Message-ID: <4EFDE57D.6090303@mejor.pl>
Date: Fri, 30 Dec 2011 17:23:25 +0100
From: =?UTF-8?B?TWFyY2luIE1pcm9zxYJhdw==?= <marcin@mejor.pl>
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To: pgsql-performance@postgresql.org
Subject: Re: partitioned table: differents plans, slow on some situations
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W dniu 30.12.2011 17:01, Matteo Sgalaberni pisze:
> Hi,

Hello,

> I have a two tables that are partitioned by month.
> 
> I have different results for the same query (query A/query B), the only thing that differ from A and B is the customer id.

Not only:

> Query A:
> 
> SELECT sms.id AS id_sms
>                             
>                       FROM
>                        sms_messaggio AS sms,
>                        sms_messaggio_dlr AS dlr
>                       WHERE sms.id = dlr.id_sms_messaggio
>                         AND sms.timestamp_todeliver >= '1/3/2010'::timestamp
>                         AND sms.timestamp_todeliver < '30/4/2010'::timestamp
>                         AND dlr.timestamp_todeliver >= '1/3/2010'::timestamp
>                         AND dlr.timestamp_todeliver < '30/4/2010'::timestamp
>                          AND sms.id_cliente = '13'
>                       ORDER BY dlr.timestamp_todeliver DESC LIMIT 50;
                                                       ^^^^^^^

> Query B:
> EXPLAIN  ANALYZE SELECT sms.id AS id_sms,
>                              dlr.msisdn,
>                              to_char(dlr.timestamp_stato,'DD/MM/YYYY HH24:MI:SS') AS timestamp_stato,
>                              dlr.stato,
>                              dlr.id AS id_dlr,
>                              dlr.numero_pdu,
>                              dlr.costo_cli
>                       FROM
>                        sms_messaggio AS sms,
>                        sms_messaggio_dlr AS dlr
>                       WHERE sms.id = dlr.id_sms_messaggio
>                         AND sms.timestamp_todeliver >= '1/3/2010'::timestamp
>                         AND sms.timestamp_todeliver < '30/4/2010'::timestamp
>                         AND dlr.timestamp_todeliver >= '1/3/2010'::timestamp
>                         AND dlr.timestamp_todeliver < '30/4/2010'::timestamp
>                          AND sms.id_cliente = '7'
>                       ORDER BY dlr.timestamp_todeliver ASC LIMIT 50;
                                                        ^^^^^
> I'm using pg 9.1
> 
> Can someone explain me why the planner do this?

Those queries are diffrent.
Regards.