From ffe8c7c677197ef8062a71309b14a1847841118c Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Mon, 3 May 2010 11:17:52 +0000
Subject: [PATCH] Need to hold ControlFileLock while updating control file.
Update minRecoveryPoint in control file when replaying a parameter change
record, to ensure that we don't allow hot standby on WAL generated without
wal_level='hot_standby' after a standby restart.
---
src/backend/access/transam/xlog.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 99e53b76321..a39d455a7f0 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.408 2010/05/02 02:10:33 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.409 2010/05/03 11:17:52 heikki Exp $
*
*-------------------------------------------------------------------------
*/
@@ -7920,11 +7920,28 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
/* Update our copy of the parameters in pg_control */
memcpy(&xlrec, XLogRecGetData(record), sizeof(xl_parameter_change));
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
ControlFile->MaxConnections = xlrec.MaxConnections;
ControlFile->max_prepared_xacts = xlrec.max_prepared_xacts;
ControlFile->max_locks_per_xact = xlrec.max_locks_per_xact;
ControlFile->wal_level = xlrec.wal_level;
+ /*
+ * Update minRecoveryPoint to ensure that if recovery is aborted,
+ * we recover back up to this point before allowing hot standby
+ * again. This is particularly important if wal_level was set to
+ * 'archive' before, and is now 'hot_standby', to ensure you don't
+ * run queries against the WAL preceding the wal_level change.
+ * Same applies to decreasing max_* settings.
+ */
+ minRecoveryPoint = ControlFile->minRecoveryPoint;
+ if ((minRecoveryPoint.xlogid != 0 || minRecoveryPoint.xrecoff != 0)
+ && XLByteLT(minRecoveryPoint, lsn))
+ {
+ ControlFile->minRecoveryPoint = lsn;
+ }
+
UpdateControlFile();
+ LWLockRelease(ControlFileLock);
/* Check to see if any changes to max_connections give problems */
CheckRequiredParameterValues();
--
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