Re: Poor performance problem with Materialize, 8.4 -> 9.1 (enable_material)

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От Claudio Freire
Тема Re: Poor performance problem with Materialize, 8.4 -> 9.1 (enable_material)
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Msg-id CAGTBQpbeJo1+UwT_fNA1KJ1sTxeJfLZOzP0gti2MNw-aAysBsQ@mail.gmail.com
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Ответ на Poor performance problem with Materialize, 8.4 -> 9.1 (enable_material)  (Eoghan Murray <eoghan@qatano.com>)
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On Fri, Jul 13, 2012 at 3:22 PM, Eoghan Murray <eoghan@qatano.com> wrote:
> This is with `enable_material=off`, with `enable_material=on` it also
> doesn't go for the Merge Join, but the Materialize step pushes it up to over
> 7,000ms.

I think this one could stem from what Tom observed, that the rowcount
estimate is way off.

It usually helps a great deal if you can get PG to estimate correctly,
be it by doing analyze, incrementing statistics or simply formulating
your query in a way that's friendlier for PG's estimator.

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