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Cache eval cost of qualification expressions in RestrictInfo nodes to

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avoid repeated evaluations in cost_qual_eval().  This turns out to save
a useful fraction of planning time.  No change to external representation
of RestrictInfo --- although that node type doesn't appear in stored
rules anyway.
This commit is contained in:
Tom Lane
2000-12-12 23:33:34 +00:00
parent 77c443f8cd
commit 17b843d677
7 changed files with 54 additions and 24 deletions
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46
src/backend/optimizer/path/costsize.c
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@@ -42,7 +42,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.64 2000/10/05 19:48:26 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.65 2000/12/12 23:33:33 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -672,8 +672,38 @@ Cost
cost_qual_eval(List *quals)
{
Cost total = 0;
List *l;
cost_qual_eval_walker((Node *) quals, &total);
/* We don't charge any cost for the implicit ANDing at top level ... */
foreach(l, quals)
{
Node *qual = (Node *) lfirst(l);
/*
* RestrictInfo nodes contain an eval_cost field reserved for this
* routine's use, so that it's not necessary to evaluate the qual
* clause's cost more than once. If the clause's cost hasn't been
* computed yet, the field will contain -1.
*/
if (qual && IsA(qual, RestrictInfo))
{
RestrictInfo *restrictinfo = (RestrictInfo *) qual;
if (restrictinfo->eval_cost < 0)
{
restrictinfo->eval_cost = 0;
cost_qual_eval_walker((Node *) restrictinfo->clause,
&restrictinfo->eval_cost);
}
total += restrictinfo->eval_cost;
}
else
{
/* If it's a bare expression, must always do it the hard way */
cost_qual_eval_walker(qual, &total);
}
}
return total;
}
@@ -748,18 +778,6 @@ cost_qual_eval_walker(Node *node, Cost *total)
}
/* fall through to examine args of Expr node */
}
/*
* expression_tree_walker doesn't know what to do with RestrictInfo
* nodes, but we just want to recurse through them.
*/
if (IsA(node, RestrictInfo))
{
RestrictInfo *restrictinfo = (RestrictInfo *) node;
return cost_qual_eval_walker((Node *) restrictinfo->clause, total);
}
/* Otherwise, recurse. */
return expression_tree_walker(node, cost_qual_eval_walker,
(void *) total);
}