Re: Rowcounts marked by create_foreignscan_path()

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Rowcounts marked by create_foreignscan_path()
Date: 2014-02-18 03:03:20
Message-ID: 12798.1392692600@sss.pgh.pa.us
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Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> writes:
> Why does create_foreignscan_path() not set the rowcounts based on
> ParamPathInfo when the path is a parameterized path?

The calling FDW is supposed to do that; note the header comment.
I'm not sure that it'd be an improvement to change the API spec
to be "create_foreignscan_path has no intelligence, except that
sometimes it will decide to override your rows estimate anyway;
nonetheless, it takes your cost estimate as gospel".

regards, tom lane

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