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Ensure that the remainder of the current pg_clog page is zeroed during

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startup, just to be sure that there's no leftover junk there.
This commit is contained in:
Tom Lane 2004-08-30 19:00:42 +00:00
parent 9cf4eaa00b
commit 64cb889106
1 changed files with 33 additions and 2 deletions
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35
src/backend/access/transam/clog.c
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@ -24,7 +24,7 @@
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group * Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.25 2004/08/29 05:06:40 momjian Exp $ * $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.26 2004/08/30 19:00:42 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -210,10 +210,41 @@ ZeroCLOGPage(int pageno, bool writeXlog)
void void
StartupCLOG(void) StartupCLOG(void)
{ {
TransactionId xid = ShmemVariableCache->nextXid;
int pageno = TransactionIdToPage(xid);
int byteno = TransactionIdToByte(xid);
int bshift = TransactionIdToBIndex(xid) * CLOG_BITS_PER_XACT;
int slotno;
char *byteptr;
LWLockAcquire(CLogControlLock, LW_EXCLUSIVE);
/* /*
* Initialize our idea of the latest page number. * Initialize our idea of the latest page number.
*/ */
ClogCtl->shared->latest_page_number = TransactionIdToPage(ShmemVariableCache->nextXid); ClogCtl->shared->latest_page_number = pageno;
/*
* Zero out the remainder of the current clog page. Under normal
* circumstances it should be zeroes already, but it seems at least
* theoretically possible that XLOG replay will have settled on a
* nextXID value that is less than the last XID actually used and
* marked by the previous database lifecycle (since subtransaction
* commit writes clog but makes no WAL entry). Let's just be safe.
* (We need not worry about pages beyond the current one, since those
* will be zeroed when first used.)
*/
slotno = SimpleLruReadPage(ClogCtl, pageno, xid);
byteptr = ClogCtl->shared->page_buffer[slotno] + byteno;
/* Zero so-far-unused positions in the current byte */
*byteptr &= (1 << bshift) - 1;
/* Zero the rest of the page */
MemSet(byteptr + 1, 0, BLCKSZ - byteno - 1);
ClogCtl->shared->page_status[slotno] = SLRU_PAGE_DIRTY;
LWLockRelease(CLogControlLock);
} }
/* /*