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Send status updates back from standby server to master, indicating how far

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the standby has written, flushed, and applied the WAL. At the moment, this
is for informational purposes only, the values are only shown in
pg_stat_replication system view, but in the future they will also be needed
for synchronous replication.

Extracted from Simon riggs' synchronous replication patch by Robert Haas, with
some tweaking by me.
This commit is contained in:
Heikki Linnakangas
2011-02-10 21:00:29 +02:00
parent 4c468b37a2
commit b186523fd9
15 changed files with 352 additions and 22 deletions
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25
src/backend/access/transam/xlog.c
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@ -9317,6 +9317,25 @@ pg_last_xlog_receive_location(PG_FUNCTION_ARGS)
PG_RETURN_TEXT_P(cstring_to_text(location));
}
/*
* Get latest redo apply position.
*
* Exported to allow WALReceiver to read the pointer directly.
*/
XLogRecPtr
GetXLogReplayRecPtr(void)
{
/* use volatile pointer to prevent code rearrangement */
volatile XLogCtlData *xlogctl = XLogCtl;
XLogRecPtr recptr;
SpinLockAcquire(&xlogctl->info_lck);
recptr = xlogctl->recoveryLastRecPtr;
SpinLockRelease(&xlogctl->info_lck);
return recptr;
}
/*
* Report the last WAL replay location (same format as pg_start_backup etc)
*
@ -9326,14 +9345,10 @@ pg_last_xlog_receive_location(PG_FUNCTION_ARGS)
Datum
pg_last_xlog_replay_location(PG_FUNCTION_ARGS)
{
/* use volatile pointer to prevent code rearrangement */
volatile XLogCtlData *xlogctl = XLogCtl;
XLogRecPtr recptr;
char location[MAXFNAMELEN];
SpinLockAcquire(&xlogctl->info_lck);
recptr = xlogctl->recoveryLastRecPtr;
SpinLockRelease(&xlogctl->info_lck);
recptr = GetXLogReplayRecPtr();
if (recptr.xlogid == 0 && recptr.xrecoff == 0)
PG_RETURN_NULL();