Re: POC: GROUP BY optimization

From: Teodor Sigaev <teodor(at)sigaev(dot)ru>
To: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: POC: GROUP BY optimization
Date: 2018-06-28 16:52:03
Views: Raw Message | Whole Thread | Download mbox | Resend email
Lists: pgsql-hackers

> I'm afraid that's a misunderstanding - my objections did not really go
> away. I'm just saying my claim that we're not messing with order of
> grouping keys is not entirely accurate, because we do that in one
> particular case.
> I still think we need to be careful when introducing new optimizations
> in this area - reordering the grouping keys by ndistinct, ORDER BY or
> whatever. In particular I don't think we should commit these patches
> that may quite easily cause regressions, and then hope some hypothetical
> future patch fixes the costing. Those objections still stand.

Pls, have a look at
I tried to attack the cost_sort() issues and hope on that basis we can solve
problems with 0002 patch and improve incremental sort patch.

Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru

In response to


Browse pgsql-hackers by date

  From Date Subject
Next Message Alvaro Herrera 2018-06-28 16:52:14 Re: Tips on committing
Previous Message Teodor Sigaev 2018-06-28 16:47:22 cost_sort() improvements