLogSources, for debugging output */
-static const char *xlogSourceNames[] = {"any", "archive", "pg_xlog", "stream"};
+static const char *xlogSourceNames[] = {"any", "archive", "pg_wal", "stream"};
 
 /*
  * openLogFile is -1 or a kernel FD for an open log file segment.
@@ -3345,7 +3345,7 @@ XLogFileOpen(XLogSegNo segno)
  * Open a logfile segment for reading (during recovery).
  *
  * If source == XLOG_FROM_ARCHIVE, the segment is retrieved from archive.
- * Otherwise, it's assumed to be already available in pg_xlog.
+ * Otherwise, it's assumed to be already available in pg_wal.
  */
 static int
 XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
@@ -3374,7 +3374,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 				return -1;
 			break;
 
-		case XLOG_FROM_PG_XLOG:
+		case XLOG_FROM_PG_WAL:
 		case XLOG_FROM_STREAM:
 			XLogFilePath(path, tli, segno);
 			restoredFromArchive = false;
@@ -3393,7 +3393,7 @@ XLogFileRead(XLogSegNo segno, int emode, TimeLineID tli,
 		KeepFileRestoredFromArchive(path, xlogfname);
 
 		/*
-		 * Set path to point at the new file in pg_xlog.
+		 * Set path to point at the new file in pg_wal.
 		 */
 		snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlogfname);
 	}
@@ -3481,10 +3481,10 @@ XLogFileReadAnyTLI(XLogSegNo segno, int emode, int source)
 			}
 		}
 
-		if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_XLOG)
+		if (source == XLOG_FROM_ANY || source == XLOG_FROM_PG_WAL)
 		{
 			fd = XLogFileRead(segno, emode, tli,
-							  XLOG_FROM_PG_XLOG, true);
+							  XLOG_FROM_PG_WAL, true);
 			if (fd != -1)
 			{
 				if (!expectedTLEs)
@@ -3693,10 +3693,10 @@ RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
  *
  * This is called during recovery, whenever we switch to follow a new
  * timeline, and at the end of recovery when we create a new timeline. We
- * wouldn't otherwise care about extra WAL files lying in pg_xlog, but they
+ * wouldn't otherwise care about extra WAL files lying in pg_wal, but they
  * might be leftover pre-allocated or recycled WAL segments on the old timeline
  * that we haven't used yet, and contain garbage. If we just leave them in
- * pg_xlog, they will eventually be archived, and we can't let that happen.
+ * pg_wal, they will eventually be archived, and we can't let that happen.
  * Files that belong to our timeline history are valid, because we have
  * successfully replayed them, but from others we can't be sure.
  *
@@ -3853,15 +3853,15 @@ RemoveXlogFile(const char *segname, XLogRecPtr PriorRedoPtr, XLogRecPtr endptr)
 }
 
 /*
- * Verify whether pg_xlog and pg_xlog/archive_status exist.
+ * Verify whether pg_wal and pg_wal/archive_status exist.
  * If the latter does not exist, recreate it.
  *
  * It is not the goal of this function to verify the contents of these
  * directories, but to help in cases where someone has performed a cluster
- * copy for PITR purposes but omitted pg_xlog from the copy.
+ * copy for PITR purposes but omitted pg_wal from the copy.
  *
- * We could also recreate pg_xlog if it doesn't exist, but a deliberate
- * policy decision was made not to.  It is fairly common for pg_xlog to be
+ * We could also recreate pg_wal if it doesn't exist, but a deliberate
+ * policy decision was made not to.  It is fairly common for pg_wal to be
  * a symlink, and if that was the DBA's intent then automatically making a
  * plain directory would result in degraded performance with no notice.
  */
@@ -3871,7 +3871,7 @@ ValidateXLOGDirectoryStructure(void)
 	char		path[MAXPGPATH];
 	struct stat stat_buf;
 
-	/* Check for pg_xlog; if it doesn't exist, error out */
+	/* Check for pg_wal; if it doesn't exist, error out */
 	if (stat(XLOGDIR, &stat_buf) != 0 ||
 		!S_ISDIR(stat_buf.st_mode))
 		ereport(FATAL,
@@ -4027,11 +4027,11 @@ ReadRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int emode,
 			 * If archive recovery was requested, but we were still doing
 			 * crash recovery, switch to archive recovery and retry using the
 			 * offline archive. We have now replayed all the valid WAL in
-			 * pg_xlog, so we are presumably now consistent.
+			 * pg_wal, so we are presumably now consistent.
 			 *
 			 * We require that there's at least some valid WAL present in
-			 * pg_xlog, however (!fetch_ckpt). We could recover using the WAL
-			 * from the archive, even if pg_xlog is completely empty, but we'd
+			 * pg_wal, however (!fetch_ckpt). We could recover using the WAL
+			 * from the archive, even if pg_wal is completely empty, but we'd
 			 * have no idea how far we'd have to replay to reach consistency.
 			 * So err on the safe side and give up.
 			 */
@@ -4039,7 +4039,7 @@ ReadRecord(XLogReaderState *xlogreader, XLogRecPtr RecPtr, int emode,
 				!fetching_ckpt)
 			{
 				ereport(DEBUG1,
-						(errmsg_internal("reached end of WAL in pg_xlog, entering archive recovery")));
+						(errmsg_internal("reached end of WAL in pg_wal, entering archive recovery")));
 				InArchiveRecovery = true;
 				if (StandbyModeRequested)
 					StandbyMode = true;
@@ -4156,7 +4156,7 @@ rescanLatestTimeLine(void)
 
 	/*
 	 * As in StartupXLOG(), try to ensure we have all the history files
-	 * between the old target and new target in pg_xlog.
+	 * between the old target and new target in pg_wal.
 	 */
 	restoreTimeLineHistoryFiles(oldtarget + 1, newtarget);
 
@@ -5189,7 +5189,7 @@ readRecoveryCommandFile(void)
 			ereport(WARNING,
 					(errmsg("recovery command file \"%s\" specified neither primary_conninfo nor restore_command",
 							RECOVERY_COMMAND_FILE),
-					 errhint("The database server will regularly poll the pg_xlog subdirectory to check for files placed there.")));
+					 errhint("The database server will regularly poll the pg_wal subdirectory to check for files placed there.")));
 	}
 	else
 	{
@@ -6056,7 +6056,7 @@ StartupXLOG(void)
 #endif
 
 	/*
-	 * Verify that pg_xlog and pg_xlog/archive_status exist.  In cases where
+	 * Verify that pg_wal and pg_wal/archive_status exist.  In cases where
 	 * someone has performed a copy for PITR, these directories may have been
 	 * excluded and need to be re-created.
 	 */
@@ -6269,7 +6269,7 @@ StartupXLOG(void)
 		 * and put it into archive recovery by creating a recovery.conf file.
 		 *
 		 * Our strategy in that case is to perform crash recovery first,
-		 * replaying all the WAL present in pg_xlog, and only enter archive
+		 * replaying all the WAL present in pg_wal, and only enter archive
 		 * recovery after that.
 		 *
 		 * But usually we already know how far we need to replay the WAL (up
@@ -6473,7 +6473,7 @@ StartupXLOG(void)
 
 	/*
 	 * Copy any missing timeline history files between 'now' and the recovery
-	 * target timeline from archive to pg_xlog. While we don't need those
+	 * target timeline from archive to pg_wal. While we don't need those
 	 * files ourselves - the history file of the recovery target timeline
 	 * covers all the previous timelines in the history too - a cascading
 	 * standby server might be interested in them. Or, if you archive the WAL
@@ -7094,7 +7094,7 @@ StartupXLOG(void)
 	/*
 	 * We are now done reading the xlog from stream. Turn off streaming
 	 * recovery to force fetching the files (which would be required at end of
-	 * recovery, e.g., timeline history file) from archive or pg_xlog.
+	 * recovery, e.g., timeline history file) from archive or pg_wal.
 	 */
 	StandbyMode = false;
 
@@ -7382,7 +7382,7 @@ StartupXLOG(void)
 		 * As a compromise, we rename the last segment with the .partial
 		 * suffix, and archive it. Archive recovery will never try to read
 		 * .partial segments, so they will normally go unused. But in the odd
-		 * PITR case, the administrator can copy them manually to the pg_xlog
+		 * PITR case, the administrator can copy them manually to the pg_wal
 		 * directory (removing the suffix). They can be useful in debugging,
 		 * too.
 		 *
@@ -9958,7 +9958,7 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
 		 * first WAL segment containing the startup checkpoint has pages in
 		 * the beginning with the old timeline ID.  That can cause trouble at
 		 * recovery: we won't have a history file covering the old timeline if
-		 * pg_xlog directory was not included in the base backup and the WAL
+		 * pg_wal directory was not included in the base backup and the WAL
 		 * archive was cleared too before starting the backup.
 		 *
 		 * This also ensures that we have emitted a WAL page header that has
@@ -10605,7 +10605,7 @@ do_pg_stop_backup(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
 	 * archived before returning. If archiving isn't enabled, the required WAL
 	 * needs to be transported via streaming replication (hopefully with
 	 * wal_keep_segments set high enough), or some more exotic mechanism like
-	 * polling and copying files from pg_xlog with script. We have no
+	 * polling and copying files from pg_wal with script. We have no
 	 * knowledge of those mechanisms, so it's up to the user to ensure that he
 	 * gets all the required WAL.
 	 *
@@ -11195,9 +11195,9 @@ next_record_is_invalid:
  * Open the WAL segment containing WAL position 'RecPtr'.
  *
  * The segment can be fetched via restore_command, or via walreceiver having
- * streamed the record, or it can already be present in pg_xlog. Checking
- * pg_xlog is mainly for crash recovery, but it will be polled in standby mode
- * too, in case someone copies a new segment directly to pg_xlog. That is not
+ * streamed the record, or it can already be present in pg_wal. Checking
+ * pg_wal is mainly for crash recovery, but it will be polled in standby mode
+ * too, in case someone copies a new segment directly to pg_wal. That is not
  * documented or recommended, though.
  *
  * If 'fetching_ckpt' is true, we're fetching a checkpoint record, and should
@@ -11227,8 +11227,8 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 	/*-------
 	 * Standby mode is implemented by a state machine:
 	 *
-	 * 1. Read from either archive or pg_xlog (XLOG_FROM_ARCHIVE), or just
-	 *	  pg_xlog (XLOG_FROM_XLOG)
+	 * 1. Read from either archive or pg_wal (XLOG_FROM_ARCHIVE), or just
+	 *	  pg_wal (XLOG_FROM_PG_WAL)
 	 * 2. Check trigger file
 	 * 3. Read from primary server via walreceiver (XLOG_FROM_STREAM)
 	 * 4. Rescan timelines
@@ -11244,7 +11244,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 	 *-------
 	 */
 	if (!InArchiveRecovery)
-		currentSource = XLOG_FROM_PG_XLOG;
+		currentSource = XLOG_FROM_PG_WAL;
 	else if (currentSource == 0)
 		currentSource = XLOG_FROM_ARCHIVE;
 
@@ -11263,13 +11263,13 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 			switch (currentSource)
 			{
 				case XLOG_FROM_ARCHIVE:
-				case XLOG_FROM_PG_XLOG:
+				case XLOG_FROM_PG_WAL:
 
 					/*
 					 * Check to see if the trigger file exists. Note that we
 					 * do this only after failure, so when you create the
 					 * trigger file, we still finish replaying as much as we
-					 * can from archive and pg_xlog before failover.
+					 * can from archive and pg_wal before failover.
 					 */
 					if (StandbyMode && CheckForStandbyTrigger())
 					{
@@ -11279,7 +11279,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 
 					/*
 					 * Not in standby mode, and we've now tried the archive
-					 * and pg_xlog.
+					 * and pg_wal.
 					 */
 					if (!StandbyMode)
 						return false;
@@ -11339,7 +11339,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					 * little chance that the problem will just go away, but
 					 * PANIC is not good for availability either, especially
 					 * in hot standby mode. So, we treat that the same as
-					 * disconnection, and retry from archive/pg_xlog again.
+					 * disconnection, and retry from archive/pg_wal again.
 					 * The WAL in the archive should be identical to what was
 					 * streamed, so it's unlikely that it helps, but one can
 					 * hope...
@@ -11400,11 +11400,11 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					elog(ERROR, "unexpected WAL source %d", currentSource);
 			}
 		}
-		else if (currentSource == XLOG_FROM_PG_XLOG)
+		else if (currentSource == XLOG_FROM_PG_WAL)
 		{
 			/*
-			 * We just successfully read a file in pg_xlog. We prefer files in
-			 * the archive over ones in pg_xlog, so try the next file again
+			 * We just successfully read a file in pg_wal. We prefer files in
+			 * the archive over ones in pg_wal, so try the next file again
 			 * from the archive first.
 			 */
 			if (InArchiveRecovery)
@@ -11425,7 +11425,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 		switch (currentSource)
 		{
 			case XLOG_FROM_ARCHIVE:
-			case XLOG_FROM_PG_XLOG:
+			case XLOG_FROM_PG_WAL:
 				/* Close any old file we might have open. */
 				if (readFile >= 0)
 				{
@@ -11438,7 +11438,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 
 				/*
 				 * Try to restore the file from archive, or read an existing
-				 * file from pg_xlog.
+				 * file from pg_wal.
 				 */
 				readFile = XLogFileReadAnyTLI(readSegNo, DEBUG2,
 						 currentSource == XLOG_FROM_ARCHIVE ? XLOG_FROM_ANY :
@@ -11447,7 +11447,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					return true;	/* success! */
 
 				/*
-				 * Nope, not found in archive or pg_xlog.
+				 * Nope, not found in archive or pg_wal.
 				 */
 				lastSourceFailed = true;
 				break;
@@ -11503,7 +11503,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 						 * not open already.  Also read the timeline history
 						 * file if we haven't initialized timeline history
 						 * yet; it should be streamed over and present in
-						 * pg_xlog by now.  Use XLOG_FROM_STREAM so that
+						 * pg_wal by now.  Use XLOG_FROM_STREAM so that
 						 * source info is set correctly and XLogReceiptTime
 						 * isn't changed.
 						 */
@@ -11535,10 +11535,10 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 						/*
 						 * Note that we don't "return false" immediately here.
 						 * After being triggered, we still want to replay all
-						 * the WAL that was already streamed. It's in pg_xlog
+						 * the WAL that was already streamed. It's in pg_wal
 						 * now, so we just treat this as a failure, and the
 						 * state machine will move on to replay the streamed
-						 * WAL from pg_xlog, and then recheck the trigger and
+						 * WAL from pg_wal, and then recheck the trigger and
 						 * exit replay.
 						 */
 						lastSourceFailed = true;
@@ -11578,7 +11578,7 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
  * or legitimate end-of-WAL situation.   Generally, we use it as-is, but if
  * we're retrying the exact same record that we've tried previously, only
  * complain the first time to keep the noise down.  However, we only do when
- * reading from pg_xlog, because we don't expect any invalid records in archive
+ * reading from pg_wal, because we don't expect any invalid records in archive
  * or in records streamed from master. Files in the archive should be complete,
  * and we should never hit the end of WAL because we stop and wait for more WAL
  * to arrive before replaying it.
@@ -11593,7 +11593,7 @@ emode_for_corrupt_record(int emode, XLogRecPtr RecPtr)
 {
 	static XLogRecPtr lastComplaint = 0;
 
-	if (readSource == XLOG_FROM_PG_XLOG && emode == LOG)
+	if (readSource == XLOG_FROM_PG_WAL && emode == LOG)
 	{
 		if (RecPtr == lastComplaint)
 			emode = DEBUG1;
diff --git a/src/backend/access/transam/xlogarchive.c b/src/backend/access/transam/xlogarchive.c
index d153a44..b919164 100644
--- a/src/backend/access/transam/xlogarchive.c
+++ b/src/backend/access/transam/xlogarchive.c
@@ -421,7 +421,7 @@ ExecuteRecoveryCommand(char *command, char *commandName, bool failOnSignal)
 /*
  * A file was restored from the archive under a temporary filename (path),
  * and now we want to keep it. Rename it under the permanent filename in
- * in pg_xlog (xlogfname), replacing any existing file with the same name.
+ * in pg_wal (xlogfname), replacing any existing file with the same name.
  */
 void
 KeepFileRestoredFromArchive(char *path, char *xlogfname)
diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 33383b4..01cbd90 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -128,7 +128,7 @@ pg_start_backup(PG_FUNCTION_ARGS)
  * pg_stop_backup: finish taking an on-line backup dump
  *
  * We write an end-of-backup WAL record, and remove the backup label file
- * created by pg_start_backup, creating a backup history file in pg_xlog
+ * created by pg_start_backup, creating a backup history file in pg_wal
  * instead (whence it will immediately be archived). The backup history file
  * contains the same info found in the label file, plus the backup-end time
  * and WAL location. Before 9.0, the backup-end time was read from the backup
diff --git a/src/backend/replication/README b/src/backend/replication/README
index ad4864d..0cbb990 100644
--- a/src/backend/replication/README
+++ b/src/backend/replication/README
@@ -54,7 +54,7 @@ and WalRcvData->slotname, and initializes the starting point in
 WalRcvData->receiveStart.
 
 As walreceiver receives WAL from the master server, and writes and flushes
-it to disk (in pg_xlog), it updates WalRcvData->receivedUpto and signals
+it to disk (in pg_wal), it updates WalRcvData->receivedUpto and signals
 the startup process to know how far WAL replay can advance.
 
 Walreceiver sends information about replication progress to the master server
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index fa75930..ffc7e58 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -346,7 +346,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		TimeLineID	tli;
 
 		/*
-		 * I'd rather not worry about timelines here, so scan pg_xlog and
+		 * I'd rather not worry about timelines here, so scan pg_wal and
 		 * include all WAL files in the range between 'startptr' and 'endptr',
 		 * regardless of the timeline the file is stamped with. If there are
 		 * some spurious WAL files belonging to timelines that don't belong in
@@ -359,11 +359,11 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		XLByteToPrevSeg(endptr, endsegno);
 		XLogFileName(lastoff, ThisTimeLineID, endsegno);
 
-		dir = AllocateDir("pg_xlog");
+		dir = AllocateDir("pg_wal");
 		if (!dir)
 			ereport(ERROR,
-				 (errmsg("could not open directory \"%s\": %m", "pg_xlog")));
-		while ((de = ReadDir(dir, "pg_xlog")) != NULL)
+				 (errmsg("could not open directory \"%s\": %m", "pg_wal")));
+		while ((de = ReadDir(dir, "pg_wal")) != NULL)
 		{
 			/* Does it look like a WAL segment, and is it in the range? */
 			if (IsXLogFileName(de->d_name) &&
@@ -401,7 +401,7 @@ perform_base_backup(basebackup_options *opt, DIR *tblspcdir)
 		qsort(walFiles, nWalFiles, sizeof(char *), compareWalFileNames);
 
 		/*
-		 * There must be at least one xlog file in the pg_xlog directory,
+		 * There must be at least one xlog file in the pg_wal directory,
 		 * since we are doing backup-including-xlog.
 		 */
 		if (nWalFiles < 1)
@@ -1054,23 +1054,23 @@ sendDir(char *path, int basepathlen, bool sizeonly, List *tablespaces,
 		}
 
 		/*
-		 * We can skip pg_xlog, the WAL segments need to be fetched from the
+		 * We can skip pg_wal, the WAL segments need to be fetched from the
 		 * WAL archive anyway. But include it as an empty directory anyway, so
 		 * we get permissions right.
 		 */
-		if (strcmp(pathbuf, "./pg_xlog") == 0)
+		if (strcmp(pathbuf, "./pg_wal") == 0)
 		{
-			/* If pg_xlog is a symlink, write it as a directory anyway */
+			/* If pg_wal is a symlink, write it as a directory anyway */
 			size += _tarWriteDir(pathbuf, basepathlen, &statbuf, sizeonly);
 
 			/*
 			 * Also send archive_status directory (by hackishly reusing
 			 * statbuf from above ...).
 			 */
-			size += _tarWriteHeader("./pg_xlog/archive_status", NULL, &statbuf,
+			size += _tarWriteHeader("./pg_wal/archive_status", NULL, &statbuf,
 									sizeonly);
 
-			continue;			/* don't recurse into pg_xlog */
+			continue;			/* don't recurse into pg_wal */
 		}
 
 		/* Allow symbolic links in pg_tblspc only */
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index eed6eff..2bb3dce 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -18,7 +18,7 @@
  * If the primary server ends streaming, but doesn't disconnect, walreceiver
  * goes into "waiting" mode, and waits for the startup process to give new
  * instructions. The startup process will treat that the same as
- * disconnection, and will rescan the archive/pg_xlog directory. But when the
+ * disconnection, and will rescan the archive/pg_wal directory. But when the
  * startup process wants to try streaming replication again, it will just
  * nudge the existing walreceiver process that's waiting, instead of launching
  * a new one.
@@ -365,7 +365,7 @@ WalReceiverMain(void)
 		 * we've already reached the end of the old timeline, the server will
 		 * finish the streaming immediately, and we will go back to await
 		 * orders from the startup process. If recovery_target_timeline is
-		 * 'latest', the startup process will scan pg_xlog and find the new
+		 * 'latest', the startup process will scan pg_wal and find the new
 		 * history file, bump recovery target timeline, and ask us to restart
 		 * on the new timeline.
 		 */
@@ -742,7 +742,7 @@ WalRcvFetchTimeLineHistoryFiles(TimeLineID first, TimeLineID last)
 										 tli)));
 
 			/*
-			 * Write the file to pg_xlog.
+			 * Write the file to pg_wal.
 			 */
 			writeTimeLineHistoryFile(tli, content, len);
 
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 0f3ced2..bc5e508 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -586,7 +586,7 @@ StartReplication(StartReplicationCmd *cmd)
 			 * segment that contains switchpoint, but on the new timeline, so
 			 * that it doesn't end up with a partial segment. If you ask for a
 			 * too old starting point, you'll get an error later when we fail
-			 * to find the requested WAL segment in pg_xlog.
+			 * to find the requested WAL segment in pg_wal.
 			 *
 			 * XXX: we could be more strict here and only allow a startpoint
 			 * that's older than the switchpoint, if it's still in the same
@@ -2058,7 +2058,7 @@ retry:
 			 *
 			 * For example, imagine that this server is currently on timeline
 			 * 5, and we're streaming timeline 4. The switch from timeline 4
-			 * to 5 happened at 0/13002088. In pg_xlog, we have these files:
+			 * to 5 happened at 0/13002088. In pg_wal, we have these files:
 			 *
 			 * ...
 			 * 000000040000000000000012
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 03143f1..b7ff5ef 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -2787,7 +2787,7 @@ looks_like_temp_rel_name(const char *name)
  * Issue fsync recursively on PGDATA and all its contents.
  *
  * We fsync regular files and directories wherever they are, but we
- * follow symlinks only for pg_xlog and immediately under pg_tblspc.
+ * follow symlinks only for pg_wal and immediately under pg_tblspc.
  * Other symlinks are presumed to point at files we're not responsible
  * for fsyncing, and might not have privileges to write at all.
  *
@@ -2811,7 +2811,7 @@ SyncDataDirectory(void)
 		return;
 
 	/*
-	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * If pg_wal is a symlink, we'll need to recurse into it separately,
 	 * because the first walkdir below will ignore it.
 	 */
 	xlog_is_symlink = false;
@@ -2820,16 +2820,16 @@ SyncDataDirectory(void)
 	{
 		struct stat st;
 
-		if (lstat("pg_xlog", &st) < 0)
+		if (lstat("pg_wal", &st) < 0)
 			ereport(LOG,
 					(errcode_for_file_access(),
 					 errmsg("could not stat file \"%s\": %m",
-							"pg_xlog")));
+							"pg_wal")));
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
 #else
-	if (pgwin32_is_junction("pg_xlog"))
+	if (pgwin32_is_junction("pg_wal"))
 		xlog_is_symlink = true;
 #endif
 
@@ -2841,7 +2841,7 @@ SyncDataDirectory(void)
 #ifdef PG_FLUSH_DATA_WORKS
 	walkdir(".", pre_sync_fname, false, DEBUG1);
 	if (xlog_is_symlink)
-		walkdir("pg_xlog", pre_sync_fname, false, DEBUG1);
+		walkdir("pg_wal", pre_sync_fname, false, DEBUG1);
 	walkdir("pg_tblspc", pre_sync_fname, true, DEBUG1);
 #endif
 
@@ -2849,14 +2849,14 @@ SyncDataDirectory(void)
 	 * Now we do the fsync()s in the same order.
 	 *
 	 * The main call ignores symlinks, so in addition to specially processing
-	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * pg_wal if it's a symlink, pg_tblspc has to be visited separately with
 	 * process_symlinks = true.  Note that if there are any plain directories
 	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
 	 * so we don't worry about optimizing it.
 	 */
 	walkdir(".", datadir_fsync_fname, false, LOG);
 	if (xlog_is_symlink)
-		walkdir("pg_xlog", datadir_fsync_fname, false, LOG);
+		walkdir("pg_wal", datadir_fsync_fname, false, LOG);
 	walkdir("pg_tblspc", datadir_fsync_fname, true, LOG);
 }
 
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index e52e67d..385e808 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -195,7 +195,7 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 
 static const char *const subdirs[] = {
 	"global",
-	"pg_xlog/archive_status",
+	"pg_wal/archive_status",
 	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
@@ -2091,8 +2091,6 @@ make_postgres(FILE *cmdfd)
 		PG_CMD_PUTS(*line);
 }
 
-
-
 /*
  * signal handler in case we are interrupted.
  *
@@ -2830,7 +2828,7 @@ create_xlog_or_symlink(void)
 	char	   *subdirloc;
 
 	/* form name of the place for the subdirectory or symlink */
-	subdirloc = psprintf("%s/pg_xlog", pg_data);
+	subdirloc = psprintf("%s/pg_wal", pg_data);
 
 	if (strcmp(xlog_dir, "") != 0)
 	{
@@ -2963,7 +2961,7 @@ initialize_data_directory(void)
 
 	create_xlog_or_symlink();
 
-	/* Create required subdirectories (other than pg_xlog) */
+	/* Create required subdirectories (other than pg_wal) */
 	printf(_("creating subdirectories ... "));
 	fflush(stdout);
 
@@ -3258,7 +3256,7 @@ main(int argc, char *argv[])
 
 		fputs(_("syncing data to disk ... "), stdout);
 		fflush(stdout);
-		fsync_pgdata(pg_data, progname);
+		fsync_pgdata(pg_data, progname, PG_VERSION_NUM);
 		check_ok();
 		return 0;
 	}
@@ -3324,7 +3322,7 @@ main(int argc, char *argv[])
 	{
 		fputs(_("syncing data to disk ... "), stdout);
 		fflush(stdout);
-		fsync_pgdata(pg_data, progname);
+		fsync_pgdata(pg_data, progname, PG_VERSION_NUM);
 		check_ok();
 	}
 	else
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 0f5d9d6..6b2a01f 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -55,6 +55,12 @@ typedef struct TablespaceList
 	TablespaceListCell *tail;
 } TablespaceList;
 
+/*
+ * pg_xlog has been renamed to pg_wal in version 10.  This version number
+ * should be compared with PQserverVersion().
+ */
+#define MINIMUM_VERSION_FOR_PG_WAL	100000
+
 /* Global options */
 static char *basedir = NULL;
 static TablespaceList tablespace_dirs = {NULL, NULL};
@@ -526,15 +532,22 @@ StartLogStreamer(char *startpos, uint32 timeline, char *sysidentifier)
 		/* Error message already written in GetConnection() */
 		exit(1);
 
-	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/pg_xlog", basedir);
+	/* In post-10 cluster, pg_xlog has been renamed to pg_wal */
+	snprintf(param->xlogdir, sizeof(param->xlogdir), "%s/%s",
+			 basedir,
+			 PQserverVersion(conn) < MINIMUM_VERSION_FOR_PG_WAL ?
+				"pg_xlog" : "pg_wal");
 
 	/*
-	 * Create pg_xlog/archive_status (and thus pg_xlog) so we can write to
-	 * basedir/pg_xlog as the directory entry in the tar file may arrive
-	 * later.
+	 * Create pg_wal/archive_status or pg_xlog/archive_status (and thus
+	 * pg_wal or pg_xlog) depending on the target server so we can write to
+	 * basedir/pg_wal or basedir/pg_xlog as the directory entry in the tar
+	 * file may arrive later.
 	 */
-	snprintf(statusdir, sizeof(statusdir), "%s/pg_xlog/archive_status",
-			 basedir);
+	snprintf(statusdir, sizeof(statusdir), "%s/%s/archive_status",
+			 basedir,
+			 PQserverVersion(conn) < MINIMUM_VERSION_FOR_PG_WAL ?
+				"pg_xlog" : "pg_wal");
 
 	if (pg_mkdir_p(statusdir, S_IRWXU) != 0 && errno != EEXIST)
 	{
@@ -1338,15 +1351,17 @@ ReceiveAndUnpackTarFile(PGconn *conn, PGresult *res, int rownum)
 					if (mkdir(filename, S_IRWXU) != 0)
 					{
 						/*
-						 * When streaming WAL, pg_xlog will have been created
-						 * by the wal receiver process. Also, when transaction
-						 * log directory location was specified, pg_xlog has
-						 * already been created as a symbolic link before
-						 * starting the actual backup. So just ignore creation
-						 * failures on related directories.
+						 * When streaming WAL, pg_wal (or pg_xlog for pre-9.6
+						 * clusters) will have been created by the wal receiver
+						 * process. Also, when transaction log directory location
+						 * was specified, pg_wal (or pg_xlog) has already been
+						 * created as a symbolic link before starting the actual
+						 * backup. So just ignore creation failures on related
+						 * directories.
 						 */
-						if (!((pg_str_endswith(filename, "/pg_xlog") ||
-							 pg_str_endswith(filename, "/archive_status")) &&
+						if (!((pg_str_endswith(filename, "/pg_wal") ||
+							   pg_str_endswith(filename, "/pg_xlog")||
+							   pg_str_endswith(filename, "/archive_status")) &&
 							  errno == EEXIST))
 						{
 							fprintf(stderr,
@@ -1634,15 +1649,10 @@ BaseBackup(void)
 	char		xlogend[64];
 	int			minServerMajor,
 				maxServerMajor;
-	int			serverMajor;
+	int			serverVersion,
+				serverMajor;
 
-	/*
-	 * Connect in replication mode to the server
-	 */
-	conn = GetConnection();
-	if (!conn)
-		/* Error message already written in GetConnection() */
-		exit(1);
+	Assert(conn != NULL);
 
