database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-05 07:21:24 +03:00
Code Activity

Improve planner's estimation of the size of an append relation: rather than

Browse Source 
taking the maximum of any child rel's width, we should weight the widths
proportionally to the number of rows expected from each child.  In hindsight
this is obviously correct because row width is really a proxy for the total
physical size of the relation.  Per discussion with Scott Carey (bug #4264).
This commit is contained in:
Tom Lane
2008-06-27 03:56:55 +00:00
parent f95b5334a7
commit 2c2161a47d
2 changed files with 66 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
src/backend/optimizer/plan/createplan.c
View File

@ -10,13 +10,14 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.240 2008/04/17 21:22:14 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/createplan.c,v 1.241 2008/06/27 03:56:55 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <limits.h>
#include <math.h>
#include "access/skey.h"
#include "nodes/makefuncs.h"
@ -2312,6 +2313,7 @@ make_append(List *appendplans, bool isTarget, List *tlist)
{
Append *node = makeNode(Append);
Plan *plan = &node->plan;
double total_size;
ListCell *subnode;
/*
@ -2322,7 +2324,7 @@ make_append(List *appendplans, bool isTarget, List *tlist)
plan->startup_cost = 0;
plan->total_cost = 0;
plan->plan_rows = 0;
plan->plan_width = 0;
total_size = 0;
foreach(subnode, appendplans)
{
Plan *subplan = (Plan *) lfirst(subnode);
@ -2331,9 +2333,12 @@ make_append(List *appendplans, bool isTarget, List *tlist)
plan->startup_cost = subplan->startup_cost;
plan->total_cost += subplan->total_cost;
plan->plan_rows += subplan->plan_rows;
if (plan->plan_width < subplan->plan_width)
plan->plan_width = subplan->plan_width;
total_size += subplan->plan_width * subplan->plan_rows;
}
if (plan->plan_rows > 0)
plan->plan_width = rint(total_size / plan->plan_rows);
else
plan->plan_width = 0;
plan->targetlist = tlist;
plan->qual = NIL;