Re: Query runs too long for indexed tables

From: Scott Marlowe <smarlowe(at)g2switchworks(dot)com>
To: Andrus <eetasoft(at)online(dot)ee>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Query runs too long for indexed tables
Date: 2006-04-04 19:48:48
Message-ID: 1144180128.32266.56.camel@state.g2switchworks.com
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On Tue, 2006-04-04 at 14:37, Andrus wrote:
> I have relatively small tables (toode and rid) in fast server.
> Both tables are indexed on toode field.
>
> Following query takes long time to run.
> toode field type is char(20). It is difficult to change this field type.
>
> Any idea how to speed up this query ?
>
> UPDATE firma1.rid SET toode=NULL
> WHERE toode IS NOT NULL AND
> toode NOT IN (SELECT TOODE FROM firma1.TOODE);
>
> Query returned successfully: 0 rows affected, 594813 ms execution time.
>
> explain window shows:
>
> Seq Scan on rid (cost=2581.07..20862553.77 rows=51848 width=1207)
> Filter: ((toode IS NOT NULL) AND (NOT (subplan)))
> SubPlan
> -> Materialize (cost=2581.07..2944.41 rows=14734 width=84)
> -> Seq Scan on toode (cost=0.00..2350.34 rows=14734 width=84)

Let me guess, you've updated it a lot and aren't familiar with Vacuum?

run a vacuum full on your database. schedule a vacuum (plain one) to
run every so often (hours or days are a good interval for most folks)

If that's NOT your problem, then please, let us know.

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