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Re: Very slow queries

From: Sidar López Cruz <sidarlopez(at)hotmail(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Cc: chad(dot)wagner(at)gmail(dot)com
Subject: Re: Very slow queries
Date: 2007-01-31 14:19:41
Message-ID: BAY132-F1209F4D7B2DF92759FA080CEA50@phx.gbl (view raw or flat)
Thread:
Lists: pgsql-performance


>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: [PERFORM] Very slow queries
>Date: Tue, 30 Jan 2007 17:37:17 -0500
>
>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?

Rows:
Patronos: 1032980
Salarios:  28480200

>
>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?

No, this is not cascade delete case because I need to delete from salarios 
not from patronos.


>http://www.postgresql.org/docs/8.2/static/ddl-constraints.html
>
>
>--
>Chad
>http://www.postgresqlforums.com/

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

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