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Reorder snapshot checks to save a couple comparisons in the common case,

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where the tuple's xmin or xmax is older than the snapshot xmin.  There
is no need to check it against snapshot xmax in that case.
This commit is contained in:
Tom Lane 2002-05-06 02:39:01 +00:00
parent 205b5c2f4b
commit 1cf693ab86
1 changed files with 8 additions and 6 deletions
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14
src/backend/utils/time/tqual.c
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@ -16,7 +16,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.49 2002/01/16 23:51:56 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.50 2002/05/06 02:39:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -707,13 +707,12 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot)
* By here, the inserting transaction has committed - have to check
* when...
*/
if (TransactionIdFollowsOrEquals(tuple->t_xmin, snapshot->xmax))
return false;
if (TransactionIdFollowsOrEquals(tuple->t_xmin, snapshot->xmin))
{
uint32 i;
if (TransactionIdFollowsOrEquals(tuple->t_xmin, snapshot->xmax))
return false;
for (i = 0; i < snapshot->xcnt; i++)
{
if (TransactionIdEquals(tuple->t_xmin, snapshot->xip[i]))
@ -748,12 +747,15 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot)
tuple->t_infomask |= HEAP_XMAX_COMMITTED;
}
if (TransactionIdFollowsOrEquals(tuple->t_xmax, snapshot->xmax))
return true;
/*
* OK, the deleting transaction committed too ... but when?
*/
if (TransactionIdFollowsOrEquals(tuple->t_xmax, snapshot->xmin))
{
uint32 i;
if (TransactionIdFollowsOrEquals(tuple->t_xmax, snapshot->xmax))
return true;
for (i = 0; i < snapshot->xcnt; i++)
{
if (TransactionIdEquals(tuple->t_xmax, snapshot->xip[i]))