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.

Author: hlinnaka

src/backend/access/transam/xlog.c

@@ -554,7 +554,13 @@ static TimeLineID lastPageTLI = 0;
 static XLogRecPtr minRecoveryPoint;		/* local copy of
 										 * ControlFile->minRecoveryPoint */
 static bool updateMinRecoveryPoint = true;
-static 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.
+ */
+static bool reachedConsistency = false;
 
 static bool InRedo = false;
 
@@ -6952,14 +6958,21 @@ 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))
 	{
-		reachedMinRecoveryPoint = true;
+		reachedConsistency = true;
 		ereport(LOG,
 				(errmsg("consistent recovery state reached at %X/%X",
 						EndRecPtr.xlogid, EndRecPtr.xrecoff)));
@@ -6972,7 +6985,7 @@ CheckRecoveryConsistency(void)
 	 */
 	if (standbyState == STANDBY_SNAPSHOT_READY &&
 		!LocalHotStandbyActive &&
-		reachedMinRecoveryPoint &&
+		reachedConsistency &&
 		IsUnderPostmaster)
 	{
 		/* use volatile pointer to prevent code rearrangement */