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Teach nodeSort and nodeMaterial to optimize out unnecessary overhead

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when the passed-down eflags indicate they can.
Simon Riggs and Tom Lane
This commit is contained in:
Tom Lane
2006-02-28 05:48:44 +00:00
parent 2c0ef9777c
commit d2c555ee53
3 changed files with 80 additions and 31 deletions
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22
src/backend/executor/nodeSort.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeSort.c,v 1.54 2006/02/28 04:10:27 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeSort.c,v 1.55 2006/02/28 05:48:44 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -89,7 +89,7 @@ ExecSort(SortState *node)
plannode->sortOperators,
plannode->sortColIdx,
work_mem,
true /* randomAccess */ );
node->randomAccess);
node->tuplesortstate = (void *) tuplesortstate;
/*
@ -164,6 +164,15 @@ ExecInitSort(Sort *node, EState *estate, int eflags)
sortstate->ss.ps.plan = (Plan *) node;
sortstate->ss.ps.state = estate;
/*
* We must have random access to the sort output to do backward scan
* or mark/restore. We also prefer to materialize the sort output
* if we might be called on to rewind and replay it many times.
*/
sortstate->randomAccess = (eflags & (EXEC_FLAG_REWIND |
EXEC_FLAG_BACKWARD |
EXEC_FLAG_MARK)) != 0;
sortstate->sort_Done = false;
sortstate->tuplesortstate = NULL;
@ -308,11 +317,18 @@ ExecReScanSort(SortState *node, ExprContext *exprCtxt)
*
* Otherwise we can just rewind and rescan the sorted output.
*/
if (((PlanState *) node)->lefttree->chgParam != NULL)
if (((PlanState *) node)->lefttree->chgParam != NULL ||
!node->randomAccess)
{
node->sort_Done = false;
tuplesort_end((Tuplesortstate *) node->tuplesortstate);
node->tuplesortstate = NULL;
/*
* if chgParam of subnode is not null then plan will be re-scanned by
* first ExecProcNode.
*/
if (((PlanState *) node)->lefttree->chgParam == NULL)
ExecReScan(((PlanState *) node)->lefttree, exprCtxt);
}
else
tuplesort_rescan((Tuplesortstate *) node->tuplesortstate);