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Re: Why does the number of rows are different in actual and estimated. - Mailing list pgsql-performance

From Claudio Freire
Subject Re: Why does the number of rows are different in actual and estimated.
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Msg-id CAGTBQpZfLp5C=qCR68UVOOrUXeSCoz_mJrkvM3+Svpahh+J4tg@mail.gmail.com
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In response to Re: Why does the number of rows are different in actual and estimated.  (AI Rumman <rummandba@gmail.com>)
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On Fri, Dec 14, 2012 at 4:01 PM, AI Rumman <rummandba@gmail.com> wrote:
> Does FK Constraint help to improve performance? Or it is only for
> maintaining data integrity?

I'm not entirely sure it's taken into account, I think it is, but a FK
would tell the planner that every non-null value will produce a row.
It seems to think there are a large portion of non-null values that
don't.

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