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Simple constraint exclusion. For now, only child tables of inheritance

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scans are candidates for exclusion; this should be fixed eventually.
Simon Riggs, with some help from Tom Lane.
This commit is contained in:
Tom Lane
2005-07-23 21:05:48 +00:00
parent 9af9d674c6
commit d007a95055
14 changed files with 621 additions and 105 deletions
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40
src/backend/optimizer/path/allpaths.c
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@ -8,13 +8,14 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.134 2005/06/10 03:32:21 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.135 2005/07/23 21:05:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "nodes/makefuncs.h"
#ifdef OPTIMIZER_DEBUG
#include "nodes/print.h"
#endif
@ -25,6 +26,7 @@
#include "optimizer/paths.h"
#include "optimizer/plancat.h"
#include "optimizer/planner.h"
#include "optimizer/predtest.h"
#include "optimizer/prep.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
@ -34,6 +36,7 @@
/* These parameters are set by GUC */
bool enable_constraint_exclusion = false;
bool enable_geqo = false; /* just in case GUC doesn't set it */
int geqo_threshold;
@ -311,7 +314,37 @@ set_inherited_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
childOID);
/*
* Now compute child access paths, and save the cheapest.
* If we can prove we don't need to scan this child via constraint
* exclusion, just ignore it. (We have to have converted the
* baserestrictinfo Vars before we can make the test.)
*/
if (enable_constraint_exclusion)
{
List *constraint_pred;
constraint_pred = get_relation_constraints(childOID, childrel);
/*
* We do not currently enforce that CHECK constraints contain
* only immutable functions, so it's necessary to check here.
* We daren't draw conclusions from plan-time evaluation of
* non-immutable functions.
*/
if (!contain_mutable_functions((Node *) constraint_pred))
{
/*
* The constraints are effectively ANDed together, so we can
* just try to refute the entire collection at once. This may
* allow us to make proofs that would fail if we took them
* individually.
*/
if (predicate_refuted_by(constraint_pred,
childrel->baserestrictinfo))
continue;
}
}
/*
* Compute the child's access paths, and save the cheapest.
*/
set_plain_rel_pathlist(root, childrel, childrte);
@ -345,7 +378,8 @@ set_inherited_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
/*
* Finally, build Append path and install it as the only access path
* for the parent rel.
* for the parent rel. (Note: this is correct even if we have zero
* or one live subpath due to constraint exclusion.)
*/
add_path(rel, (Path *) create_append_path(rel, subpaths));