Date: Thu, 22 Jul 2021 11:41:27 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, David Rowley <dgrowleyml@gmail.com>,
	"ldh@laurent-hasson.com" <ldh@laurent-hasson.com>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Big performance slowdown from 11.2 to 13.3
Message-ID: <20210722164127.GI19620@telsasoft.com>
References: 
 <MN2PR15MB2560778595BB7AF6E691B26785E39@MN2PR15MB2560.namprd15.prod.outlook.com>
 <MN2PR15MB2560D429866BD65A70574A6C85E49@MN2PR15MB2560.namprd15.prod.outlook.com>
 <CAApHDvqoF7y7SQjGT=940njnAd_CUcUG6oRYChcP_+eJyuNiug@mail.gmail.com>
 <MN2PR15MB25603D3CE06C8F9C312EA58985E49@MN2PR15MB2560.namprd15.prod.outlook.com>
 <MN2PR15MB2560E4574A6E2B5AED2C03CB85E49@MN2PR15MB2560.namprd15.prod.outlook.com>
 <784576.1626968702@sss.pgh.pa.us>
 <785218.1626969409@sss.pgh.pa.us>
 <CAApHDvo+Gb80BVPKYCwHbLa7a7ZXp9ziq9URrpQaKdvXsd46bg@mail.gmail.com>
 <786600.1626970898@sss.pgh.pa.us>
 <CAH2-WzmftijCna_aY-HyCUfswwfPCC4d2HjKab1cxM0QCFrRUQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: 
 <CAH2-WzmftijCna_aY-HyCUfswwfPCC4d2HjKab1cxM0QCFrRUQ@mail.gmail.com>
User-Agent: Mutt/1.9.4 (2018-02-28)
Archived-At: 
 <https://www.postgresql.org/message-id/20210722164127.GI19620%40telsasoft.com>
Precedence: bulk

On Thu, Jul 22, 2021 at 09:36:02AM -0700, Peter Geoghegan wrote:
> I don't see how it's possible for get_hash_mem() to be unable to
> return a hash_mem value that could be represented by work_mem
> directly. MAX_KILOBYTES is an annoyingly low limit on Windows, where
> sizeof(long) is 4. But that's nothing new.

Oh.  So the problem seems to be that:

1) In v12, HashAgg now obeyes work_mem*hash_mem_multiplier;
2) Under windows, work_mem is limited to 2GB.

-- 
Justin