On 22/11/2024 18:12, Ba Jinsheng wrote:
I think the key difference is that the patch disables the usage of Hash Join, which incurs a worse performance.I see here a problem with a number of groups: when predicting it incorrectly, Postgres doesn't use the Memoize node. Disabling HashJoin puts NestLoop+Memoize at the place of the best path, which is chosen later. Unfortunately, we can't see a prediction on the number of groups in Memoize and can only guess the issue.
-- regards, Andrei Lepikhov
