From 931b6db39b808608a3c80c42b47e3cbcda9e66db Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Mon, 1 Nov 2010 09:56:45 +0200
Subject: [PATCH] Fix corner-case bug in tracking of latest removed WAL segment
during streaming replication. We used log/seg 0/0 to indicate that no WAL
segments have been removed since startup, but 0/0 is a valid value for the
very first WAL segment after initdb. To make that disambiguous, store (latest
removed WAL segment + 1) in the global variable.
Per report from Matt Chesler, also reproduced by Greg Smith.
---
src/backend/access/transam/xlog.c | 9 ++++++---
src/backend/replication/walsender.c | 2 +-
2 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 6f1fedd1140..97dced113a9 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -364,7 +364,7 @@ typedef struct XLogCtlData
uint32 ckptXidEpoch; /* nextXID & epoch of latest checkpoint */
TransactionId ckptXid;
XLogRecPtr asyncXactLSN; /* LSN of newest async commit/abort */
- uint32 lastRemovedLog; /* latest removed/recycled XLOG segment */
+ uint32 lastRemovedLog; /* latest removed/recycled XLOG segment + 1 */
uint32 lastRemovedSeg;
/* Protected by WALWriteLock: */
@@ -3218,8 +3218,10 @@ PreallocXlogFiles(XLogRecPtr endptr)
}
/*
- * Get the log/seg of the latest removed or recycled WAL segment.
- * Returns 0 if no WAL segments have been removed since startup.
+ * Get the log/seg of the first WAL segment that has not been removed or
+ * recycled. In other words, the log/seg of the last removed/recycled WAL
+ * segment + 1.
+ * Returns 0/0 if no WAL segments have been removed since startup.
*/
void
XLogGetLastRemoved(uint32 *log, uint32 *seg)
@@ -3247,6 +3249,7 @@ UpdateLastRemovedPtr(char *filename)
seg;
XLogFromFileName(filename, &tli, &log, &seg);
+ NextLogSeg(log, seg);
SpinLockAcquire(&xlogctl->info_lck);
if (log > xlogctl->lastRemovedLog ||
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index d2b9e5c5f9a..3dc794ccc9c 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -654,7 +654,7 @@ XLogRead(char *buf, XLogRecPtr recptr, Size nbytes)
XLogGetLastRemoved(&lastRemovedLog, &lastRemovedSeg);
XLByteToSeg(startRecPtr, log, seg);
if (log < lastRemovedLog ||
- (log == lastRemovedLog && seg <= lastRemovedSeg))
+ (log == lastRemovedLog && seg < lastRemovedSeg))
{
char filename[MAXFNAMELEN];
--
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