Revert the patch to check if we've reached end-of-backup also when doing

crash recovery, and throw an error if not. hubert depesz lubaczewski pointed
out that that situation also happens in the crash recovery following a
system crash that happens during an online backup.

We might want to do something smarter in 9.1, like put the check back for
backups taken with pg_basebackup, but that's for another patch.

Author: hlinnaka

src/backend/access/transam/xlog.c

@@ -6651,17 +6651,32 @@ StartupXLOG(void)
 		(XLByteLT(EndOfLog, minRecoveryPoint) ||
 		 !XLogRecPtrIsInvalid(ControlFile->backupStartPoint)))
 	{
-		if (reachedStopPoint)	/* stopped because of stop request */
+		if (reachedStopPoint)
+		{
+			/* stopped because of stop request */
 			ereport(FATAL,
 					(errmsg("requested recovery stop point is before consistent recovery point")));
-		/* ran off end of WAL */
-		if (!XLogRecPtrIsInvalid(ControlFile->backupStartPoint))
-			ereport(FATAL,
-					(errmsg("WAL ends before end of online backup"),
-					 errhint("Online backup started with pg_start_backup() must be ended with pg_stop_backup(), and all WAL up to that point must be available at recovery.")));
-		else
-			ereport(FATAL,
-					(errmsg("WAL ends before consistent recovery point")));
+		}
+		/*
+		 * Ran off end of WAL before reaching end-of-backup WAL record,
+		 * or minRecoveryPoint. That's usually a bad sign, indicating that
+		 * you tried to recover from an online backup but never called
+		 * pg_stop_backup(), or you didn't archive all the WAL up to that
+		 * point. However, this also happens in crash recovery, if the
+		 * system crashes while an online backup is in progress. We
+		 * must not treat that as an error, or the database will refuse
+		 * to start up.
+		 */
+		if (InArchiveRecovery)
+		{
+			if (!XLogRecPtrIsInvalid(ControlFile->backupStartPoint))
+				ereport(FATAL,
+						(errmsg("WAL ends before end of online backup"),
+						 errhint("Online backup started with pg_start_backup() must be ended with pg_stop_backup(), and all WAL up to that point must be available at recovery.")));
+			else
+				ereport(FATAL,
+						(errmsg("WAL ends before consistent recovery point")));
+		}
 	}
 
 	/*
@@ -8353,7 +8368,8 @@ xlog_redo(XLogRecPtr lsn, XLogRecord *record)
 		 * record, the backup was cancelled and the end-of-backup record will
 		 * never arrive.
 		 */
-		if (!XLogRecPtrIsInvalid(ControlFile->backupStartPoint))
+		if (InArchiveRecovery &&
+			!XLogRecPtrIsInvalid(ControlFile->backupStartPoint))
 			ereport(ERROR,
 					(errmsg("online backup was cancelled, recovery cannot continue")));