Re: Problems with plan estimates in postgres_fdw

From: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Problems with plan estimates in postgres_fdw
Date: 2018-12-28 06:50:29
Message-ID: 5C25C7B5.2010802@lab.ntt.co.jp
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(2018/12/26 16:35), Etsuro Fujita wrote:
> Attached is an updated version of the patch. Other changes:

While self-reviewing the patch I noticed a thinko in the patch 0001 for
pushing down the final sort: I estimated the costs for that using
estimate_path_cost_size that was modified so that it factored the
limit_tuples limit (if any) into the costs, but I think that was wrong;
that should not factor that because the remote query corresponding to
the pushdown step won't have LIMIT. So I fixed that. Also, a new data
structure I added to include/nodes/relation.h (ie, OrderedPathExtraData)
is no longer needed, so I removed that. Attached is a new version of
the patch.

Best regards,
Etsuro Fujita

Attachment Content-Type Size
0001-postgres_fdw-Perform-UPPERREL_ORDERED-step-remotely-v2.patch text/x-patch 43.9 KB
0002-postgres_fdw-Perform-UPPERREL_FINAL-step-remotely-v2.patch text/x-patch 95.4 KB

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