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Add test to WAL replay to verify that xl_prev points back to the previous 

WAL record; this is necessary to be sure we recognize stale WAL records
when a WAL page was only partially written during a system crash.
This commit is contained in:
Tom Lane 2005-05-31 19:10:28 +00:00
parent 5b3625f1b7
commit a91fa39028
1 changed files with 34 additions and 3 deletions
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37
src/backend/access/transam/xlog.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.193 2005/05/20 14:53:25 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.194 2005/05/31 19:10:28 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -417,8 +417,8 @@ static char *readRecordBuf = NULL;
static uint32 readRecordBufSize = 0;
/* State information for XLOG reading */
static XLogRecPtr ReadRecPtr;
static XLogRecPtr EndRecPtr;
static XLogRecPtr ReadRecPtr; /* start of last record read */
static XLogRecPtr EndRecPtr; /* end+1 of last record read */
static XLogRecord *nextRecord = NULL;
static TimeLineID lastPageTLI = 0;
@ -2525,6 +2525,37 @@ got_record:;
record->xl_rmid, RecPtr->xlogid, RecPtr->xrecoff)));
goto next_record_is_invalid;
}
if (randAccess)
{
/*
* We can't exactly verify the prev-link, but surely it should be
* less than the record's own address.
*/
if (!XLByteLT(record->xl_prev, *RecPtr))
{
ereport(emode,
(errmsg("record with incorrect prev-link %X/%X at %X/%X",
record->xl_prev.xlogid, record->xl_prev.xrecoff,
RecPtr->xlogid, RecPtr->xrecoff)));
goto next_record_is_invalid;
}
}
else
{
/*
* Record's prev-link should exactly match our previous location.
* This check guards against torn WAL pages where a stale but
* valid-looking WAL record starts on a sector boundary.
*/
if (!XLByteEQ(record->xl_prev, ReadRecPtr))
{
ereport(emode,
(errmsg("record with incorrect prev-link %X/%X at %X/%X",
record->xl_prev.xlogid, record->xl_prev.xrecoff,
RecPtr->xlogid, RecPtr->xrecoff)));
goto next_record_is_invalid;
}
}
/*
* Compute total length of record including any appended backup