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