Re: poor execution plan because column dependence

=?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