Horton

Re: Big performance slowdown from 11.2 to 13.3

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: "ldh@laurent-hasson.com" <ldh@laurent-hasson.com>
Cc: David Rowley <dgrowleyml@gmail.com>, Peter Geoghegan <pg@bowt.ie>, Justin Pryzby <pryzby@telsasoft.com>, "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Date: 2021-07-22T15:45:02Z
Lists: pgsql-performance 
"ldh@laurent-hasson.com" <ldh@laurent-hasson.com> writes:
> So, I went possibly nuclear, and still no cigar. Something's not right.
> - hash_mem_multiplier = '10'
> - work_mem = '1GB'

> The results are
> 	Batches: 5  Memory Usage: 2,449,457kB  Disk Usage: 105,936kB
> 	Execution Time: 1,837,126.766 ms

> It's still spilling to disk and seems to cap at 2.5GB of memory usage in spite of configuration.

That is ... weird.  Maybe you have found a bug in the spill-to-disk logic;
it's quite new after all.  Can you extract a self-contained test case that
behaves this way?

			regards, tom lane

Commits

  1. Get rid of artificial restriction on hash table sizes on Windows.