From e4892c68184e199c3117a8f8b52da22a77702a05 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter_e@gmx.net>
Date: Wed, 16 Aug 2017 19:46:50 -0400
Subject: [PATCH] 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>
---
doc/src/sgml/ref/pg_dump.sgml | 18 ++++++++++--------
src/bin/pg_dump/pg_dump.c | 4 ++--
2 files changed, 12 insertions(+), 10 deletions(-)
diff --git a/doc/src/sgml/ref/pg_dump.sgml b/doc/src/sgml/ref/pg_dump.sgml
index bafa031e1a8..3c088f33558 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 2d8bb32dc07..b93dd8bf3c1 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -1131,9 +1131,9 @@ 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");
--
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