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Re: Very slow queries

From: "Chad Wagner" <chad(dot)wagner(at)gmail(dot)com>
To: Sidar López Cruz <sidarlopez(at)hotmail(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Very slow queries
Date: 2007-01-30 22:37:17
Message-ID: 81961ff50701301437t60c5370bvdf165215cbeaeb25@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On 1/30/07, Sidar López Cruz <sidarlopez(at)hotmail(dot)com> wrote:
>
> query: Delete From ceroriesgo.salarios Where numero_patrono Not In (Select
> numero_patrono From ceroriesgo.patronos)
>
> Seq Scan on salarios  (cost=51021.78..298803854359.95 rows=14240077
> width=6)
>   Filter: (NOT (subplan))
>   SubPlan
>     ->  Materialize  (cost=51021.78..69422.58 rows=1032980 width=25)
>           ->  Seq Scan on patronos  (cost=0.00..41917.80 rows=1032980
> width=25)
>

How many rows exist in salarios, but not in patronos?  How many rows are
there in salarios?

What does the explain look like for:

delete
 from ceroriesgo.salarios s
where not exists (select 1
                            from ceroriesgo.patronos
                          where numero_patrono = s.numero_patrono);

Also, is this not a case for a foreign key with a cascade delete?

http://www.postgresql.org/docs/8.2/static/ddl-constraints.html


-- 
Chad
http://www.postgresqlforums.com/

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Subject: Re: Querying distinct values from a large table
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Subject: Re: Very slow queries

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