1 files changed, 24 insertions, 9 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 09d4dffc75e..0d2540c3c23 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -570,6 +570,7 @@ static uint32 readRecordBufSize = 0;
 static XLogRecPtr ReadRecPtr;	/* start of last record read */
 static XLogRecPtr EndRecPtr;	/* end+1 of last record read */
 static TimeLineID lastPageTLI = 0;
+static TimeLineID lastSegmentTLI = 0;
 
 static XLogRecPtr minRecoveryPoint;		/* local copy of
 										 * ControlFile->minRecoveryPoint */
@@ -644,7 +645,7 @@ static void CleanupBackupHistory(void);
 static void UpdateMinRecoveryPoint(XLogRecPtr lsn, bool force);
 static XLogRecord *ReadRecord(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt);
 static void CheckRecoveryConsistency(void);
-static bool ValidXLogPageHeader(XLogPageHeader hdr, int emode);
+static bool ValidXLogPageHeader(XLogPageHeader hdr, int emode, bool segmentonly);
 static bool ValidXLogRecordHeader(XLogRecPtr *RecPtr, XLogRecord *record,
 					  int emode, bool randAccess);
 static XLogRecord *ReadCheckpointRecord(XLogRecPtr RecPtr, int whichChkpt);
@@ -3339,7 +3340,8 @@ ReadRecord(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt)
 		 * to go backwards (but we can't reset that variable right here, since
 		 * we might not change files at all).
 		 */
-		lastPageTLI = 0;		/* see comment in ValidXLogPageHeader */
+		/* see comment in ValidXLogPageHeader */
+		lastPageTLI = lastSegmentTLI = 0;
 		randAccess = true;		/* allow curFileTLI to go backwards too */
 	}
 
@@ -3579,7 +3581,7 @@ next_record_is_invalid:
  * ReadRecord.	It's not intended for use from anywhere else.
  */
 static bool
-ValidXLogPageHeader(XLogPageHeader hdr, int emode)
+ValidXLogPageHeader(XLogPageHeader hdr, int emode, bool segmentonly)
 {
 	XLogRecPtr	recaddr;
 
@@ -3681,19 +3683,32 @@ ValidXLogPageHeader(XLogPageHeader hdr, int emode)
 	 * successive pages of a consistent WAL sequence.
 	 *
 	 * Of course this check should only be applied when advancing sequentially
-	 * across pages; therefore ReadRecord resets lastPageTLI to zero when
-	 * going to a random page.
+	 * across pages; therefore ReadRecord resets lastPageTLI and
+	 * lastSegmentTLI to zero when going to a random page.
+	 *
+	 * Sometimes we re-open a segment that's already been partially replayed.
+	 * In that case we cannot perform the normal TLI check: if there is a
+	 * timeline switch within the segment, the first page has a smaller TLI
+	 * than later pages following the timeline switch, and we might've read
+	 * them already. As a weaker test, we still check that it's not smaller
+	 * than the TLI we last saw at the beginning of a segment. Pass
+	 * segmentonly = true when re-validating the first page like that, and the
+	 * page you're actually interested in comes later.
 	 */
-	if (hdr->xlp_tli < lastPageTLI)
+	if (hdr->xlp_tli < (segmentonly ? lastSegmentTLI : lastPageTLI))
 	{
 		ereport(emode_for_corrupt_record(emode, recaddr),
 				(errmsg("out-of-sequence timeline ID %u (after %u) in log segment %s, offset %u",
-						hdr->xlp_tli, lastPageTLI,
+						hdr->xlp_tli,
+						segmentonly ? lastSegmentTLI : lastPageTLI,
 						XLogFileNameP(curFileTLI, readSegNo),
 						readOff)));
 		return false;
 	}
 	lastPageTLI = hdr->xlp_tli;
+	if (readOff == 0)
+		lastSegmentTLI = hdr->xlp_tli;
+
 	return true;
 }
 
@@ -9366,7 +9381,7 @@ retry:
 							fname, readOff)));
 			goto next_record_is_invalid;
 		}
-		if (!ValidXLogPageHeader((XLogPageHeader) readBuf, emode))
+		if (!ValidXLogPageHeader((XLogPageHeader) readBuf, emode, true))
 			goto next_record_is_invalid;
 	}
 
@@ -9392,7 +9407,7 @@ retry:
 				fname, readOff)));
 		goto next_record_is_invalid;
 	}
-	if (!ValidXLogPageHeader((XLogPageHeader) readBuf, emode))
+	if (!ValidXLogPageHeader((XLogPageHeader) readBuf, emode, false))
 		goto next_record_is_invalid;
 
 	readFileHeaderValidated = true;