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From: Jeff Davis <pgsql@j-davis.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Melanie Plageman <melanieplageman@gmail.com>
Cc: Thomas Munro <thomas.munro@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Cc: HeikkiLinnakangas <hlinnaka@iki.fi>
Subject: Re: Trouble with hashagg spill I/O pattern and costing
Date: Fri, 29 May 2020 13:12:40 -0700
Message-ID: <312bf7eb53b0b9f953e4eb0c704ed4f2121bce4d.camel@j-davis.com> (raw)
In-Reply-To: <20200529130454.el6qyuukj3ofs4eu@development>
References: <20200525225909.aifxjm53hw4xyzxd@development>
	<CA+hUKG+q3Ma+sTKn2316Ofof6u21hh0cGJHcJ-fAnLxw=LXevw@mail.gmail.com>
	<20200526141524.ohtvrp23vxosgivl@development>
	<e913544f6c236d37e8b0597cabd086570b5806f2.camel@j-davis.com>
	<20200526191511.d7pwz4awrvdm4p6j@development>
	<0589f869969de2f3e9713689159c7c4fbe1fcfa5.camel@j-davis.com>
	<CAAKRu_YNGQ-zw9rpXGtYhURMqdPk+HnMa+Wj-tnNx9cwENgDxg@mail.gmail.com>
	<20200527090704.onkjogxeg34ib5cn@development>
	<20200528185750.aamptuqdzrggqi5c@development>
	<0fb3456095d469cc20a9ee7e76edfe9237dae24f.camel@j-davis.com>
	<20200529130454.el6qyuukj3ofs4eu@development>

On Fri, 2020-05-29 at 15:04 +0200, Tomas Vondra wrote:
> Ah, right. Yeah, we only need to check for AGG_HASH here. Moreover,
> AGG_MIXED probably does not need the tlist tweak, because the input
> should be pre-sorted as with AGG_SORTED.
> 
> And we should probably do similar check in the
> create_groupinsets_path,
> I guess. At first I thought we can't do that before inspecting
> rollups,
> which only happens later in the function, but now I see there's
> aggstrategy in GroupingSetsPath too.

Looks good.

	Jeff







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  Subject: Re: Trouble with hashagg spill I/O pattern and costing
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