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Date: Wed, 17 Jan 2007 13:04:28 +0000
From: Richard Huxton <dev@archonet.com>
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To: Andrew Sullivan <ajs@crankycanuck.ca>
Cc: pgsql-sql@postgresql.org
Subject: Re: Postgresql & Oracle Heteregenous services - strange behaviour
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Andrew Sullivan wrote:
> On Wed, Jan 17, 2007 at 01:52:25PM +0100, Marcin St?pnicki wrote:
>> I see this in postgresql logs:
>>
>> [6210]   DEBUG:  query: select * from "zew_patients"
>> [6210]   DEBUG:  query:  SELECT "A1"."p_nr_pesel" FROM "zew_patients"
>> "A1" WHERE ("A1"."p_patient_id" = 19300)
>>
>> The point is, I don't why oh why the first select is issued (some cache?),
> 
> <speculation level="rank">
> 
> I bet it's getting the column list from the table or some such thing. 
> This is a lousy way to do it (the information_schema would be more
> correct, although maybe no faster).

That'd be my guess. And then it's not fetching any rows, expecting 
cursor-like behaviour. Of course we fetch all the rows before returning 
any results.

The real solution would be to add "LIMIT 0" or "LIMIT 1" to the 
column-finding query, but I doubt that's possible with the Oracle plugin.

Perhaps check if there's a "fetch N rows at a time" option for the ODBC 
setup that might help you.

-- 
   Richard Huxton
   Archonet Ltd