Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3

From: Alvaro Herrera
Subject: Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3
Date: ,
Msg-id: 20070313130945.GB4490@alvh.no-ip.org
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In response to: Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>)
Responses: Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>)
List: pgsql-performance

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Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
 Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Michael Fuhr, )
  Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
   Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Richard Huxton, )
    Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
     Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  ("Dave Dutcher", )
      Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
       Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  ("Dave Dutcher", )
     Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Richard Huxton, )
   Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Alvaro Herrera, )
    Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
     Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Alvaro Herrera, )
      Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )
       Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (Tom Lane, )
        Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3  (<>, )

 wrote:
> I have attached the requested information.
>
> You will see that the query is quite messy and could be easily improved.
> Unfortunately, it came from a third party application and we do not have
> access to the source code.

There are only nested loops and hash joins, while the other plan seems
to be more elaborate -- I wonder if you have disabled bitmap scan, merge
joins, in 8.2?   Try a SHOW enable_mergejoin in psql.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.


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