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Modify planner's implied-equality-deduction code so that when a set

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of known-equal expressions includes any constant expressions (including
Params from outer queries), we actively suppress any 'var = var'
clauses that are or could be deduced from the set, generating only the
deducible 'var = const' clauses instead.  The idea here is to push down
the restrictions implied by the equality set to base relations whenever
possible.  Once we have applied the 'var = const' clauses, the 'var = var'
clauses are redundant, and should be suppressed both to save work at
execution and to avoid double-counting restrictivity.
This commit is contained in:
Tom Lane
2003-01-24 03:58:44 +00:00
parent ef7422510e
commit f5e83662d0
12 changed files with 395 additions and 168 deletions
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10
src/backend/optimizer/path/indxpath.c
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@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.132 2003/01/20 18:54:49 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.133 2003/01/24 03:58:34 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1596,12 +1596,14 @@ make_innerjoin_index_path(Query *root,
* nconc the two lists; then we might have some restriction
* clauses appearing twice, which'd mislead
* restrictlist_selectivity into double-counting their
* selectivity.)
* selectivity. However, since RestrictInfo nodes aren't copied when
* linking them into different lists, it should be sufficient to use
* pointer comparison to remove duplicates.)
*/
pathnode->rows = rel->tuples *
restrictlist_selectivity(root,
set_union(rel->baserestrictinfo,
clausegroup),
set_ptrUnion(rel->baserestrictinfo,
clausegroup),
lfirsti(rel->relids));
/* Like costsize.c, force estimate to be at least one row */
if (pathnode->rows < 1.0)