From 2af568c6b50293bedb10d4ebb8dca9fe13f435c5 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Fri, 6 Feb 2015 11:18:14 +0200
Subject: [PATCH] Report WAL flush, not insert, position in replication
IDENTIFY_SYSTEM
When beginning streaming replication, the client usually issues the
IDENTIFY_SYSTEM command, which used to return the current WAL insert
position. That's not suitable for the intended purpose of that field,
however. pg_receivexlog uses it to start replication from the reported
point, but if it hasn't been flushed to disk yet, it will fail. Change
IDENTIFY_SYSTEM to report the flush position instead.
Backpatch to 9.1 and above. 9.0 doesn't report any WAL position.
---
doc/src/sgml/protocol.sgml | 2 +-
src/backend/replication/walsender.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 08c2f008936..87741f3b374 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -1338,7 +1338,7 @@ The commands accepted in walsender mode are:
</term>
<listitem>
<para>
- Current xlog write location. Useful to get a known location in the
+ Current xlog flush location. Useful to get a known location in the
transaction log where streaming can start.
</para>
</listitem>
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 7deaa82fd64..94da622f057 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -298,7 +298,7 @@ IdentifySystem(void)
GetSystemIdentifier());
snprintf(tli, sizeof(tli), "%u", ThisTimeLineID);
- logptr = am_cascading_walsender ? GetStandbyFlushRecPtr(NULL) : GetInsertRecPtr();
+ logptr = am_cascading_walsender ? GetStandbyFlushRecPtr(NULL) : GetFlushRecPtr();
snprintf(xpos, sizeof(xpos), "%X/%X",
logptr.xlogid, logptr.xrecoff);
--
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