| From: | Teodor Sigaev <teodor(at)sigaev(dot)ru> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com> |
| Cc: | PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: POC: GROUP BY optimization |
| Date: | 2018-06-07 15:16:13 |
| Message-ID: | d8b7a8a4-426d-5010-79a4-1b0cb9750ee2@sigaev.ru |
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| Thread: | |
| Lists: | pgsql-hackers |
>> Again agree. If we have fixed order of columns (ORDER BY) then we should not
>> try to reorder it. Current patch follows that if I didn't a mistake.
>>
>
> This part seems to be more a misunderstanding between me and Claudio. I believe
> Claudio was referring to the column order in a GROUP BY, not ORDER BY. In which
> case we don't add any Sort, of course.
I hope so
>
> I'm still opposed to adding arbitrary handicap to prioritize the order specified
> by user, for the reasons I explained before. We should aim to make the
> heuristics/costing reliable enough to make this unnecessary.
+1
--
Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru
WWW: http://www.sigaev.ru/
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