From: | Greg Stark <gsstark(at)mit(dot)edu> |
---|---|
To: | Brian Ceccarelli <ceccareb(at)talusmusic(dot)com> |
Cc: | pgsql-bugs(at)postgresql(dot)org |
Subject: | Re: BUG #5000: Optimizer does not use function-based index for an order by |
Date: | 2009-08-20 21:54:56 |
Message-ID: | 407d949e0908201454v1a9e19fate65b1c5d6c3df661@mail.gmail.com |
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Thread: | |
Lists: | pgsql-bugs |
> Description: Optimizer does not use function-based index for an order
> by
> Details:
>
> Subject line says it all.
The optimizer makes an educated guess about whether to use indexes or
not. Without more information it's impossible to second-guess it.
You might want to ask on pgsql-general for advice on whether it's
making a good choice and how to influence it. But you'll have to
provide more information such as the actual schema and explain plans
of with and without enable_sort or enable_seqscan disabled.
Also 8.2 came out two years ago, if you're just starting with Postgres
you might as well use 8.4 which has features which will make this
easier -- including the ability to tell the planner how expensive your
function is.
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