From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: performance regression in 9.2 CTE with SRF function |
Date: | 2013-02-11 19:49:51 |
Message-ID: | CAFj8pRA2e_CLb3ONkkrmHtiAdspSLtZCgdVNZGBhxmn8C_ArZw@mail.gmail.com |
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Lists: | pgsql-hackers |
2013/2/11 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)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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