database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-28 23:42:10 +03:00
Code Activity

Add hooks to let plugins override the planner's lookups in pg_statistic.

Browse Source 
Simon Riggs, with some editorialization by me.
This commit is contained in:
Tom Lane
2008-09-28 19:51:40 +00:00
parent bc965e840a
commit 7b7df9f0b1
4 changed files with 109 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
src/backend/utils/cache/lsyscache.c vendored
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.159 2008/08/02 21:32:00 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.160 2008/09/28 19:51:40 tgl Exp $
*
* NOTES
* Eventually, the index information should go through here, too.
@ -35,6 +35,9 @@
#include "utils/lsyscache.h"
#include "utils/syscache.h"
/* Hook for plugins to get control in get_attavgwidth() */
get_attavgwidth_hook_type get_attavgwidth_hook = NULL;
/* ---------- AMOP CACHES ---------- */
@ -2492,20 +2495,30 @@ get_typmodout(Oid typid)
*
* Given the table and attribute number of a column, get the average
* width of entries in the column. Return zero if no data available.
*
* Calling a hook at this point looks somewhat strange, but is required
* because the optimizer calls this function without any other way for
* plug-ins to control the result.
*/
int32
get_attavgwidth(Oid relid, AttrNumber attnum)
{
HeapTuple tp;
int32 stawidth;
if (get_attavgwidth_hook)
{
stawidth = (*get_attavgwidth_hook) (relid, attnum);
if (stawidth > 0)
return stawidth;
}
tp = SearchSysCache(STATRELATT,
ObjectIdGetDatum(relid),
Int16GetDatum(attnum),
0, 0);
if (HeapTupleIsValid(tp))
{
int32 stawidth = ((Form_pg_statistic) GETSTRUCT(tp))->stawidth;
stawidth = ((Form_pg_statistic) GETSTRUCT(tp))->stawidth;
ReleaseSysCache(tp);
if (stawidth > 0)
return stawidth;
@ -2523,6 +2536,9 @@ get_attavgwidth(Oid relid, AttrNumber attnum)
* already-looked-up tuple in the pg_statistic cache. We do this since
* most callers will want to extract more than one value from the cache
* entry, and we don't want to repeat the cache lookup unnecessarily.
* Also, this API allows this routine to be used with statistics tuples
* that have been provided by a stats hook and didn't really come from
* pg_statistic.
*
* statstuple: pg_statistics tuple to be examined.
* atttype: type OID of attribute (can be InvalidOid if values == NULL).