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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Dave Cramer <pg@fastcrypt.com>
cc: pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: performance regression with 9.2
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Comments: In-reply-to Dave Cramer <pg@fastcrypt.com>
	message dated "Mon, 12 Nov 2012 14:49:00 -0500"
Date: Thu, 15 Nov 2012 14:21:13 -0500
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Dave Cramer <pg@fastcrypt.com> writes:
> This query is a couple orders of magnitude slower the first result is
> 9.2.1, the second 9.1

Thanks for sending me the test case off-list.  I found the reason why
I'd not been able to reproduce the problem: the index you're hoping it
will use is declared

"note_sets_parent_id_idx" btree (parent_id) WHERE parent_id IS NOT NULL

Apparently 9.2 is less bright than 9.1 about when it can use a partial
index.  I'm not sure where I broke that, but will look.

			regards, tom lane