 	/*
 	 * Check server version. BASE_BACKUP command was introduced in 9.1, so we
@@ -1650,7 +1660,8 @@ BaseBackup(void)
 	 */
 	minServerMajor = 901;
 	maxServerMajor = PG_VERSION_NUM / 100;
-	serverMajor = PQserverVersion(conn) / 100;
+	serverVersion = PQserverVersion(conn);
+	serverMajor = serverVersion / 100;
 	if (serverMajor < minServerMajor || serverMajor > maxServerMajor)
 	{
 		const char *serverver = PQparameterStatus(conn, "server_version");
@@ -1979,7 +1990,7 @@ BaseBackup(void)
 		}
 		else
 		{
-			(void) fsync_pgdata(basedir, progname);
+			(void) fsync_pgdata(basedir, progname, serverVersion);
 		}
 	}
 
@@ -2296,6 +2307,14 @@ main(int argc, char **argv)
 	if (format == 'p' || strcmp(basedir, "-") != 0)
 		verify_dir_is_empty_or_create(basedir, &made_new_pgdata, &found_existing_pgdata);
 
+	/* connection in replication mode to server */
+	conn = GetConnection();
+	if (!conn)
+	{
+		/* Error message already written in GetConnection() */
+		exit(1);
+	}
+
 	/* Create transaction log symlink, if required */
 	if (strcmp(xlog_dir, "") != 0)
 	{
@@ -2303,19 +2322,24 @@ main(int argc, char **argv)
 
 		verify_dir_is_empty_or_create(xlog_dir, &made_new_xlogdir, &found_existing_xlogdir);
 
-		/* form name of the place where the symlink must go */
-		linkloc = psprintf("%s/pg_xlog", basedir);
+		/*
+		 * Form name of the place where the symlink must go. pg_xlog has
+		 * been renamed to pg_wal in post-10 clusters.
+		 */
+		linkloc = psprintf("%s/%s", basedir,
+						   PQserverVersion(conn) < MINIMUM_VERSION_FOR_PG_WAL ?
+								"pg_xlog" : "pg_wal");
 
 #ifdef HAVE_SYMLINK
 		if (symlink(xlog_dir, linkloc) != 0)
 		{
 			fprintf(stderr, _("%s: could not create symbolic link \"%s\": %s\n"),
 					progname, linkloc, strerror(errno));
-			exit(1);
+			disconnect_and_exit(1);
 		}
 #else
 		fprintf(stderr, _("%s: symlinks are not supported on this platform\n"));
-		exit(1);
+		disconnect_and_exit(1);
 #endif
 		free(linkloc);
 	}
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index a52bd4e..c8abbeb 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -67,9 +67,9 @@ $node->command_ok([ 'pg_basebackup', '-D', "$tempdir/backup" ],
 	'pg_basebackup runs');
 ok(-f "$tempdir/backup/PG_VERSION", 'backup was created');
 
-# Only archive_status directory should be copied in pg_xlog/.
+# Only archive_status directory should be copied in pg_wal/.
 is_deeply(
-	[ sort(slurp_dir("$tempdir/backup/pg_xlog/")) ],
+	[ sort(slurp_dir("$tempdir/backup/pg_wal/")) ],
 	[ sort qw(. .. archive_status) ],
 	'no WAL files copied');
 
@@ -230,12 +230,12 @@ like(
 $node->command_ok(
 	[ 'pg_basebackup', '-D', "$tempdir/backupxf", '-X', 'fetch' ],
 	'pg_basebackup -X fetch runs');
-ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_xlog")),
+ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_wal")),
 	'WAL files copied');
 $node->command_ok(
 	[ 'pg_basebackup', '-D', "$tempdir/backupxs", '-X', 'stream' ],
 	'pg_basebackup -X stream runs');
-ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_xlog")),
+ok(grep(/^[0-9A-F]{24}$/, slurp_dir("$tempdir/backupxf/pg_wal")),
 	'WAL files copied');
 
 $node->command_fails(
diff --git a/src/bin/pg_resetxlog/pg_resetxlog.c b/src/bin/pg_resetxlog/pg_resetxlog.c
index 525b82ba..2b76f64 100644
--- a/src/bin/pg_resetxlog/pg_resetxlog.c
+++ b/src/bin/pg_resetxlog/pg_resetxlog.c
@@ -890,7 +890,7 @@ FindEndOfXLOG(void)
 	newXlogSegNo = ControlFile.checkPointCopy.redo / ControlFile.xlog_seg_size;
 
 	/*
-	 * Scan the pg_xlog directory to find existing WAL segment files. We
+	 * Scan the pg_wal directory to find existing WAL segment files. We
 	 * assume any present have been used; in most scenarios this should be
 	 * conservative, because of xlog.c's attempts to pre-create files.
 	 */
diff --git a/src/bin/pg_rewind/copy_fetch.c b/src/bin/pg_rewind/copy_fetch.c
index 327e7ef..d0c1586 100644
--- a/src/bin/pg_rewind/copy_fetch.c
+++ b/src/bin/pg_rewind/copy_fetch.c
@@ -131,10 +131,10 @@ recurse_dir(const char *datadir, const char *parentpath,
 			/*
 			 * If it's a symlink within pg_tblspc, we need to recurse into it,
 			 * to process all the tablespaces.  We also follow a symlink if
-			 * it's for pg_xlog.  Symlinks elsewhere are ignored.
+			 * it's for pg_wal.  Symlinks elsewhere are ignored.
 			 */
 			if ((parentpath && strcmp(parentpath, "pg_tblspc") == 0) ||
-				strcmp(path, "pg_xlog") == 0)
+				strcmp(path, "pg_wal") == 0)
 				recurse_dir(datadir, path, callback);
 #else
 			pg_fatal("\"%s\" is a symbolic link, but symbolic links are not supported on this platform\n",
diff --git a/src/bin/pg_rewind/filemap.c b/src/bin/pg_rewind/filemap.c
index 9b00dc1..3905a5d 100644
--- a/src/bin/pg_rewind/filemap.c
+++ b/src/bin/pg_rewind/filemap.c
@@ -79,11 +79,11 @@ process_source_file(const char *path, file_type_t type, size_t newsize,
 		return;
 
 	/*
-	 * Pretend that pg_xlog is a directory, even if it's really a symlink. We
+	 * Pretend that pg_wal is a directory, even if it's really a symlink. We
 	 * don't want to mess with the symlink itself, nor complain if it's a
 	 * symlink in source but not in target or vice versa.
 	 */
-	if (strcmp(path, "pg_xlog") == 0 && type == FILE_TYPE_SYMLINK)
+	if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK)
 		type = FILE_TYPE_DIRECTORY;
 
 	/*
@@ -120,7 +120,7 @@ process_source_file(const char *path, file_type_t type, size_t newsize,
 	switch (type)
 	{
 		case FILE_TYPE_DIRECTORY:
-			if (exists && !S_ISDIR(statbuf.st_mode) && strcmp(path, "pg_xlog") != 0)
+			if (exists && !S_ISDIR(statbuf.st_mode) && strcmp(path, "pg_wal") != 0)
 			{
 				/* it's a directory in source, but not in target. Strange.. */
 				pg_fatal("\"%s\" is not a directory\n", localpath);
@@ -296,7 +296,7 @@ process_target_file(const char *path, file_type_t type, size_t oldsize,
 	/*
 	 * Like in process_source_file, pretend that xlog is always a  directory.
 	 */
-	if (strcmp(path, "pg_xlog") == 0 && type == FILE_TYPE_SYMLINK)
+	if (strcmp(path, "pg_wal") == 0 && type == FILE_TYPE_SYMLINK)
 		type = FILE_TYPE_DIRECTORY;
 
 	key.path = (char *) path;
diff --git a/src/bin/pg_rewind/parsexlog.c b/src/bin/pg_rewind/parsexlog.c
index b53591d..23ac4e7 100644
--- a/src/bin/pg_rewind/parsexlog.c
+++ b/src/bin/pg_rewind/parsexlog.c
@@ -54,7 +54,7 @@ static int SimpleXLogPageRead(XLogReaderState *xlogreader,
 				   TimeLineID *pageTLI);
 
 /*
- * Read WAL from the datadir/pg_xlog, starting from 'startpoint' on timeline
+ * Read WAL from the datadir/pg_wal, starting from 'startpoint' on timeline
  * index 'tliIndex' in target timeline history, until 'endpoint'. Make note of
  * the data blocks touched by the WAL records, and return them in a page map.
  */
diff --git a/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl b/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
index bdcab56..12950ea 100644
--- a/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
+++ b/src/bin/pg_rewind/t/004_pg_xlog_symlink.pl
@@ -1,5 +1,5 @@
 #
-# Test pg_rewind when the target's pg_xlog directory is a symlink.
+# Test pg_rewind when the target's pg_wal directory is a symlink.
 #
 use strict;
 use warnings;
@@ -30,10 +30,10 @@ sub run_test
 
 	my $test_master_datadir = $node_master->data_dir;
 
-	# turn pg_xlog into a symlink
-	print("moving $test_master_datadir/pg_xlog to $master_xlogdir\n");
-	move("$test_master_datadir/pg_xlog", $master_xlogdir) or die;
-	symlink($master_xlogdir, "$test_master_datadir/pg_xlog") or die;
+	# turn pg_wal into a symlink
+	print("moving $test_master_datadir/pg_wal to $master_xlogdir\n");
+	move("$test_master_datadir/pg_wal", $master_xlogdir) or die;
+	symlink($master_xlogdir, "$test_master_datadir/pg_wal") or die;
 
 	RewindTest::start_master();
 
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 6d04e56..55a6f0d 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -14,7 +14,7 @@
 #include <fcntl.h>
 #include <sys/types.h>
 
-static void check_data_dir(const char *pg_data);
+static void check_data_dir(ClusterInfo *cluster);
 static void check_bin_dir(ClusterInfo *cluster);
 static void validate_exec(const char *dir, const char *cmdName);
 
@@ -220,9 +220,9 @@ verify_directories(void)
 		pg_fatal("You must have read and write access in the current directory.\n");
 
 	check_bin_dir(&old_cluster);
-	check_data_dir(old_cluster.pgdata);
+	check_data_dir(&old_cluster);
 	check_bin_dir(&new_cluster);
-	check_data_dir(new_cluster.pgdata);
+	check_data_dir(&new_cluster);
 }
 
 
@@ -253,6 +253,32 @@ win32_check_directory_write_permissions(void)
 
 
 /*
+ * check_single_dir()
+ *
+ *  Check for the presence of a single directory in PGDATA, and fail if
+ * is it missing or not accessible.
+ */
+static void
+check_single_dir(const char *pg_data, const char *subdir)
+{
+	struct stat statBuf;
+	char		subDirName[MAXPGPATH];
+
+	snprintf(subDirName, sizeof(subDirName), "%s%s%s", pg_data,
+			 /* Win32 can't stat() a directory with a trailing slash. */
+			 *subdir ? "/" : "",
+			 subdir);
+
+	if (stat(subDirName, &statBuf) != 0)
+		report_status(PG_FATAL, "check for \"%s\" failed: %s\n",
+					  subDirName, strerror(errno));
+	else if (!S_ISDIR(statBuf.st_mode))
+		report_status(PG_FATAL, "%s is not a directory\n",
+					  subDirName);
+}
+
+
+/*
  * check_data_dir()
  *
  *	This function validates the given cluster directory - we search for a
@@ -262,34 +288,27 @@ win32_check_directory_write_permissions(void)
  *
  */
 static void
-check_data_dir(const char *pg_data)
+check_data_dir(ClusterInfo *cluster)
 {
-	char		subDirName[MAXPGPATH];
-	int			subdirnum;
-
-	/* start check with top-most directory */
-	const char *requiredSubdirs[] = {"", "base", "global", "pg_clog",
-		"pg_multixact", "pg_subtrans", "pg_tblspc", "pg_twophase",
-	"pg_xlog"};
-
-	for (subdirnum = 0;
-		 subdirnum < sizeof(requiredSubdirs) / sizeof(requiredSubdirs[0]);
-		 ++subdirnum)
-	{
-		struct stat statBuf;
-
-		snprintf(subDirName, sizeof(subDirName), "%s%s%s", pg_data,
-		/* Win32 can't stat() a directory with a trailing slash. */
-				 *requiredSubdirs[subdirnum] ? "/" : "",
-				 requiredSubdirs[subdirnum]);
-
-		if (stat(subDirName, &statBuf) != 0)
-			report_status(PG_FATAL, "check for \"%s\" failed: %s\n",
-						  subDirName, strerror(errno));
-		else if (!S_ISDIR(statBuf.st_mode))
-			report_status(PG_FATAL, "%s is not a directory\n",
-						  subDirName);
-	}
+	const char *pg_data = cluster->pgdata;
+
+	/* get old and new cluster versions */
+	old_cluster.major_version = get_major_server_version(&old_cluster);
+	new_cluster.major_version = get_major_server_version(&new_cluster);
+
+	check_single_dir(pg_data, "");
+	check_single_dir(pg_data, "base");
+	check_single_dir(pg_data, "global");
+	check_single_dir(pg_data, "pg_multixact");
+	check_single_dir(pg_data, "pg_subtrans");
+	check_single_dir(pg_data, "pg_tblspc");
+	check_single_dir(pg_data, "pg_twophase");
+
+	/* pg_xlog has been renamed to pg_wal in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_xlog");
+	else
+		check_single_dir(pg_data, "pg_wal");
 }
 
 
diff --git a/src/bin/pg_xlogdump/pg_xlogdump.c b/src/bin/pg_xlogdump/pg_xlogdump.c
index 9ad9321..7490398 100644
--- a/src/bin/pg_xlogdump/pg_xlogdump.c
+++ b/src/bin/pg_xlogdump/pg_xlogdump.c
@@ -680,7 +680,7 @@ usage(void)
 	printf("  -f, --follow           keep retrying after reaching end of WAL\n");
 	printf("  -n, --limit=N          number of records to display\n");
 	printf("  -p, --path=PATH        directory in which to find log segment files\n");
-	printf("                         (default: ./pg_xlog)\n");
+	printf("                         (default: ./pg_wal)\n");
 	printf("  -r, --rmgr=RMGR        only show records generated by resource manager RMGR\n");
 	printf("                         use --rmgr=list to list valid resource manager names\n");
 	printf("  -s, --start=RECPTR     start reading at log position RECPTR\n");
diff --git a/src/common/file_utils.c b/src/common/file_utils.c
index 1855e23..2fdb469 100644
--- a/src/common/file_utils.c
+++ b/src/common/file_utils.c
@@ -29,6 +29,11 @@
 #define PG_FLUSH_DATA_WORKS 1
 #endif
 
+/*
+ * pg_xlog has been renamed to pg_wal in version 10.
+ */
+#define MINIMUM_VERSION_FOR_PG_WAL  100000
+
 #ifdef PG_FLUSH_DATA_WORKS
 static int pre_sync_fname(const char *fname, bool isdir,
 						   const char *progname);
@@ -40,25 +45,31 @@ static void walkdir(const char *path,
 /*
  * Issue fsync recursively on PGDATA and all its contents.
  *
- * We fsync regular files and directories wherever they are, but we
- * follow symlinks only for pg_xlog and immediately under pg_tblspc.
- * Other symlinks are presumed to point at files we're not responsible
- * for fsyncing, and might not have privileges to write at all.
+ * We fsync regular files and directories wherever they are, but we follow
+ * symlinks only for pg_wal (or pg_xlog) and immediately under pg_tblspc.
+ * Other symlinks are presumed to point at files we're not responsible for
+ * fsyncing, and might not have privileges to write at all.
+ *
+ * serverVersion indicates the version of the server to be fsync'd.
  *
  * Errors are reported but not considered fatal.
  */
 void
-fsync_pgdata(const char *pg_data, const char *progname)
+fsync_pgdata(const char *pg_data,
+			 const char *progname,
+			 int serverVersion)
 {
 	bool		xlog_is_symlink;
-	char		pg_xlog[MAXPGPATH];
+	char		pg_wal[MAXPGPATH];
 	char		pg_tblspc[MAXPGPATH];
 
-	snprintf(pg_xlog, MAXPGPATH, "%s/pg_xlog", pg_data);
+	/* handle renaming of pg_xlog to pg_wal in post-10 clusters */
+	snprintf(pg_wal, MAXPGPATH, "%s/%s", pg_data,
+		serverVersion < MINIMUM_VERSION_FOR_PG_WAL ? "pg_xlog" : "pg_wal");
 	snprintf(pg_tblspc, MAXPGPATH, "%s/pg_tblspc", pg_data);
 
 	/*
-	 * If pg_xlog is a symlink, we'll need to recurse into it separately,
+	 * If pg_wal is a symlink, we'll need to recurse into it separately,
 	 * because the first walkdir below will ignore it.
 	 */
 	xlog_is_symlink = false;
@@ -67,14 +78,14 @@ fsync_pgdata(const char *pg_data, const char *progname)
 	{
 		struct stat st;
 
-		if (lstat(pg_xlog, &st) < 0)
+		if (lstat(pg_wal, &st) < 0)
 			fprintf(stderr, _("%s: could not stat file \"%s\": %s\n"),
-					progname, pg_xlog, strerror(errno));
+					progname, pg_wal, strerror(errno));
 		else if (S_ISLNK(st.st_mode))
 			xlog_is_symlink = true;
 	}
 #else
-	if (pgwin32_is_junction(pg_xlog))
+	if (pgwin32_is_junction(pg_wal))
 		xlog_is_symlink = true;
 #endif
 
@@ -85,7 +96,7 @@ fsync_pgdata(const char *pg_data, const char *progname)
 #ifdef PG_FLUSH_DATA_WORKS
 	walkdir(pg_data, pre_sync_fname, false, progname);
 	if (xlog_is_symlink)
-		walkdir(pg_xlog, pre_sync_fname, false, progname);
+		walkdir(pg_wal, pre_sync_fname, false, progname);
 	walkdir(pg_tblspc, pre_sync_fname, true, progname);
 #endif
 
@@ -93,14 +104,14 @@ fsync_pgdata(const char *pg_data, const char *progname)
 	 * Now we do the fsync()s in the same order.
 	 *
 	 * The main call ignores symlinks, so in addition to specially processing
-	 * pg_xlog if it's a symlink, pg_tblspc has to be visited separately with
+	 * pg_wal if it's a symlink, pg_tblspc has to be visited separately with
 	 * process_symlinks = true.  Note that if there are any plain directories
 	 * in pg_tblspc, they'll get fsync'd twice.  That's not an expected case
 	 * so we don't worry about optimizing it.
 	 */
 	walkdir(pg_data, fsync_fname, false, progname);
 	if (xlog_is_symlink)
-		walkdir(pg_xlog, fsync_fname, false, progname);
+		walkdir(pg_wal, fsync_fname, false, progname);
 	walkdir(pg_tblspc, fsync_fname, true, progname);
 }
 
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 0a595cc..ceb0462 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -128,7 +128,7 @@ typedef XLogLongPageHeaderData *XLogLongPageHeader;
 /*
  * The XLog directory and control file (relative to $PGDATA)
  */
-#define XLOGDIR				"pg_xlog"
+#define XLOGDIR				"pg_wal"
 #define XLOG_CONTROL_FILE	"global/pg_control"
 
 /*
diff --git a/src/include/common/file_utils.h b/src/include/common/file_utils.h
index 1cb263d..b83c398 100644
--- a/src/include/common/file_utils.h
+++ b/src/include/common/file_utils.h
@@ -17,7 +17,8 @@
 
 extern int fsync_fname(const char *fname, bool isdir,
 					   const char *progname);
-extern void fsync_pgdata(const char *pg_data, const char *progname);
+extern void fsync_pgdata(const char *pg_data, const char *progname,
+						 int serverVersion);
 extern int durable_rename(const char *oldfile, const char *newfile,
 						  const char *progname);
 extern int fsync_parent_path(const char *fname, const char *progname);
diff --git a/src/include/postmaster/pgarch.h b/src/include/postmaster/pgarch.h
index f2cbfb3..6df73c9 100644
--- a/src/include/postmaster/pgarch.h
+++ b/src/include/postmaster/pgarch.h
@@ -16,7 +16,7 @@
 /* ----------
  * Archiver control info.
  *
- * We expect that archivable files within pg_xlog will have names between
+ * We expect that archivable files within pg_wal will have names between
  * MIN_XFN_CHARS and MAX_XFN_CHARS in length, consisting only of characters
  * appearing in VALID_XFN_CHARS.  The status files in archive_status have
  * corresponding names with ".ready" or ".done" appended.
-- 
2.10.1

From c5188910213699db4dcf201b2f854e825703f222 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 4 Oct 2016 14:41:15 +0900
Subject: [PATCH 2/2] Rename pg_clog to pg_xact

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml               |  4 ++--
 doc/src/sgml/catalogs.sgml             |  4 ++--
 doc/src/sgml/config.sgml               |  2 +-
 doc/src/sgml/func.sgml                 |  2 +-
 doc/src/sgml/maintenance.sgml          |  8 ++++----
 doc/src/sgml/ref/pg_resetxlog.sgml     |  4 ++--
 doc/src/sgml/ref/pg_rewind.sgml        |  2 +-
 doc/src/sgml/storage.sgml              | 10 +++++-----
 doc/src/sgml/wal.sgml                  |  2 +-
 src/backend/access/heap/heapam.c       |  4 ++--
 src/backend/access/transam/README      | 10 +++++-----
 src/backend/access/transam/clog.c      |  2 +-
 src/backend/access/transam/commit_ts.c |  2 +-
 src/backend/access/transam/multixact.c |  2 +-
 src/backend/access/transam/subtrans.c  |  5 ++---
 src/backend/access/transam/transam.c   |  2 +-
 src/backend/access/transam/twophase.c  |  4 ++--
 src/backend/access/transam/xact.c      | 16 ++++++++--------
 src/backend/access/transam/xlog.c      |  2 +-
 src/backend/commands/vacuum.c          | 10 +++++-----
 src/backend/postmaster/autovacuum.c    |  2 +-
 src/backend/storage/buffer/README      |  2 +-
 src/backend/storage/ipc/procarray.c    |  4 ++--
 src/backend/utils/time/tqual.c         |  6 +++---
 src/bin/initdb/initdb.c                |  2 +-
 src/bin/pg_upgrade/exec.c              |  6 ++++++
 src/bin/pg_upgrade/pg_upgrade.c        | 30 ++++++++++++++++++------------
 src/include/access/slru.h              |  4 ++--
 28 files changed, 82 insertions(+), 71 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 6eaed1e..d22af0d 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -382,10 +382,10 @@ tar -cf backup.tar /usr/local/pgsql/data
       directories. This will <emphasis>not</> work because the
       information contained in these files is not usable without
       the commit log files,
-      <filename>pg_clog/*</filename>, which contain the commit status of
+      <filename>pg_xact/*</filename>, which contain the commit status of
       all transactions. A table file is only usable with this
       information. Of course it is also impossible to restore only a
-      table and the associated <filename>pg_clog</filename> data
+      table and the associated <filename>pg_xact</filename> data
       because that would render all other tables in the database
       cluster useless.  So file system backups only work for complete
       backup and restoration of an entire database cluster.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 29738b0..839b52a 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1847,7 +1847,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this table.  This is used to track
        whether the table needs to be vacuumed in order to prevent transaction
-       ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
+       ID wraparound or to allow <literal>pg_xact</> to be shrunk.  Zero
        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
       </entry>
      </row>
@@ -2514,7 +2514,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this database.  This is used to
        track whether the database needs to be vacuumed in order to prevent
-       transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
+       transaction ID wraparound or to allow <literal>pg_xact</> to be shrunk.
        It is the minimum of the per-table
        <structname>pg_class</>.<structfield>relfrozenxid</> values.
       </entry>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 1bb501c..3e6296e 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5822,7 +5822,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
 
        <para>
         Vacuum also allows removal of old files from the
-        <filename>pg_clog</> subdirectory, which is why the default
+        <filename>pg_xact</> subdirectory, which is why the default
         is a relatively low 200 million transactions.
         This parameter can only be set at server start, but the setting
         can be reduced for individual tables by
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 2e64cc4..e9cfb06 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15323,7 +15323,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  postmaster.pid  |  9
  pg_ident.conf   | 10
  global          | 11
- pg_clog         | 12
+ pg_xact         | 12
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index f87f3e0..65a64c8 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -527,18 +527,18 @@
    <para>
     The sole disadvantage of increasing <varname>autovacuum_freeze_max_age</>
     (and <varname>vacuum_freeze_table_age</> along with it)
-    is that the <filename>pg_clog</> subdirectory of the database cluster
+    is that the <filename>pg_xact</> subdirectory of the database cluster
     will take more space, because it must store the commit status of all
     transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
     The commit status uses two bits per transaction, so if
     <varname>autovacuum_freeze_max_age</> is set to its maximum allowed
-    value of two billion, <filename>pg_clog</> can be expected to
+    value of two billion, <filename>pg_xact</> can be expected to
     grow to about half a gigabyte.  If this is trivial compared to your
     total database size, setting <varname>autovacuum_freeze_max_age</> to
     its maximum allowed value is recommended.  Otherwise, set it depending
-    on what you are willing to allow for <filename>pg_clog</> storage.
+    on what you are willing to allow for <filename>pg_xact</> storage.
     (The default, 200 million transactions, translates to about 50MB of
-    <filename>pg_clog</> storage.)
+    <filename>pg_xact</> storage.)
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index c949c5e..6ebc68b 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -256,12 +256,12 @@ PostgreSQL documentation
 
      <para>
       A safe value can be determined by looking for the numerically largest
-      file name in the directory <filename>pg_clog</> under the data directory,
+      file name in the directory <filename>pg_xact</> under the data directory,
       adding one,
       and then multiplying by 1048576 (0x100000).  Note that the file names are in
       hexadecimal.  It is usually easiest to specify the option value in
       hexadecimal too. For example, if <filename>0011</> is the largest entry
-      in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
+      in <filename>pg_xact</>, <literal>-x 0x1200000</> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 371c4a4..d5430d4 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -229,7 +229,7 @@ PostgreSQL documentation
     </step>
     <step>
      <para>
-      Copy all other files such as <filename>pg_clog</filename> and
+      Copy all other files such as <filename>pg_xact</filename> and
       configuration files from the source cluster to the target cluster
       (everything except the relation files).
      </para>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index fddb69b..56aef3c 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -72,11 +72,6 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_clog</></entry>
- <entry>Subdirectory containing transaction commit status data</entry>
-</row>
-
-<row>
  <entry><filename>pg_dynshmem</></entry>
  <entry>Subdirectory containing files used by the dynamic shared memory
   subsystem</entry>
@@ -146,6 +141,11 @@ Item
 </row>
 
 <row>
+ <entry><filename>pg_xact</></entry>
+ <entry>Subdirectory containing transaction commit status data</entry>
+</row>
+
+<row>
  <entry><filename>postgresql.auto.conf</></entry>
  <entry>A file used for storing configuration parameters that are set by
 <command>ALTER SYSTEM</command></entry>
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 346aa76..1f9fac9 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_clog</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_xact</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index b019bc1..560a8da 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -6762,8 +6762,8 @@ heap_prepare_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
  * Note: it might seem we could make the changes without exclusive lock, since
  * TransactionId read/write is assumed atomic anyway.  However there is a race
  * condition: someone who just fetched an old XID that we overwrite here could
- * conceivably not finish checking the XID against pg_clog before we finish
- * the VACUUM and perhaps truncate off the part of pg_clog he needs.  Getting
+ * conceivably not finish checking the XID against pg_xact before we finish
+ * the VACUUM and perhaps truncate off the part of pg_xact he needs.  Getting
  * exclusive lock ensures no other backend is in process of checking the
  * tuple status.  Also, getting exclusive lock makes it safe to adjust the
  * infomask bits.
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index 4ae4715..e7dd19f 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -331,17 +331,17 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_clog and pg_subtrans
+pg_xact and pg_subtrans
 -----------------------
 
-pg_clog and pg_subtrans are permanent (on-disk) storage of transaction related
+pg_xact and pg_subtrans are permanent (on-disk) storage of transaction related
 information.  There is a limited number of pages of each kept in memory, so
 in many cases there is no need to actually read from disk.  However, if
 there's a long running transaction or a backend sitting idle with an open
 transaction, it may be necessary to be able to read and write this information
 from disk.  They also allow information to be permanent across server restarts.
 
-pg_clog records the commit status for each transaction that has been assigned
+pg_xact records the commit status for each transaction that has been assigned
 an XID.  A transaction can be in progress, committed, aborted, or
 "sub-committed".  This last state means that it's a subtransaction that's no
 longer running, but its parent has not updated its state yet.  It is not
@@ -381,9 +381,9 @@ each transaction we keep a "cache" of Xids that are known to be part of the
 transaction tree, so we can skip looking at pg_subtrans unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_clog and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_xact and pg_subtrans.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
-for pg_clog are implemented in transam.c, while the low-level functions are in
+for pg_xact are implemented in transam.c, while the low-level functions are in
 clog.c.  pg_subtrans is contained completely in subtrans.c.
 
