From: Jesper Krogh <jesper@krogh.cc>
To: Craig Ringer <craig@2ndquadrant.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Slow query-plan generation (fast query) PG 9.2
Date: Tue, 03 Sep 2013 21:34:10 +0200
Message-ID: <522639B2.4010309@krogh.cc> (raw)
In-Reply-To: <522593FC.3010302@2ndquadrant.com>
References: <e9ed24069c06d8b504fbef3e28df52d7.squirrel@shrek.krogh.cc>
<522593FC.3010302@2ndquadrant.com>
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On 03/09/13 09:47, Craig Ringer wrote:
> On 09/03/2013 03:46 PM, jesper@krogh.cc wrote:
>> Hi.
>>
>> I have a strange situation where generating the query plan takes 6s+ and
>> executing it takes very little time.
> How do you determine that it's planning time at fault here?
Not that I'm sure, but the timing I send were only for "explain" not
"explain analyze". The database is constantly updating and at the moment
i cannot reproduce it any more. But at the time I picked the numbers it
were very reproducible.. (tried 10+ times over 15 minutes).
Please take separate timing for: PREPARE testq AS select table.id
from db.table left join db.tablepro on db.id = tablepro.table_id
where table.fts @@ to_tsquery('english','q12345') ; and then:
EXPLAIN ANALYZE EXECUTE testq;
I'll try to do that if i see the problem re-occour. I'm just very
interested in what explain then does if it is not only the time for the
query plan. When I did try the "PREPARE / EXECUTE" dance as you
described .. i didnt see the prepare state take time, which seems to be
consistent with that the planning time is in the EXECUTE step according
to the documentation.
--
Jesper
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To: pgsql-performance@postgresql.org
Cc: jesper@krogh.cc, craig@2ndquadrant.com
Subject: Re: Slow query-plan generation (fast query) PG 9.2
In-Reply-To: <522639B2.4010309@krogh.cc>
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