Re: performance regression in 9.2 CTE with SRF function

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От Pavel Stehule
Тема Re: performance regression in 9.2 CTE with SRF function
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Msg-id CAFj8pRA2e_CLb3ONkkrmHtiAdspSLtZCgdVNZGBhxmn8C_ArZw@mail.gmail.com
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Ответ на Re: performance regression in 9.2 CTE with SRF function  (Tom Lane <tgl@sss.pgh.pa.us>)
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2013/2/11 Tom Lane <tgl@sss.pgh.pa.us>:
> Pavel Stehule <pavel.stehule@gmail.com> writes:
>>> no, there is strange estimation
>>>
>>> SubPlan 2
>>> ->  CTE Scan on pl pl_1  (cost=0.00..468.59
>>> rows=89000 width=4) (actual time=0.023..8.379 rows=566 loops=1000)
>>> Output: foo(pl_1.a)
>
> Nothing strange about it.  89 rows out from the underlying CTE (which
> appears to be dead accurate) times 1000 for the SRF's expansion.
>
>> respective why estimation is unstrable
>
> It isn't --- you are looking at two different subplans there, one with
> a SRF in it and one without.

ok, I understand now

Thank you

Regards

Pavel

>
>                         regards, tom lane



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