Re: totally different plan when using partitions

From: Scara Maccai <m_lists(at)yahoo(dot)it>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: pgsql-general <pgsql-general(at)postgresql(dot)org>
Subject: Re: totally different plan when using partitions
Date: 2009-08-13 14:26:04
Message-ID: 885905.40826.qm@web24612.mail.ird.yahoo.com
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> Huh, clearly not the same query (you're using the partition
> directly in
> the first query) ...  Doing two changes at once is not
> helping your
> case.

Sorry, I don't understand... of course I used the partition directly in the first query... it's the difference between the two... what I don't like is that since the tables used are in fact the same, the plan shouldn't be that different.

My conclusion is that the planner thinks there could be some data in the "root" partition, even if that will always be empty.
What I would like is a way to tell Postgres "hey, don't even look at the root table. That's just a placeholder for the partitions. It will never contain any data" when I create the tables.

Otherwise the planner might get fooled by an empty table index scan in a loop (which is what happens here), thinking that that will take time.

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