Andres Freund <and...@anarazel.de> writes: > Not sure I follow. Unless the values are equivalent (i.e. duplicate key > values), why should non-uniformity in key space translate to hash space?
Duplicates are exactly the problem. See estimate_hash_bucket_stats. > And if there's duplicates it shouldn't hurt much either, unless doing > a semi/anti-join? All rows are going to be returned and IIRC we quite > cheaply continue a bucket scan? If the bucket containing the MCV is bigger than work_mem, you gotta problem --- one not necessarily shared by the other relation. regards, tom lane