 
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 2634476..08e1edd 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -450,7 +450,7 @@ CLOGShmemInit(void)
 {
 	ClogCtl->PagePrecedes = CLOGPagePrecedes;
 	SimpleLruInit(ClogCtl, "clog", CLOGShmemBuffers(), CLOG_LSNS_PER_PAGE,
-				  CLogControlLock, "pg_clog", LWTRANCHE_CLOG_BUFFERS);
+				  CLogControlLock, "pg_xact", LWTRANCHE_CLOG_BUFFERS);
 }
 
 /*
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index a8d275f..0d03700 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -3,7 +3,7 @@
  * commit_ts.c
  *		PostgreSQL commit timestamp manager
  *
- * This module is a pg_clog-like system that stores the commit timestamp
+ * This module is a pg_xact-like system that stores the commit timestamp
  * for each transaction.
  *
  * XLOG interactions: this module generates an XLOG record whenever a new
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index e9588a7..287e435 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3,7 +3,7 @@
  * multixact.c
  *		PostgreSQL multi-transaction-log manager
  *
- * The pg_multixact manager is a pg_clog-like manager that stores an array of
+ * The pg_multixact manager is a pg_xact-like manager that stores an array of
  * MultiXactMember for each MultiXactId.  It is a fundamental part of the
  * shared-row-lock implementation.  Each MultiXactMember is comprised of a
  * TransactionId and a set of flag bits.  The name is a bit historical:
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 908fe2d..6871239 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,15 +3,14 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_clog-like manager that stores the parent
+ * The pg_subtrans manager is a pg_xact-like manager that stores the parent
  * transaction Id for each transaction.  It is a fundamental part of the
  * nested transactions implementation.  A main transaction has a parent
  * of InvalidTransactionId, and each subtransaction has its immediate parent.
  * The tree can easily be walked from child to parent, but not in the
  * opposite direction.
  *
- * This code is based on clog.c, but the robustness requirements
- * are completely different from pg_clog, because we only need to remember
+ * are completely different from pg_xact, because we only need to remember
  * pg_subtrans information for currently-open transactions.  Thus, there is
  * no need to preserve data over a crash and restart.
  *
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index 1eba49a..0a103c3 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -224,7 +224,7 @@ TransactionIdDidAbort(TransactionId transactionId)
  *		True iff transaction associated with the identifier is currently
  *		known to have either committed or aborted.
  *
- * This does NOT look into pg_clog but merely probes our local cache
+ * This does NOT look into pg_xact but merely probes our local cache
  * (and so it's not named TransactionIdDidComplete, which would be the
  * appropriate name for a function that worked that way).  The intended
  * use is just to short-circuit TransactionIdIsInProgress calls when doing
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 5415604..8bed3f5 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1379,7 +1379,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	/*
 	 * The order of operations here is critical: make the XLOG entry for
 	 * commit or abort, then mark the transaction committed or aborted in
-	 * pg_clog, then remove its PGPROC from the global ProcArray (which means
+	 * pg_xact, then remove its PGPROC from the global ProcArray (which means
 	 * TransactionIdIsInProgress will stop saying the prepared xact is in
 	 * progress), then run the post-commit or post-abort callbacks. The
 	 * callbacks will release the locks the transaction held.
@@ -2093,7 +2093,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	/* Flush XLOG to disk */
 	XLogFlush(recptr);
 
-	/* Mark the transaction committed in pg_clog */
+	/* Mark the transaction committed in pg_xact */
 	TransactionIdCommitTree(xid, nchildren, children);
 
 	/* Checkpoint can proceed now */
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index e11b229..6d6b3e4 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1206,8 +1206,8 @@ RecordTransactionCommit(void)
 		/*
 		 * Mark ourselves as within our "commit critical section".  This
 		 * forces any concurrent checkpoint to wait until we've updated
-		 * pg_clog.  Without this, it is possible for the checkpoint to set
-		 * REDO after the XLOG record but fail to flush the pg_clog update to
+		 * pg_xact.  Without this, it is possible for the checkpoint to set
+		 * REDO after the XLOG record but fail to flush the pg_xact update to
 		 * disk, leading to loss of the transaction commit if the system
 		 * crashes a little later.
 		 *
@@ -2033,7 +2033,7 @@ CommitTransaction(void)
 	if (!is_parallel_worker)
 	{
 		/*
-		 * We need to mark our XIDs as committed in pg_clog.  This is where we
+		 * We need to mark our XIDs as committed in pg_xact.  This is where we
 		 * durably commit.
 		 */
 		latestXid = RecordTransactionCommit();
@@ -4625,7 +4625,7 @@ AbortSubTransaction(void)
 								s->parent->subTransactionId);
 		AtSubAbort_Notify();
 
-		/* Advertise the fact that we aborted in pg_clog. */
+		/* Advertise the fact that we aborted in pg_xact. */
 		(void) RecordTransactionAbort(true);
 
 		/* Post-abort cleanup */
@@ -5371,7 +5371,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 	if (standbyState == STANDBY_DISABLED)
 	{
 		/*
-		 * Mark the transaction committed in pg_clog.
+		 * Mark the transaction committed in pg_xact.
 		 */
 		TransactionIdCommitTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
@@ -5389,7 +5389,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		RecordKnownAssignedTransactionIds(max_xid);
 
 		/*
-		 * Mark the transaction committed in pg_clog. We use async commit
+		 * Mark the transaction committed in pg_xact. We use async commit
 		 * protocol during recovery to provide information on database
 		 * consistency for when users try to set hint bits. It is important
 		 * that we do not set hint bits until the minRecoveryPoint is past
@@ -5526,7 +5526,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 
 	if (standbyState == STANDBY_DISABLED)
 	{
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_xact, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
 	else
@@ -5542,7 +5542,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 		 */
 		RecordKnownAssignedTransactionIds(max_xid);
 
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_xact, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 
 		/*
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 4fda179..c754a91 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8488,7 +8488,7 @@ CreateCheckPoint(int flags)
 	 * that are currently in commit critical sections.  If an xact inserted
 	 * its commit record into XLOG just before the REDO point, then a crash
 	 * restart from the REDO point would not replay that record, which means
-	 * that our flushing had better include the xact's update of pg_clog.  So
+	 * that our flushing had better include the xact's update of pg_xact.  So
 	 * we wait till he's out of his commit critical section before proceeding.
 	 * See notes in RecordTransactionCommit().
 	 *
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 58bbf55..d673031 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -356,7 +356,7 @@ vacuum(int options, RangeVar *relation, Oid relid, VacuumParams *params,
 	if ((options & VACOPT_VACUUM) && !IsAutoVacuumWorkerProcess())
 	{
 		/*
-		 * Update pg_database.datfrozenxid, and truncate pg_clog if possible.
+		 * Update pg_database.datfrozenxid, and truncate pg_xact if possible.
 		 * (autovacuum.c does this for itself.)
 		 */
 		vac_update_datfrozenxid();
@@ -880,7 +880,7 @@ vac_update_relstats(Relation relation,
  *		pg_class.relminmxid values.
  *
  *		If we are able to advance either pg_database value, also try to
- *		truncate pg_clog and pg_multixact.
+ *		truncate pg_xact and pg_multixact.
  *
  *		We violate transaction semantics here by overwriting the database's
  *		existing pg_database tuple with the new values.  This is reasonably
@@ -1026,7 +1026,7 @@ vac_update_datfrozenxid(void)
 
 	/*
 	 * If we were able to advance datfrozenxid or datminmxid, see if we can
-	 * truncate pg_clog and/or pg_multixact.  Also do it if the shared
+	 * truncate pg_xact and/or pg_multixact.  Also do it if the shared
 	 * XID-wrap-limit info is stale, since this action will update that too.
 	 */
 	if (dirty || ForceTransactionIdLimitUpdate())
@@ -1039,7 +1039,7 @@ vac_update_datfrozenxid(void)
  *	vac_truncate_clog() -- attempt to truncate the commit log
  *
  *		Scan pg_database to determine the system-wide oldest datfrozenxid,
- *		and use it to truncate the transaction commit log (pg_clog).
+ *		and use it to truncate the transaction commit log (pg_xact).
  *		Also update the XID wrap limit info maintained by varsup.c.
  *		Likewise for datminmxid.
  *
@@ -1086,7 +1086,7 @@ vac_truncate_clog(TransactionId frozenXID,
 	 * of the interlock against copying a DB containing an active backend.
 	 * Hence the new entry will not reduce the minimum.  Also, if two VACUUMs
 	 * concurrently modify the datfrozenxid's of different databases, the
-	 * worst possible outcome is that pg_clog is not truncated as aggressively
+	 * worst possible outcome is that pg_xact is not truncated as aggressively
 	 * as it could be.
 	 */
 	relation = heap_open(DatabaseRelationId, AccessShareLock);
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index e3a6911..29a555e 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2395,7 +2395,7 @@ deleted:
 	 */
 
 	/*
-	 * Update pg_database.datfrozenxid, and truncate pg_clog if possible. We
+	 * Update pg_database.datfrozenxid, and truncate pg_xact if possible. We
 	 * only need to do this once, not after each table.
 	 */
 	vac_update_datfrozenxid();
diff --git a/src/backend/storage/buffer/README b/src/backend/storage/buffer/README
index 248883f..bc80777 100644
--- a/src/backend/storage/buffer/README
+++ b/src/backend/storage/buffer/README
@@ -63,7 +63,7 @@ at about the same time would OR the same bits into the field, so there
 is little or no risk of conflicting update; what's more, if there did
 manage to be a conflict it would merely mean that one bit-update would
 be lost and need to be done again later.  These four bits are only hints
-(they cache the results of transaction status lookups in pg_clog), so no
+(they cache the results of transaction status lookups in pg_xact), so no
 great harm is done if they get reset to zero by conflicting updates.
 Note, however, that a tuple is frozen by setting both HEAP_XMIN_INVALID
 and HEAP_XMIN_COMMITTED; this is a critical update and accordingly requires
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index e5d487d..d41a79f 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -388,7 +388,7 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
  * ProcArrayEndTransaction -- mark a transaction as no longer running
  *
  * This is used interchangeably for commit and abort cases.  The transaction
- * commit/abort must already be reported to WAL and pg_clog.
+ * commit/abort must already be reported to WAL and pg_xact.
  *
  * proc is currently always MyProc, but we pass it explicitly for flexibility.
  * latestXid is the latest Xid among the transaction's main XID and
@@ -1180,7 +1180,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
 	 * subtransaction, we want to say "not running" even though its parent may
-	 * still be running.  So first, check pg_clog to see if it's been aborted.
+	 * still be running.  So first, check pg_xact to see if it's been aborted.
 	 */
 	xc_slow_answer_inc();
 
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 26a3be3..41e89e1 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -13,9 +13,9 @@
  * NOTE: When using a non-MVCC snapshot, we must check
  * TransactionIdIsInProgress (which looks in the PGXACT array)
  * before TransactionIdDidCommit/TransactionIdDidAbort (which look in
- * pg_clog).  Otherwise we have a race condition: we might decide that a
+ * pg_xact).  Otherwise we have a race condition: we might decide that a
  * just-committed transaction crashed, because none of the tests succeed.
- * xact.c is careful to record commit/abort in pg_clog before it unsets
+ * xact.c is careful to record commit/abort in pg_xact before it unsets
  * MyPgXact->xid in the PGXACT array.  That fixes that problem, but it
  * also means there is a window where TransactionIdIsInProgress and
  * TransactionIdDidCommit will both return true.  If we check only
@@ -29,7 +29,7 @@
  *
  * When using an MVCC snapshot, we rely on XidInMVCCSnapshot rather than
  * TransactionIdIsInProgress, but the logic is otherwise the same: do not
- * check pg_clog until after deciding that the xact is no longer in progress.
+ * check pg_xact until after deciding that the xact is no longer in progress.
  *
  *
  * Summary of visibility functions:
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 385e808..72a60ee 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -196,7 +196,6 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 static const char *const subdirs[] = {
 	"global",
 	"pg_wal/archive_status",
-	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
 	"pg_notify",
@@ -213,6 +212,7 @@ static const char *const subdirs[] = {
 	"pg_tblspc",
 	"pg_stat",
 	"pg_stat_tmp",
+	"pg_xact",
 	"pg_logical",
 	"pg_logical/snapshots",
 	"pg_logical/mappings"
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 55a6f0d..b242e30 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -309,6 +309,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_xlog");
 	else
 		check_single_dir(pg_data, "pg_wal");
+
+	/* pg_clog has been renamed to pg_xact in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_clog");
+	else
+		check_single_dir(pg_data, "pg_xact");
 }
 
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 90c0720..9c475df 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -47,7 +47,7 @@
 static void prepare_new_cluster(void);
 static void prepare_new_databases(void);
 static void create_new_objects(void);
-static void copy_clog_xlog_xid(void);
+static void copy_xact_xlog_xid(void);
 static void set_frozenxids(bool minmxid_only);
 static void setup(char *argv0, bool *live_check);
 static void cleanup(void);
@@ -113,7 +113,7 @@ main(int argc, char **argv)
 	 * Destructive Changes to New Cluster
 	 */
 
-	copy_clog_xlog_xid();
+	copy_xact_xlog_xid();
 
 	/* New now using xids of the old system */
 
@@ -374,17 +374,17 @@ remove_new_subdir(char *subdir, bool rmtopdir)
  * Copy the files from the old cluster into it
  */
 static void
-copy_subdir_files(char *subdir)
+copy_subdir_files(char *old_subdir, char *new_subdir)
 {
 	char		old_path[MAXPGPATH];
 	char		new_path[MAXPGPATH];
 
-	remove_new_subdir(subdir, true);
+	remove_new_subdir(new_subdir, true);
 
-	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, subdir);
-	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, subdir);
+	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, old_subdir);
+	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, new_subdir);
 
-	prep_status("Copying old %s to new server", subdir);
+	prep_status("Copying old %s to new server", old_subdir);
 
 	exec_prog(UTILITY_LOG_FILE, NULL, true,
 #ifndef WIN32
@@ -399,10 +399,16 @@ copy_subdir_files(char *subdir)
 }
 
 static void
-copy_clog_xlog_xid(void)
+copy_xact_xlog_xid(void)
 {
-	/* copy old commit logs to new data dir */
-	copy_subdir_files("pg_clog");
+	/*
+	 * Copy old commit logs to new data dir. pg_clog has been renamed to
+	 * pg_xact in post-10 clusters.
+	 */
+	copy_subdir_files(GET_MAJOR_VERSION(old_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_xact",
+					  GET_MAJOR_VERSION(new_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_xact");
 
 	/* set the next transaction id and epoch of the new cluster */
 	prep_status("Setting next transaction ID and epoch for new cluster");
@@ -432,8 +438,8 @@ copy_clog_xlog_xid(void)
 	if (old_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER &&
 		new_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER)
 	{
-		copy_subdir_files("pg_multixact/offsets");
-		copy_subdir_files("pg_multixact/members");
+		copy_subdir_files("pg_multixact/offsets", "pg_multixact/offsets");
+		copy_subdir_files("pg_multixact/members", "pg_multixact/members");
 
 		prep_status("Setting next multixact ID and offset for new cluster");
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 5fcebc5..96a1e44 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,7 +76,7 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_clog, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
+	 * for pg_xact, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
 	 * has lsn_groups_per_page entries per buffer slot, each containing the
 	 * highest LSN known for a contiguous group of SLRU entries on that slot's
 	 * page.
@@ -120,7 +120,7 @@ typedef struct SlruCtlData
 	SlruShared	shared;
 
 	/*
-	 * This flag tells whether to fsync writes (true for pg_clog and multixact
+	 * This flag tells whether to fsync writes (true for pg_xact and multixact
 	 * stuff, false for pg_subtrans and pg_notify).
 	 */
 	bool		do_fsync;
-- 
2.10.1

From 0d30ef662a52b6b02496a6618c0457d6d6773992 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 4 Oct 2016 14:41:15 +0900
Subject: [PATCH 2/2] Rename pg_clog to pg_transaction

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml               |  6 +++---
 doc/src/sgml/catalogs.sgml             |  6 +++---
 doc/src/sgml/config.sgml               |  2 +-
 doc/src/sgml/func.sgml                 |  2 +-
 doc/src/sgml/maintenance.sgml          | 12 +++++------
 doc/src/sgml/ref/pg_resetxlog.sgml     |  6 +++---
 doc/src/sgml/ref/pg_rewind.sgml        |  2 +-
 doc/src/sgml/storage.sgml              | 10 ++++-----
 doc/src/sgml/wal.sgml                  |  2 +-
 src/backend/access/heap/heapam.c       | 10 ++++-----
 src/backend/access/transam/README      | 22 ++++++++++----------
 src/backend/access/transam/clog.c      |  2 +-
 src/backend/access/transam/commit_ts.c |  4 ++--
 src/backend/access/transam/multixact.c |  8 +++----
 src/backend/access/transam/subtrans.c  | 18 ++++++++--------
 src/backend/access/transam/transam.c   |  2 +-
 src/backend/access/transam/twophase.c  |  6 +++---
 src/backend/access/transam/xact.c      | 38 ++++++++++++++++++++--------------
 src/backend/access/transam/xlog.c      |  6 +++---
 src/backend/commands/vacuum.c          | 14 ++++++-------
 src/backend/postmaster/autovacuum.c    |  4 ++--
 src/backend/storage/buffer/README      |  4 ++--
 src/backend/storage/ipc/procarray.c    |  5 +++--
 src/backend/utils/time/tqual.c         | 29 +++++++++++++-------------
 src/bin/initdb/initdb.c                |  2 +-
 src/bin/pg_upgrade/exec.c              |  6 ++++++
 src/bin/pg_upgrade/pg_upgrade.c        | 30 ++++++++++++++++-----------
 src/include/access/slru.h              | 12 +++++------
 28 files changed, 145 insertions(+), 125 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 6eaed1e..eb4f962 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -382,10 +382,10 @@ tar -cf backup.tar /usr/local/pgsql/data
       directories. This will <emphasis>not</> work because the
       information contained in these files is not usable without
       the commit log files,
-      <filename>pg_clog/*</filename>, which contain the commit status of
-      all transactions. A table file is only usable with this
+      <filename>pg_transaction/*</filename>, which contain the commit status
+      of all transactions. A table file is only usable with this
       information. Of course it is also impossible to restore only a
-      table and the associated <filename>pg_clog</filename> data
+      table and the associated <filename>pg_transaction</filename> data
       because that would render all other tables in the database
       cluster useless.  So file system backups only work for complete
       backup and restoration of an entire database cluster.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 29738b0..77b395e 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1847,7 +1847,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this table.  This is used to track
        whether the table needs to be vacuumed in order to prevent transaction
-       ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
+       ID wraparound or to allow <literal>pg_transaction</> to be shrunk.  Zero
        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
       </entry>
      </row>
@@ -2514,8 +2514,8 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this database.  This is used to
        track whether the database needs to be vacuumed in order to prevent
-       transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
-       It is the minimum of the per-table
+       transaction ID wraparound or to allow <literal>pg_transaction</> to be
+       shrunk.  It is the minimum of the per-table
        <structname>pg_class</>.<structfield>relfrozenxid</> values.
       </entry>
      </row>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 1bb501c..b0b7215 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5822,7 +5822,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
 
        <para>
         Vacuum also allows removal of old files from the
-        <filename>pg_clog</> subdirectory, which is why the default
+        <filename>pg_transaction</> subdirectory, which is why the default
         is a relatively low 200 million transactions.
         This parameter can only be set at server start, but the setting
         can be reduced for individual tables by
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 2e64cc4..a9d2ec4 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15323,7 +15323,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  postmaster.pid  |  9
  pg_ident.conf   | 10
  global          | 11
- pg_clog         | 12
+ pg_transaction  | 12
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index f87f3e0..c741a9b 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -527,18 +527,18 @@
    <para>
     The sole disadvantage of increasing <varname>autovacuum_freeze_max_age</>
     (and <varname>vacuum_freeze_table_age</> along with it)
-    is that the <filename>pg_clog</> subdirectory of the database cluster
-    will take more space, because it must store the commit status of all
-    transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
+    is that the <filename>pg_transaction</> subdirectory of the database
+    cluster will take more space, because it must store the commit status of
+    all transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
     The commit status uses two bits per transaction, so if
     <varname>autovacuum_freeze_max_age</> is set to its maximum allowed
-    value of two billion, <filename>pg_clog</> can be expected to
+    value of two billion, <filename>pg_transaction</> can be expected to
     grow to about half a gigabyte.  If this is trivial compared to your
     total database size, setting <varname>autovacuum_freeze_max_age</> to
     its maximum allowed value is recommended.  Otherwise, set it depending
-    on what you are willing to allow for <filename>pg_clog</> storage.
+    on what you are willing to allow for <filename>pg_transaction</> storage.
     (The default, 200 million transactions, translates to about 50MB of
-    <filename>pg_clog</> storage.)
+    <filename>pg_transaction</> storage.)
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index c949c5e..67b048b 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -256,12 +256,12 @@ PostgreSQL documentation
 
      <para>
       A safe value can be determined by looking for the numerically largest
-      file name in the directory <filename>pg_clog</> under the data directory,
-      adding one,
+      file name in the directory <filename>pg_transaction</> under the data
+      directory, adding one,
       and then multiplying by 1048576 (0x100000).  Note that the file names are in
       hexadecimal.  It is usually easiest to specify the option value in
       hexadecimal too. For example, if <filename>0011</> is the largest entry
-      in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
+      in <filename>pg_transaction</>, <literal>-x 0x1200000</> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 371c4a4..34ef4f1 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -229,7 +229,7 @@ PostgreSQL documentation
     </step>
     <step>
      <para>
-      Copy all other files such as <filename>pg_clog</filename> and
+      Copy all other files such as <filename>pg_transaction</filename> and
       configuration files from the source cluster to the target cluster
       (everything except the relation files).
      </para>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index fddb69b..61d15d4 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -72,11 +72,6 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_clog</></entry>
- <entry>Subdirectory containing transaction commit status data</entry>
-</row>
-
-<row>
  <entry><filename>pg_dynshmem</></entry>
  <entry>Subdirectory containing files used by the dynamic shared memory
   subsystem</entry>
@@ -136,6 +131,11 @@ Item
 </row>
 
 <row>
+ <entry><filename>pg_transaction</></entry>
+ <entry>Subdirectory containing transaction commit status data</entry>
+</row>
+
+<row>
  <entry><filename>pg_twophase</></entry>
  <entry>Subdirectory containing state files for prepared transactions</entry>
 </row>
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 346aa76..aac0a8d 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_clog</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_transaction</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index b019bc1..075d06a 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -6762,11 +6762,11 @@ heap_prepare_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
  * Note: it might seem we could make the changes without exclusive lock, since
  * TransactionId read/write is assumed atomic anyway.  However there is a race
  * condition: someone who just fetched an old XID that we overwrite here could
- * conceivably not finish checking the XID against pg_clog before we finish
- * the VACUUM and perhaps truncate off the part of pg_clog he needs.  Getting
- * exclusive lock ensures no other backend is in process of checking the
- * tuple status.  Also, getting exclusive lock makes it safe to adjust the
- * infomask bits.
+ * conceivably not finish checking the XID against pg_transaction before we
+ * finish the VACUUM and perhaps truncate off the part of pg_transaction he
+ * needs.  Getting exclusive lock ensures no other backend is in process of
+ * checking the tuple status.  Also, getting exclusive lock makes it safe to
+ * adjust the infomask bits.
  *
  * NB: All code in here must be safe to execute during crash recovery!
  */
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index 4ae4715..36bcde9 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -331,18 +331,18 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_clog and pg_subtrans
------------------------
+pg_transaction and pg_subtrans
+------------------------------
 
-pg_clog and pg_subtrans are permanent (on-disk) storage of transaction related
-information.  There is a limited number of pages of each kept in memory, so
-in many cases there is no need to actually read from disk.  However, if
-there's a long running transaction or a backend sitting idle with an open
+pg_transaction and pg_subtrans are permanent (on-disk) storage of transaction
+related information.  There is a limited number of pages of each kept in
+memory, so in many cases there is no need to actually read from disk.  However,
+if there's a long running transaction or a backend sitting idle with an open
 transaction, it may be necessary to be able to read and write this information
 from disk.  They also allow information to be permanent across server restarts.
 
-pg_clog records the commit status for each transaction that has been assigned
-an XID.  A transaction can be in progress, committed, aborted, or
+pg_transaction records the commit status for each transaction that has been
+assigned an XID.  A transaction can be in progress, committed, aborted, or
 "sub-committed".  This last state means that it's a subtransaction that's no
 longer running, but its parent has not updated its state yet.  It is not
 necessary to update a subtransaction's transaction status to subcommit, so we
@@ -381,10 +381,10 @@ each transaction we keep a "cache" of Xids that are known to be part of the
 transaction tree, so we can skip looking at pg_subtrans unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_clog and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_transaction and pg_subtrans.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
-for pg_clog are implemented in transam.c, while the low-level functions are in
-clog.c.  pg_subtrans is contained completely in subtrans.c.
+for pg_transaction are implemented in transam.c, while the low-level functions
+are in clog.c.  pg_subtrans is contained completely in subtrans.c.
 
 
 Write-Ahead Log Coding
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 2634476..c7a3cbb 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -450,7 +450,7 @@ CLOGShmemInit(void)
 {
 	ClogCtl->PagePrecedes = CLOGPagePrecedes;
 	SimpleLruInit(ClogCtl, "clog", CLOGShmemBuffers(), CLOG_LSNS_PER_PAGE,
-				  CLogControlLock, "pg_clog", LWTRANCHE_CLOG_BUFFERS);
+				  CLogControlLock, "pg_transaction", LWTRANCHE_CLOG_BUFFERS);
 }
 
 /*
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index a8d275f..4a48f76 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -3,8 +3,8 @@
  * commit_ts.c
  *		PostgreSQL commit timestamp manager
  *
- * This module is a pg_clog-like system that stores the commit timestamp
- * for each transaction.
+ * This module is a pg_transaction-like system that stores the commit
+ * timestamp for each transaction.
  *
  * XLOG interactions: this module generates an XLOG record whenever a new
  * CommitTs page is initialized to zeroes.  Also, one XLOG record is
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index e9588a7..aa8e07e 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3,10 +3,10 @@
  * multixact.c
  *		PostgreSQL multi-transaction-log manager
  *
- * The pg_multixact manager is a pg_clog-like manager that stores an array of
- * MultiXactMember for each MultiXactId.  It is a fundamental part of the
- * shared-row-lock implementation.  Each MultiXactMember is comprised of a
- * TransactionId and a set of flag bits.  The name is a bit historical:
+ * The pg_multixact manager is a pg_transaction-like manager that stores an
+ * array of MultiXactMember for each MultiXactId.  It is a fundamental part
+ * of the shared-row-lock implementation.  Each MultiXactMember is comprised
+ * of a TransactionId and a set of flag bits.  The name is a bit historical:
  * originally, a MultiXactId consisted of more than one TransactionId (except
  * in rare corner cases), hence "multi".  Nowadays, however, it's perfectly
  * legitimate to have MultiXactIds that only include a single Xid.
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 908fe2d..d96a487 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,17 +3,17 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_clog-like manager that stores the parent
- * transaction Id for each transaction.  It is a fundamental part of the
- * nested transactions implementation.  A main transaction has a parent
- * of InvalidTransactionId, and each subtransaction has its immediate parent.
- * The tree can easily be walked from child to parent, but not in the
- * opposite direction.
+ * The pg_subtrans manager is a pg_transaction-like manager that stores
+ * the parent transaction Id for each transaction.  It is a fundamental
+ * part of the nested transactions implementation.  A main transaction has
+ * a parent of InvalidTransactionId, and each subtransaction has its
+ * immediate parent.  The tree can easily be walked from child to parent,
+ * but not in the opposite direction.
  *
  * This code is based on clog.c, but the robustness requirements
- * are completely different from pg_clog, because we only need to remember
- * pg_subtrans information for currently-open transactions.  Thus, there is
- * no need to preserve data over a crash and restart.
+ * are completely different from pg_transaction, because we only need to
+ * remember pg_subtrans information for currently-open transactions.  Thus,
+ * there is no need to preserve data over a crash and restart.
  *
  * There are no XLOG interactions since we do not care about preserving
  * data across crashes.  During database startup, we simply force the
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index 1eba49a..8a41c7f 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -224,7 +224,7 @@ TransactionIdDidAbort(TransactionId transactionId)
  *		True iff transaction associated with the identifier is currently
  *		known to have either committed or aborted.
  *
- * This does NOT look into pg_clog but merely probes our local cache
+ * This does NOT look into pg_transaction but merely probes our local cache
  * (and so it's not named TransactionIdDidComplete, which would be the
  * appropriate name for a function that worked that way).  The intended
  * use is just to short-circuit TransactionIdIsInProgress calls when doing
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 5415604..52de336 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1379,8 +1379,8 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	/*
 	 * The order of operations here is critical: make the XLOG entry for
 	 * commit or abort, then mark the transaction committed or aborted in
-	 * pg_clog, then remove its PGPROC from the global ProcArray (which means
-	 * TransactionIdIsInProgress will stop saying the prepared xact is in
+	 * pg_transaction, then remove its PGPROC from the global ProcArray (which
+	 * means TransactionIdIsInProgress will stop saying the prepared xact is in
 	 * progress), then run the post-commit or post-abort callbacks. The
 	 * callbacks will release the locks the transaction held.
 	 */
@@ -2093,7 +2093,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	/* Flush XLOG to disk */
 	XLogFlush(recptr);
 
-	/* Mark the transaction committed in pg_clog */
+	/* Mark the transaction committed in pg_transaction */
 	TransactionIdCommitTree(xid, nchildren, children);
 
 	/* Checkpoint can proceed now */
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index e11b229..817b323 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1206,10 +1206,10 @@ RecordTransactionCommit(void)
 		/*
 		 * Mark ourselves as within our "commit critical section".  This
 		 * forces any concurrent checkpoint to wait until we've updated
-		 * pg_clog.  Without this, it is possible for the checkpoint to set
-		 * REDO after the XLOG record but fail to flush the pg_clog update to
-		 * disk, leading to loss of the transaction commit if the system
-		 * crashes a little later.
+		 * pg_transaction.  Without this, it is possible for the checkpoint
+		 * to set REDO after the XLOG record but fail to flush the pg_trans
+		 * update to disk, leading to loss of the transaction commit if the
+		 * system crashes a little later.
 		 *
 		 * Note: we could, but don't bother to, set this flag in
 		 * RecordTransactionAbort.  That's because loss of a transaction abort
@@ -2033,8 +2033,8 @@ CommitTransaction(void)
 	if (!is_parallel_worker)
 	{
 		/*
-		 * We need to mark our XIDs as committed in pg_clog.  This is where we
-		 * durably commit.
+		 * We need to mark our XIDs as committed in pg_transaction.  This is
+		 * where we durably commit.
 		 */
 		latestXid = RecordTransactionCommit();
 	}
@@ -2539,10 +2539,10 @@ AbortTransaction(void)
 	AtAbort_Twophase();
 
 	/*
-	 * Advertise the fact that we aborted in pg_clog (assuming that we got as
-	 * far as assigning an XID to advertise).  But if we're inside a parallel
-	 * worker, skip this; the user backend must be the one to write the abort
-	 * record.
+	 * Advertise the fact that we aborted in pg_transaction (assuming that we
+	 * got as far as assigning an XID to advertise).  But if we're inside a
+	 * parallel worker, skip this; the user backend must be the one to write
+	 * the abort record.
 	 */
 	if (!is_parallel_worker)
 		latestXid = RecordTransactionAbort(false);
@@ -4625,7 +4625,7 @@ AbortSubTransaction(void)
 								s->parent->subTransactionId);
 		AtSubAbort_Notify();
 
-		/* Advertise the fact that we aborted in pg_clog. */
+		/* Advertise the fact that we aborted in pg_transaction. */
 		(void) RecordTransactionAbort(true);
 
 		/* Post-abort cleanup */
@@ -5371,7 +5371,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 	if (standbyState == STANDBY_DISABLED)
 	{
 		/*
-		 * Mark the transaction committed in pg_clog.
+		 * Mark the transaction committed in pg_transaction.
 		 */
 		TransactionIdCommitTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
@@ -5389,8 +5389,8 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		RecordKnownAssignedTransactionIds(max_xid);
 
 		/*
-		 * Mark the transaction committed in pg_clog. We use async commit
-		 * protocol during recovery to provide information on database
+		 * Mark the transaction committed in pg_transaction. We use async
+		 * commit protocol during recovery to provide information on database
 		 * consistency for when users try to set hint bits. It is important
 		 * that we do not set hint bits until the minRecoveryPoint is past
 		 * this commit record. This ensures that if we crash we don't see hint
@@ -5526,7 +5526,10 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 
 	if (standbyState == STANDBY_DISABLED)
 	{
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/*
+		 * Mark the transaction aborted in pg_transaction, no need for async
+		 * stuff.
+		 */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
 	else
@@ -5542,7 +5545,10 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 		 */
 		RecordKnownAssignedTransactionIds(max_xid);
 
