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Tweak code so that pg_subtrans is never consulted for XIDs older than

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RecentXmin (== MyProc->xmin).  This ensures that it will be safe to
truncate pg_subtrans at RecentGlobalXmin, which should largely eliminate
any fear of bloat.  Along the way, eliminate SubTransXidsHaveCommonAncestor,
which isn't really needed and could not give a trustworthy result anyway
under the lookback restriction.
In an unrelated but nearby change, #ifdef out GetUndoRecPtr, which has
been dead code since 2001 and seems unlikely to ever be resurrected.
This commit is contained in:
Tom Lane
2004-08-22 02:41:58 +00:00
parent 37d937ea2c
commit f009c316ba
7 changed files with 40 additions and 56 deletions
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28
src/backend/access/transam/transam.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/transam/transam.c,v 1.57 2004/07/01 00:49:42 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/transam.c,v 1.58 2004/08/22 02:41:57 tgl Exp $
*
* NOTES
* This file contains the high level access-method interface to the
@ -22,6 +22,7 @@
#include "access/clog.h"
#include "access/subtrans.h"
#include "access/transam.h"
#include "utils/tqual.h"
/* ----------------
@ -199,11 +200,15 @@ TransactionIdDidCommit(TransactionId transactionId)
/*
* If it's marked subcommitted, we have to check the parent recursively.
* However, if it's older than RecentXmin, we can't look at pg_subtrans;
* instead assume that the parent crashed without cleaning up its children.
*/
if (xidstatus == TRANSACTION_STATUS_SUB_COMMITTED)
{
TransactionId parentXid;
if (TransactionIdPrecedes(transactionId, RecentXmin))
return false;
parentXid = SubTransGetParent(transactionId);
Assert(TransactionIdIsValid(parentXid));
return TransactionIdDidCommit(parentXid);
@ -243,24 +248,17 @@ TransactionIdDidAbort(TransactionId transactionId)
/*
* If it's marked subcommitted, we have to check the parent recursively.
*
* If we detect that the parent has aborted, update pg_clog to show the
* subtransaction as aborted. This is only needed when the parent
* crashed before either committing or aborting. We want to clean up
* pg_clog so future visitors don't need to make this check again.
* However, if it's older than RecentXmin, we can't look at pg_subtrans;
* instead assume that the parent crashed without cleaning up its children.
*/
if (xidstatus == TRANSACTION_STATUS_SUB_COMMITTED)
{
TransactionId parentXid;
bool parentAborted;
if (TransactionIdPrecedes(transactionId, RecentXmin))
return true;
parentXid = SubTransGetParent(transactionId);
parentAborted = TransactionIdDidAbort(parentXid);
if (parentAborted)
TransactionIdAbort(transactionId);
return parentAborted;
return TransactionIdDidAbort(parentXid);
}
/*