On Tue, 2020-06-09 at 18:20 -0700, Melanie Plageman wrote: > So, I was catching up on email and noticed the last email in this > thread. > > I think I am not fully understanding what > enable_groupingsets_hash_disk > does. Is it only for testing?
It's mostly for testing. I could imagine cases where it would be useful to force groupingsets to use the disk, but I mainly wanted the setting there for testing the grouping sets hash disk code path. > Using the tests you added to src/test/regress/sql/groupingsets.sql, I > did get a plan that looks like hashagg is spilling to disk (goes > through I had something that worked as a test for a while, but then when I tweaked the costing, it started using the Sort path (therefore not testing my grouping sets hash disk code at all) and a bug crept in. So I thought it would be best to have a more forceful knob. Perhaps I should just get rid of that GUC and use the stats trick? Regards, Jeff Davis