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/*
+		 * Mark the transaction aborted in pg_transaction, no need for async
+		 * stuff.
+		 */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 
 		/*
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 48c18e8..2262ae0 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8487,9 +8487,9 @@ CreateCheckPoint(int flags)
 	 * that are currently in commit critical sections.  If an xact inserted
 	 * its commit record into XLOG just before the REDO point, then a crash
 	 * restart from the REDO point would not replay that record, which means
-	 * that our flushing had better include the xact's update of pg_clog.  So
-	 * we wait till he's out of his commit critical section before proceeding.
-	 * See notes in RecordTransactionCommit().
+	 * that our flushing had better include the xact's update of
+	 * pg_transaction.  So we wait till he's out of his commit critical
+	 * section before proceeding.  See notes in RecordTransactionCommit().
 	 *
 	 * Because we've already released the insertion locks, this test is a bit
 	 * fuzzy: it is possible that we will wait for xacts we didn't really need
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 58bbf55..5c61d1a 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -356,8 +356,8 @@ vacuum(int options, RangeVar *relation, Oid relid, VacuumParams *params,
 	if ((options & VACOPT_VACUUM) && !IsAutoVacuumWorkerProcess())
 	{
 		/*
-		 * Update pg_database.datfrozenxid, and truncate pg_clog if possible.
-		 * (autovacuum.c does this for itself.)
+		 * Update pg_database.datfrozenxid, and truncate pg_transaction if
+		 * possible. (autovacuum.c does this for itself.)
 		 */
 		vac_update_datfrozenxid();
 	}
@@ -880,7 +880,7 @@ vac_update_relstats(Relation relation,
  *		pg_class.relminmxid values.
  *
  *		If we are able to advance either pg_database value, also try to
- *		truncate pg_clog and pg_multixact.
+ *		truncate pg_transaction and pg_multixact.
  *
  *		We violate transaction semantics here by overwriting the database's
  *		existing pg_database tuple with the new values.  This is reasonably
@@ -1026,7 +1026,7 @@ vac_update_datfrozenxid(void)
 
 	/*
 	 * If we were able to advance datfrozenxid or datminmxid, see if we can
-	 * truncate pg_clog and/or pg_multixact.  Also do it if the shared
+	 * truncate pg_transaction and/or pg_multixact.  Also do it if the shared
 	 * XID-wrap-limit info is stale, since this action will update that too.
 	 */
 	if (dirty || ForceTransactionIdLimitUpdate())
@@ -1039,7 +1039,7 @@ vac_update_datfrozenxid(void)
  *	vac_truncate_clog() -- attempt to truncate the commit log
  *
  *		Scan pg_database to determine the system-wide oldest datfrozenxid,
- *		and use it to truncate the transaction commit log (pg_clog).
+ *		and use it to truncate the transaction commit log (pg_transaction).
  *		Also update the XID wrap limit info maintained by varsup.c.
  *		Likewise for datminmxid.
  *
@@ -1086,8 +1086,8 @@ vac_truncate_clog(TransactionId frozenXID,
 	 * of the interlock against copying a DB containing an active backend.
 	 * Hence the new entry will not reduce the minimum.  Also, if two VACUUMs
 	 * concurrently modify the datfrozenxid's of different databases, the
-	 * worst possible outcome is that pg_clog is not truncated as aggressively
-	 * as it could be.
+	 * worst possible outcome is that pg_transaction is not truncated as
+	 * aggressively as it could be.
 	 */
 	relation = heap_open(DatabaseRelationId, AccessShareLock);
 
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 1a92ca1..31fcd51 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2394,8 +2394,8 @@ deleted:
 	 */
 
 	/*
-	 * Update pg_database.datfrozenxid, and truncate pg_clog if possible. We
-	 * only need to do this once, not after each table.
+	 * Update pg_database.datfrozenxid, and truncate pg_transaction if
+	 * possible. We only need to do this once, not after each table.
 	 */
 	vac_update_datfrozenxid();
 
diff --git a/src/backend/storage/buffer/README b/src/backend/storage/buffer/README
index 248883f..94da258 100644
--- a/src/backend/storage/buffer/README
+++ b/src/backend/storage/buffer/README
@@ -63,8 +63,8 @@ at about the same time would OR the same bits into the field, so there
 is little or no risk of conflicting update; what's more, if there did
 manage to be a conflict it would merely mean that one bit-update would
 be lost and need to be done again later.  These four bits are only hints
-(they cache the results of transaction status lookups in pg_clog), so no
-great harm is done if they get reset to zero by conflicting updates.
+(they cache the results of transaction status lookups in pg_transaction),
+so no great harm is done if they get reset to zero by conflicting updates.
 Note, however, that a tuple is frozen by setting both HEAP_XMIN_INVALID
 and HEAP_XMIN_COMMITTED; this is a critical update and accordingly requires
 an exclusive buffer lock (and it must also be WAL-logged).
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index e5d487d..dd5c79a 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -388,7 +388,7 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
  * ProcArrayEndTransaction -- mark a transaction as no longer running
  *
  * This is used interchangeably for commit and abort cases.  The transaction
- * commit/abort must already be reported to WAL and pg_clog.
+ * commit/abort must already be reported to WAL and pg_transaction.
  *
  * proc is currently always MyProc, but we pass it explicitly for flexibility.
  * latestXid is the latest Xid among the transaction's main XID and
@@ -1180,7 +1180,8 @@ TransactionIdIsInProgress(TransactionId xid)
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
 	 * subtransaction, we want to say "not running" even though its parent may
-	 * still be running.  So first, check pg_clog to see if it's been aborted.
+	 * still be running.  So first, check pg_transaction to see if it's been
+	 * aborted.
 	 */
 	xc_slow_answer_inc();
 
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 26a3be3..fbf9c6c 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -13,23 +13,24 @@
  * NOTE: When using a non-MVCC snapshot, we must check
  * TransactionIdIsInProgress (which looks in the PGXACT array)
  * before TransactionIdDidCommit/TransactionIdDidAbort (which look in
- * pg_clog).  Otherwise we have a race condition: we might decide that a
- * just-committed transaction crashed, because none of the tests succeed.
- * xact.c is careful to record commit/abort in pg_clog before it unsets
- * MyPgXact->xid in the PGXACT array.  That fixes that problem, but it
- * also means there is a window where TransactionIdIsInProgress and
- * TransactionIdDidCommit will both return true.  If we check only
- * TransactionIdDidCommit, we could consider a tuple committed when a
- * later GetSnapshotData call will still think the originating transaction
- * is in progress, which leads to application-level inconsistency.  The
- * upshot is that we gotta check TransactionIdIsInProgress first in all
- * code paths, except for a few cases where we are looking at
- * subtransactions of our own main transaction and so there can't be any
- * race condition.
+ * pg_transaction).  Otherwise we have a race condition: we might decide
+ * that a just-committed transaction crashed, because none of the tests
+ * succeed.  xact.c is careful to record commit/abort in pg_transaction
+ * before it unsets MyPgXact->xid in the PGXACT array.  That fixes that
+ * problem, but it also means there is a window where
+ * TransactionIdIsInProgress and TransactionIdDidCommit will both return
+ * true.  If we check only TransactionIdDidCommit, we could consider a
+ * tuple committed when a later GetSnapshotData call will still think
+ * the originating transaction is in progress, which leads to
+ * application-level inconsistency.  The upshot is that we gotta check
+ * TransactionIdIsInProgress first in all code paths, except for a few
+ * cases where we are looking at subtransactions of our own main
+ * transaction and so there can't be any race condition.
  *
  * When using an MVCC snapshot, we rely on XidInMVCCSnapshot rather than
  * TransactionIdIsInProgress, but the logic is otherwise the same: do not
- * check pg_clog until after deciding that the xact is no longer in progress.
+ * check pg_transaction until after deciding that the xact is no longer
+ * in progress.
  *
  *
  * Summary of visibility functions:
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 385e808..974f11a 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -196,7 +196,6 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 static const char *const subdirs[] = {
 	"global",
 	"pg_wal/archive_status",
-	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
 	"pg_notify",
@@ -213,6 +212,7 @@ static const char *const subdirs[] = {
 	"pg_tblspc",
 	"pg_stat",
 	"pg_stat_tmp",
+	"pg_transaction",
 	"pg_logical",
 	"pg_logical/snapshots",
 	"pg_logical/mappings"
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 55a6f0d..a3a0a0f 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -309,6 +309,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_xlog");
 	else
 		check_single_dir(pg_data, "pg_wal");
+
+	/* pg_clog has been renamed to pg_transaction in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_clog");
+	else
+		check_single_dir(pg_data, "pg_transaction");
 }
 
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 90c0720..04704c2 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -47,7 +47,7 @@
 static void prepare_new_cluster(void);
 static void prepare_new_databases(void);
 static void create_new_objects(void);
-static void copy_clog_xlog_xid(void);
+static void copy_trans_xlog_xid(void);
 static void set_frozenxids(bool minmxid_only);
 static void setup(char *argv0, bool *live_check);
 static void cleanup(void);
@@ -113,7 +113,7 @@ main(int argc, char **argv)
 	 * Destructive Changes to New Cluster
 	 */
 
-	copy_clog_xlog_xid();
+	copy_trans_xlog_xid();
 
 	/* New now using xids of the old system */
 
@@ -374,17 +374,17 @@ remove_new_subdir(char *subdir, bool rmtopdir)
  * Copy the files from the old cluster into it
  */
 static void
-copy_subdir_files(char *subdir)
+copy_subdir_files(char *old_subdir, char *new_subdir)
 {
 	char		old_path[MAXPGPATH];
 	char		new_path[MAXPGPATH];
 
-	remove_new_subdir(subdir, true);
+	remove_new_subdir(new_subdir, true);
 
-	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, subdir);
-	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, subdir);
+	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, old_subdir);
+	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, new_subdir);
 
-	prep_status("Copying old %s to new server", subdir);
+	prep_status("Copying old %s to new server", old_subdir);
 
 	exec_prog(UTILITY_LOG_FILE, NULL, true,
 #ifndef WIN32
@@ -399,10 +399,16 @@ copy_subdir_files(char *subdir)
 }
 
 static void
-copy_clog_xlog_xid(void)
+copy_trans_xlog_xid(void)
 {
-	/* copy old commit logs to new data dir */
-	copy_subdir_files("pg_clog");
+	/*
+	 * Copy old commit logs to new data dir. pg_clog has been renamed to
+	 * pg_transaction in post-10 clusters.
+	 */
+	copy_subdir_files(GET_MAJOR_VERSION(old_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_transaction",
+					  GET_MAJOR_VERSION(new_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_transaction");
 
 	/* set the next transaction id and epoch of the new cluster */
 	prep_status("Setting next transaction ID and epoch for new cluster");
@@ -432,8 +438,8 @@ copy_clog_xlog_xid(void)
 	if (old_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER &&
 		new_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER)
 	{
-		copy_subdir_files("pg_multixact/offsets");
-		copy_subdir_files("pg_multixact/members");
+		copy_subdir_files("pg_multixact/offsets", "pg_multixact/offsets");
+		copy_subdir_files("pg_multixact/members", "pg_multixact/members");
 
 		prep_status("Setting next multixact ID and offset for new cluster");
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 5fcebc5..001817f 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,10 +76,10 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_clog, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
-	 * has lsn_groups_per_page entries per buffer slot, each containing the
-	 * highest LSN known for a contiguous group of SLRU entries on that slot's
-	 * page.
+	 * for pg_transaction, false for multixact, pg_subtrans, pg_notify).
+	 * group_lsn[] has lsn_groups_per_page entries per buffer slot, each
+	 * containing the highest LSN known for a contiguous group of SLRU entries
+	 * on that slot's page.
 	 */
 	XLogRecPtr *group_lsn;
 	int			lsn_groups_per_page;
@@ -120,8 +120,8 @@ typedef struct SlruCtlData
 	SlruShared	shared;
 
 	/*
-	 * This flag tells whether to fsync writes (true for pg_clog and multixact
-	 * stuff, false for pg_subtrans and pg_notify).
+	 * This flag tells whether to fsync writes (true for pg_transaction and
+	 * multixact stuff, false for pg_subtrans and pg_notify).
 	 */
 	bool		do_fsync;
 
-- 
2.10.0

From 1711e73fe59b37c0626c1382c6f044b28c01f3d9 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Sun, 23 Oct 2016 20:52:22 +0900
Subject: [PATCH 1/2] Rename pg_clog to pg_xact

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml               |  4 ++--
 doc/src/sgml/catalogs.sgml             |  4 ++--
 doc/src/sgml/config.sgml               |  2 +-
 doc/src/sgml/func.sgml                 |  2 +-
 doc/src/sgml/maintenance.sgml          |  8 ++++----
 doc/src/sgml/ref/pg_resetxlog.sgml     |  4 ++--
 doc/src/sgml/ref/pg_rewind.sgml        |  2 +-
 doc/src/sgml/storage.sgml              | 10 +++++-----
 doc/src/sgml/wal.sgml                  |  2 +-
 src/backend/access/heap/heapam.c       |  4 ++--
 src/backend/access/transam/README      | 10 +++++-----
 src/backend/access/transam/clog.c      |  2 +-
 src/backend/access/transam/commit_ts.c |  2 +-
 src/backend/access/transam/multixact.c |  2 +-
 src/backend/access/transam/subtrans.c  |  5 ++---
 src/backend/access/transam/transam.c   |  2 +-
 src/backend/access/transam/twophase.c  |  4 ++--
 src/backend/access/transam/xact.c      | 18 +++++++++---------
 src/backend/access/transam/xlog.c      |  2 +-
 src/backend/commands/vacuum.c          | 10 +++++-----
 src/backend/postmaster/autovacuum.c    |  2 +-
 src/backend/storage/buffer/README      |  2 +-
 src/backend/storage/ipc/procarray.c    |  4 ++--
 src/backend/utils/time/tqual.c         |  6 +++---
 src/bin/initdb/initdb.c                |  2 +-
 src/bin/pg_upgrade/exec.c              |  6 ++++++
 src/bin/pg_upgrade/pg_upgrade.c        | 30 ++++++++++++++++++------------
 src/include/access/slru.h              |  4 ++--
 28 files changed, 83 insertions(+), 72 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 6eaed1e..d22af0d 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -382,10 +382,10 @@ tar -cf backup.tar /usr/local/pgsql/data
       directories. This will <emphasis>not</> work because the
       information contained in these files is not usable without
       the commit log files,
-      <filename>pg_clog/*</filename>, which contain the commit status of
+      <filename>pg_xact/*</filename>, which contain the commit status of
       all transactions. A table file is only usable with this
       information. Of course it is also impossible to restore only a
-      table and the associated <filename>pg_clog</filename> data
+      table and the associated <filename>pg_xact</filename> data
       because that would render all other tables in the database
       cluster useless.  So file system backups only work for complete
       backup and restoration of an entire database cluster.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 29738b0..839b52a 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1847,7 +1847,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this table.  This is used to track
        whether the table needs to be vacuumed in order to prevent transaction
-       ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
+       ID wraparound or to allow <literal>pg_xact</> to be shrunk.  Zero
        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
       </entry>
      </row>
@@ -2514,7 +2514,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this database.  This is used to
        track whether the database needs to be vacuumed in order to prevent
-       transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
+       transaction ID wraparound or to allow <literal>pg_xact</> to be shrunk.
        It is the minimum of the per-table
        <structname>pg_class</>.<structfield>relfrozenxid</> values.
       </entry>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index adab2f8..8a5d202 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5834,7 +5834,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
 
        <para>
         Vacuum also allows removal of old files from the
-        <filename>pg_clog</> subdirectory, which is why the default
+        <filename>pg_xact</> subdirectory, which is why the default
         is a relatively low 200 million transactions.
         This parameter can only be set at server start, but the setting
         can be reduced for individual tables by
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 2e64cc4..e9cfb06 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15323,7 +15323,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  postmaster.pid  |  9
  pg_ident.conf   | 10
  global          | 11
- pg_clog         | 12
+ pg_xact         | 12
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index f87f3e0..65a64c8 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -527,18 +527,18 @@
    <para>
     The sole disadvantage of increasing <varname>autovacuum_freeze_max_age</>
     (and <varname>vacuum_freeze_table_age</> along with it)
-    is that the <filename>pg_clog</> subdirectory of the database cluster
+    is that the <filename>pg_xact</> subdirectory of the database cluster
     will take more space, because it must store the commit status of all
     transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
     The commit status uses two bits per transaction, so if
     <varname>autovacuum_freeze_max_age</> is set to its maximum allowed
-    value of two billion, <filename>pg_clog</> can be expected to
+    value of two billion, <filename>pg_xact</> can be expected to
     grow to about half a gigabyte.  If this is trivial compared to your
     total database size, setting <varname>autovacuum_freeze_max_age</> to
     its maximum allowed value is recommended.  Otherwise, set it depending
-    on what you are willing to allow for <filename>pg_clog</> storage.
+    on what you are willing to allow for <filename>pg_xact</> storage.
     (The default, 200 million transactions, translates to about 50MB of
-    <filename>pg_clog</> storage.)
+    <filename>pg_xact</> storage.)
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index c949c5e..6ebc68b 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -256,12 +256,12 @@ PostgreSQL documentation
 
      <para>
       A safe value can be determined by looking for the numerically largest
-      file name in the directory <filename>pg_clog</> under the data directory,
+      file name in the directory <filename>pg_xact</> under the data directory,
       adding one,
       and then multiplying by 1048576 (0x100000).  Note that the file names are in
       hexadecimal.  It is usually easiest to specify the option value in
       hexadecimal too. For example, if <filename>0011</> is the largest entry
-      in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
+      in <filename>pg_xact</>, <literal>-x 0x1200000</> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 371c4a4..d5430d4 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -229,7 +229,7 @@ PostgreSQL documentation
     </step>
     <step>
      <para>
-      Copy all other files such as <filename>pg_clog</filename> and
+      Copy all other files such as <filename>pg_xact</filename> and
       configuration files from the source cluster to the target cluster
       (everything except the relation files).
      </para>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index fddb69b..56aef3c 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -72,11 +72,6 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_clog</></entry>
- <entry>Subdirectory containing transaction commit status data</entry>
-</row>
-
-<row>
  <entry><filename>pg_dynshmem</></entry>
  <entry>Subdirectory containing files used by the dynamic shared memory
   subsystem</entry>
@@ -146,6 +141,11 @@ Item
 </row>
 
 <row>
+ <entry><filename>pg_xact</></entry>
+ <entry>Subdirectory containing transaction commit status data</entry>
+</row>
+
+<row>
  <entry><filename>postgresql.auto.conf</></entry>
  <entry>A file used for storing configuration parameters that are set by
 <command>ALTER SYSTEM</command></entry>
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 346aa76..1f9fac9 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_clog</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_xact</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index b019bc1..560a8da 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -6762,8 +6762,8 @@ heap_prepare_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
  * Note: it might seem we could make the changes without exclusive lock, since
  * TransactionId read/write is assumed atomic anyway.  However there is a race
  * condition: someone who just fetched an old XID that we overwrite here could
- * conceivably not finish checking the XID against pg_clog before we finish
- * the VACUUM and perhaps truncate off the part of pg_clog he needs.  Getting
+ * conceivably not finish checking the XID against pg_xact before we finish
+ * the VACUUM and perhaps truncate off the part of pg_xact he needs.  Getting
  * exclusive lock ensures no other backend is in process of checking the
  * tuple status.  Also, getting exclusive lock makes it safe to adjust the
  * infomask bits.
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index 4ae4715..e7dd19f 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -331,17 +331,17 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_clog and pg_subtrans
+pg_xact and pg_subtrans
 -----------------------
 
-pg_clog and pg_subtrans are permanent (on-disk) storage of transaction related
+pg_xact and pg_subtrans are permanent (on-disk) storage of transaction related
 information.  There is a limited number of pages of each kept in memory, so
 in many cases there is no need to actually read from disk.  However, if
 there's a long running transaction or a backend sitting idle with an open
 transaction, it may be necessary to be able to read and write this information
 from disk.  They also allow information to be permanent across server restarts.
 
-pg_clog records the commit status for each transaction that has been assigned
+pg_xact records the commit status for each transaction that has been assigned
 an XID.  A transaction can be in progress, committed, aborted, or
 "sub-committed".  This last state means that it's a subtransaction that's no
 longer running, but its parent has not updated its state yet.  It is not
@@ -381,9 +381,9 @@ each transaction we keep a "cache" of Xids that are known to be part of the
 transaction tree, so we can skip looking at pg_subtrans unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_clog and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_xact and pg_subtrans.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
-for pg_clog are implemented in transam.c, while the low-level functions are in
+for pg_xact are implemented in transam.c, while the low-level functions are in
 clog.c.  pg_subtrans is contained completely in subtrans.c.
 
 
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 2634476..08e1edd 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -450,7 +450,7 @@ CLOGShmemInit(void)
 {
 	ClogCtl->PagePrecedes = CLOGPagePrecedes;
 	SimpleLruInit(ClogCtl, "clog", CLOGShmemBuffers(), CLOG_LSNS_PER_PAGE,
-				  CLogControlLock, "pg_clog", LWTRANCHE_CLOG_BUFFERS);
+				  CLogControlLock, "pg_xact", LWTRANCHE_CLOG_BUFFERS);
 }
 
 /*
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index a8d275f..0d03700 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -3,7 +3,7 @@
  * commit_ts.c
  *		PostgreSQL commit timestamp manager
  *
- * This module is a pg_clog-like system that stores the commit timestamp
+ * This module is a pg_xact-like system that stores the commit timestamp
  * for each transaction.
  *
  * XLOG interactions: this module generates an XLOG record whenever a new
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index e9588a7..287e435 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3,7 +3,7 @@
  * multixact.c
  *		PostgreSQL multi-transaction-log manager
  *
- * The pg_multixact manager is a pg_clog-like manager that stores an array of
+ * The pg_multixact manager is a pg_xact-like manager that stores an array of
  * MultiXactMember for each MultiXactId.  It is a fundamental part of the
  * shared-row-lock implementation.  Each MultiXactMember is comprised of a
  * TransactionId and a set of flag bits.  The name is a bit historical:
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 908fe2d..6871239 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,15 +3,14 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_clog-like manager that stores the parent
+ * The pg_subtrans manager is a pg_xact-like manager that stores the parent
  * transaction Id for each transaction.  It is a fundamental part of the
  * nested transactions implementation.  A main transaction has a parent
  * of InvalidTransactionId, and each subtransaction has its immediate parent.
  * The tree can easily be walked from child to parent, but not in the
  * opposite direction.
  *
- * This code is based on clog.c, but the robustness requirements
- * are completely different from pg_clog, because we only need to remember
+ * are completely different from pg_xact, because we only need to remember
  * pg_subtrans information for currently-open transactions.  Thus, there is
  * no need to preserve data over a crash and restart.
  *
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index 1eba49a..0a103c3 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -224,7 +224,7 @@ TransactionIdDidAbort(TransactionId transactionId)
  *		True iff transaction associated with the identifier is currently
  *		known to have either committed or aborted.
  *
- * This does NOT look into pg_clog but merely probes our local cache
+ * This does NOT look into pg_xact but merely probes our local cache
  * (and so it's not named TransactionIdDidComplete, which would be the
  * appropriate name for a function that worked that way).  The intended
  * use is just to short-circuit TransactionIdIsInProgress calls when doing
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 5415604..8bed3f5 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1379,7 +1379,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	/*
 	 * The order of operations here is critical: make the XLOG entry for
 	 * commit or abort, then mark the transaction committed or aborted in
-	 * pg_clog, then remove its PGPROC from the global ProcArray (which means
+	 * pg_xact, then remove its PGPROC from the global ProcArray (which means
 	 * TransactionIdIsInProgress will stop saying the prepared xact is in
 	 * progress), then run the post-commit or post-abort callbacks. The
 	 * callbacks will release the locks the transaction held.
@@ -2093,7 +2093,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	/* Flush XLOG to disk */
 	XLogFlush(recptr);
 
-	/* Mark the transaction committed in pg_clog */
+	/* Mark the transaction committed in pg_xact */
 	TransactionIdCommitTree(xid, nchildren, children);
 
 	/* Checkpoint can proceed now */
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index e11b229..0dc4d43 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1206,8 +1206,8 @@ RecordTransactionCommit(void)
 		/*
 		 * Mark ourselves as within our "commit critical section".  This
 		 * forces any concurrent checkpoint to wait until we've updated
-		 * pg_clog.  Without this, it is possible for the checkpoint to set
-		 * REDO after the XLOG record but fail to flush the pg_clog update to
+		 * pg_xact.  Without this, it is possible for the checkpoint to set
+		 * REDO after the XLOG record but fail to flush the pg_xact update to
 		 * disk, leading to loss of the transaction commit if the system
 		 * crashes a little later.
 		 *
@@ -2033,7 +2033,7 @@ CommitTransaction(void)
 	if (!is_parallel_worker)
 	{
 		/*
-		 * We need to mark our XIDs as committed in pg_clog.  This is where we
+		 * We need to mark our XIDs as committed in pg_xact.  This is where we
 		 * durably commit.
 		 */
 		latestXid = RecordTransactionCommit();
@@ -2539,7 +2539,7 @@ AbortTransaction(void)
 	AtAbort_Twophase();
 
 	/*
-	 * Advertise the fact that we aborted in pg_clog (assuming that we got as
+	 * Advertise the fact that we aborted in pg_xact (assuming that we got as
 	 * far as assigning an XID to advertise).  But if we're inside a parallel
 	 * worker, skip this; the user backend must be the one to write the abort
 	 * record.
@@ -4625,7 +4625,7 @@ AbortSubTransaction(void)
 								s->parent->subTransactionId);
 		AtSubAbort_Notify();
 
-		/* Advertise the fact that we aborted in pg_clog. */
+		/* Advertise the fact that we aborted in pg_xact. */
 		(void) RecordTransactionAbort(true);
 
 		/* Post-abort cleanup */
@@ -5371,7 +5371,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 	if (standbyState == STANDBY_DISABLED)
 	{
 		/*
-		 * Mark the transaction committed in pg_clog.
+		 * Mark the transaction committed in pg_xact.
 		 */
 		TransactionIdCommitTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
@@ -5389,7 +5389,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		RecordKnownAssignedTransactionIds(max_xid);
 
 		/*
-		 * Mark the transaction committed in pg_clog. We use async commit
+		 * Mark the transaction committed in pg_xact. We use async commit
 		 * protocol during recovery to provide information on database
 		 * consistency for when users try to set hint bits. It is important
 		 * that we do not set hint bits until the minRecoveryPoint is past
@@ -5526,7 +5526,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 
 	if (standbyState == STANDBY_DISABLED)
 	{
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_xact, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
 	else
@@ -5542,7 +5542,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 		 */
 		RecordKnownAssignedTransactionIds(max_xid);
 
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_xact, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 
 		/*
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index d6c057a..ba1bce2 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8488,7 +8488,7 @@ CreateCheckPoint(int flags)
 	 * that are currently in commit critical sections.  If an xact inserted
 	 * its commit record into XLOG just before the REDO point, then a crash
 	 * restart from the REDO point would not replay that record, which means
-	 * that our flushing had better include the xact's update of pg_clog.  So
+	 * that our flushing had better include the xact's update of pg_xact.  So
 	 * we wait till he's out of his commit critical section before proceeding.
 	 * See notes in RecordTransactionCommit().
 	 *
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 58bbf55..d673031 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -356,7 +356,7 @@ vacuum(int options, RangeVar *relation, Oid relid, VacuumParams *params,
 	if ((options & VACOPT_VACUUM) && !IsAutoVacuumWorkerProcess())
 	{
 		/*
-		 * Update pg_database.datfrozenxid, and truncate pg_clog if possible.
+		 * Update pg_database.datfrozenxid, and truncate pg_xact if possible.
 		 * (autovacuum.c does this for itself.)
 		 */
 		vac_update_datfrozenxid();
@@ -880,7 +880,7 @@ vac_update_relstats(Relation relation,
  *		pg_class.relminmxid values.
  *
  *		If we are able to advance either pg_database value, also try to
- *		truncate pg_clog and pg_multixact.
+ *		truncate pg_xact and pg_multixact.
  *
  *		We violate transaction semantics here by overwriting the database's
  *		existing pg_database tuple with the new values.  This is reasonably
@@ -1026,7 +1026,7 @@ vac_update_datfrozenxid(void)
 
 	/*
 	 * If we were able to advance datfrozenxid or datminmxid, see if we can
-	 * truncate pg_clog and/or pg_multixact.  Also do it if the shared
+	 * truncate pg_xact and/or pg_multixact.  Also do it if the shared
 	 * XID-wrap-limit info is stale, since this action will update that too.
 	 */
 	if (dirty || ForceTransactionIdLimitUpdate())
@@ -1039,7 +1039,7 @@ vac_update_datfrozenxid(void)
  *	vac_truncate_clog() -- attempt to truncate the commit log
  *
  *		Scan pg_database to determine the system-wide oldest datfrozenxid,
- *		and use it to truncate the transaction commit log (pg_clog).
+ *		and use it to truncate the transaction commit log (pg_xact).
  *		Also update the XID wrap limit info maintained by varsup.c.
  *		Likewise for datminmxid.
  *
@@ -1086,7 +1086,7 @@ vac_truncate_clog(TransactionId frozenXID,
 	 * of the interlock against copying a DB containing an active backend.
 	 * Hence the new entry will not reduce the minimum.  Also, if two VACUUMs
 	 * concurrently modify the datfrozenxid's of different databases, the
-	 * worst possible outcome is that pg_clog is not truncated as aggressively
+	 * worst possible outcome is that pg_xact is not truncated as aggressively
 	 * as it could be.
 	 */
 	relation = heap_open(DatabaseRelationId, AccessShareLock);
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index e3a6911..29a555e 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2395,7 +2395,7 @@ deleted:
 	 */
 
 	/*
-	 * Update pg_database.datfrozenxid, and truncate pg_clog if possible. We
+	 * Update pg_database.datfrozenxid, and truncate pg_xact if possible. We
 	 * only need to do this once, not after each table.
 	 */
 	vac_update_datfrozenxid();
diff --git a/src/backend/storage/buffer/README b/src/backend/storage/buffer/README
index 248883f..bc80777 100644
--- a/src/backend/storage/buffer/README
+++ b/src/backend/storage/buffer/README
@@ -63,7 +63,7 @@ at about the same time would OR the same bits into the field, so there
 is little or no risk of conflicting update; what's more, if there did
 manage to be a conflict it would merely mean that one bit-update would
 be lost and need to be done again later.  These four bits are only hints
-(they cache the results of transaction status lookups in pg_clog), so no
+(they cache the results of transaction status lookups in pg_xact), so no
 great harm is done if they get reset to zero by conflicting updates.
 Note, however, that a tuple is frozen by setting both HEAP_XMIN_INVALID
 and HEAP_XMIN_COMMITTED; this is a critical update and accordingly requires
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index e5d487d..d41a79f 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -388,7 +388,7 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
  * ProcArrayEndTransaction -- mark a transaction as no longer running
  *
  * This is used interchangeably for commit and abort cases.  The transaction
- * commit/abort must already be reported to WAL and pg_clog.
+ * commit/abort must already be reported to WAL and pg_xact.
  *
  * proc is currently always MyProc, but we pass it explicitly for flexibility.
  * latestXid is the latest Xid among the transaction's main XID and
@@ -1180,7 +1180,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
 	 * subtransaction, we want to say "not running" even though its parent may
-	 * still be running.  So first, check pg_clog to see if it's been aborted.
+	 * still be running.  So first, check pg_xact to see if it's been aborted.
 	 */
 	xc_slow_answer_inc();
 
