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Re: [PERFORM] Slow query: bitmap scan troubles

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PERFORM] Slow query: bitmap scan troubles
Date: 2013-01-14 16:45:01
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackerspgsql-performance
On Thu, Jan 10, 2013 at 8:07 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Comments?

I'm not sure I have anything intelligent to add to this conversation -
does that make me the wisest of all the Greeks? - but I do think it
worth mentioning that I have heard occasional reports within EDB of
the query planner refusing to use extremely large indexes no matter
how large a hammer was applied.  I have never been able to obtain
enough details to understand the parameters of the problem, let alone
reproduce it, but I thought it might be worth mentioning anyway in
case it's both real and related to the case at hand.  Basically I
guess that boils down to: it would be good to consider whether the
costing model is correct for an index of, say, 1TB.

Robert Haas
The Enterprise PostgreSQL Company

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