Re: poor execution plan because column dependence - Mailing list pgsql-performance

From Tom Lane
Subject Re: poor execution plan because column dependence
Date
Msg-id 13172.1302790244@sss.pgh.pa.us
Whole thread Raw
In response to Re: poor execution plan because column dependence  (Václav Ovsík <vaclav.ovsik@i.cz>)
Responses Re: poor execution plan because column dependence
List pgsql-performance
=?iso-8859-1?Q?V=E1clav_Ovs=EDk?= <vaclav.ovsik@i.cz> writes:
> I'm not certain about your sentence touching int4eq() and index. The
> execution plan as show in my previous mail contains information about
> using index tickets5:

>                ->  Index Scan using tickets5 on tickets main  (cost=0.00..4.38 rows=1 width=162) (actual
time=0.006..0.006rows=0 loops=15593) 
>                      Index Cond: (main.id = transactions_1.objectid)
>                      Filter: (((main.status)::text <> 'deleted'::text) AND (main.lastupdated > '2008-12-31
23:00:00'::timestampwithout time zone) AND (main.created > '2005-12-31 23:00:00'::timestamp without time zone) AND
int4eq(main.effectiveid,main.id) AND (main.queue = 15) AND ((main.type)::text = 'ticket'::text) AND
((main.status)::text= 'resolved'::text)) 

> That means tickets5 index was used for int4eq(main.effectiveid, main.id).
> Is it right? Or am I something missing?

No, the clause that's being used with the index is
    main.id = transactions_1.objectid
The "filter condition" is just along for the ride --- it doesn't matter
what sort of expressions are in there, so long as they only use
variables available at this point in the plan.  But if you had coded
that clause as
    int4eq(main.id, transactions_1.objectid)
it would have been unable to create this plan at all.

            regards, tom lane

pgsql-performance by date:

Previous
From: Cédric Villemain
Date:
Subject: Re: Performance
Next
From: Scott Carey
Date:
Subject: Re: Linux: more cores = less concurrency.