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 26a3be3..41e89e1 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -13,9 +13,9 @@
  * NOTE: When using a non-MVCC snapshot, we must check
  * TransactionIdIsInProgress (which looks in the PGXACT array)
  * before TransactionIdDidCommit/TransactionIdDidAbort (which look in
- * pg_clog).  Otherwise we have a race condition: we might decide that a
+ * pg_xact).  Otherwise we have a race condition: we might decide that a
  * just-committed transaction crashed, because none of the tests succeed.
- * xact.c is careful to record commit/abort in pg_clog before it unsets
+ * xact.c is careful to record commit/abort in pg_xact before it unsets
  * MyPgXact->xid in the PGXACT array.  That fixes that problem, but it
  * also means there is a window where TransactionIdIsInProgress and
  * TransactionIdDidCommit will both return true.  If we check only
@@ -29,7 +29,7 @@
  *
  * When using an MVCC snapshot, we rely on XidInMVCCSnapshot rather than
  * TransactionIdIsInProgress, but the logic is otherwise the same: do not
- * check pg_clog until after deciding that the xact is no longer in progress.
+ * check pg_xact until after deciding that the xact is no longer in progress.
  *
  *
  * Summary of visibility functions:
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index c8a8c52..9b82622 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -196,7 +196,6 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 static const char *const subdirs[] = {
 	"global",
 	"pg_wal/archive_status",
-	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
 	"pg_notify",
@@ -213,6 +212,7 @@ static const char *const subdirs[] = {
 	"pg_tblspc",
 	"pg_stat",
 	"pg_stat_tmp",
+	"pg_xact",
 	"pg_logical",
 	"pg_logical/snapshots",
 	"pg_logical/mappings"
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 55a6f0d..b242e30 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -309,6 +309,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_xlog");
 	else
 		check_single_dir(pg_data, "pg_wal");
+
+	/* pg_clog has been renamed to pg_xact in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_clog");
+	else
+		check_single_dir(pg_data, "pg_xact");
 }
 
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 90c0720..9c475df 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -47,7 +47,7 @@
 static void prepare_new_cluster(void);
 static void prepare_new_databases(void);
 static void create_new_objects(void);
-static void copy_clog_xlog_xid(void);
+static void copy_xact_xlog_xid(void);
 static void set_frozenxids(bool minmxid_only);
 static void setup(char *argv0, bool *live_check);
 static void cleanup(void);
@@ -113,7 +113,7 @@ main(int argc, char **argv)
 	 * Destructive Changes to New Cluster
 	 */
 
-	copy_clog_xlog_xid();
+	copy_xact_xlog_xid();
 
 	/* New now using xids of the old system */
 
@@ -374,17 +374,17 @@ remove_new_subdir(char *subdir, bool rmtopdir)
  * Copy the files from the old cluster into it
  */
 static void
-copy_subdir_files(char *subdir)
+copy_subdir_files(char *old_subdir, char *new_subdir)
 {
 	char		old_path[MAXPGPATH];
 	char		new_path[MAXPGPATH];
 
-	remove_new_subdir(subdir, true);
+	remove_new_subdir(new_subdir, true);
 
-	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, subdir);
-	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, subdir);
+	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, old_subdir);
+	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, new_subdir);
 
-	prep_status("Copying old %s to new server", subdir);
+	prep_status("Copying old %s to new server", old_subdir);
 
 	exec_prog(UTILITY_LOG_FILE, NULL, true,
 #ifndef WIN32
@@ -399,10 +399,16 @@ copy_subdir_files(char *subdir)
 }
 
 static void
-copy_clog_xlog_xid(void)
+copy_xact_xlog_xid(void)
 {
-	/* copy old commit logs to new data dir */
-	copy_subdir_files("pg_clog");
+	/*
+	 * Copy old commit logs to new data dir. pg_clog has been renamed to
+	 * pg_xact in post-10 clusters.
+	 */
+	copy_subdir_files(GET_MAJOR_VERSION(old_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_xact",
+					  GET_MAJOR_VERSION(new_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_xact");
 
 	/* set the next transaction id and epoch of the new cluster */
 	prep_status("Setting next transaction ID and epoch for new cluster");
@@ -432,8 +438,8 @@ copy_clog_xlog_xid(void)
 	if (old_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER &&
 		new_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER)
 	{
-		copy_subdir_files("pg_multixact/offsets");
-		copy_subdir_files("pg_multixact/members");
+		copy_subdir_files("pg_multixact/offsets", "pg_multixact/offsets");
+		copy_subdir_files("pg_multixact/members", "pg_multixact/members");
 
 		prep_status("Setting next multixact ID and offset for new cluster");
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 5fcebc5..96a1e44 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,7 +76,7 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_clog, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
+	 * for pg_xact, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
 	 * has lsn_groups_per_page entries per buffer slot, each containing the
 	 * highest LSN known for a contiguous group of SLRU entries on that slot's
 	 * page.
@@ -120,7 +120,7 @@ typedef struct SlruCtlData
 	SlruShared	shared;
 
 	/*
-	 * This flag tells whether to fsync writes (true for pg_clog and multixact
+	 * This flag tells whether to fsync writes (true for pg_xact and multixact
 	 * stuff, false for pg_subtrans and pg_notify).
 	 */
 	bool		do_fsync;
-- 
2.10.1

From f7b2413b716ae93bd5f2b7b3abb892c8a936f271 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Sun, 23 Oct 2016 21:33:02 +0900
Subject: [PATCH 2/2] Rename pg_subtrans to pg_subxact

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/func.sgml                       |  2 +-
 doc/src/sgml/storage.sgml                    |  2 +-
 doc/src/sgml/wal.sgml                        |  2 +-
 src/backend/access/transam/README            | 18 +++++++++---------
 src/backend/access/transam/subtrans.c        |  8 ++++----
 src/backend/access/transam/transam.c         | 10 +++++-----
 src/backend/access/transam/twophase.c        |  6 +++---
 src/backend/access/transam/varsup.c          |  6 +++---
 src/backend/access/transam/xact.c            |  2 +-
 src/backend/access/transam/xlog.c            |  8 ++++----
 src/backend/replication/basebackup.c         |  2 +-
 src/backend/replication/logical/snapbuild.c  |  2 +-
 src/backend/storage/ipc/procarray.c          | 14 +++++++-------
 src/backend/utils/time/tqual.c               |  2 +-
 src/bin/initdb/initdb.c                      |  2 +-
 src/bin/pg_basebackup/t/010_pg_basebackup.pl |  2 +-
 src/bin/pg_upgrade/exec.c                    |  7 ++++++-
 src/include/access/slru.h                    |  4 ++--
 src/include/storage/proc.h                   |  2 +-
 19 files changed, 53 insertions(+), 48 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index e9cfb06..74ccb77 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15330,7 +15330,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  pg_wal          | 16
  pg_hba.conf     | 17
  pg_stat_tmp     | 18
- pg_subtrans     | 19
+ pg_subxact      | 19
 (19 rows)
 </programlisting>
   </para>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 56aef3c..e72331d 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -121,7 +121,7 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_subtrans</></entry>
+ <entry><filename>pg_subxact</></entry>
  <entry>Subdirectory containing subtransaction status data</entry>
 </row>
 
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 1f9fac9..aa0eccb 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_xact</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_xact</filename>, <filename>pg_subxact</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index e7dd19f..94553f1 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -198,7 +198,7 @@ parent.  This maintains the invariant that child transactions have XIDs later
 than their parents, which is assumed in a number of places.
 
 The subsidiary actions of obtaining a lock on the XID and entering it into
-pg_subtrans and PG_PROC are done at the time it is assigned.
+pg_subxact and PG_PROC are done at the time it is assigned.
 
 A transaction that has no XID still needs to be identified for various
 purposes, notably holding locks.  For this purpose we assign a "virtual
@@ -331,10 +331,10 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_xact and pg_subtrans
+pg_xact and pg_subxact
 -----------------------
 
-pg_xact and pg_subtrans are permanent (on-disk) storage of transaction related
+pg_xact and pg_subxact are permanent (on-disk) storage of transaction related
 information.  There is a limited number of pages of each kept in memory, so
 in many cases there is no need to actually read from disk.  However, if
 there's a long running transaction or a backend sitting idle with an open
@@ -367,24 +367,24 @@ allow unlimited transaction nesting depth, so any particular subtransaction's
 commit state is dependent on the commit status of each and every ancestor
 transaction.
 
-The "subtransaction parent" (pg_subtrans) mechanism records, for each
+The "subtransaction parent" (pg_subxact) mechanism records, for each
 transaction with an XID, the TransactionId of its parent transaction.  This
 information is stored as soon as the subtransaction is assigned an XID.
-Top-level transactions do not have a parent, so they leave their pg_subtrans
+Top-level transactions do not have a parent, so they leave their pg_subxact
 entries set to the default value of zero (InvalidTransactionId).
 
-pg_subtrans is used to check whether the transaction in question is still
+pg_subxact is used to check whether the transaction in question is still
 running --- the main Xid of a transaction is recorded in the PGXACT struct,
 but since we allow arbitrary nesting of subtransactions, we can't fit all Xids
 in shared memory, so we have to store them on disk.  Note, however, that for
 each transaction we keep a "cache" of Xids that are known to be part of the
-transaction tree, so we can skip looking at pg_subtrans unless we know the
+transaction tree, so we can skip looking at pg_subxact unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_xact and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_xact and pg_subxact.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
 for pg_xact are implemented in transam.c, while the low-level functions are in
-clog.c.  pg_subtrans is contained completely in subtrans.c.
+clog.c.  pg_subxact is contained completely in subtrans.c.
 
 
 Write-Ahead Log Coding
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 6871239..e0f0395 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,7 +3,7 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_xact-like manager that stores the parent
+ * The pg_subxact manager is a pg_xact-like manager that stores the parent
  * transaction Id for each transaction.  It is a fundamental part of the
  * nested transactions implementation.  A main transaction has a parent
  * of InvalidTransactionId, and each subtransaction has its immediate parent.
@@ -11,7 +11,7 @@
  * opposite direction.
  *
  * are completely different from pg_xact, because we only need to remember
- * pg_subtrans information for currently-open transactions.  Thus, there is
+ * pg_subxact information for currently-open transactions.  Thus, there is
  * no need to preserve data over a crash and restart.
  *
  * There are no XLOG interactions since we do not care about preserving
@@ -179,7 +179,7 @@ SUBTRANSShmemInit(void)
 {
 	SubTransCtl->PagePrecedes = SubTransPagePrecedes;
 	SimpleLruInit(SubTransCtl, "subtrans", NUM_SUBTRANS_BUFFERS, 0,
-				  SubtransControlLock, "pg_subtrans",
+				  SubtransControlLock, "pg_subxact",
 				  LWTRANCHE_SUBTRANS_BUFFERS);
 	/* Override default assumption that writes should be fsync'd */
 	SubTransCtl->do_fsync = false;
@@ -240,7 +240,7 @@ StartupSUBTRANS(TransactionId oldestActiveXID)
 	int			endPage;
 
 	/*
-	 * Since we don't expect pg_subtrans to be valid across crashes, we
+	 * Since we don't expect pg_subxact to be valid across crashes, we
 	 * initialize the currently-active page(s) to zeroes during startup.
 	 * Whenever we advance into a new page, ExtendSUBTRANS will likewise zero
 	 * the new page without regard to whatever was previously on disk.
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index 0a103c3..9f11dfd 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -137,13 +137,13 @@ TransactionIdDidCommit(TransactionId transactionId)
 	/*
 	 * If it's marked subcommitted, we have to check the parent recursively.
 	 * However, if it's older than TransactionXmin, we can't look at
-	 * pg_subtrans; instead assume that the parent crashed without cleaning up
+	 * pg_subxact; instead assume that the parent crashed without cleaning up
 	 * its children.
 	 *
 	 * Originally we Assert'ed that the result of SubTransGetParent was not
 	 * zero. However with the introduction of prepared transactions, there can
 	 * be a window just after database startup where we do not have complete
-	 * knowledge in pg_subtrans of the transactions after TransactionXmin.
+	 * knowledge in pg_subxact of the transactions after TransactionXmin.
 	 * StartupSUBTRANS() has ensured that any missing information will be
 	 * zeroed.  Since this case should not happen under normal conditions, it
 	 * seems reasonable to emit a WARNING for it.
@@ -157,7 +157,7 @@ TransactionIdDidCommit(TransactionId transactionId)
 		parentXid = SubTransGetParent(transactionId);
 		if (!TransactionIdIsValid(parentXid))
 		{
-			elog(WARNING, "no pg_subtrans entry for subcommitted XID %u",
+			elog(WARNING, "no pg_subxact entry for subcommitted XID %u",
 				 transactionId);
 			return false;
 		}
@@ -193,7 +193,7 @@ TransactionIdDidAbort(TransactionId transactionId)
 	/*
 	 * If it's marked subcommitted, we have to check the parent recursively.
 	 * However, if it's older than TransactionXmin, we can't look at
-	 * pg_subtrans; instead assume that the parent crashed without cleaning up
+	 * pg_subxact; instead assume that the parent crashed without cleaning up
 	 * its children.
 	 */
 	if (xidstatus == TRANSACTION_STATUS_SUB_COMMITTED)
@@ -206,7 +206,7 @@ TransactionIdDidAbort(TransactionId transactionId)
 		if (!TransactionIdIsValid(parentXid))
 		{
 			/* see notes in TransactionIdDidCommit */
-			elog(WARNING, "no pg_subtrans entry for subcommitted XID %u",
+			elog(WARNING, "no pg_subxact entry for subcommitted XID %u",
 				 transactionId);
 			return true;
 		}
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 8bed3f5..5b3831a 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1674,7 +1674,7 @@ CheckPointTwoPhase(XLogRecPtr redo_horizon)
  *
  * Our other responsibility is to determine and return the oldest valid XID
  * among the prepared xacts (if none, return ShmemVariableCache->nextXid).
- * This is needed to synchronize pg_subtrans startup properly.
+ * This is needed to synchronize pg_subxact startup properly.
  *
  * If xids_p and nxids_p are not NULL, pointer to a palloc'd array of all
  * top-level xids is stored in *xids_p. The number of entries in the array
@@ -1819,7 +1819,7 @@ PrescanPreparedTransactions(TransactionId **xids_p, int *nxids_p)
  *
  * Currently we simply call SubTransSetParent() for any subxids of prepared
  * transactions. If overwriteOK is true, it's OK if some XIDs have already
- * been marked in pg_subtrans.
+ * been marked in pg_subxact.
  */
 void
 StandbyRecoverPreparedTransactions(bool overwriteOK)
@@ -1976,7 +1976,7 @@ RecoverPreparedTransactions(void)
 
 			/*
 			 * Reconstruct subtrans state for the transaction --- needed
-			 * because pg_subtrans is not preserved over a restart.  Note that
+			 * because pg_subxact is not preserved over a restart.  Note that
 			 * we are linking all the subtransactions directly to the
 			 * top-level XID; there may originally have been a more complex
 			 * hierarchy, but there's no need to restore that exactly.
diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 2f7e645..8703eea 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -166,7 +166,7 @@ GetNewTransactionId(bool isSubXact)
 	 * XID before we zero the page.  Fortunately, a page of the commit log
 	 * holds 32K or more transactions, so we don't have to do this very often.
 	 *
-	 * Extend pg_subtrans and pg_commit_ts too.
+	 * Extend pg_subxact and pg_commit_ts too.
 	 */
 	ExtendCLOG(xid);
 	ExtendCommitTs(xid);
@@ -203,9 +203,9 @@ GetNewTransactionId(bool isSubXact)
 	 *
 	 * If there's no room to fit a subtransaction XID into PGPROC, set the
 	 * cache-overflowed flag instead.  This forces readers to look in
-	 * pg_subtrans to map subtransaction XIDs up to top-level XIDs. There is a
+	 * pg_subxact to map subtransaction XIDs up to top-level XIDs. There is a
 	 * race-condition window, in that the new XID will not appear as running
-	 * until its parent link has been placed into pg_subtrans. However, that
+	 * until its parent link has been placed into pg_subxact. However, that
 	 * will happen before anyone could possibly have a reason to inquire about
 	 * the status of the XID, so it seems OK.  (Snapshots taken during this
 	 * window *will* include the parent XID, so they will deliver the correct
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 0dc4d43..5703234 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -544,7 +544,7 @@ AssignTransactionId(TransactionState s)
 		log_unknown_top = true;
 
 	/*
-	 * Generate a new Xid and record it in PG_PROC and pg_subtrans.
+	 * Generate a new Xid and record it in PG_PROC and pg_subxact.
 	 *
 	 * NB: we must make the subtrans entry BEFORE the Xid appears anywhere in
 	 * shared storage other than PG_PROC; because if there's no room for it in
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index ba1bce2..c21362d 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8640,9 +8640,9 @@ CreateCheckPoint(int flags)
 		PreallocXlogFiles(recptr);
 
 	/*
-	 * Truncate pg_subtrans if possible.  We can throw away all data before
+	 * Truncate pg_subxact if possible.  We can throw away all data before
 	 * the oldest XMIN of any running transaction.  No future transaction will
-	 * attempt to reference any pg_subtrans entry older than that (see Asserts
+	 * attempt to reference any pg_subxact entry older than that (see Asserts
 	 * in subtrans.c).  During recovery, though, we mustn't do this because
 	 * StartupSUBTRANS hasn't been called yet.
 	 */
@@ -8979,9 +8979,9 @@ CreateRestartPoint(int flags)
 	}
 
 	/*
-	 * Truncate pg_subtrans if possible.  We can throw away all data before
+	 * Truncate pg_subxact if possible.  We can throw away all data before
 	 * the oldest XMIN of any running transaction.  No future transaction will
-	 * attempt to reference any pg_subtrans entry older than that (see Asserts
+	 * attempt to reference any pg_subxact entry older than that (see Asserts
 	 * in subtrans.c).  When hot standby is disabled, though, we mustn't do
 	 * this because StartupSUBTRANS hasn't been called yet.
 	 */
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index ffc7e58..32c1998 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -134,7 +134,7 @@ static const char *excludeDirContents[] =
 	"pg_snapshots",
 
 	/* Contents zeroed on startup, see StartupSUBTRANS(). */
-	"pg_subtrans",
+	"pg_subxact",
 
 	/* end of list */
 	NULL
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index 8b59fc5..2d73734 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -20,7 +20,7 @@
  * tables since the data we decode is wholly contained in the WAL
  * records. Also, our snapshots need to be different in comparison to normal
  * MVCC ones because in contrast to those we cannot fully rely on the clog and
- * pg_subtrans for information about committed transactions because they might
+ * pg_subxact for information about committed transactions because they might
  * commit in the future from the POV of the WAL entry we're currently
  * decoding. This definition has the advantage that we only need to prevent
  * removal of catalog rows, while normal table's rows can still be
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index d41a79f..e4e88a9 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -935,7 +935,7 @@ ProcArrayApplyXidAssignment(TransactionId topxid,
 	RecordKnownAssignedTransactionIds(max_xid);
 
 	/*
-	 * Notice that we update pg_subtrans with the top-level xid, rather than
+	 * Notice that we update pg_subxact with the top-level xid, rather than
 	 * the parent xid. This is a difference between normal processing and
 	 * recovery, yet is still correct in all cases. The reason is that
 	 * subtransaction commit is not marked in clog until commit processing, so
@@ -1152,7 +1152,7 @@ TransactionIdIsInProgress(TransactionId xid)
 		}
 
 		/*
-		 * If the KnownAssignedXids overflowed, we have to check pg_subtrans
+		 * If the KnownAssignedXids overflowed, we have to check pg_subxact
 		 * too.  Fetch all xids from KnownAssignedXids that are lower than
 		 * xid, since if xid is a subtransaction its parent will always have a
 		 * lower value.  Note we will collect both main and subXIDs here, but
@@ -1166,7 +1166,7 @@ TransactionIdIsInProgress(TransactionId xid)
 
 	/*
 	 * If none of the relevant caches overflowed, we know the Xid is not
-	 * running without even looking at pg_subtrans.
+	 * running without even looking at pg_subxact.
 	 */
 	if (nxids == 0)
 	{
@@ -1175,7 +1175,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	}
 
 	/*
-	 * Step 4: have to check pg_subtrans.
+	 * Step 4: have to check pg_subxact.
 	 *
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
@@ -1276,7 +1276,7 @@ TransactionIdIsActive(TransactionId xid)
  * ignore concurrently running lazy VACUUMs because (a) they must be working
  * on other tables, and (b) they don't need to do snapshot-based lookups.
  *
- * This is also used to determine where to truncate pg_subtrans.  For that
+ * This is also used to determine where to truncate pg_subxact.  For that
  * backends in all databases have to be considered, so rel = NULL has to be
  * passed in.
  *
@@ -3081,14 +3081,14 @@ DisplayXidCache(void)
  * KnownAssignedXids list.  In backends, this is copied into snapshots in
  * GetSnapshotData(), taking advantage of the fact that XidInMVCCSnapshot()
  * doesn't care about the distinction either.  Subtransaction XIDs are
- * effectively treated as top-level XIDs and in the typical case pg_subtrans
+ * effectively treated as top-level XIDs and in the typical case pg_subxact
  * links are *not* maintained (which does not affect visibility).
  *
  * We have room in KnownAssignedXids and in snapshots to hold maxProcs *
  * (1 + PGPROC_MAX_CACHED_SUBXIDS) XIDs, so every master transaction must
  * report its subtransaction XIDs in a WAL XLOG_XACT_ASSIGNMENT record at
  * least every PGPROC_MAX_CACHED_SUBXIDS.  When we receive one of these
- * records, we mark the subXIDs as children of the top XID in pg_subtrans,
+ * records, we mark the subXIDs as children of the top XID in pg_subxact,
  * and then remove them from KnownAssignedXids.  This prevents overflow of
  * KnownAssignedXids and snapshots, at the cost that status checks for these
  * subXIDs will take a slower path through TransactionIdIsInProgress().
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 41e89e1..5cfa917 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -1490,7 +1490,7 @@ XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)
 		 * If the snapshot contains full subxact data, the fastest way to
 		 * check things is just to compare the given XID against both subxact
 		 * XIDs and top-level XIDs.  If the snapshot overflowed, we have to
-		 * use pg_subtrans to convert a subxact XID to its parent XID, but
+		 * use pg_subxact to convert a subxact XID to its parent XID, but
 		 * then we need only look at top-level XIDs not subxacts.
 		 */
 		if (!snapshot->suboverflowed)
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 9b82622..8f0460d 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -201,7 +201,7 @@ static const char *const subdirs[] = {
 	"pg_notify",
 	"pg_serial",
 	"pg_snapshots",
-	"pg_subtrans",
+	"pg_subxact",
 	"pg_twophase",
 	"pg_multixact",
 	"pg_multixact/members",
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 579d7a1..61a1491 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -74,7 +74,7 @@ is_deeply(
 	'no WAL files copied');
 
 # Contents of these directories should not be copied.
-foreach my $dirname (qw(pg_dynshmem pg_notify pg_replslot pg_serial pg_snapshots pg_stat_tmp pg_subtrans))
+foreach my $dirname (qw(pg_dynshmem pg_notify pg_replslot pg_serial pg_snapshots pg_stat_tmp pg_subxact))
 {
 	is_deeply(
 		[ sort(slurp_dir("$tempdir/backup/$dirname/")) ],
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index b242e30..c6633c9 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -300,7 +300,6 @@ check_data_dir(ClusterInfo *cluster)
 	check_single_dir(pg_data, "base");
 	check_single_dir(pg_data, "global");
 	check_single_dir(pg_data, "pg_multixact");
-	check_single_dir(pg_data, "pg_subtrans");
 	check_single_dir(pg_data, "pg_tblspc");
 	check_single_dir(pg_data, "pg_twophase");
 
@@ -315,6 +314,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_clog");
 	else
 		check_single_dir(pg_data, "pg_xact");
+
+	/* pg_clog has been renamed to pg_xact in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_subtrans");
+	else
+		check_single_dir(pg_data, "pg_subxact");
 }
 
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 96a1e44..54ad056 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,7 +76,7 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_xact, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
+	 * for pg_xact, false for multixact, pg_subxact, pg_notify).  group_lsn[]
 	 * has lsn_groups_per_page entries per buffer slot, each containing the
 	 * highest LSN known for a contiguous group of SLRU entries on that slot's
 	 * page.
@@ -121,7 +121,7 @@ typedef struct SlruCtlData
 
 	/*
 	 * This flag tells whether to fsync writes (true for pg_xact and multixact
-	 * stuff, false for pg_subtrans and pg_notify).
+	 * stuff, false for pg_subxact and pg_notify).
 	 */
 	bool		do_fsync;
 
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 7dc8dac..08c2d68 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -30,7 +30,7 @@
  * generated at least one subtransaction that didn't fit in the cache).
  * If none of the caches have overflowed, we can assume that an XID that's not
  * listed anywhere in the PGPROC array is not a running transaction.  Else we
- * have to look at pg_subtrans.
+ * have to look at pg_subxact.
  */
 #define PGPROC_MAX_CACHED_SUBXIDS 64	/* XXX guessed-at value */
 
-- 
2.10.1

From fcf26703672232a77c29ad08146ab97a7626fc5e Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Sun, 23 Oct 2016 20:52:22 +0900
Subject: [PATCH 1/2] Rename pg_clog to pg_xact

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml               |  4 ++--
 doc/src/sgml/catalogs.sgml             |  4 ++--
 doc/src/sgml/config.sgml               |  2 +-
 doc/src/sgml/func.sgml                 |  2 +-
 doc/src/sgml/maintenance.sgml          |  8 ++++----
 doc/src/sgml/ref/pg_resetxlog.sgml     |  4 ++--
 doc/src/sgml/ref/pg_rewind.sgml        |  2 +-
 doc/src/sgml/storage.sgml              | 10 +++++-----
 doc/src/sgml/wal.sgml                  |  2 +-
 src/backend/access/heap/heapam.c       |  4 ++--
 src/backend/access/transam/README      | 10 +++++-----
 src/backend/access/transam/clog.c      |  2 +-
 src/backend/access/transam/commit_ts.c |  2 +-
 src/backend/access/transam/multixact.c |  2 +-
 src/backend/access/transam/subtrans.c  |  5 ++---
 src/backend/access/transam/transam.c   |  2 +-
 src/backend/access/transam/twophase.c  |  4 ++--
 src/backend/access/transam/xact.c      | 18 +++++++++---------
 src/backend/access/transam/xlog.c      |  2 +-
 src/backend/commands/vacuum.c          | 10 +++++-----
 src/backend/postmaster/autovacuum.c    |  2 +-
 src/backend/storage/buffer/README      |  2 +-
 src/backend/storage/ipc/procarray.c    |  4 ++--
 src/backend/utils/time/tqual.c         |  6 +++---
 src/bin/initdb/initdb.c                |  2 +-
 src/bin/pg_upgrade/exec.c              |  6 ++++++
 src/bin/pg_upgrade/pg_upgrade.c        | 30 ++++++++++++++++++------------
 src/include/access/slru.h              |  4 ++--
 28 files changed, 83 insertions(+), 72 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index d7df91090d..0c56c9d068 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -382,10 +382,10 @@ tar -cf backup.tar /usr/local/pgsql/data
       directories. This will <emphasis>not</> work because the
       information contained in these files is not usable without
       the commit log files,
-      <filename>pg_clog/*</filename>, which contain the commit status of
+      <filename>pg_xact/*</filename>, which contain the commit status of
       all transactions. A table file is only usable with this
       information. Of course it is also impossible to restore only a
-      table and the associated <filename>pg_clog</filename> data
+      table and the associated <filename>pg_xact</filename> data
       because that would render all other tables in the database
       cluster useless.  So file system backups only work for complete
       backup and restoration of an entire database cluster.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 493050618d..cdd72b88eb 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1866,7 +1866,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this table.  This is used to track
        whether the table needs to be vacuumed in order to prevent transaction
-       ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
+       ID wraparound or to allow <literal>pg_xact</> to be shrunk.  Zero
        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
       </entry>
      </row>
@@ -2543,7 +2543,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this database.  This is used to
        track whether the database needs to be vacuumed in order to prevent
-       transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
+       transaction ID wraparound or to allow <literal>pg_xact</> to be shrunk.
        It is the minimum of the per-table
        <structname>pg_class</>.<structfield>relfrozenxid</> values.
       </entry>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 07afa3c77a..e77d01d572 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -5902,7 +5902,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
 
        <para>
         Vacuum also allows removal of old files from the
-        <filename>pg_clog</> subdirectory, which is why the default
+        <filename>pg_xact</> subdirectory, which is why the default
         is a relatively low 200 million transactions.
         This parameter can only be set at server start, but the setting
         can be reduced for individual tables by
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 10e31868ba..865f74a260 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15321,7 +15321,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  postmaster.pid  |  9
  pg_ident.conf   | 10
  global          | 11
- pg_clog         | 12
+ pg_xact         | 12
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index f87f3e00de..65a64c85ec 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -527,18 +527,18 @@
    <para>
     The sole disadvantage of increasing <varname>autovacuum_freeze_max_age</>
     (and <varname>vacuum_freeze_table_age</> along with it)
-    is that the <filename>pg_clog</> subdirectory of the database cluster
+    is that the <filename>pg_xact</> subdirectory of the database cluster
     will take more space, because it must store the commit status of all
     transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
     The commit status uses two bits per transaction, so if
     <varname>autovacuum_freeze_max_age</> is set to its maximum allowed
-    value of two billion, <filename>pg_clog</> can be expected to
+    value of two billion, <filename>pg_xact</> can be expected to
     grow to about half a gigabyte.  If this is trivial compared to your
     total database size, setting <varname>autovacuum_freeze_max_age</> to
     its maximum allowed value is recommended.  Otherwise, set it depending
-    on what you are willing to allow for <filename>pg_clog</> storage.
+    on what you are willing to allow for <filename>pg_xact</> storage.
     (The default, 200 million transactions, translates to about 50MB of
-    <filename>pg_clog</> storage.)
+    <filename>pg_xact</> storage.)
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/pg_resetxlog.sgml b/doc/src/sgml/ref/pg_resetxlog.sgml
index c949c5e849..6ebc68b454 100644
--- a/doc/src/sgml/ref/pg_resetxlog.sgml
+++ b/doc/src/sgml/ref/pg_resetxlog.sgml
@@ -256,12 +256,12 @@ PostgreSQL documentation
 
      <para>
       A safe value can be determined by looking for the numerically largest
-      file name in the directory <filename>pg_clog</> under the data directory,
+      file name in the directory <filename>pg_xact</> under the data directory,
       adding one,
       and then multiplying by 1048576 (0x100000).  Note that the file names are in
       hexadecimal.  It is usually easiest to specify the option value in
       hexadecimal too. For example, if <filename>0011</> is the largest entry
-      in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
+      in <filename>pg_xact</>, <literal>-x 0x1200000</> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 371c4a475f..d5430d4324 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -229,7 +229,7 @@ PostgreSQL documentation
     </step>
     <step>
      <para>
-      Copy all other files such as <filename>pg_clog</filename> and
+      Copy all other files such as <filename>pg_xact</filename> and
       configuration files from the source cluster to the target cluster
       (everything except the relation files).
      </para>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 5c52824dfc..91b44d4cc5 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -72,11 +72,6 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_clog</></entry>
- <entry>Subdirectory containing transaction commit status data</entry>
-</row>
-
-<row>
  <entry><filename>pg_dynshmem</></entry>
  <entry>Subdirectory containing files used by the dynamic shared memory
   subsystem</entry>
@@ -146,6 +141,11 @@ Item
 </row>
 
 <row>
+ <entry><filename>pg_xact</></entry>
+ <entry>Subdirectory containing transaction commit status data</entry>
+</row>
+
+<row>
  <entry><filename>postgresql.auto.conf</></entry>
  <entry>A file used for storing configuration parameters that are set by
 <command>ALTER SYSTEM</command></entry>
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 346aa769a8..1f9fac9be9 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_clog</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_xact</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 1ce42ea970..0649b35d2c 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -6762,8 +6762,8 @@ heap_prepare_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
  * Note: it might seem we could make the changes without exclusive lock, since
  * TransactionId read/write is assumed atomic anyway.  However there is a race
  * condition: someone who just fetched an old XID that we overwrite here could
- * conceivably not finish checking the XID against pg_clog before we finish
- * the VACUUM and perhaps truncate off the part of pg_clog he needs.  Getting
+ * conceivably not finish checking the XID against pg_xact before we finish
+ * the VACUUM and perhaps truncate off the part of pg_xact he needs.  Getting
  * exclusive lock ensures no other backend is in process of checking the
  * tuple status.  Also, getting exclusive lock makes it safe to adjust the
  * infomask bits.
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index 4ae4715339..e7dd19fd7b 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -331,17 +331,17 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_clog and pg_subtrans
+pg_xact and pg_subtrans
 -----------------------
 
-pg_clog and pg_subtrans are permanent (on-disk) storage of transaction related
+pg_xact and pg_subtrans are permanent (on-disk) storage of transaction related
 information.  There is a limited number of pages of each kept in memory, so
 in many cases there is no need to actually read from disk.  However, if
 there's a long running transaction or a backend sitting idle with an open
 transaction, it may be necessary to be able to read and write this information
 from disk.  They also allow information to be permanent across server restarts.
 
