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Create hooks to let a loadable plugin monitor (or even replace) the planner

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and/or create plans for hypothetical situations; in particular, investigate
plans that would be generated using hypothetical indexes.  This is a
heavily-rewritten version of the hooks proposed by Gurjeet Singh for his
Index Advisor project.  In this formulation, the index advisor can be
entirely a loadable module instead of requiring a significant part to be
in the core backend, and plans can be generated for hypothetical indexes
without requiring the creation and rolling-back of system catalog entries.

The index advisor patch as-submitted is not compatible with these hooks,
but it needs significant work anyway due to other 8.2-to-8.3 planner
changes.  With these hooks in the core backend, development of the advisor
can proceed as a pgfoundry project.
This commit is contained in:
Tom Lane
2007-05-25 17:54:25 +00:00
parent ce5b24abed
commit 604ffd280b
9 changed files with 168 additions and 62 deletions
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26
src/backend/optimizer/plan/planner.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.219 2007/05/04 01:13:44 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.220 2007/05/25 17:54:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -42,6 +42,10 @@
#include "utils/syscache.h"
/* Hook for plugins to get control in planner() */
planner_hook_type planner_hook = NULL;
/* Expression kind codes for preprocess_expression */
#define EXPRKIND_QUAL 0
#define EXPRKIND_TARGET 1
@ -79,9 +83,29 @@ static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
*
* Query optimizer entry point
*
* To support loadable plugins that monitor or modify planner behavior,
* we provide a hook variable that lets a plugin get control before and
* after the standard planning process. The plugin would normally call
* standard_planner().
*
* Note to plugin authors: standard_planner() scribbles on its Query input,
* so you'd better copy that data structure if you want to plan more than once.
*
*****************************************************************************/
PlannedStmt *
planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
{
PlannedStmt *result;
if (planner_hook)
result = (*planner_hook) (parse, cursorOptions, boundParams);
else
result = standard_planner(parse, cursorOptions, boundParams);
return result;
}
PlannedStmt *
standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
{
PlannedStmt *result;
PlannerGlobal *glob;

13
src/backend/optimizer/util/plancat.c
View File

@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.134 2007/04/21 21:01:45 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.135 2007/05/25 17:54:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -40,6 +40,9 @@
/* GUC parameter */
bool constraint_exclusion = false;
/* Hook for plugins to get control in get_relation_info() */
get_relation_info_hook_type get_relation_info_hook = NULL;
static void estimate_rel_size(Relation rel, int32 *attr_widths,
BlockNumber *pages, double *tuples);
@ -279,6 +282,14 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
rel->indexlist = indexinfos;
heap_close(relation, NoLock);
/*
* Allow a plugin to editorialize on the info we obtained from the
* catalogs. Actions might include altering the assumed relation size,
* removing an index, or adding a hypothetical index to the indexlist.
*/
if (get_relation_info_hook)
(*get_relation_info_hook) (root, relationObjectId, inhparent, rel);
}
/*