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Fix up LIMIT/OFFSET planning so that we cope with non-constant LIMIT

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or OFFSET clauses by using estimate_expression_value().  The main advantage
of this is that if the expression is a Param and we have a value for the
Param, we'll use that value rather than defaulting.  Also, fix some
thinkos in the logic for combining LIMIT/OFFSET with an externally
supplied tuple fraction (this covers cases like EXISTS(...LIMIT...)).
And make sure the results of all this are shown by EXPLAIN.  Per a
gripe from Merlin Moncure.
This commit is contained in:
Tom Lane
2005-08-18 17:51:12 +00:00
parent 96f63aebc8
commit dfdf07aab1
4 changed files with 204 additions and 104 deletions
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5
src/include/optimizer/planmain.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/optimizer/planmain.h,v 1.86 2005/06/05 22:32:58 tgl Exp $
* $PostgreSQL: pgsql/src/include/optimizer/planmain.h,v 1.87 2005/08/18 17:51:12 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -54,7 +54,8 @@ extern Group *make_group(PlannerInfo *root, List *tlist, List *qual,
extern Material *make_material(Plan *lefttree);
extern Plan *materialize_finished_plan(Plan *subplan);
extern Unique *make_unique(Plan *lefttree, List *distinctList);
extern Limit *make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount);
extern Limit *make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount,
int offset_est, int count_est);
extern SetOp *make_setop(SetOpCmd cmd, Plan *lefttree,
List *distinctList, AttrNumber flagColIdx);
extern Result *make_result(List *tlist, Node *resconstantqual, Plan *subplan);