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Re: declare/fetch problem with pgpool 2.2.3; Postgres 8.4; ODBC

From: Hiroshi Inoue <inoue(at)tpf(dot)co(dot)jp>
To: Andreas Gaab <A(dot)Gaab(at)scanlab(dot)de>
Cc: "'pgsql-odbc(at)postgresql(dot)org'" <pgsql-odbc(at)postgresql(dot)org>
Subject: Re: declare/fetch problem with pgpool 2.2.3; Postgres 8.4; ODBC
Date: 2009-11-22 00:21:16
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-odbc
Andreas Gaab wrote:
>> -----Urspr√ľngliche Nachricht-----
>> Von: Hiroshi Inoue [mailto:inoue(at)tpf(dot)co(dot)jp] 
>> Gesendet: Donnerstag, 19. November 2009 23:12
>> An: Andreas Gaab
>> Cc: 'pgsql-odbc(at)postgresql(dot)org'
>> Betreff: Re: [ODBC] declare/fetch problem with pgpool 2.2.3; Postgres 8.4; ODBC
>> Hi Andreas,
>> Andreas Gaab wrote:
>>> I encountered a problem using pgpool with two identical postgres 8.4 
>>> servers as  backends.>  
>>> Activating the odbc-setting declare/fetch, our application creates an 
>>> data mismatch error.  
>>> As far as I can track down the problem, it is caused because the cursors 
>>> are defined after an BEGIN, thus with load balancing disabled, but are 
>>> CLOSED after the COMMIT, thus are only closed on one server. This leads 
>>> to data inconsistency for the next query DECLARING an cursor.
>> Unfortunately I'm not familiar with pgpool.
>> Are DECLARE, FETCH and CLOSE regarded as members of SELECT family ?
>> If so, I'm suspicios if it's appropriate.
>> I would ask pgpool guys about it.
>> regards,
>> Hiroshi Inoue
> Hi Hiroshi,
> DECLARE, FETCH and CLOSE are probably regarded as members of the SELECT family and thus are load balanced. The problem arises, because the cursors are defined inside BEGIN; ... COMMIT; , and thus are send to all backends, but are CLOSEd after the transaction, and thus load balanced, which leaves on cursor defined on one backend.
> The transaction block and handling of cursor is done by the odbc, isn't it?

Hi Andreas,
I told pgpool guys this issue at JPUGCon Yesterday.
I would get a reply in a few days.

Hiroshi Inoue

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