Re: Considering fractional paths in Append node

From: Andrei Lepikhov <lepihov(at)gmail(dot)com>
To: Nikita Malakhov <hukutoc(at)gmail(dot)com>, Andy Fan <zhihuifan1213(at)163(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, David Rowley <dgrowleyml(at)gmail(dot)com>
Subject: Re: Considering fractional paths in Append node
Date: 2024-12-06 08:13:00
Message-ID: 311bb2ba-07dd-448d-9e30-c4bdc1e57642@gmail.com
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On 12/6/24 13:48, Andrei Lepikhov wrote:
> On 11/2/24 01:18, Nikita Malakhov wrote:
>> I've corrected failing test and created a patch at Commitfest:
>> https://commitfest.postgresql.org/51/5361/ <https://
>> commitfest.postgresql.org/51/5361/>
> I have played around with this feature, which looks promising for such a
> tiny change. It provides a 'bottom boundary' recommendation for
> appending subpaths, participating in the 'fractional branch' of paths.
> As I see it works consistently with the plans, created for plain tables
> filled with similar data.
> According to the proposal to change SeqScan logic, IMO, Andy is right.
> But it is a separate improvement because it wouldn't work in the case of
> LIMIT 10 or 100, as the newly added regression tests demonstrate.
> I think this feature gives sensible profit for partitionwise paths.
> Pushing this knowledge into subpaths could help postgres_fdw to reduce
> network traffic.
>
See the attached patch: regression tests added; *_ext function removed -
I think we wouldn't back-patch it into minor releases.

--
regards, Andrei Lepikhov

Attachment Content-Type Size
v1-0001-Teach-Append-to-consider-tuple_fraction-when-accu.patch text/x-patch 11.1 KB

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