Re: Default setting for enable_hashagg_disk

On Tue, 2020-07-14 at 21:12 -0700, Peter Geoghegan wrote:
> Attached is a WIP patch implementing hash_mem_multiplier, with 1.0 as
> the GUC's default value (i.e. the patch introduces no behavioral
> changes by default). The first patch in the series renames some local
> variables whose name is made ambiguous by the second, main patch.

The idea is growing on me a bit. It doesn't give exactly v12 behavior,
but it does offer another lever that might tackle a lot of the
practical cases. If I were making the decision alone, I'd still choose
the escape hatch based on simplicity, but I'm fine with this approach
as well.

The patch itself looks reasonable to me. I don't see a lot of obvious
dangers, but perhaps someone would like to take a closer look at the
planner changes as you suggest.

Regards,
    Jeff Davis