Re: Disk-based hash aggregate's cost model

From: Jeff Davis <pgsql(at)j-davis(dot)com>
To: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: Peter Geoghegan <pg(at)bowt(dot)ie>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Disk-based hash aggregate's cost model
Date: 2020-09-04 00:53:43
Message-ID: a0e8a1e42d377eba095d01a377bd99c1d7f11828.camel@j-davis.com
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On Tue, 2020-09-01 at 23:19 +0200, Tomas Vondra wrote:
> FWIW any thoughts about the different in temp size compared to
> CP_SMALL_TLIST?

Are you referring to results from a while ago? In this thread I don't
see what you're referring to.

I tried in a simple case on REL_13_STABLE, with and without the
CP_SMALL_TLIST change, and I saw only a tiny difference. Do you have a
current case that shows a larger difference?

The only thing I can think of that might change is the size of the null
bitmap or how fields are aligned.

Regards,
Jeff Davis

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