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

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]))