-----Original Message----- From: Peter Geoghegan <pg@xxxxxxx> Sent: Thursday, July 22, 2021 12:14 To: Tom Lane <tgl@xxxxxxxxxxxxx> Cc: Jeff Davis <pgsql@xxxxxxxxxxx>; ldh@xxxxxxxxxxxxxxxxxx; David Rowley <dgrowleyml@xxxxxxxxx>; Justin Pryzby <pryzby@xxxxxxxxxxxxx>; pgsql-performance@xxxxxxxxxxxxxx Subject: Re: Big performance slowdown from 11.2 to 13.3 On Thu, Jul 22, 2021 at 8:45 AM Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > 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? I wonder if this has something to do with the way that the input data is clustered. I recall noticing that that could significantly alter the behavior of HashAggs as of Postgres 13. -- Peter Geoghegan I could execute that test and re-cluster against the index. But I believe that's already done? Let me check. Thank you, Laurent.
