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Bootstrap WAL to begin at segment logid=0 logseg=1 (000000010000000000000001)

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rather than 0/0, so that we can safely use 0/0 as an invalid value. This is a
more future-proof fix for the corner-case bug in streaming replication that
was fixed yesterday. We had a similar corner-case bug with log/seg 0/0 back in
February as well. Avoiding 0/0 as a valid value should prevent bugs like that
in the future. Per Tom Lane's idea.

Back-patch to 9.0. Since this only affects bootstrapping, it makes no
difference to existing installations. We don't need to worry about the
bug in existing installations, because if you've managed to get past the
initial base backup already, you won't hit the bug in the future either.
This commit is contained in:
Heikki Linnakangas 2010-11-02 11:23:43 +02:00
parent 0811ff2063
commit 8c843fff2d
2 changed files with 13 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
src/backend/access/transam/xlog.c
View File

@ -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 + 1 */
uint32 lastRemovedLog; /* latest removed/recycled XLOG segment */
uint32 lastRemovedSeg;
/* Protected by WALWriteLock: */
@ -3218,9 +3218,7 @@ PreallocXlogFiles(XLogRecPtr endptr)
}
/*
* 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.
* Get the log/seg of the latest removed or recycled WAL segment.
* Returns 0/0 if no WAL segments have been removed since startup.
*/
void
@ -3249,7 +3247,6 @@ UpdateLastRemovedPtr(char *filename)
seg;
XLogFromFileName(filename, &tli, &log, &seg);
NextLogSeg(log, seg);
SpinLockAcquire(&xlogctl->info_lck);
if (log > xlogctl->lastRemovedLog ||
@ -4903,9 +4900,15 @@ BootStrapXLOG(void)
page = (XLogPageHeader) TYPEALIGN(ALIGNOF_XLOG_BUFFER, buffer);
memset(page, 0, XLOG_BLCKSZ);
/* Set up information for the initial checkpoint record */
/*
* Set up information for the initial checkpoint record
*
* The initial checkpoint record is written to the beginning of the
* WAL segment with logid=0 logseg=1. The very first WAL segment, 0/0, is
* not used, so that we can use 0/0 to mean "before any valid WAL segment".
*/
checkPoint.redo.xlogid = 0;
checkPoint.redo.xrecoff = SizeOfXLogLongPHD;
checkPoint.redo.xrecoff = XLogSegSize + SizeOfXLogLongPHD;
checkPoint.ThisTimeLineID = ThisTimeLineID;
checkPoint.nextXidEpoch = 0;
checkPoint.nextXid = FirstNormalTransactionId;
@ -4928,7 +4931,7 @@ BootStrapXLOG(void)
page->xlp_info = XLP_LONG_HEADER;
page->xlp_tli = ThisTimeLineID;
page->xlp_pageaddr.xlogid = 0;
page->xlp_pageaddr.xrecoff = 0;
page->xlp_pageaddr.xrecoff = XLogSegSize;
longpage = (XLogLongPageHeader) page;
longpage->xlp_sysid = sysidentifier;
longpage->xlp_seg_size = XLogSegSize;
@ -4954,7 +4957,7 @@ BootStrapXLOG(void)
/* Create first XLOG segment file */
use_existent = false;
openLogFile = XLogFileInit(0, 0, &use_existent, false);
openLogFile = XLogFileInit(0, 1, &use_existent, false);
/* Write the first page with the initial record */
errno = 0;

2
src/backend/replication/walsender.c
View File

@ -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];