From: Peter Eisentraut <peter_e@gmx.net>
Date: Wed, 16 Aug 2017 23:46:50 +0000 (-0400)
Subject: pg_dump: Support using synchronized snapshots on standbys
X-Git-Tag: REL_11_BETA1~1774
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=cf851519d40e85c8129515c06532515386eaf41c;p=postgresql

pg_dump: Support using synchronized snapshots on standbys

This became possible by commit
6c2003f8a1bbc7c192a2e83ec51581c018aa162f.  This just makes pg_dump aware
of it and updates the documentation.

Author: Petr Jelinek <petr.jelinek@2ndquadrant.com>
---

diff --git a/doc/src/sgml/ref/pg_dump.sgml b/doc/src/sgml/ref/pg_dump.sgml
index ad5b6fc703..7ccbee4855 100644
--- a/doc/src/sgml/ref/pg_dump.sgml
+++ b/doc/src/sgml/ref/pg_dump.sgml
@@ -337,14 +337,16 @@ PostgreSQL documentation
         but to abort the dump.
        </para>
        <para>
-        For a consistent backup, the database server needs to support synchronized snapshots,
-        a feature that was introduced in <productname>PostgreSQL</productname> 9.2. With this
-        feature, database clients can ensure they see the same data set even though they use
-        different connections. <command>pg_dump -j</command> uses multiple database
-        connections; it connects to the database once with the master process and
-        once again for each worker job. Without the synchronized snapshot feature, the
-        different worker jobs wouldn't be guaranteed to see the same data in each connection,
-        which could lead to an inconsistent backup.
+        For a consistent backup, the database server needs to support
+        synchronized snapshots, a feature that was introduced in
+        <productname>PostgreSQL</productname> 9.2 for primary servers and 10
+        for standbys. With this feature, database clients can ensure they see
+        the same data set even though they use different connections.
+        <command>pg_dump -j</command> uses multiple database connections; it
+        connects to the database once with the master process and once again
+        for each worker job. Without the synchronized snapshot feature, the
+        different worker jobs wouldn't be guaranteed to see the same data in
+        each connection, which could lead to an inconsistent backup.
        </para>
        <para>
         If you want to run a parallel dump of a pre-9.2 server, you need to make sure that the
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index b6e66267ff..75f08cd792 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -1134,9 +1134,9 @@ setup_connection(Archive *AH, const char *dumpencoding,
 			 AH->remoteVersion >= 90200 &&
 			 !dopt->no_synchronized_snapshots)
 	{
-		if (AH->isStandby)
+		if (AH->isStandby && AH->remoteVersion < 100000)
 			exit_horribly(NULL,
-						  "Synchronized snapshots are not supported on standby servers.\n"
+						  "Synchronized snapshots on standby servers are not supported by this server version.\n"
 						  "Run with --no-synchronized-snapshots instead if you do not need\n"
 						  "synchronized snapshots.\n");