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Clean up handling of variable-free qual clauses. System now does the

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right thing with variable-free clauses that contain noncachable functions,
such as 'WHERE random() < 0.5' --- these are evaluated once per
potential output tuple.  Expressions that contain only Params are
now candidates to be indexscan quals --- for example, 'var = ($1 + 1)'
can now be indexed.  Cope with RelabelType nodes atop potential indexscan
variables --- this oversight prevents 7.0.* from recognizing some
potentially indexscanable situations.
This commit is contained in:
Tom Lane
2000-08-13 02:50:35 +00:00
parent 766fb7f707
commit 37168b8da4
15 changed files with 410 additions and 177 deletions
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22
src/backend/optimizer/plan/planmain.c
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@@ -14,7 +14,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.57 2000/07/27 04:51:04 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.58 2000/08/13 02:50:07 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -78,7 +78,8 @@ query_planner(Query *root,
List *qual,
double tuple_fraction)
{
List *constant_qual = NIL;
List *noncachable_qual;
List *constant_qual;
List *var_only_tlist;
Plan *subplan;
@@ -106,9 +107,14 @@ query_planner(Query *root,
* have been optimized away by eval_const_expressions(). What we're
* mostly interested in here is quals that depend only on outer-level
* vars, although if the qual reduces to "WHERE FALSE" this path will
* also be taken.
* also be taken. We also need a special case for quals that contain
* noncachable functions but no vars, such as "WHERE random() < 0.5".
* These cannot be treated as normal restriction or join quals, but
* they're not constants either. Instead, attach them to the qpqual
* of the top-level plan, so that they get evaluated once per potential
* output tuple.
*/
qual = pull_constant_clauses(qual, &constant_qual);
qual = pull_constant_clauses(qual, &noncachable_qual, &constant_qual);
/*
* Create a target list that consists solely of (resdom var) target
@@ -128,6 +134,12 @@ query_planner(Query *root,
*/
subplan = subplanner(root, var_only_tlist, qual, tuple_fraction);
/*
* Handle the noncachable quals.
*/
if (noncachable_qual)
subplan->qual = nconc(subplan->qual, noncachable_qual);
/*
* Build a result node to control the plan if we have constant quals.
*/
@@ -163,7 +175,7 @@ query_planner(Query *root,
* for processing a single level of attributes.
*
* flat_tlist is the flattened target list
* qual is the qualification to be satisfied
* qual is the qualification to be satisfied (restrict and join quals only)
* tuple_fraction is the fraction of tuples we expect will be retrieved
*
* See query_planner() comments about the interpretation of tuple_fraction.