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Re: simple join uses indexes, very slow

From: "Steinar H(dot) Gunderson" <sgunderson(at)bigfoot(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: simple join uses indexes, very slow
Date: 2006-03-28 16:29:08
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On Tue, Mar 28, 2006 at 10:18:25AM -0600, Dave Dutcher wrote:
>>     "parameters_idx" btree (run, opset_num, step_num, opset,
> opset_ver,
>> step, step_ver, name, split, wafers)
>>     "parameters_opset_idx" btree (opset, step, name)
>>     "parameters_step_idx" btree (step, name)
> Have you tried creating some different indexes on parameters?  I don't
> know if it should matter or not, but I would try some indexes like:
> (run, opset_num) //Without all the other columns
> (opset_num, run) //Backwards
> (opset_num)

An index on (A,B,C) can be used for a query on (A,B) or (A), so it doesn't
really matter. It isn't usable for a query on (B), (C) or (B,C), though. (The
index rows will get bigger, of course, so you'll need more I/O if you want to
scan large parts of it, but I guess that's beside the point.)

/* Steinar */

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