On Wed, Jul 29, 2020 at 03:34:22PM -0700, Peter Geoghegan wrote:
> Hi Bruce,
>
> On Fri, Jun 26, 2020 at 3:24 PM Bruce Momjian <bruce@momjian.us> wrote:
> > Patch attached and applied to PG 13.
>
> I committed the hash_mem_multiplier GUC to Postgres 13 just now.
>
> There should be a note about this in the Postgres 13 release notes,
> for the usual reasons. More importantly, the "Allow hash aggregation
> to use disk storage for large aggregation result sets" feature should
> reference the new GUC directly. Users should be advised that the GUC
> may be useful in cases where they upgrade and experience a performance
> regression linked to slower hash aggregation. Just including a
> documentation link for the GUC would be very helpful.
I came up with the attached patch.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EnterpriseDB https://enterprisedb.com
The usefulness of a cup is in its emptiness, Bruce Lee