Message-ID: <422D9904.5010904@bigfoot.com>
Date: Tue, 08 Mar 2005 13:22:28 +0100
From: Gaetano Mendola <mendola@bigfoot.com>
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To: Richard Huxton <dev@archonet.com>
Cc: Gaetano Mendola <mendola@bigfoot.com>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: bad plan
References: <422D7F23.7000109@bigfoot.com> <422D8F0E.8000906@archonet.com>
In-Reply-To: <422D8F0E.8000906@archonet.com>
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Richard Huxton wrote:
> Gaetano Mendola wrote:
> 
>> running a 7.4.5 engine, I'm facing this bad plan:
>>
>> empdb=# explain analyze SELECT
>> name,url,descr,request_status,url_status,size_mb,estimated_start,request_time_stamp
>>
>> empdb-#                    FROM v_sc_user_request
>> empdb-#                    WHERE
>> empdb-#                         login = 'babinow1'
>> empdb-#                    LIMIT 10 ;
> 
> 
>>                      ->  Subquery Scan vsp  (cost=985.73..1016.53
>> rows=1103 width=12) (actual time=25.328..1668.754 rows=493 loops=31)
>>                            ->  Merge Join  (cost=985.73..1011.01
>> rows=1103 width=130) (actual time=25.321..1666.666 rows=493 loops=31)
>>                                  Merge Cond: ("outer".id_program =
>> "inner".id_program)
> 
> 
> The problem to address is in this subquery. That's a total of 31 x
> (1668.754 - 25.328) = 50seconds (about).
> 
> Since your query is so simple, I'm guessing v_sc_user_request is a view.
> Can you provide the definition?

Of course:


CREATE OR REPLACE VIEW v_sc_user_request AS
  SELECT
      *
  FROM
      v_sat_request vsr LEFT OUTER JOIN v_sc_packages vsp USING ( id_package )
  WHERE
      vsr.request_time > now() - '1 month'::interval AND
      vsr.expired = FALSE
  ORDER BY id_sat_request DESC
;


CREATE OR REPLACE VIEW v_sc_packages AS
  SELECT
     *
  FROM
      v_programs           vpr,
      v_packages           vpk,
      v_sequences          vs

  WHERE
     ------------ JOIN -------------
      vpr.id_program = vs.id_program AND
      vpk.id_package = vs.id_package AND
     -------------------------------
      vs.estimated_start IS NOT NULL
;

CREATE OR REPLACE VIEW v_sat_request AS
  SELECT
     *
  FROM
     sat_request sr,
     url         u,
     user_login  ul
  WHERE
     ---------------- JOIN ---------------------
     sr.id_url  = u.id_url AND
     sr.id_user = ul.id_user
     -------------------------------------------
;


that column expired was added since yesterday

Regards
Gaetano Mendola


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