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Report WAL flush, not insert, position in replication IDENTIFY_SYSTEM

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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.
This commit is contained in:
Heikki Linnakangas
2015-02-06 11:18:14 +02:00
parent eae798ae1d
commit 2af568c6b5
2 changed files with 2 additions and 2 deletions
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2
doc/src/sgml/protocol.sgml
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@ -1338,7 +1338,7 @@ The commands accepted in walsender mode are:
</term> </term>
<listitem> <listitem>
<para> <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. transaction log where streaming can start.
</para> </para>
</listitem> </listitem>

2
src/backend/replication/walsender.c
View File

@ -298,7 +298,7 @@ IdentifySystem(void)
GetSystemIdentifier()); GetSystemIdentifier());
snprintf(tli, sizeof(tli), "%u", ThisTimeLineID); 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", snprintf(xpos, sizeof(xpos), "%X/%X",
logptr.xlogid, logptr.xrecoff); logptr.xlogid, logptr.xrecoff);