-pg_clog records the commit status for each transaction that has been assigned
+pg_xact records the commit status for each transaction that has been assigned
 an XID.  A transaction can be in progress, committed, aborted, or
 "sub-committed".  This last state means that it's a subtransaction that's no
 longer running, but its parent has not updated its state yet.  It is not
@@ -381,9 +381,9 @@ each transaction we keep a "cache" of Xids that are known to be part of the
 transaction tree, so we can skip looking at pg_subtrans unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_clog and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_xact and pg_subtrans.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
-for pg_clog are implemented in transam.c, while the low-level functions are in
+for pg_xact are implemented in transam.c, while the low-level functions are in
 clog.c.  pg_subtrans is contained completely in subtrans.c.
 
 
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 1a43819736..5b1d13dac1 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -450,7 +450,7 @@ CLOGShmemInit(void)
 {
 	ClogCtl->PagePrecedes = CLOGPagePrecedes;
 	SimpleLruInit(ClogCtl, "clog", CLOGShmemBuffers(), CLOG_LSNS_PER_PAGE,
-				  CLogControlLock, "pg_clog", LWTRANCHE_CLOG_BUFFERS);
+				  CLogControlLock, "pg_xact", LWTRANCHE_CLOG_BUFFERS);
 }
 
 /*
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index 2403de3ae3..a7ef495973 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -3,7 +3,7 @@
  * commit_ts.c
  *		PostgreSQL commit timestamp manager
  *
- * This module is a pg_clog-like system that stores the commit timestamp
+ * This module is a pg_xact-like system that stores the commit timestamp
  * for each transaction.
  *
  * XLOG interactions: this module generates an XLOG record whenever a new
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 59d1252ddc..51f8fa22c5 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3,7 +3,7 @@
  * multixact.c
  *		PostgreSQL multi-transaction-log manager
  *
- * The pg_multixact manager is a pg_clog-like manager that stores an array of
+ * The pg_multixact manager is a pg_xact-like manager that stores an array of
  * MultiXactMember for each MultiXactId.  It is a fundamental part of the
  * shared-row-lock implementation.  Each MultiXactMember is comprised of a
  * TransactionId and a set of flag bits.  The name is a bit historical:
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index a66fc0f2ad..70828e5170 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,15 +3,14 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_clog-like manager that stores the parent
+ * The pg_subtrans manager is a pg_xact-like manager that stores the parent
  * transaction Id for each transaction.  It is a fundamental part of the
  * nested transactions implementation.  A main transaction has a parent
  * of InvalidTransactionId, and each subtransaction has its immediate parent.
  * The tree can easily be walked from child to parent, but not in the
  * opposite direction.
  *
- * This code is based on clog.c, but the robustness requirements
- * are completely different from pg_clog, because we only need to remember
+ * are completely different from pg_xact, because we only need to remember
  * pg_subtrans information for currently-open transactions.  Thus, there is
  * no need to preserve data over a crash and restart.
  *
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index c2b4318bd3..b91a259e80 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -224,7 +224,7 @@ TransactionIdDidAbort(TransactionId transactionId)
  *		True iff transaction associated with the identifier is currently
  *		known to have either committed or aborted.
  *
- * This does NOT look into pg_clog but merely probes our local cache
+ * This does NOT look into pg_xact but merely probes our local cache
  * (and so it's not named TransactionIdDidComplete, which would be the
  * appropriate name for a function that worked that way).  The intended
  * use is just to short-circuit TransactionIdIsInProgress calls when doing
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 5b72c1dcf5..3c1f7b596d 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1379,7 +1379,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	/*
 	 * The order of operations here is critical: make the XLOG entry for
 	 * commit or abort, then mark the transaction committed or aborted in
-	 * pg_clog, then remove its PGPROC from the global ProcArray (which means
+	 * pg_xact, then remove its PGPROC from the global ProcArray (which means
 	 * TransactionIdIsInProgress will stop saying the prepared xact is in
 	 * progress), then run the post-commit or post-abort callbacks. The
 	 * callbacks will release the locks the transaction held.
@@ -2093,7 +2093,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	/* Flush XLOG to disk */
 	XLogFlush(recptr);
 
-	/* Mark the transaction committed in pg_clog */
+	/* Mark the transaction committed in pg_xact */
 	TransactionIdCommitTree(xid, nchildren, children);
 
 	/* Checkpoint can proceed now */
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index f5346f024e..fc603a575e 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1207,8 +1207,8 @@ RecordTransactionCommit(void)
 		/*
 		 * Mark ourselves as within our "commit critical section".  This
 		 * forces any concurrent checkpoint to wait until we've updated
-		 * pg_clog.  Without this, it is possible for the checkpoint to set
-		 * REDO after the XLOG record but fail to flush the pg_clog update to
+		 * pg_xact.  Without this, it is possible for the checkpoint to set
+		 * REDO after the XLOG record but fail to flush the pg_xact update to
 		 * disk, leading to loss of the transaction commit if the system
 		 * crashes a little later.
 		 *
@@ -2034,7 +2034,7 @@ CommitTransaction(void)
 	if (!is_parallel_worker)
 	{
 		/*
-		 * We need to mark our XIDs as committed in pg_clog.  This is where we
+		 * We need to mark our XIDs as committed in pg_xact.  This is where we
 		 * durably commit.
 		 */
 		latestXid = RecordTransactionCommit();
@@ -2543,7 +2543,7 @@ AbortTransaction(void)
 	AtAbort_Twophase();
 
 	/*
-	 * Advertise the fact that we aborted in pg_clog (assuming that we got as
+	 * Advertise the fact that we aborted in pg_xact (assuming that we got as
 	 * far as assigning an XID to advertise).  But if we're inside a parallel
 	 * worker, skip this; the user backend must be the one to write the abort
 	 * record.
@@ -4629,7 +4629,7 @@ AbortSubTransaction(void)
 								s->parent->subTransactionId);
 		AtSubAbort_Notify();
 
-		/* Advertise the fact that we aborted in pg_clog. */
+		/* Advertise the fact that we aborted in pg_xact. */
 		(void) RecordTransactionAbort(true);
 
 		/* Post-abort cleanup */
@@ -5373,7 +5373,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 	if (standbyState == STANDBY_DISABLED)
 	{
 		/*
-		 * Mark the transaction committed in pg_clog.
+		 * Mark the transaction committed in pg_xact.
 		 */
 		TransactionIdCommitTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
@@ -5391,7 +5391,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		RecordKnownAssignedTransactionIds(max_xid);
 
 		/*
-		 * Mark the transaction committed in pg_clog. We use async commit
+		 * Mark the transaction committed in pg_xact. We use async commit
 		 * protocol during recovery to provide information on database
 		 * consistency for when users try to set hint bits. It is important
 		 * that we do not set hint bits until the minRecoveryPoint is past
@@ -5528,7 +5528,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 
 	if (standbyState == STANDBY_DISABLED)
 	{
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_xact, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
 	else
@@ -5544,7 +5544,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 		 */
 		RecordKnownAssignedTransactionIds(max_xid);
 
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_xact, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 
 		/*
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 70edafadff..41b721b1dd 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8550,7 +8550,7 @@ CreateCheckPoint(int flags)
 	 * that are currently in commit critical sections.  If an xact inserted
 	 * its commit record into XLOG just before the REDO point, then a crash
 	 * restart from the REDO point would not replay that record, which means
-	 * that our flushing had better include the xact's update of pg_clog.  So
+	 * that our flushing had better include the xact's update of pg_xact.  So
 	 * we wait till he's out of his commit critical section before proceeding.
 	 * See notes in RecordTransactionCommit().
 	 *
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 0f72c1c36a..e92372d06d 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -356,7 +356,7 @@ vacuum(int options, RangeVar *relation, Oid relid, VacuumParams *params,
 	if ((options & VACOPT_VACUUM) && !IsAutoVacuumWorkerProcess())
 	{
 		/*
-		 * Update pg_database.datfrozenxid, and truncate pg_clog if possible.
+		 * Update pg_database.datfrozenxid, and truncate pg_xact if possible.
 		 * (autovacuum.c does this for itself.)
 		 */
 		vac_update_datfrozenxid();
@@ -880,7 +880,7 @@ vac_update_relstats(Relation relation,
  *		pg_class.relminmxid values.
  *
  *		If we are able to advance either pg_database value, also try to
- *		truncate pg_clog and pg_multixact.
+ *		truncate pg_xact and pg_multixact.
  *
  *		We violate transaction semantics here by overwriting the database's
  *		existing pg_database tuple with the new values.  This is reasonably
@@ -1026,7 +1026,7 @@ vac_update_datfrozenxid(void)
 
 	/*
 	 * If we were able to advance datfrozenxid or datminmxid, see if we can
-	 * truncate pg_clog and/or pg_multixact.  Also do it if the shared
+	 * truncate pg_xact and/or pg_multixact.  Also do it if the shared
 	 * XID-wrap-limit info is stale, since this action will update that too.
 	 */
 	if (dirty || ForceTransactionIdLimitUpdate())
@@ -1039,7 +1039,7 @@ vac_update_datfrozenxid(void)
  *	vac_truncate_clog() -- attempt to truncate the commit log
  *
  *		Scan pg_database to determine the system-wide oldest datfrozenxid,
- *		and use it to truncate the transaction commit log (pg_clog).
+ *		and use it to truncate the transaction commit log (pg_xact).
  *		Also update the XID wrap limit info maintained by varsup.c.
  *		Likewise for datminmxid.
  *
@@ -1086,7 +1086,7 @@ vac_truncate_clog(TransactionId frozenXID,
 	 * of the interlock against copying a DB containing an active backend.
 	 * Hence the new entry will not reduce the minimum.  Also, if two VACUUMs
 	 * concurrently modify the datfrozenxid's of different databases, the
-	 * worst possible outcome is that pg_clog is not truncated as aggressively
+	 * worst possible outcome is that pg_xact is not truncated as aggressively
 	 * as it could be.
 	 */
 	relation = heap_open(DatabaseRelationId, AccessShareLock);
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 251b9fe372..b3fdd29c49 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2468,7 +2468,7 @@ deleted:
 	 */
 
 	/*
-	 * Update pg_database.datfrozenxid, and truncate pg_clog if possible. We
+	 * Update pg_database.datfrozenxid, and truncate pg_xact if possible. We
 	 * only need to do this once, not after each table.
 	 */
 	vac_update_datfrozenxid();
diff --git a/src/backend/storage/buffer/README b/src/backend/storage/buffer/README
index 248883f0da..bc80777bb1 100644
--- a/src/backend/storage/buffer/README
+++ b/src/backend/storage/buffer/README
@@ -63,7 +63,7 @@ at about the same time would OR the same bits into the field, so there
 is little or no risk of conflicting update; what's more, if there did
 manage to be a conflict it would merely mean that one bit-update would
 be lost and need to be done again later.  These four bits are only hints
-(they cache the results of transaction status lookups in pg_clog), so no
+(they cache the results of transaction status lookups in pg_xact), so no
 great harm is done if they get reset to zero by conflicting updates.
 Note, however, that a tuple is frozen by setting both HEAP_XMIN_INVALID
 and HEAP_XMIN_COMMITTED; this is a critical update and accordingly requires
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 3f47b984ee..ce34e8a8de 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -381,7 +381,7 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
  * ProcArrayEndTransaction -- mark a transaction as no longer running
  *
  * This is used interchangeably for commit and abort cases.  The transaction
- * commit/abort must already be reported to WAL and pg_clog.
+ * commit/abort must already be reported to WAL and pg_xact.
  *
  * proc is currently always MyProc, but we pass it explicitly for flexibility.
  * latestXid is the latest Xid among the transaction's main XID and
@@ -1174,7 +1174,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
 	 * subtransaction, we want to say "not running" even though its parent may
-	 * still be running.  So first, check pg_clog to see if it's been aborted.
+	 * still be running.  So first, check pg_xact to see if it's been aborted.
 	 */
 	xc_slow_answer_inc();
 
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 053a6d1c70..2431d8794a 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -13,9 +13,9 @@
  * NOTE: When using a non-MVCC snapshot, we must check
  * TransactionIdIsInProgress (which looks in the PGXACT array)
  * before TransactionIdDidCommit/TransactionIdDidAbort (which look in
- * pg_clog).  Otherwise we have a race condition: we might decide that a
+ * pg_xact).  Otherwise we have a race condition: we might decide that a
  * just-committed transaction crashed, because none of the tests succeed.
- * xact.c is careful to record commit/abort in pg_clog before it unsets
+ * xact.c is careful to record commit/abort in pg_xact before it unsets
  * MyPgXact->xid in the PGXACT array.  That fixes that problem, but it
  * also means there is a window where TransactionIdIsInProgress and
  * TransactionIdDidCommit will both return true.  If we check only
@@ -29,7 +29,7 @@
  *
  * When using an MVCC snapshot, we rely on XidInMVCCSnapshot rather than
  * TransactionIdIsInProgress, but the logic is otherwise the same: do not
- * check pg_clog until after deciding that the xact is no longer in progress.
+ * check pg_xact until after deciding that the xact is no longer in progress.
  *
  *
  * Summary of visibility functions:
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 1e7d677244..8ad3879e13 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -196,7 +196,6 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 static const char *const subdirs[] = {
 	"global",
 	"pg_wal/archive_status",
-	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
 	"pg_notify",
@@ -213,6 +212,7 @@ static const char *const subdirs[] = {
 	"pg_tblspc",
 	"pg_stat",
 	"pg_stat_tmp",
+	"pg_xact",
 	"pg_logical",
 	"pg_logical/snapshots",
 	"pg_logical/mappings"
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 3a30ea7438..6810a6fb58 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -309,6 +309,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_xlog");
 	else
 		check_single_dir(pg_data, "pg_wal");
+
+	/* pg_clog has been renamed to pg_xact in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_clog");
+	else
+		check_single_dir(pg_data, "pg_xact");
 }
 
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index 797e36d253..1760636c25 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -47,7 +47,7 @@
 static void prepare_new_cluster(void);
 static void prepare_new_databases(void);
 static void create_new_objects(void);
-static void copy_clog_xlog_xid(void);
+static void copy_xact_xlog_xid(void);
 static void set_frozenxids(bool minmxid_only);
 static void setup(char *argv0, bool *live_check);
 static void cleanup(void);
@@ -114,7 +114,7 @@ main(int argc, char **argv)
 	 * Destructive Changes to New Cluster
 	 */
 
-	copy_clog_xlog_xid();
+	copy_xact_xlog_xid();
 
 	/* New now using xids of the old system */
 
@@ -375,17 +375,17 @@ remove_new_subdir(char *subdir, bool rmtopdir)
  * Copy the files from the old cluster into it
  */
 static void
-copy_subdir_files(char *subdir)
+copy_subdir_files(char *old_subdir, char *new_subdir)
 {
 	char		old_path[MAXPGPATH];
 	char		new_path[MAXPGPATH];
 
-	remove_new_subdir(subdir, true);
+	remove_new_subdir(new_subdir, true);
 
-	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, subdir);
-	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, subdir);
+	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, old_subdir);
+	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, new_subdir);
 
-	prep_status("Copying old %s to new server", subdir);
+	prep_status("Copying old %s to new server", old_subdir);
 
 	exec_prog(UTILITY_LOG_FILE, NULL, true,
 #ifndef WIN32
@@ -400,10 +400,16 @@ copy_subdir_files(char *subdir)
 }
 
 static void
-copy_clog_xlog_xid(void)
+copy_xact_xlog_xid(void)
 {
-	/* copy old commit logs to new data dir */
-	copy_subdir_files("pg_clog");
+	/*
+	 * Copy old commit logs to new data dir. pg_clog has been renamed to
+	 * pg_xact in post-10 clusters.
+	 */
+	copy_subdir_files(GET_MAJOR_VERSION(old_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_xact",
+					  GET_MAJOR_VERSION(new_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_xact");
 
 	/* set the next transaction id and epoch of the new cluster */
 	prep_status("Setting next transaction ID and epoch for new cluster");
@@ -433,8 +439,8 @@ copy_clog_xlog_xid(void)
 	if (old_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER &&
 		new_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER)
 	{
-		copy_subdir_files("pg_multixact/offsets");
-		copy_subdir_files("pg_multixact/members");
+		copy_subdir_files("pg_multixact/offsets", "pg_multixact/offsets");
+		copy_subdir_files("pg_multixact/members", "pg_multixact/members");
 
 		prep_status("Setting next multixact ID and offset for new cluster");
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index cf6edc3bdb..722867d5d2 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,7 +76,7 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_clog, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
+	 * for pg_xact, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
 	 * has lsn_groups_per_page entries per buffer slot, each containing the
 	 * highest LSN known for a contiguous group of SLRU entries on that slot's
 	 * page.
@@ -119,7 +119,7 @@ typedef struct SlruCtlData
 	SlruShared	shared;
 
 	/*
-	 * This flag tells whether to fsync writes (true for pg_clog and multixact
+	 * This flag tells whether to fsync writes (true for pg_xact and multixact
 	 * stuff, false for pg_subtrans and pg_notify).
 	 */
 	bool		do_fsync;
-- 
2.11.0

From 3964348533b73cd68c11074c173b66d37b8b51d1 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 17 Jan 2017 16:29:32 +0900
Subject: [PATCH 2/2] Rename pg_subtrans to pg_subxact

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml                     |  2 +-
 doc/src/sgml/func.sgml                       |  2 +-
 doc/src/sgml/protocol.sgml                   |  2 +-
 doc/src/sgml/storage.sgml                    |  2 +-
 doc/src/sgml/wal.sgml                        |  2 +-
 src/backend/access/transam/README            | 18 +++++++++---------
 src/backend/access/transam/subtrans.c        |  8 ++++----
 src/backend/access/transam/transam.c         | 10 +++++-----
 src/backend/access/transam/twophase.c        |  6 +++---
 src/backend/access/transam/varsup.c          |  6 +++---
 src/backend/access/transam/xact.c            |  2 +-
 src/backend/access/transam/xlog.c            |  8 ++++----
 src/backend/replication/basebackup.c         |  2 +-
 src/backend/replication/logical/snapbuild.c  |  2 +-
 src/backend/storage/ipc/procarray.c          | 14 +++++++-------
 src/backend/utils/time/tqual.c               |  2 +-
 src/bin/initdb/initdb.c                      |  2 +-
 src/bin/pg_basebackup/t/010_pg_basebackup.pl |  2 +-
 src/bin/pg_upgrade/exec.c                    |  7 ++++++-
 src/include/access/slru.h                    |  4 ++--
 src/include/storage/proc.h                   |  2 +-
 21 files changed, 55 insertions(+), 50 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 0c56c9d068..a5a9b879e7 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -1093,7 +1093,7 @@ SELECT pg_stop_backup();
     The contents of the directories <filename>pg_dynshmem/</>,
     <filename>pg_notify/</>, <filename>pg_serial/</>,
     <filename>pg_snapshots/</>, <filename>pg_stat_tmp/</>,
-    and <filename>pg_subtrans/</> (but not the directories themselves) can be
+    and <filename>pg_subxact/</> (but not the directories themselves) can be
     omitted from the backup as they will be initialized on postmaster startup.
     If <xref linkend="guc-stats-temp-directory"> is set and is under the data
     directory then the contents of that directory can also be omitted.
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 865f74a260..e433b99f30 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15328,7 +15328,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  pg_wal          | 16
  pg_hba.conf     | 17
  pg_stat_tmp     | 18
- pg_subtrans     | 19
+ pg_subxact      | 19
 (19 rows)
 </programlisting>
   </para>
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 9ba147cae5..d40dd42eaa 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -2098,7 +2098,7 @@ The commands accepted in walsender mode are:
          <filename>pg_dynshmem</>, <filename>pg_notify</>,
          <filename>pg_replslot</>, <filename>pg_serial</>,
          <filename>pg_snapshots</>, <filename>pg_stat_tmp</>, and
-         <filename>pg_subtrans</> are copied as empty directories (even if
+         <filename>pg_subxact</> are copied as empty directories (even if
          they are symbolic links).
         </para>
        </listitem>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 91b44d4cc5..2fb858a149 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -121,7 +121,7 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_subtrans</></entry>
+ <entry><filename>pg_subxact</></entry>
  <entry>Subdirectory containing subtransaction status data</entry>
 </row>
 
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 1f9fac9be9..aa0eccb048 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_xact</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_xact</filename>, <filename>pg_subxact</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index e7dd19fd7b..94553f1f15 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -198,7 +198,7 @@ parent.  This maintains the invariant that child transactions have XIDs later
 than their parents, which is assumed in a number of places.
 
 The subsidiary actions of obtaining a lock on the XID and entering it into
-pg_subtrans and PG_PROC are done at the time it is assigned.
+pg_subxact and PG_PROC are done at the time it is assigned.
 
 A transaction that has no XID still needs to be identified for various
 purposes, notably holding locks.  For this purpose we assign a "virtual
@@ -331,10 +331,10 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_xact and pg_subtrans
+pg_xact and pg_subxact
 -----------------------
 
-pg_xact and pg_subtrans are permanent (on-disk) storage of transaction related
+pg_xact and pg_subxact are permanent (on-disk) storage of transaction related
 information.  There is a limited number of pages of each kept in memory, so
 in many cases there is no need to actually read from disk.  However, if
 there's a long running transaction or a backend sitting idle with an open
@@ -367,24 +367,24 @@ allow unlimited transaction nesting depth, so any particular subtransaction's
 commit state is dependent on the commit status of each and every ancestor
 transaction.
 
-The "subtransaction parent" (pg_subtrans) mechanism records, for each
+The "subtransaction parent" (pg_subxact) mechanism records, for each
 transaction with an XID, the TransactionId of its parent transaction.  This
 information is stored as soon as the subtransaction is assigned an XID.
-Top-level transactions do not have a parent, so they leave their pg_subtrans
+Top-level transactions do not have a parent, so they leave their pg_subxact
 entries set to the default value of zero (InvalidTransactionId).
 
-pg_subtrans is used to check whether the transaction in question is still
+pg_subxact is used to check whether the transaction in question is still
 running --- the main Xid of a transaction is recorded in the PGXACT struct,
 but since we allow arbitrary nesting of subtransactions, we can't fit all Xids
 in shared memory, so we have to store them on disk.  Note, however, that for
 each transaction we keep a "cache" of Xids that are known to be part of the
-transaction tree, so we can skip looking at pg_subtrans unless we know the
+transaction tree, so we can skip looking at pg_subxact unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_xact and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_xact and pg_subxact.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
 for pg_xact are implemented in transam.c, while the low-level functions are in
-clog.c.  pg_subtrans is contained completely in subtrans.c.
+clog.c.  pg_subxact is contained completely in subtrans.c.
 
 
 Write-Ahead Log Coding
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 70828e5170..3c535b0645 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,7 +3,7 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_xact-like manager that stores the parent
+ * The pg_subxact manager is a pg_xact-like manager that stores the parent
  * transaction Id for each transaction.  It is a fundamental part of the
  * nested transactions implementation.  A main transaction has a parent
  * of InvalidTransactionId, and each subtransaction has its immediate parent.
@@ -11,7 +11,7 @@
  * opposite direction.
  *
  * are completely different from pg_xact, because we only need to remember
- * pg_subtrans information for currently-open transactions.  Thus, there is
+ * pg_subxact information for currently-open transactions.  Thus, there is
  * no need to preserve data over a crash and restart.
  *
  * There are no XLOG interactions since we do not care about preserving
@@ -179,7 +179,7 @@ SUBTRANSShmemInit(void)
 {
 	SubTransCtl->PagePrecedes = SubTransPagePrecedes;
 	SimpleLruInit(SubTransCtl, "subtrans", NUM_SUBTRANS_BUFFERS, 0,
-				  SubtransControlLock, "pg_subtrans",
+				  SubtransControlLock, "pg_subxact",
 				  LWTRANCHE_SUBTRANS_BUFFERS);
 	/* Override default assumption that writes should be fsync'd */
 	SubTransCtl->do_fsync = false;
@@ -240,7 +240,7 @@ StartupSUBTRANS(TransactionId oldestActiveXID)
 	int			endPage;
 
 	/*
-	 * Since we don't expect pg_subtrans to be valid across crashes, we
+	 * Since we don't expect pg_subxact to be valid across crashes, we
 	 * initialize the currently-active page(s) to zeroes during startup.
 	 * Whenever we advance into a new page, ExtendSUBTRANS will likewise zero
 	 * the new page without regard to whatever was previously on disk.
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index b91a259e80..066a0a4800 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -137,13 +137,13 @@ TransactionIdDidCommit(TransactionId transactionId)
 	/*
 	 * If it's marked subcommitted, we have to check the parent recursively.
 	 * However, if it's older than TransactionXmin, we can't look at
-	 * pg_subtrans; instead assume that the parent crashed without cleaning up
+	 * pg_subxact; instead assume that the parent crashed without cleaning up
 	 * its children.
 	 *
 	 * Originally we Assert'ed that the result of SubTransGetParent was not
 	 * zero. However with the introduction of prepared transactions, there can
 	 * be a window just after database startup where we do not have complete
-	 * knowledge in pg_subtrans of the transactions after TransactionXmin.
+	 * knowledge in pg_subxact of the transactions after TransactionXmin.
 	 * StartupSUBTRANS() has ensured that any missing information will be
 	 * zeroed.  Since this case should not happen under normal conditions, it
 	 * seems reasonable to emit a WARNING for it.
@@ -157,7 +157,7 @@ TransactionIdDidCommit(TransactionId transactionId)
 		parentXid = SubTransGetParent(transactionId);
 		if (!TransactionIdIsValid(parentXid))
 		{
-			elog(WARNING, "no pg_subtrans entry for subcommitted XID %u",
+			elog(WARNING, "no pg_subxact entry for subcommitted XID %u",
 				 transactionId);
 			return false;
 		}
@@ -193,7 +193,7 @@ TransactionIdDidAbort(TransactionId transactionId)
 	/*
 	 * If it's marked subcommitted, we have to check the parent recursively.
 	 * However, if it's older than TransactionXmin, we can't look at
-	 * pg_subtrans; instead assume that the parent crashed without cleaning up
+	 * pg_subxact; instead assume that the parent crashed without cleaning up
 	 * its children.
 	 */
 	if (xidstatus == TRANSACTION_STATUS_SUB_COMMITTED)
@@ -206,7 +206,7 @@ TransactionIdDidAbort(TransactionId transactionId)
 		if (!TransactionIdIsValid(parentXid))
 		{
 			/* see notes in TransactionIdDidCommit */
-			elog(WARNING, "no pg_subtrans entry for subcommitted XID %u",
+			elog(WARNING, "no pg_subxact entry for subcommitted XID %u",
 				 transactionId);
 			return true;
 		}
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 3c1f7b596d..9da228dc1d 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1674,7 +1674,7 @@ CheckPointTwoPhase(XLogRecPtr redo_horizon)
  *
  * Our other responsibility is to determine and return the oldest valid XID
  * among the prepared xacts (if none, return ShmemVariableCache->nextXid).
- * This is needed to synchronize pg_subtrans startup properly.
+ * This is needed to synchronize pg_subxact startup properly.
  *
  * If xids_p and nxids_p are not NULL, pointer to a palloc'd array of all
  * top-level xids is stored in *xids_p. The number of entries in the array
@@ -1819,7 +1819,7 @@ PrescanPreparedTransactions(TransactionId **xids_p, int *nxids_p)
  *
  * Currently we simply call SubTransSetParent() for any subxids of prepared
  * transactions. If overwriteOK is true, it's OK if some XIDs have already
- * been marked in pg_subtrans.
+ * been marked in pg_subxact.
  */
 void
 StandbyRecoverPreparedTransactions(bool overwriteOK)
@@ -1976,7 +1976,7 @@ RecoverPreparedTransactions(void)
 
