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Message-ID: <84fb38e30612161003gded26aalfcd3aa0a5176c75c@mail.gmail.com>
Date: Sat, 16 Dec 2006 12:03:38 -0600
From: tsuraan <tsuraan@gmail.com>
To: tsuraan <tsuraan@gmail.com>, pgsql-performance@postgresql.org
Subject: Re: Scaling concerns
In-Reply-To: <20061216173221.GA25410@uio.no>
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References: <84fb38e30612160926l609ec55cs352b2495289bae0c@mail.gmail.com>
	<20061216173221.GA25410@uio.no>

> Unqualified SELECT COUNT(*) FROM foo is one of the most expensive operations
> you can do on your system, since the visibility information has to be
> checked
> on disk for each row. Instead, try real queries on real data, and post here
> if some are too slow for you.

Ok, that's a bad example.  I'm learning :-)  Is insert ... select also
really expensive then?  I have a table loaded with message-id and path
information of currently-existing messages.  It has ~20 million rows.
Trying to do "INSERT INTO Messages(path, msgid) SELECT (path, msgid)
FROM tmpMessages" took a really long time before psql died with an
out-of-memory error.  Is there a more sane way to do a table copy, or
should I have just dropped all the indices from the Message table and
loaded into that?

Thanks!