To: josh@agliodbs.com
Cc: pgsql-sql@postgresql.org
Subject: Re: count(*), EXISTS, indexes
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From: Itai Zukerman <zukerman@math-hat.com>
Date: Fri, 11 Apr 2003 18:02:37 -0400
In-Reply-To: <200304111442.48107.josh@agliodbs.com> (Josh Berkus's message
	of "Fri, 11 Apr 2003 14:42:48 -0700")
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>>   # explain select sum(weight) from rprofile rp where exists (select 1 from 
> rcount_prof rcp where rcp.profile ~<= rp.profile and ~rcp.psig ~<= rp.psig 
> and rcp.filter='{734,1944}');
>
> I'm not familiar with the "~" that you have in the query.  What are those for?

They are my own operators and functions.  profile is a integer array
and the ~'s are subset operators.  psig is a bit signature, "~" is
complement, and the ~ operators again are subset operators.

> Do you have an index on rcp.profile, rcp.psig, rcp.filter?

Yes, yes, and yes.  ATM, though, there are only about 50 rows in
rcount_prof.  The vast majority of time is spent scanning the
600,000-row rprofile table.

-- 
Itai Zukerman  <http://www.math-hat.com/~zukerman/>