From 68219aaf6b8c6214e5f4a6124bd5607254aad6b3 Mon Sep 17 00:00:00 2001
From: Simon Riggs <simon@2ndQuadrant.com>
Date: Thu, 29 Mar 2012 14:55:30 +0100
Subject: [PATCH] Correct epoch of txid_current() when executed on a Hot
Standby server. Initialise ckptXidEpoch from starting checkpoint and maintain
the correct value as we roll forwards. This allows GetNextXidAndEpoch() to
return the correct epoch when executed during recovery. Backpatch to 9.0 when
the problem is first observable by a user.
Bug report from Daniel Farina
---
src/backend/access/transam/xlog.c | 30 ++++++++++++++++++++++++++----
1 file changed, 26 insertions(+), 4 deletions(-)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index ff7f521a1b1..d2680149f49 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6320,6 +6320,10 @@ StartupXLOG(void)
/* No need to hold ControlFileLock yet, we aren't up far enough */
UpdateControlFile();
+ /* initialize shared-memory copy of latest checkpoint XID/epoch */
+ XLogCtl->ckptXidEpoch = ControlFile->checkPointCopy.nextXidEpoch;
+ XLogCtl->ckptXid = ControlFile->checkPointCopy.nextXid;
+
/* initialize our local copy of minRecoveryPoint */
minRecoveryPoint = ControlFile->minRecoveryPoint;
@@ -6915,10 +6919,6 @@ StartupXLOG(void)
/* start the archive_timeout timer running */
XLogCtl->Write.lastSegSwitchTime = (pg_time_t) time(NULL);
- /* initialize shared-memory copy of latest checkpoint XID/epoch */
- XLogCtl->ckptXidEpoch = ControlFile->checkPointCopy.nextXidEpoch;
- XLogCtl->ckptXid = ControlFile->checkPointCopy.nextXid;
-
/* also initialize latestCompletedXid, to nextXid - 1 */
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
ShmemVariableCache->latestCompletedXid = ShmemVariableCache->nextXid;
@@ -8601,6 +8601,17 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
ControlFile->checkPointCopy.nextXidEpoch = checkPoint.nextXidEpoch;
ControlFile->checkPointCopy.nextXid = checkPoint.nextXid;
+ /* Update shared-memory copy of checkpoint XID/epoch */
+ {
+ /* use volatile pointer to prevent code rearrangement */
+ volatile XLogCtlData *xlogctl = XLogCtl;
+
+ SpinLockAcquire(&xlogctl->info_lck);
+ xlogctl->ckptXidEpoch = checkPoint.nextXidEpoch;
+ xlogctl->ckptXid = checkPoint.nextXid;
+ SpinLockRelease(&xlogctl->info_lck);
+ }
+
/*
* TLI may change in a shutdown checkpoint, but it shouldn't decrease
*/
@@ -8645,6 +8656,17 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
ControlFile->checkPointCopy.nextXidEpoch = checkPoint.nextXidEpoch;
ControlFile->checkPointCopy.nextXid = checkPoint.nextXid;
+ /* Update shared-memory copy of checkpoint XID/epoch */
+ {
+ /* use volatile pointer to prevent code rearrangement */
+ volatile XLogCtlData *xlogctl = XLogCtl;
+
+ SpinLockAcquire(&xlogctl->info_lck);
+ xlogctl->ckptXidEpoch = checkPoint.nextXidEpoch;
+ xlogctl->ckptXid = checkPoint.nextXid;
+ SpinLockRelease(&xlogctl->info_lck);
+ }
+
/* TLI should not change in an on-line checkpoint */
if (checkPoint.ThisTimeLineID != ThisTimeLineID)
ereport(PANIC,
--
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