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Force VACUUM to recalculate oldestXmin even when we haven't changed our

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own database's datfrozenxid, if the current value is old enough to be
forcing autovacuums or warning messages.  This ensures that a bogus
value is replaced as soon as possible.  Per a comment from Heikki.
This commit is contained in:
Tom Lane 2009-09-01 04:46:49 +00:00
parent 14f445fccf
commit 794e3e81a0
3 changed files with 22 additions and 12 deletions
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23
src/backend/access/transam/varsup.c
View File

@ -6,7 +6,7 @@
* Copyright (c) 2000-2009, PostgreSQL Global Development Group
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/transam/varsup.c,v 1.85 2009/08/31 02:23:21 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/varsup.c,v 1.86 2009/09/01 04:46:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -372,32 +372,41 @@ SetTransactionIdLimit(TransactionId oldest_datfrozenxid, Oid oldest_datoid)
/*
* TransactionIdLimitIsValid -- is the shared XID wrap-limit data sane?
* ForceTransactionIdLimitUpdate -- does the XID wrap-limit data need updating?
*
* We primarily check whether oldestXidDB is valid. The cases we have in
* mind are that that database was dropped, or the field was reset to zero
* by pg_resetxlog. In either case we should force recalculation of the
* wrap limit. In future we might add some more sanity checks here.
* wrap limit. Also do it if oldestXid is old enough to be forcing
* autovacuums or other actions; this ensures we update our state as soon
* as possible once extra overhead is being incurred.
*/
bool
TransactionIdLimitIsValid(void)
ForceTransactionIdLimitUpdate(void)
{
TransactionId nextXid;
TransactionId xidVacLimit;
TransactionId oldestXid;
Oid oldestXidDB;
/* Locking is probably not really necessary, but let's be careful */
LWLockAcquire(XidGenLock, LW_SHARED);
nextXid = ShmemVariableCache->nextXid;
xidVacLimit = ShmemVariableCache->xidVacLimit;
oldestXid = ShmemVariableCache->oldestXid;
oldestXidDB = ShmemVariableCache->oldestXidDB;
LWLockRelease(XidGenLock);
if (!TransactionIdIsNormal(oldestXid))
return false; /* shouldn't happen, but just in case */
return true; /* shouldn't happen, but just in case */
if (TransactionIdFollowsOrEquals(nextXid, xidVacLimit) &&
TransactionIdIsValid(xidVacLimit))
return true; /* past VacLimit, don't delay updating */
if (!SearchSysCacheExists(DATABASEOID,
ObjectIdGetDatum(oldestXidDB),
0, 0, 0))
return false; /* could happen, per comment above */
return true;
return true; /* could happen, per comments above */
return false;
}

7
src/backend/commands/vacuum.c
View File

@ -13,7 +13,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.392 2009/09/01 02:54:51 alvherre Exp $
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.393 2009/09/01 04:46:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -893,9 +893,10 @@ vac_update_datfrozenxid(void)
/*
* If we were able to advance datfrozenxid, see if we can truncate pg_clog.
* Also do it if the shared XID-wrap-limit info is stale.
* Also do it if the shared XID-wrap-limit info is stale, since this
* action will update that too.
*/
if (dirty || !TransactionIdLimitIsValid())
if (dirty || ForceTransactionIdLimitUpdate())
vac_truncate_clog(newFrozenXid);
}

4
src/include/access/transam.h
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/transam.h,v 1.69 2009/08/31 02:23:23 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/transam.h,v 1.70 2009/09/01 04:46:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -156,7 +156,7 @@ extern TransactionId GetNewTransactionId(bool isSubXact);
extern TransactionId ReadNewTransactionId(void);
extern void SetTransactionIdLimit(TransactionId oldest_datfrozenxid,
Oid oldest_datoid);
extern bool TransactionIdLimitIsValid(void);
extern bool ForceTransactionIdLimitUpdate(void);
extern Oid GetNewObjectId(void);
#endif /* TRAMSAM_H */