From 9f0d2bdc88630781485a17178e2b50e49ce70040 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Fri, 9 Dec 2011 14:32:42 +0200
Subject: [PATCH] Don't set reachedMinRecoveryPoint during crash recovery. In
 crash recovery, we don't reach consistency before replaying all of the WAL.
 Rename the variable to reachedConsistency, to make its intention clearer.

In master, that was an active bug because of the recent patch to
immediately PANIC if a reference to a missing page is found in WAL after
reaching consistency, as Tom Lane's test case demonstrated. In 9.1 and 9.0,
the only consequence was a misleading "consistent recovery state reached at
%X/%X" message in the log at the beginning of crash recovery (the database
is not consistent at that point yet). In 8.4, the log message was not
printed in crash recovery, even though there was a similar
reachedMinRecoveryPoint local variable that was also set early. So,
backpatch to 9.1 and 9.0.
---
 src/backend/access/transam/xlog.c      | 21 +++++++++++++++++----
 src/backend/access/transam/xlogutils.c |  2 +-
 src/include/access/xlog.h              |  2 +-
 3 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 9bec660992..9d96044cbd 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -562,7 +562,13 @@ static TimeLineID lastPageTLI = 0;
 static XLogRecPtr minRecoveryPoint;		/* local copy of
 										 * ControlFile->minRecoveryPoint */
 static bool updateMinRecoveryPoint = true;
-bool reachedMinRecoveryPoint = false;
+
+/*
+ * Have we reached a consistent database state? In crash recovery, we have
+ * to replay all the WAL, so reachedConsistency is never set. During archive
+ * recovery, the database is consistent once minRecoveryPoint is reached.
+ */
+bool reachedConsistency = false;
 
 static bool InRedo = false;
 
@@ -6893,10 +6899,17 @@ StartupXLOG(void)
 static void
 CheckRecoveryConsistency(void)
 {
+	/*
+	 * During crash recovery, we don't reach a consistent state until we've
+	 * replayed all the WAL.
+	 */
+	if (XLogRecPtrIsInvalid(minRecoveryPoint))
+		return;
+
 	/*
 	 * Have we passed our safe starting point?
 	 */
-	if (!reachedMinRecoveryPoint &&
+	if (!reachedConsistency &&
 		XLByteLE(minRecoveryPoint, EndRecPtr) &&
 		XLogRecPtrIsInvalid(ControlFile->backupStartPoint))
 	{
@@ -6906,7 +6919,7 @@ CheckRecoveryConsistency(void)
 		 */
 		XLogCheckInvalidPages();
 
-		reachedMinRecoveryPoint = true;
+		reachedConsistency = true;
 		ereport(LOG,
 				(errmsg("consistent recovery state reached at %X/%X",
 						EndRecPtr.xlogid, EndRecPtr.xrecoff)));
@@ -6919,7 +6932,7 @@ CheckRecoveryConsistency(void)
 	 */
 	if (standbyState == STANDBY_SNAPSHOT_READY &&
 		!LocalHotStandbyActive &&
-		reachedMinRecoveryPoint &&
+		reachedConsistency &&
 		IsUnderPostmaster)
 	{
 		/* use volatile pointer to prevent code rearrangement */
diff --git a/src/backend/access/transam/xlogutils.c b/src/backend/access/transam/xlogutils.c
index 350d434562..b280434a82 100644
--- a/src/backend/access/transam/xlogutils.c
+++ b/src/backend/access/transam/xlogutils.c
@@ -85,7 +85,7 @@ log_invalid_page(RelFileNode node, ForkNumber forkno, BlockNumber blkno,
 	 * linger in the hash table until the end of recovery and PANIC there,
 	 * which might come only much later if this is a standby server.
 	 */
-	if (reachedMinRecoveryPoint)
+	if (reachedConsistency)
 	{
 		report_invalid_page(WARNING, node, forkno, blkno, present);
 		elog(PANIC, "WAL contains references to invalid pages");
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 1fb56cdfd5..1b31414060 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -190,7 +190,7 @@ typedef enum
 
 extern XLogRecPtr XactLastRecEnd;
 
-extern bool reachedMinRecoveryPoint;
+extern bool reachedConsistency;
 
 /* these variables are GUC parameters related to XLOG */
 extern int	CheckPointSegments;