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

From Tom Lane
Subject Re: Why does the number of rows are different in actual and estimated.
Date
Msg-id 4673.1355512925@sss.pgh.pa.us
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In response to Re: Why does the number of rows are different in actual and estimated.  ("Kevin Grittner" <kgrittn@mail.com>)
Responses Re: Why does the number of rows are different in actual and estimated.  (AI Rumman <rummandba@gmail.com>)
Re: Why does the number of rows are different in actual and estimated.  (Claudio Freire <klaussfreire@gmail.com>)
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"Kevin Grittner" <kgrittn@mail.com> writes:
> AI Rumman wrote:
>> Does FK Constraint help to improve performance? Or it is only
>> for maintaining data integrity?

> I'm not aware of any situation where adding a foreign key
> constraint would improve performance.

There's been talk of teaching the planner to use the existence of FK
constraints to improve plans, but I don't believe any such thing is
in the code today.

            regards, tom lane

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