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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Merlin Moncure <mmoncure@gmail.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: join to view over custom aggregate seems like it should be faster
Date: Tue, 10 Apr 2007 14:21:24 -0400
Message-ID: <28253.1176229284@sss.pgh.pa.us> (raw)
In-Reply-To: <b42b73150704101053x297e5cb3kfe81b8979dad3002@mail.gmail.com>
References: <b42b73150704091205o668a084y1693520c974f3c6b@mail.gmail.com>
	<10651.1176152866@sss.pgh.pa.us>
	<b42b73150704091436g7fd1f903q1209218fc5eee88d@mail.gmail.com>
	<b42b73150704100559n3ccb9d89p1767a0fa94324375@mail.gmail.com>
	<27416.1176224586@sss.pgh.pa.us>
	<b42b73150704101053x297e5cb3kfe81b8979dad3002@mail.gmail.com>

"Merlin Moncure" <mmoncure@gmail.com> writes:
> right, i see that it's actually the 'group by' that does it:
> select a, b from foo join (select a, b from bar group by a,b) q using (a,b);
> is enough to keep it from using the index on a,b from bar.  thats too bad...

Some day it'd be nice to be able to reorder grouping/aggregation steps
relative to joins, the way we can now reorder outer joins.  Don't hold
your breath though ... I think it'll take some pretty major surgery on
the planner.

			regards, tom lane

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