 			/*
 			 * Reconstruct subtrans state for the transaction --- needed
-			 * because pg_subtrans is not preserved over a restart.  Note that
+			 * because pg_subxact is not preserved over a restart.  Note that
 			 * we are linking all the subtransactions directly to the
 			 * top-level XID; there may originally have been a more complex
 			 * hierarchy, but there's no need to restore that exactly.
diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fc084c5bdb..9c987ff91b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -166,7 +166,7 @@ GetNewTransactionId(bool isSubXact)
 	 * XID before we zero the page.  Fortunately, a page of the commit log
 	 * holds 32K or more transactions, so we don't have to do this very often.
 	 *
-	 * Extend pg_subtrans and pg_commit_ts too.
+	 * Extend pg_subxact and pg_commit_ts too.
 	 */
 	ExtendCLOG(xid);
 	ExtendCommitTs(xid);
@@ -203,9 +203,9 @@ GetNewTransactionId(bool isSubXact)
 	 *
 	 * If there's no room to fit a subtransaction XID into PGPROC, set the
 	 * cache-overflowed flag instead.  This forces readers to look in
-	 * pg_subtrans to map subtransaction XIDs up to top-level XIDs. There is a
+	 * pg_subxact to map subtransaction XIDs up to top-level XIDs. There is a
 	 * race-condition window, in that the new XID will not appear as running
-	 * until its parent link has been placed into pg_subtrans. However, that
+	 * until its parent link has been placed into pg_subxact. However, that
 	 * will happen before anyone could possibly have a reason to inquire about
 	 * the status of the XID, so it seems OK.  (Snapshots taken during this
 	 * window *will* include the parent XID, so they will deliver the correct
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index fc603a575e..fe0904fc11 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -545,7 +545,7 @@ AssignTransactionId(TransactionState s)
 		log_unknown_top = true;
 
 	/*
-	 * Generate a new Xid and record it in PG_PROC and pg_subtrans.
+	 * Generate a new Xid and record it in PG_PROC and pg_subxact.
 	 *
 	 * NB: we must make the subtrans entry BEFORE the Xid appears anywhere in
 	 * shared storage other than PG_PROC; because if there's no room for it in
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 41b721b1dd..9838a00f7a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8702,9 +8702,9 @@ CreateCheckPoint(int flags)
 		PreallocXlogFiles(recptr);
 
 	/*
-	 * Truncate pg_subtrans if possible.  We can throw away all data before
+	 * Truncate pg_subxact if possible.  We can throw away all data before
 	 * the oldest XMIN of any running transaction.  No future transaction will
-	 * attempt to reference any pg_subtrans entry older than that (see Asserts
+	 * attempt to reference any pg_subxact entry older than that (see Asserts
 	 * in subtrans.c).  During recovery, though, we mustn't do this because
 	 * StartupSUBTRANS hasn't been called yet.
 	 */
@@ -9065,9 +9065,9 @@ CreateRestartPoint(int flags)
 	}
 
 	/*
-	 * Truncate pg_subtrans if possible.  We can throw away all data before
+	 * Truncate pg_subxact if possible.  We can throw away all data before
 	 * the oldest XMIN of any running transaction.  No future transaction will
-	 * attempt to reference any pg_subtrans entry older than that (see Asserts
+	 * attempt to reference any pg_subxact entry older than that (see Asserts
 	 * in subtrans.c).  When hot standby is disabled, though, we mustn't do
 	 * this because StartupSUBTRANS hasn't been called yet.
 	 */
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index 09ecc15365..6f1bce13d4 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -134,7 +134,7 @@ static const char *excludeDirContents[] =
 	"pg_snapshots",
 
 	/* Contents zeroed on startup, see StartupSUBTRANS(). */
-	"pg_subtrans",
+	"pg_subxact",
 
 	/* end of list */
 	NULL
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index 1e02aa9bd8..7ade4759dd 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -20,7 +20,7 @@
  * tables since the data we decode is wholly contained in the WAL
  * records. Also, our snapshots need to be different in comparison to normal
  * MVCC ones because in contrast to those we cannot fully rely on the clog and
- * pg_subtrans for information about committed transactions because they might
+ * pg_subxact for information about committed transactions because they might
  * commit in the future from the POV of the WAL entry we're currently
  * decoding. This definition has the advantage that we only need to prevent
  * removal of catalog rows, while normal table's rows can still be
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index ce34e8a8de..75736e3de9 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -929,7 +929,7 @@ ProcArrayApplyXidAssignment(TransactionId topxid,
 	RecordKnownAssignedTransactionIds(max_xid);
 
 	/*
-	 * Notice that we update pg_subtrans with the top-level xid, rather than
+	 * Notice that we update pg_subxact with the top-level xid, rather than
 	 * the parent xid. This is a difference between normal processing and
 	 * recovery, yet is still correct in all cases. The reason is that
 	 * subtransaction commit is not marked in clog until commit processing, so
@@ -1146,7 +1146,7 @@ TransactionIdIsInProgress(TransactionId xid)
 		}
 
 		/*
-		 * If the KnownAssignedXids overflowed, we have to check pg_subtrans
+		 * If the KnownAssignedXids overflowed, we have to check pg_subxact
 		 * too.  Fetch all xids from KnownAssignedXids that are lower than
 		 * xid, since if xid is a subtransaction its parent will always have a
 		 * lower value.  Note we will collect both main and subXIDs here, but
@@ -1160,7 +1160,7 @@ TransactionIdIsInProgress(TransactionId xid)
 
 	/*
 	 * If none of the relevant caches overflowed, we know the Xid is not
-	 * running without even looking at pg_subtrans.
+	 * running without even looking at pg_subxact.
 	 */
 	if (nxids == 0)
 	{
@@ -1169,7 +1169,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	}
 
 	/*
-	 * Step 4: have to check pg_subtrans.
+	 * Step 4: have to check pg_subxact.
 	 *
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
@@ -1270,7 +1270,7 @@ TransactionIdIsActive(TransactionId xid)
  * ignore concurrently running lazy VACUUMs because (a) they must be working
  * on other tables, and (b) they don't need to do snapshot-based lookups.
  *
- * This is also used to determine where to truncate pg_subtrans.  For that
+ * This is also used to determine where to truncate pg_subxact.  For that
  * backends in all databases have to be considered, so rel = NULL has to be
  * passed in.
  *
@@ -3075,14 +3075,14 @@ DisplayXidCache(void)
  * KnownAssignedXids list.  In backends, this is copied into snapshots in
  * GetSnapshotData(), taking advantage of the fact that XidInMVCCSnapshot()
  * doesn't care about the distinction either.  Subtransaction XIDs are
- * effectively treated as top-level XIDs and in the typical case pg_subtrans
+ * effectively treated as top-level XIDs and in the typical case pg_subxact
  * links are *not* maintained (which does not affect visibility).
  *
  * We have room in KnownAssignedXids and in snapshots to hold maxProcs *
  * (1 + PGPROC_MAX_CACHED_SUBXIDS) XIDs, so every master transaction must
  * report its subtransaction XIDs in a WAL XLOG_XACT_ASSIGNMENT record at
  * least every PGPROC_MAX_CACHED_SUBXIDS.  When we receive one of these
- * records, we mark the subXIDs as children of the top XID in pg_subtrans,
+ * records, we mark the subXIDs as children of the top XID in pg_subxact,
  * and then remove them from KnownAssignedXids.  This prevents overflow of
  * KnownAssignedXids and snapshots, at the cost that status checks for these
  * subXIDs will take a slower path through TransactionIdIsInProgress().
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 2431d8794a..295d3a975c 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -1490,7 +1490,7 @@ XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)
 		 * If the snapshot contains full subxact data, the fastest way to
 		 * check things is just to compare the given XID against both subxact
 		 * XIDs and top-level XIDs.  If the snapshot overflowed, we have to
-		 * use pg_subtrans to convert a subxact XID to its parent XID, but
+		 * use pg_subxact to convert a subxact XID to its parent XID, but
 		 * then we need only look at top-level XIDs not subxacts.
 		 */
 		if (!snapshot->suboverflowed)
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 8ad3879e13..621e1be8c3 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -201,7 +201,7 @@ static const char *const subdirs[] = {
 	"pg_notify",
 	"pg_serial",
 	"pg_snapshots",
-	"pg_subtrans",
+	"pg_subxact",
 	"pg_twophase",
 	"pg_multixact",
 	"pg_multixact/members",
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 2c5a3658d5..d560650566 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -74,7 +74,7 @@ is_deeply(
 	'no WAL files copied');
 
 # Contents of these directories should not be copied.
-foreach my $dirname (qw(pg_dynshmem pg_notify pg_replslot pg_serial pg_snapshots pg_stat_tmp pg_subtrans))
+foreach my $dirname (qw(pg_dynshmem pg_notify pg_replslot pg_serial pg_snapshots pg_stat_tmp pg_subxact))
 {
 	is_deeply(
 		[ sort(slurp_dir("$tempdir/backup/$dirname/")) ],
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 6810a6fb58..9012310b31 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -300,7 +300,6 @@ check_data_dir(ClusterInfo *cluster)
 	check_single_dir(pg_data, "base");
 	check_single_dir(pg_data, "global");
 	check_single_dir(pg_data, "pg_multixact");
-	check_single_dir(pg_data, "pg_subtrans");
 	check_single_dir(pg_data, "pg_tblspc");
 	check_single_dir(pg_data, "pg_twophase");
 
@@ -315,6 +314,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_clog");
 	else
 		check_single_dir(pg_data, "pg_xact");
+
+	/* pg_clog has been renamed to pg_xact in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_subtrans");
+	else
+		check_single_dir(pg_data, "pg_subxact");
 }
 
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 722867d5d2..d28c768dbc 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,7 +76,7 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_xact, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
+	 * for pg_xact, false for multixact, pg_subxact, pg_notify).  group_lsn[]
 	 * has lsn_groups_per_page entries per buffer slot, each containing the
 	 * highest LSN known for a contiguous group of SLRU entries on that slot's
 	 * page.
@@ -120,7 +120,7 @@ typedef struct SlruCtlData
 
 	/*
 	 * This flag tells whether to fsync writes (true for pg_xact and multixact
-	 * stuff, false for pg_subtrans and pg_notify).
+	 * stuff, false for pg_subxact and pg_notify).
 	 */
 	bool		do_fsync;
 
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 398fa8afde..e139de8c2f 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -30,7 +30,7 @@
  * generated at least one subtransaction that didn't fit in the cache).
  * If none of the caches have overflowed, we can assume that an XID that's not
  * listed anywhere in the PGPROC array is not a running transaction.  Else we
- * have to look at pg_subtrans.
+ * have to look at pg_subxact.
  */
 #define PGPROC_MAX_CACHED_SUBXIDS 64	/* XXX guessed-at value */
 
-- 
2.11.0

From a6862702688e7af46223bd58504e8466cb0bb994 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Fri, 17 Mar 2017 10:25:58 +0900
Subject: [PATCH 2/2] Rename pg_subtrans to pg_subxact

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml                     |  2 +-
 doc/src/sgml/func.sgml                       |  2 +-
 doc/src/sgml/protocol.sgml                   |  2 +-
 doc/src/sgml/storage.sgml                    |  2 +-
 doc/src/sgml/wal.sgml                        |  2 +-
 src/backend/access/transam/README            | 18 +++++++++---------
 src/backend/access/transam/subtrans.c        |  8 ++++----
 src/backend/access/transam/transam.c         | 10 +++++-----
 src/backend/access/transam/twophase.c        |  6 +++---
 src/backend/access/transam/varsup.c          |  6 +++---
 src/backend/access/transam/xact.c            |  2 +-
 src/backend/access/transam/xlog.c            |  8 ++++----
 src/backend/replication/basebackup.c         |  2 +-
 src/backend/replication/logical/snapbuild.c  |  2 +-
 src/backend/storage/ipc/procarray.c          | 14 +++++++-------
 src/backend/utils/time/tqual.c               |  2 +-
 src/bin/initdb/initdb.c                      |  2 +-
 src/bin/pg_basebackup/t/010_pg_basebackup.pl |  2 +-
 src/bin/pg_upgrade/exec.c                    |  7 ++++++-
 src/include/access/slru.h                    |  4 ++--
 src/include/storage/proc.h                   |  2 +-
 21 files changed, 55 insertions(+), 50 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 12f2efe4e2..1853ab5fe4 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -1094,7 +1094,7 @@ SELECT pg_stop_backup();
     The contents of the directories <filename>pg_dynshmem/</>,
     <filename>pg_notify/</>, <filename>pg_serial/</>,
     <filename>pg_snapshots/</>, <filename>pg_stat_tmp/</>,
-    and <filename>pg_subtrans/</> (but not the directories themselves) can be
+    and <filename>pg_subxact/</> (but not the directories themselves) can be
     omitted from the backup as they will be initialized on postmaster startup.
     If <xref linkend="guc-stats-temp-directory"> is set and is under the data
     directory then the contents of that directory can also be omitted.
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 9408a255dc..e329f83ae4 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15623,7 +15623,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  pg_wal          | 16
  pg_hba.conf     | 17
  pg_stat_tmp     | 18
- pg_subtrans     | 19
+ pg_subxact      | 19
 (19 rows)
 </programlisting>
   </para>
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 7c82b48845..98ce89a82d 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -2215,7 +2215,7 @@ The commands accepted in walsender mode are:
          <filename>pg_dynshmem</>, <filename>pg_notify</>,
          <filename>pg_replslot</>, <filename>pg_serial</>,
          <filename>pg_snapshots</>, <filename>pg_stat_tmp</>, and
-         <filename>pg_subtrans</> are copied as empty directories (even if
+         <filename>pg_subxact</> are copied as empty directories (even if
          they are symbolic links).
         </para>
        </listitem>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index a156693ec8..686ce07440 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -127,7 +127,7 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_subtrans</></entry>
+ <entry><filename>pg_subxact</></entry>
  <entry>Subdirectory containing subtransaction status data</entry>
 </row>
 
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index a749b83dc0..3c5fa0876e 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_xact</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_xact</filename>, <filename>pg_subxact</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index e7dd19fd7b..94553f1f15 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -198,7 +198,7 @@ parent.  This maintains the invariant that child transactions have XIDs later
 than their parents, which is assumed in a number of places.
 
 The subsidiary actions of obtaining a lock on the XID and entering it into
-pg_subtrans and PG_PROC are done at the time it is assigned.
+pg_subxact and PG_PROC are done at the time it is assigned.
 
 A transaction that has no XID still needs to be identified for various
 purposes, notably holding locks.  For this purpose we assign a "virtual
@@ -331,10 +331,10 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_xact and pg_subtrans
+pg_xact and pg_subxact
 -----------------------
 
-pg_xact and pg_subtrans are permanent (on-disk) storage of transaction related
+pg_xact and pg_subxact are permanent (on-disk) storage of transaction related
 information.  There is a limited number of pages of each kept in memory, so
 in many cases there is no need to actually read from disk.  However, if
 there's a long running transaction or a backend sitting idle with an open
@@ -367,24 +367,24 @@ allow unlimited transaction nesting depth, so any particular subtransaction's
 commit state is dependent on the commit status of each and every ancestor
 transaction.
 
-The "subtransaction parent" (pg_subtrans) mechanism records, for each
+The "subtransaction parent" (pg_subxact) mechanism records, for each
 transaction with an XID, the TransactionId of its parent transaction.  This
 information is stored as soon as the subtransaction is assigned an XID.
-Top-level transactions do not have a parent, so they leave their pg_subtrans
+Top-level transactions do not have a parent, so they leave their pg_subxact
 entries set to the default value of zero (InvalidTransactionId).
 
-pg_subtrans is used to check whether the transaction in question is still
+pg_subxact is used to check whether the transaction in question is still
 running --- the main Xid of a transaction is recorded in the PGXACT struct,
 but since we allow arbitrary nesting of subtransactions, we can't fit all Xids
 in shared memory, so we have to store them on disk.  Note, however, that for
 each transaction we keep a "cache" of Xids that are known to be part of the
-transaction tree, so we can skip looking at pg_subtrans unless we know the
+transaction tree, so we can skip looking at pg_subxact unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_xact and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_xact and pg_subxact.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
 for pg_xact are implemented in transam.c, while the low-level functions are in
-clog.c.  pg_subtrans is contained completely in subtrans.c.
+clog.c.  pg_subxact is contained completely in subtrans.c.
 
 
 Write-Ahead Log Coding
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index 70828e5170..3c535b0645 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,7 +3,7 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_xact-like manager that stores the parent
+ * The pg_subxact manager is a pg_xact-like manager that stores the parent
  * transaction Id for each transaction.  It is a fundamental part of the
  * nested transactions implementation.  A main transaction has a parent
  * of InvalidTransactionId, and each subtransaction has its immediate parent.
@@ -11,7 +11,7 @@
  * opposite direction.
  *
  * are completely different from pg_xact, because we only need to remember
- * pg_subtrans information for currently-open transactions.  Thus, there is
+ * pg_subxact information for currently-open transactions.  Thus, there is
  * no need to preserve data over a crash and restart.
  *
  * There are no XLOG interactions since we do not care about preserving
@@ -179,7 +179,7 @@ SUBTRANSShmemInit(void)
 {
 	SubTransCtl->PagePrecedes = SubTransPagePrecedes;
 	SimpleLruInit(SubTransCtl, "subtrans", NUM_SUBTRANS_BUFFERS, 0,
-				  SubtransControlLock, "pg_subtrans",
+				  SubtransControlLock, "pg_subxact",
 				  LWTRANCHE_SUBTRANS_BUFFERS);
 	/* Override default assumption that writes should be fsync'd */
 	SubTransCtl->do_fsync = false;
@@ -240,7 +240,7 @@ StartupSUBTRANS(TransactionId oldestActiveXID)
 	int			endPage;
 
 	/*
-	 * Since we don't expect pg_subtrans to be valid across crashes, we
+	 * Since we don't expect pg_subxact to be valid across crashes, we
 	 * initialize the currently-active page(s) to zeroes during startup.
 	 * Whenever we advance into a new page, ExtendSUBTRANS will likewise zero
 	 * the new page without regard to whatever was previously on disk.
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index b91a259e80..066a0a4800 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -137,13 +137,13 @@ TransactionIdDidCommit(TransactionId transactionId)
 	/*
 	 * If it's marked subcommitted, we have to check the parent recursively.
 	 * However, if it's older than TransactionXmin, we can't look at
-	 * pg_subtrans; instead assume that the parent crashed without cleaning up
+	 * pg_subxact; instead assume that the parent crashed without cleaning up
 	 * its children.
 	 *
 	 * Originally we Assert'ed that the result of SubTransGetParent was not
 	 * zero. However with the introduction of prepared transactions, there can
 	 * be a window just after database startup where we do not have complete
-	 * knowledge in pg_subtrans of the transactions after TransactionXmin.
+	 * knowledge in pg_subxact of the transactions after TransactionXmin.
 	 * StartupSUBTRANS() has ensured that any missing information will be
 	 * zeroed.  Since this case should not happen under normal conditions, it
 	 * seems reasonable to emit a WARNING for it.
@@ -157,7 +157,7 @@ TransactionIdDidCommit(TransactionId transactionId)
 		parentXid = SubTransGetParent(transactionId);
 		if (!TransactionIdIsValid(parentXid))
 		{
-			elog(WARNING, "no pg_subtrans entry for subcommitted XID %u",
+			elog(WARNING, "no pg_subxact entry for subcommitted XID %u",
 				 transactionId);
 			return false;
 		}
@@ -193,7 +193,7 @@ TransactionIdDidAbort(TransactionId transactionId)
 	/*
 	 * If it's marked subcommitted, we have to check the parent recursively.
 	 * However, if it's older than TransactionXmin, we can't look at
-	 * pg_subtrans; instead assume that the parent crashed without cleaning up
+	 * pg_subxact; instead assume that the parent crashed without cleaning up
 	 * its children.
 	 */
 	if (xidstatus == TRANSACTION_STATUS_SUB_COMMITTED)
@@ -206,7 +206,7 @@ TransactionIdDidAbort(TransactionId transactionId)
 		if (!TransactionIdIsValid(parentXid))
 		{
 			/* see notes in TransactionIdDidCommit */
-			elog(WARNING, "no pg_subtrans entry for subcommitted XID %u",
+			elog(WARNING, "no pg_subxact entry for subcommitted XID %u",
 				 transactionId);
 			return true;
 		}
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index da77e3efde..751423f86c 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1674,7 +1674,7 @@ CheckPointTwoPhase(XLogRecPtr redo_horizon)
  *
  * Our other responsibility is to determine and return the oldest valid XID
  * among the prepared xacts (if none, return ShmemVariableCache->nextXid).
- * This is needed to synchronize pg_subtrans startup properly.
+ * This is needed to synchronize pg_subxact startup properly.
  *
  * If xids_p and nxids_p are not NULL, pointer to a palloc'd array of all
  * top-level xids is stored in *xids_p. The number of entries in the array
@@ -1819,7 +1819,7 @@ PrescanPreparedTransactions(TransactionId **xids_p, int *nxids_p)
  *
  * Currently we simply call SubTransSetParent() for any subxids of prepared
  * transactions. If overwriteOK is true, it's OK if some XIDs have already
- * been marked in pg_subtrans.
+ * been marked in pg_subxact.
  */
 void
 StandbyRecoverPreparedTransactions(bool overwriteOK)
@@ -1976,7 +1976,7 @@ RecoverPreparedTransactions(void)
 
 			/*
 			 * Reconstruct subtrans state for the transaction --- needed
-			 * because pg_subtrans is not preserved over a restart.  Note that
+			 * because pg_subxact is not preserved over a restart.  Note that
 			 * we are linking all the subtransactions directly to the
 			 * top-level XID; there may originally have been a more complex
 			 * hierarchy, but there's no need to restore that exactly.
diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 42fc351f7b..5be2c79b95 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -166,7 +166,7 @@ GetNewTransactionId(bool isSubXact)
 	 * XID before we zero the page.  Fortunately, a page of the commit log
 	 * holds 32K or more transactions, so we don't have to do this very often.
 	 *
-	 * Extend pg_subtrans and pg_commit_ts too.
+	 * Extend pg_subxact and pg_commit_ts too.
 	 */
 	ExtendCLOG(xid);
 	ExtendCommitTs(xid);
@@ -203,9 +203,9 @@ GetNewTransactionId(bool isSubXact)
 	 *
 	 * If there's no room to fit a subtransaction XID into PGPROC, set the
 	 * cache-overflowed flag instead.  This forces readers to look in
-	 * pg_subtrans to map subtransaction XIDs up to top-level XIDs. There is a
+	 * pg_subxact to map subtransaction XIDs up to top-level XIDs. There is a
 	 * race-condition window, in that the new XID will not appear as running
-	 * until its parent link has been placed into pg_subtrans. However, that
+	 * until its parent link has been placed into pg_subxact. However, that
 	 * will happen before anyone could possibly have a reason to inquire about
 	 * the status of the XID, so it seems OK.  (Snapshots taken during this
 	 * window *will* include the parent XID, so they will deliver the correct
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 02e0779f32..2a13e4f1c5 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -546,7 +546,7 @@ AssignTransactionId(TransactionState s)
 		log_unknown_top = true;
 
 	/*
-	 * Generate a new Xid and record it in PG_PROC and pg_subtrans.
+	 * Generate a new Xid and record it in PG_PROC and pg_subxact.
 	 *
 	 * NB: we must make the subtrans entry BEFORE the Xid appears anywhere in
 	 * shared storage other than PG_PROC; because if there's no room for it in
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index cdb3a8ac1d..df217e2bf0 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8862,9 +8862,9 @@ CreateCheckPoint(int flags)
 		PreallocXlogFiles(recptr);
 
 	/*
-	 * Truncate pg_subtrans if possible.  We can throw away all data before
+	 * Truncate pg_subxact if possible.  We can throw away all data before
 	 * the oldest XMIN of any running transaction.  No future transaction will
-	 * attempt to reference any pg_subtrans entry older than that (see Asserts
+	 * attempt to reference any pg_subxact entry older than that (see Asserts
 	 * in subtrans.c).  During recovery, though, we mustn't do this because
 	 * StartupSUBTRANS hasn't been called yet.
 	 */
@@ -9225,9 +9225,9 @@ CreateRestartPoint(int flags)
 	}
 
 	/*
-	 * Truncate pg_subtrans if possible.  We can throw away all data before
+	 * Truncate pg_subxact if possible.  We can throw away all data before
 	 * the oldest XMIN of any running transaction.  No future transaction will
-	 * attempt to reference any pg_subtrans entry older than that (see Asserts
+	 * attempt to reference any pg_subxact entry older than that (see Asserts
 	 * in subtrans.c).  When hot standby is disabled, though, we mustn't do
 	 * this because StartupSUBTRANS hasn't been called yet.
 	 */
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index e3a7ad5e9a..edf932e25f 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -134,7 +134,7 @@ static const char *excludeDirContents[] =
 	"pg_snapshots",
 
 	/* Contents zeroed on startup, see StartupSUBTRANS(). */
-	"pg_subtrans",
+	"pg_subxact",
 
 	/* end of list */
 	NULL
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index e129a6b8e4..654490caa3 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -20,7 +20,7 @@
  * tables since the data we decode is wholly contained in the WAL
  * records. Also, our snapshots need to be different in comparison to normal
  * MVCC ones because in contrast to those we cannot fully rely on the clog and
- * pg_subtrans for information about committed transactions because they might
+ * pg_subxact for information about committed transactions because they might
  * commit in the future from the POV of the WAL entry we're currently
  * decoding. This definition has the advantage that we only need to prevent
  * removal of catalog rows, while normal table's rows can still be
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 0f8f435faf..c754f758e4 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -929,7 +929,7 @@ ProcArrayApplyXidAssignment(TransactionId topxid,
 	RecordKnownAssignedTransactionIds(max_xid);
 
 	/*
-	 * Notice that we update pg_subtrans with the top-level xid, rather than
+	 * Notice that we update pg_subxact with the top-level xid, rather than
 	 * the parent xid. This is a difference between normal processing and
 	 * recovery, yet is still correct in all cases. The reason is that
 	 * subtransaction commit is not marked in clog until commit processing, so
@@ -1146,7 +1146,7 @@ TransactionIdIsInProgress(TransactionId xid)
 		}
 
 		/*
-		 * If the KnownAssignedXids overflowed, we have to check pg_subtrans
+		 * If the KnownAssignedXids overflowed, we have to check pg_subxact
 		 * too.  Fetch all xids from KnownAssignedXids that are lower than
 		 * xid, since if xid is a subtransaction its parent will always have a
 		 * lower value.  Note we will collect both main and subXIDs here, but
@@ -1160,7 +1160,7 @@ TransactionIdIsInProgress(TransactionId xid)
 
 	/*
 	 * If none of the relevant caches overflowed, we know the Xid is not
-	 * running without even looking at pg_subtrans.
+	 * running without even looking at pg_subxact.
 	 */
 	if (nxids == 0)
 	{
@@ -1169,7 +1169,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	}
 
 	/*
-	 * Step 4: have to check pg_subtrans.
+	 * Step 4: have to check pg_subxact.
 	 *
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
@@ -1270,7 +1270,7 @@ TransactionIdIsActive(TransactionId xid)
  * ignore concurrently running lazy VACUUMs because (a) they must be working
  * on other tables, and (b) they don't need to do snapshot-based lookups.
  *
- * This is also used to determine where to truncate pg_subtrans.  For that
+ * This is also used to determine where to truncate pg_subxact.  For that
  * backends in all databases have to be considered, so rel = NULL has to be
  * passed in.
  *
@@ -3109,14 +3109,14 @@ DisplayXidCache(void)
  * KnownAssignedXids list.  In backends, this is copied into snapshots in
  * GetSnapshotData(), taking advantage of the fact that XidInMVCCSnapshot()
  * doesn't care about the distinction either.  Subtransaction XIDs are
- * effectively treated as top-level XIDs and in the typical case pg_subtrans
+ * effectively treated as top-level XIDs and in the typical case pg_subxact
  * links are *not* maintained (which does not affect visibility).
  *
  * We have room in KnownAssignedXids and in snapshots to hold maxProcs *
  * (1 + PGPROC_MAX_CACHED_SUBXIDS) XIDs, so every master transaction must
  * report its subtransaction XIDs in a WAL XLOG_XACT_ASSIGNMENT record at
  * least every PGPROC_MAX_CACHED_SUBXIDS.  When we receive one of these
- * records, we mark the subXIDs as children of the top XID in pg_subtrans,
+ * records, we mark the subXIDs as children of the top XID in pg_subxact,
  * and then remove them from KnownAssignedXids.  This prevents overflow of
  * KnownAssignedXids and snapshots, at the cost that status checks for these
  * subXIDs will take a slower path through TransactionIdIsInProgress().
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 519f3b6803..d72a8b9773 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -1490,7 +1490,7 @@ XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)
 		 * If the snapshot contains full subxact data, the fastest way to
 		 * check things is just to compare the given XID against both subxact
 		 * XIDs and top-level XIDs.  If the snapshot overflowed, we have to
-		 * use pg_subtrans to convert a subxact XID to its parent XID, but
+		 * use pg_subxact to convert a subxact XID to its parent XID, but
 		 * then we need only look at top-level XIDs not subxacts.
 		 */
 		if (!snapshot->suboverflowed)
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index e0c72fbb80..c11b3b3cb8 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -202,7 +202,7 @@ static const char *const subdirs[] = {
 	"pg_notify",
 	"pg_serial",
 	"pg_snapshots",
-	"pg_subtrans",
+	"pg_subxact",
 	"pg_twophase",
 	"pg_multixact",
 	"pg_multixact/members",
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 14bd813896..4e59c7e223 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -71,7 +71,7 @@ is_deeply(
 	'no WAL files copied');
 
 # Contents of these directories should not be copied.
-foreach my $dirname (qw(pg_dynshmem pg_notify pg_replslot pg_serial pg_snapshots pg_stat_tmp pg_subtrans))
+foreach my $dirname (qw(pg_dynshmem pg_notify pg_replslot pg_serial pg_snapshots pg_stat_tmp pg_subxact))
 {
 	is_deeply(
 		[ sort(slurp_dir("$tempdir/backup/$dirname/")) ],
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index b954d19d9d..c6a6d11aeb 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -334,7 +334,6 @@ check_data_dir(ClusterInfo *cluster)
 	check_single_dir(pg_data, "base");
 	check_single_dir(pg_data, "global");
 	check_single_dir(pg_data, "pg_multixact");
-	check_single_dir(pg_data, "pg_subtrans");
 	check_single_dir(pg_data, "pg_tblspc");
 	check_single_dir(pg_data, "pg_twophase");
 
@@ -349,6 +348,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_clog");
 	else
 		check_single_dir(pg_data, "pg_xact");
+
+	/* pg_clog has been renamed to pg_xact in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_subtrans");
+	else
+		check_single_dir(pg_data, "pg_subxact");
 }
 
