Subject: Re: Query runs too long for indexed tables
From: Scott Marlowe <smarlowe@g2switchworks.com>
To: Andrus <eetasoft@online.ee>
Cc: pgsql-performance@postgresql.org
In-Reply-To: <e0ui0o$2v0m$2@news.hub.org>
References: <e0ui0o$2v0m$2@news.hub.org>
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Message-Id: <1144180128.32266.56.camel@state.g2switchworks.com>
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Date: Tue, 04 Apr 2006 14:48:48 -0500

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.