Date: Mon, 13 Jul 2020 13:43:16 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Jeff Davis <pgsql@j-davis.com>, David Rowley <dgrowleyml@gmail.com>,
	Stephen Frost <sfrost@snowman.net>, Peter Geoghegan <pg@bowt.ie>,
	Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>,
	Bruce Momjian <bruce@momjian.us>,
	Robert Haas <robertmhaas@gmail.com>,
	Melanie Plageman <melanieplageman@gmail.com>,
	Tomas Vondra <tomas.vondra@2ndquadrant.com>,
	pgsql-hackers@postgresql.org
Subject: Re: Default setting for enable_hashagg_disk
Message-ID: <20200713184316.GK23581@telsasoft.com>
References: <5cf74833a830e76cc7cc7506aa77bd6ab0c94f4c.camel@j-davis.com>
 <20200713164736.GA25726@alvherre.pgsql>
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On Mon, Jul 13, 2020 at 12:47:36PM -0400, Alvaro Herrera wrote:
> On 2020-Jul-13, Jeff Davis wrote:
> 
> > On Tue, 2020-07-14 at 02:25 +1200, David Rowley wrote:
> > > Updated summary:
> > > * For hash_mem = Tomas [7], Justin [16]
> > > * For hash_mem_multiplier with a default > 1.0 = DavidG [21]
> > > * For hash_mem_multiplier with default = 1.0 =  PeterG [15][0], Tom
> > > [20][24]
> > 
> > I am OK with these options, but I still prefer a simple escape hatch.
> 
> I'm in favor of hash_mem_multiplier.  I think a >1 default is more
> sensible than =1 in the long run, but if strategic vote is what we're
> doing, then I support the =1 option.

I recanted and support hash_mem_multiplier (or something supporting that
behavior, even if it also supports an absolute/scalar value).
https://www.postgresql.org/message-id/20200703145620.GK4107@telsasoft.com

1.0 (or -1) is fine, possibly to be >= 1.0 in master at a later date.

-- 
Justin