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 722867d5d2..d28c768dbc 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,7 +76,7 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_xact, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
+	 * for pg_xact, false for multixact, pg_subxact, pg_notify).  group_lsn[]
 	 * has lsn_groups_per_page entries per buffer slot, each containing the
 	 * highest LSN known for a contiguous group of SLRU entries on that slot's
 	 * page.
@@ -120,7 +120,7 @@ typedef struct SlruCtlData
 
 	/*
 	 * This flag tells whether to fsync writes (true for pg_xact and multixact
-	 * stuff, false for pg_subtrans and pg_notify).
+	 * stuff, false for pg_subxact and pg_notify).
 	 */
 	bool		do_fsync;
 
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 5f38fa6b4f..7929a71a7e 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -30,7 +30,7 @@
  * generated at least one subtransaction that didn't fit in the cache).
  * If none of the caches have overflowed, we can assume that an XID that's not
  * listed anywhere in the PGPROC array is not a running transaction.  Else we
- * have to look at pg_subtrans.
+ * have to look at pg_subxact.
  */
 #define PGPROC_MAX_CACHED_SUBXIDS 64	/* XXX guessed-at value */
 
-- 
2.12.0

From 9c9a05d14852b1750a18cf6c601305ec59d5c213 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Fri, 17 Mar 2017 10:24:38 +0900
Subject: [PATCH 1/2] Rename pg_clog to pg_xact

pg_upgrade is updated to handle the transfer correctly to post-10
clusters.
---
 doc/src/sgml/backup.sgml               |  4 ++--
 doc/src/sgml/catalogs.sgml             |  4 ++--
 doc/src/sgml/config.sgml               |  2 +-
 doc/src/sgml/func.sgml                 |  2 +-
 doc/src/sgml/maintenance.sgml          |  8 ++++----
 doc/src/sgml/ref/pg_resetwal.sgml      |  4 ++--
 doc/src/sgml/ref/pg_rewind.sgml        |  2 +-
 doc/src/sgml/storage.sgml              | 10 +++++-----
 doc/src/sgml/wal.sgml                  |  2 +-
 src/backend/access/heap/heapam.c       |  4 ++--
 src/backend/access/transam/README      | 10 +++++-----
 src/backend/access/transam/clog.c      |  2 +-
 src/backend/access/transam/commit_ts.c |  2 +-
 src/backend/access/transam/multixact.c |  2 +-
 src/backend/access/transam/subtrans.c  |  5 ++---
 src/backend/access/transam/transam.c   |  2 +-
 src/backend/access/transam/twophase.c  |  4 ++--
 src/backend/access/transam/xact.c      | 18 +++++++++---------
 src/backend/access/transam/xlog.c      |  2 +-
 src/backend/commands/vacuum.c          | 10 +++++-----
 src/backend/postmaster/autovacuum.c    |  2 +-
 src/backend/storage/buffer/README      |  2 +-
 src/backend/storage/ipc/procarray.c    |  4 ++--
 src/backend/utils/time/tqual.c         |  6 +++---
 src/bin/initdb/initdb.c                |  2 +-
 src/bin/pg_upgrade/exec.c              |  6 ++++++
 src/bin/pg_upgrade/pg_upgrade.c        | 30 ++++++++++++++++++------------
 src/include/access/slru.h              |  4 ++--
 28 files changed, 83 insertions(+), 72 deletions(-)

diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml
index 69c599e180..12f2efe4e2 100644
--- a/doc/src/sgml/backup.sgml
+++ b/doc/src/sgml/backup.sgml
@@ -382,10 +382,10 @@ tar -cf backup.tar /usr/local/pgsql/data
       directories. This will <emphasis>not</> work because the
       information contained in these files is not usable without
       the commit log files,
-      <filename>pg_clog/*</filename>, which contain the commit status of
+      <filename>pg_xact/*</filename>, which contain the commit status of
       all transactions. A table file is only usable with this
       information. Of course it is also impossible to restore only a
-      table and the associated <filename>pg_clog</filename> data
+      table and the associated <filename>pg_xact</filename> data
       because that would render all other tables in the database
       cluster useless.  So file system backups only work for complete
       backup and restoration of an entire database cluster.
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 2c2da2ad8a..df0435c3f0 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1893,7 +1893,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this table.  This is used to track
        whether the table needs to be vacuumed in order to prevent transaction
-       ID wraparound or to allow <literal>pg_clog</> to be shrunk.  Zero
+       ID wraparound or to allow <literal>pg_xact</> to be shrunk.  Zero
        (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
       </entry>
      </row>
@@ -2570,7 +2570,7 @@
        All transaction IDs before this one have been replaced with a permanent
        (<quote>frozen</>) transaction ID in this database.  This is used to
        track whether the database needs to be vacuumed in order to prevent
-       transaction ID wraparound or to allow <literal>pg_clog</> to be shrunk.
+       transaction ID wraparound or to allow <literal>pg_xact</> to be shrunk.
        It is the minimum of the per-table
        <structname>pg_class</>.<structfield>relfrozenxid</> values.
       </entry>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index b6daf9677c..9963cd61a1 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -6004,7 +6004,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
 
        <para>
         Vacuum also allows removal of old files from the
-        <filename>pg_clog</> subdirectory, which is why the default
+        <filename>pg_xact</> subdirectory, which is why the default
         is a relatively low 200 million transactions.
         This parameter can only be set at server start, but the setting
         can be reduced for individual tables by
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 502f99b22b..9408a255dc 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15616,7 +15616,7 @@ SELECT * FROM pg_ls_dir('.') WITH ORDINALITY AS t(ls,n);
  postmaster.pid  |  9
  pg_ident.conf   | 10
  global          | 11
- pg_clog         | 12
+ pg_xact         | 12
  pg_snapshots    | 13
  pg_multixact    | 14
  PG_VERSION      | 15
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index f87f3e00de..65a64c85ec 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -527,18 +527,18 @@
    <para>
     The sole disadvantage of increasing <varname>autovacuum_freeze_max_age</>
     (and <varname>vacuum_freeze_table_age</> along with it)
-    is that the <filename>pg_clog</> subdirectory of the database cluster
+    is that the <filename>pg_xact</> subdirectory of the database cluster
     will take more space, because it must store the commit status of all
     transactions back to the <varname>autovacuum_freeze_max_age</> horizon.
     The commit status uses two bits per transaction, so if
     <varname>autovacuum_freeze_max_age</> is set to its maximum allowed
-    value of two billion, <filename>pg_clog</> can be expected to
+    value of two billion, <filename>pg_xact</> can be expected to
     grow to about half a gigabyte.  If this is trivial compared to your
     total database size, setting <varname>autovacuum_freeze_max_age</> to
     its maximum allowed value is recommended.  Otherwise, set it depending
-    on what you are willing to allow for <filename>pg_clog</> storage.
+    on what you are willing to allow for <filename>pg_xact</> storage.
     (The default, 200 million transactions, translates to about 50MB of
-    <filename>pg_clog</> storage.)
+    <filename>pg_xact</> storage.)
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/pg_resetwal.sgml b/doc/src/sgml/ref/pg_resetwal.sgml
index 0cc6fb4c4d..0d93b56ddd 100644
--- a/doc/src/sgml/ref/pg_resetwal.sgml
+++ b/doc/src/sgml/ref/pg_resetwal.sgml
@@ -256,12 +256,12 @@ PostgreSQL documentation
 
      <para>
       A safe value can be determined by looking for the numerically largest
-      file name in the directory <filename>pg_clog</> under the data directory,
+      file name in the directory <filename>pg_xact</> under the data directory,
       adding one,
       and then multiplying by 1048576 (0x100000).  Note that the file names are in
       hexadecimal.  It is usually easiest to specify the option value in
       hexadecimal too. For example, if <filename>0011</> is the largest entry
-      in <filename>pg_clog</>, <literal>-x 0x1200000</> will work (five
+      in <filename>pg_xact</>, <literal>-x 0x1200000</> will work (five
       trailing zeroes provide the proper multiplier).
      </para>
     </listitem>
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 371c4a475f..d5430d4324 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -229,7 +229,7 @@ PostgreSQL documentation
     </step>
     <step>
      <para>
-      Copy all other files such as <filename>pg_clog</filename> and
+      Copy all other files such as <filename>pg_xact</filename> and
       configuration files from the source cluster to the target cluster
       (everything except the relation files).
      </para>
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index e0a89861f8..a156693ec8 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -78,11 +78,6 @@ Item
 </row>
 
 <row>
- <entry><filename>pg_clog</></entry>
- <entry>Subdirectory containing transaction commit status data</entry>
-</row>
-
-<row>
  <entry><filename>pg_dynshmem</></entry>
  <entry>Subdirectory containing files used by the dynamic shared memory
   subsystem</entry>
@@ -152,6 +147,11 @@ Item
 </row>
 
 <row>
+ <entry><filename>pg_xact</></entry>
+ <entry>Subdirectory containing transaction commit status data</entry>
+</row>
+
+<row>
  <entry><filename>postgresql.auto.conf</></entry>
  <entry>A file used for storing configuration parameters that are set by
 <command>ALTER SYSTEM</command></entry>
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 1468ba52a4..a749b83dc0 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -201,7 +201,7 @@
     </listitem>
     <listitem>
      <para>
-      Internal data structures such as <filename>pg_clog</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
+      Internal data structures such as <filename>pg_xact</filename>, <filename>pg_subtrans</filename>, <filename>pg_multixact</filename>,
       <filename>pg_serial</filename>, <filename>pg_notify</filename>, <filename>pg_stat</filename>, <filename>pg_snapshots</filename> are not directly
       checksummed, nor are pages protected by full page writes. However, where
       such data structures are persistent, WAL records are written that allow
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index bffc971d68..85261379b1 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -6790,8 +6790,8 @@ heap_prepare_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
  * Note: it might seem we could make the changes without exclusive lock, since
  * TransactionId read/write is assumed atomic anyway.  However there is a race
  * condition: someone who just fetched an old XID that we overwrite here could
- * conceivably not finish checking the XID against pg_clog before we finish
- * the VACUUM and perhaps truncate off the part of pg_clog he needs.  Getting
+ * conceivably not finish checking the XID against pg_xact before we finish
+ * the VACUUM and perhaps truncate off the part of pg_xact he needs.  Getting
  * exclusive lock ensures no other backend is in process of checking the
  * tuple status.  Also, getting exclusive lock makes it safe to adjust the
  * infomask bits.
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index 4ae4715339..e7dd19fd7b 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -331,17 +331,17 @@ of the xid fields is atomic, so assuming it for xmin as well is no extra
 risk.
 
 
-pg_clog and pg_subtrans
+pg_xact and pg_subtrans
 -----------------------
 
-pg_clog and pg_subtrans are permanent (on-disk) storage of transaction related
+pg_xact and pg_subtrans are permanent (on-disk) storage of transaction related
 information.  There is a limited number of pages of each kept in memory, so
 in many cases there is no need to actually read from disk.  However, if
 there's a long running transaction or a backend sitting idle with an open
 transaction, it may be necessary to be able to read and write this information
 from disk.  They also allow information to be permanent across server restarts.
 
-pg_clog records the commit status for each transaction that has been assigned
+pg_xact records the commit status for each transaction that has been assigned
 an XID.  A transaction can be in progress, committed, aborted, or
 "sub-committed".  This last state means that it's a subtransaction that's no
 longer running, but its parent has not updated its state yet.  It is not
@@ -381,9 +381,9 @@ each transaction we keep a "cache" of Xids that are known to be part of the
 transaction tree, so we can skip looking at pg_subtrans unless we know the
 cache has been overflowed.  See storage/ipc/procarray.c for the gory details.
 
-slru.c is the supporting mechanism for both pg_clog and pg_subtrans.  It
+slru.c is the supporting mechanism for both pg_xact and pg_subtrans.  It
 implements the LRU policy for in-memory buffer pages.  The high-level routines
-for pg_clog are implemented in transam.c, while the low-level functions are in
+for pg_xact are implemented in transam.c, while the low-level functions are in
 clog.c.  pg_subtrans is contained completely in subtrans.c.
 
 
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index 1a43819736..5b1d13dac1 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -450,7 +450,7 @@ CLOGShmemInit(void)
 {
 	ClogCtl->PagePrecedes = CLOGPagePrecedes;
 	SimpleLruInit(ClogCtl, "clog", CLOGShmemBuffers(), CLOG_LSNS_PER_PAGE,
-				  CLogControlLock, "pg_clog", LWTRANCHE_CLOG_BUFFERS);
+				  CLogControlLock, "pg_xact", LWTRANCHE_CLOG_BUFFERS);
 }
 
 /*
diff --git a/src/backend/access/transam/commit_ts.c b/src/backend/access/transam/commit_ts.c
index 20f60bc023..8e1df6e0ea 100644
--- a/src/backend/access/transam/commit_ts.c
+++ b/src/backend/access/transam/commit_ts.c
@@ -3,7 +3,7 @@
  * commit_ts.c
  *		PostgreSQL commit timestamp manager
  *
- * This module is a pg_clog-like system that stores the commit timestamp
+ * This module is a pg_xact-like system that stores the commit timestamp
  * for each transaction.
  *
  * XLOG interactions: this module generates an XLOG record whenever a new
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index c350dfa17f..1a7824b5d4 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -3,7 +3,7 @@
  * multixact.c
  *		PostgreSQL multi-transaction-log manager
  *
- * The pg_multixact manager is a pg_clog-like manager that stores an array of
+ * The pg_multixact manager is a pg_xact-like manager that stores an array of
  * MultiXactMember for each MultiXactId.  It is a fundamental part of the
  * shared-row-lock implementation.  Each MultiXactMember is comprised of a
  * TransactionId and a set of flag bits.  The name is a bit historical:
diff --git a/src/backend/access/transam/subtrans.c b/src/backend/access/transam/subtrans.c
index a66fc0f2ad..70828e5170 100644
--- a/src/backend/access/transam/subtrans.c
+++ b/src/backend/access/transam/subtrans.c
@@ -3,15 +3,14 @@
  * subtrans.c
  *		PostgreSQL subtransaction-log manager
  *
- * The pg_subtrans manager is a pg_clog-like manager that stores the parent
+ * The pg_subtrans manager is a pg_xact-like manager that stores the parent
  * transaction Id for each transaction.  It is a fundamental part of the
  * nested transactions implementation.  A main transaction has a parent
  * of InvalidTransactionId, and each subtransaction has its immediate parent.
  * The tree can easily be walked from child to parent, but not in the
  * opposite direction.
  *
- * This code is based on clog.c, but the robustness requirements
- * are completely different from pg_clog, because we only need to remember
+ * are completely different from pg_xact, because we only need to remember
  * pg_subtrans information for currently-open transactions.  Thus, there is
  * no need to preserve data over a crash and restart.
  *
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index c2b4318bd3..b91a259e80 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -224,7 +224,7 @@ TransactionIdDidAbort(TransactionId transactionId)
  *		True iff transaction associated with the identifier is currently
  *		known to have either committed or aborted.
  *
- * This does NOT look into pg_clog but merely probes our local cache
+ * This does NOT look into pg_xact but merely probes our local cache
  * (and so it's not named TransactionIdDidComplete, which would be the
  * appropriate name for a function that worked that way).  The intended
  * use is just to short-circuit TransactionIdIsInProgress calls when doing
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 83ca6e0408..da77e3efde 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1379,7 +1379,7 @@ FinishPreparedTransaction(const char *gid, bool isCommit)
 	/*
 	 * The order of operations here is critical: make the XLOG entry for
 	 * commit or abort, then mark the transaction committed or aborted in
-	 * pg_clog, then remove its PGPROC from the global ProcArray (which means
+	 * pg_xact, then remove its PGPROC from the global ProcArray (which means
 	 * TransactionIdIsInProgress will stop saying the prepared xact is in
 	 * progress), then run the post-commit or post-abort callbacks. The
 	 * callbacks will release the locks the transaction held.
@@ -2093,7 +2093,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	/* Flush XLOG to disk */
 	XLogFlush(recptr);
 
-	/* Mark the transaction committed in pg_clog */
+	/* Mark the transaction committed in pg_xact */
 	TransactionIdCommitTree(xid, nchildren, children);
 
 	/* Checkpoint can proceed now */
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 82f9a3c5c6..02e0779f32 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1208,8 +1208,8 @@ RecordTransactionCommit(void)
 		/*
 		 * Mark ourselves as within our "commit critical section".  This
 		 * forces any concurrent checkpoint to wait until we've updated
-		 * pg_clog.  Without this, it is possible for the checkpoint to set
-		 * REDO after the XLOG record but fail to flush the pg_clog update to
+		 * pg_xact.  Without this, it is possible for the checkpoint to set
+		 * REDO after the XLOG record but fail to flush the pg_xact update to
 		 * disk, leading to loss of the transaction commit if the system
 		 * crashes a little later.
 		 *
@@ -2035,7 +2035,7 @@ CommitTransaction(void)
 	if (!is_parallel_worker)
 	{
 		/*
-		 * We need to mark our XIDs as committed in pg_clog.  This is where we
+		 * We need to mark our XIDs as committed in pg_xact.  This is where we
 		 * durably commit.
 		 */
 		latestXid = RecordTransactionCommit();
@@ -2545,7 +2545,7 @@ AbortTransaction(void)
 	AtAbort_Twophase();
 
 	/*
-	 * Advertise the fact that we aborted in pg_clog (assuming that we got as
+	 * Advertise the fact that we aborted in pg_xact (assuming that we got as
 	 * far as assigning an XID to advertise).  But if we're inside a parallel
 	 * worker, skip this; the user backend must be the one to write the abort
 	 * record.
@@ -4631,7 +4631,7 @@ AbortSubTransaction(void)
 								s->parent->subTransactionId);
 		AtSubAbort_Notify();
 
-		/* Advertise the fact that we aborted in pg_clog. */
+		/* Advertise the fact that we aborted in pg_xact. */
 		(void) RecordTransactionAbort(true);
 
 		/* Post-abort cleanup */
@@ -5375,7 +5375,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 	if (standbyState == STANDBY_DISABLED)
 	{
 		/*
-		 * Mark the transaction committed in pg_clog.
+		 * Mark the transaction committed in pg_xact.
 		 */
 		TransactionIdCommitTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
@@ -5393,7 +5393,7 @@ xact_redo_commit(xl_xact_parsed_commit *parsed,
 		RecordKnownAssignedTransactionIds(max_xid);
 
 		/*
-		 * Mark the transaction committed in pg_clog. We use async commit
+		 * Mark the transaction committed in pg_xact. We use async commit
 		 * protocol during recovery to provide information on database
 		 * consistency for when users try to set hint bits. It is important
 		 * that we do not set hint bits until the minRecoveryPoint is past
@@ -5530,7 +5530,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 
 	if (standbyState == STANDBY_DISABLED)
 	{
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_xact, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 	}
 	else
@@ -5546,7 +5546,7 @@ xact_redo_abort(xl_xact_parsed_abort *parsed, TransactionId xid)
 		 */
 		RecordKnownAssignedTransactionIds(max_xid);
 
-		/* Mark the transaction aborted in pg_clog, no need for async stuff */
+		/* Mark the transaction aborted in pg_xact, no need for async stuff */
 		TransactionIdAbortTree(xid, parsed->nsubxacts, parsed->subxacts);
 
 		/*
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 64335f909e..cdb3a8ac1d 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8710,7 +8710,7 @@ CreateCheckPoint(int flags)
 	 * that are currently in commit critical sections.  If an xact inserted
 	 * its commit record into XLOG just before the REDO point, then a crash
 	 * restart from the REDO point would not replay that record, which means
-	 * that our flushing had better include the xact's update of pg_clog.  So
+	 * that our flushing had better include the xact's update of pg_xact.  So
 	 * we wait till he's out of his commit critical section before proceeding.
 	 * See notes in RecordTransactionCommit().
 	 *
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 3b3dfeead4..ff633faca6 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -357,7 +357,7 @@ vacuum(int options, RangeVar *relation, Oid relid, VacuumParams *params,
 	if ((options & VACOPT_VACUUM) && !IsAutoVacuumWorkerProcess())
 	{
 		/*
-		 * Update pg_database.datfrozenxid, and truncate pg_clog if possible.
+		 * Update pg_database.datfrozenxid, and truncate pg_xact if possible.
 		 * (autovacuum.c does this for itself.)
 		 */
 		vac_update_datfrozenxid();
@@ -910,7 +910,7 @@ vac_update_relstats(Relation relation,
  *		pg_class.relminmxid values.
  *
  *		If we are able to advance either pg_database value, also try to
- *		truncate pg_clog and pg_multixact.
+ *		truncate pg_xact and pg_multixact.
  *
  *		We violate transaction semantics here by overwriting the database's
  *		existing pg_database tuple with the new values.  This is reasonably
@@ -1056,7 +1056,7 @@ vac_update_datfrozenxid(void)
 
 	/*
 	 * If we were able to advance datfrozenxid or datminmxid, see if we can
-	 * truncate pg_clog and/or pg_multixact.  Also do it if the shared
+	 * truncate pg_xact and/or pg_multixact.  Also do it if the shared
 	 * XID-wrap-limit info is stale, since this action will update that too.
 	 */
 	if (dirty || ForceTransactionIdLimitUpdate())
@@ -1069,7 +1069,7 @@ vac_update_datfrozenxid(void)
  *	vac_truncate_clog() -- attempt to truncate the commit log
  *
  *		Scan pg_database to determine the system-wide oldest datfrozenxid,
- *		and use it to truncate the transaction commit log (pg_clog).
+ *		and use it to truncate the transaction commit log (pg_xact).
  *		Also update the XID wrap limit info maintained by varsup.c.
  *		Likewise for datminmxid.
  *
@@ -1116,7 +1116,7 @@ vac_truncate_clog(TransactionId frozenXID,
 	 * of the interlock against copying a DB containing an active backend.
 	 * Hence the new entry will not reduce the minimum.  Also, if two VACUUMs
 	 * concurrently modify the datfrozenxid's of different databases, the
-	 * worst possible outcome is that pg_clog is not truncated as aggressively
+	 * worst possible outcome is that pg_xact is not truncated as aggressively
 	 * as it could be.
 	 */
 	relation = heap_open(DatabaseRelationId, AccessShareLock);
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index fa8de1390e..33ca749b52 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2472,7 +2472,7 @@ deleted:
 	 */
 
 	/*
-	 * Update pg_database.datfrozenxid, and truncate pg_clog if possible. We
+	 * Update pg_database.datfrozenxid, and truncate pg_xact if possible. We
 	 * only need to do this once, not after each table.
 	 *
 	 * Even if we didn't vacuum anything, it may still be important to do
diff --git a/src/backend/storage/buffer/README b/src/backend/storage/buffer/README
index 248883f0da..bc80777bb1 100644
--- a/src/backend/storage/buffer/README
+++ b/src/backend/storage/buffer/README
@@ -63,7 +63,7 @@ at about the same time would OR the same bits into the field, so there
 is little or no risk of conflicting update; what's more, if there did
 manage to be a conflict it would merely mean that one bit-update would
 be lost and need to be done again later.  These four bits are only hints
-(they cache the results of transaction status lookups in pg_clog), so no
+(they cache the results of transaction status lookups in pg_xact), so no
 great harm is done if they get reset to zero by conflicting updates.
 Note, however, that a tuple is frozen by setting both HEAP_XMIN_INVALID
 and HEAP_XMIN_COMMITTED; this is a critical update and accordingly requires
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index c724a0e952..0f8f435faf 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -381,7 +381,7 @@ ProcArrayRemove(PGPROC *proc, TransactionId latestXid)
  * ProcArrayEndTransaction -- mark a transaction as no longer running
  *
  * This is used interchangeably for commit and abort cases.  The transaction
- * commit/abort must already be reported to WAL and pg_clog.
+ * commit/abort must already be reported to WAL and pg_xact.
  *
  * proc is currently always MyProc, but we pass it explicitly for flexibility.
  * latestXid is the latest Xid among the transaction's main XID and
@@ -1174,7 +1174,7 @@ TransactionIdIsInProgress(TransactionId xid)
 	 * At this point, we know it's either a subtransaction of one of the Xids
 	 * in xids[], or it's not running.  If it's an already-failed
 	 * subtransaction, we want to say "not running" even though its parent may
-	 * still be running.  So first, check pg_clog to see if it's been aborted.
+	 * still be running.  So first, check pg_xact to see if it's been aborted.
 	 */
 	xc_slow_answer_inc();
 
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 703bdcedaf..519f3b6803 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -13,9 +13,9 @@
  * NOTE: When using a non-MVCC snapshot, we must check
  * TransactionIdIsInProgress (which looks in the PGXACT array)
  * before TransactionIdDidCommit/TransactionIdDidAbort (which look in
- * pg_clog).  Otherwise we have a race condition: we might decide that a
+ * pg_xact).  Otherwise we have a race condition: we might decide that a
  * just-committed transaction crashed, because none of the tests succeed.
- * xact.c is careful to record commit/abort in pg_clog before it unsets
+ * xact.c is careful to record commit/abort in pg_xact before it unsets
  * MyPgXact->xid in the PGXACT array.  That fixes that problem, but it
  * also means there is a window where TransactionIdIsInProgress and
  * TransactionIdDidCommit will both return true.  If we check only
@@ -29,7 +29,7 @@
  *
  * When using an MVCC snapshot, we rely on XidInMVCCSnapshot rather than
  * TransactionIdIsInProgress, but the logic is otherwise the same: do not
- * check pg_clog until after deciding that the xact is no longer in progress.
+ * check pg_xact until after deciding that the xact is no longer in progress.
  *
  *
  * Summary of visibility functions:
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 9b71e0042d..e0c72fbb80 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -197,7 +197,6 @@ static const char *backend_options = "--single -F -O -j -c search_path=pg_catalo
 static const char *const subdirs[] = {
 	"global",
 	"pg_wal/archive_status",
-	"pg_clog",
 	"pg_commit_ts",
 	"pg_dynshmem",
 	"pg_notify",
@@ -214,6 +213,7 @@ static const char *const subdirs[] = {
 	"pg_tblspc",
 	"pg_stat",
 	"pg_stat_tmp",
+	"pg_xact",
 	"pg_logical",
 	"pg_logical/snapshots",
 	"pg_logical/mappings"
diff --git a/src/bin/pg_upgrade/exec.c b/src/bin/pg_upgrade/exec.c
index 91fa71728e..b954d19d9d 100644
--- a/src/bin/pg_upgrade/exec.c
+++ b/src/bin/pg_upgrade/exec.c
@@ -343,6 +343,12 @@ check_data_dir(ClusterInfo *cluster)
 		check_single_dir(pg_data, "pg_xlog");
 	else
 		check_single_dir(pg_data, "pg_wal");
+
+	/* pg_clog has been renamed to pg_xact in post-10 cluster */
+	if (GET_MAJOR_VERSION(cluster->major_version) < 1000)
+		check_single_dir(pg_data, "pg_clog");
+	else
+		check_single_dir(pg_data, "pg_xact");
 }
 
 
diff --git a/src/bin/pg_upgrade/pg_upgrade.c b/src/bin/pg_upgrade/pg_upgrade.c
index fc66d93dd6..ca1aa5cbb8 100644
--- a/src/bin/pg_upgrade/pg_upgrade.c
+++ b/src/bin/pg_upgrade/pg_upgrade.c
@@ -48,7 +48,7 @@
 static void prepare_new_cluster(void);
 static void prepare_new_databases(void);
 static void create_new_objects(void);
-static void copy_clog_xlog_xid(void);
+static void copy_xact_xlog_xid(void);
 static void set_frozenxids(bool minmxid_only);
 static void setup(char *argv0, bool *live_check);
 static void cleanup(void);
@@ -115,7 +115,7 @@ main(int argc, char **argv)
 	 * Destructive Changes to New Cluster
 	 */
 
-	copy_clog_xlog_xid();
+	copy_xact_xlog_xid();
 
 	/* New now using xids of the old system */
 
@@ -376,17 +376,17 @@ remove_new_subdir(char *subdir, bool rmtopdir)
  * Copy the files from the old cluster into it
  */
 static void
-copy_subdir_files(char *subdir)
+copy_subdir_files(char *old_subdir, char *new_subdir)
 {
 	char		old_path[MAXPGPATH];
 	char		new_path[MAXPGPATH];
 
-	remove_new_subdir(subdir, true);
+	remove_new_subdir(new_subdir, true);
 
-	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, subdir);
-	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, subdir);
+	snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, old_subdir);
+	snprintf(new_path, sizeof(new_path), "%s/%s", new_cluster.pgdata, new_subdir);
 
-	prep_status("Copying old %s to new server", subdir);
+	prep_status("Copying old %s to new server", old_subdir);
 
 	exec_prog(UTILITY_LOG_FILE, NULL, true,
 #ifndef WIN32
@@ -401,10 +401,16 @@ copy_subdir_files(char *subdir)
 }
 
 static void
-copy_clog_xlog_xid(void)
+copy_xact_xlog_xid(void)
 {
-	/* copy old commit logs to new data dir */
-	copy_subdir_files("pg_clog");
+	/*
+	 * Copy old commit logs to new data dir. pg_clog has been renamed to
+	 * pg_xact in post-10 clusters.
+	 */
+	copy_subdir_files(GET_MAJOR_VERSION(old_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_xact",
+					  GET_MAJOR_VERSION(new_cluster.major_version) < 1000 ?
+					  "pg_clog" : "pg_xact");
 
 	/* set the next transaction id and epoch of the new cluster */
 	prep_status("Setting next transaction ID and epoch for new cluster");
@@ -434,8 +440,8 @@ copy_clog_xlog_xid(void)
 	if (old_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER &&
 		new_cluster.controldata.cat_ver >= MULTIXACT_FORMATCHANGE_CAT_VER)
 	{
-		copy_subdir_files("pg_multixact/offsets");
-		copy_subdir_files("pg_multixact/members");
+		copy_subdir_files("pg_multixact/offsets", "pg_multixact/offsets");
+		copy_subdir_files("pg_multixact/members", "pg_multixact/members");
 
 		prep_status("Setting next multixact ID and offset for new cluster");
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index cf6edc3bdb..722867d5d2 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -76,7 +76,7 @@ typedef struct SlruSharedData
 	/*
 	 * Optional array of WAL flush LSNs associated with entries in the SLRU
 	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true
-	 * for pg_clog, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
+	 * for pg_xact, false for multixact, pg_subtrans, pg_notify).  group_lsn[]
 	 * has lsn_groups_per_page entries per buffer slot, each containing the
 	 * highest LSN known for a contiguous group of SLRU entries on that slot's
 	 * page.
@@ -119,7 +119,7 @@ typedef struct SlruCtlData
 	SlruShared	shared;
 
 	/*
-	 * This flag tells whether to fsync writes (true for pg_clog and multixact
+	 * This flag tells whether to fsync writes (true for pg_xact and multixact
 	 * stuff, false for pg_subtrans and pg_notify).
 	 */
 	bool		do_fsync;
-- 
2.12.0