Michal Taborsky <michal.taborsky@xxxxxxx> writes: > OK. Mystery (sort of) solved. After you told me it works for you I had > to assume the problem was somewhere else. And, indeed, it was, though > it's not too obvious. > The two attributes are actually not of tybe bigint, but of type > "crm_object_id", which is created as follows: > CREATE DOMAIN "public"."crm_object_id" AS > bigint NULL; Ah. The problem is that the UNION's output column is bigint, and the type discrepancy (bigint above, domain below) discourages the planner from pushing down the WHERE condition. There's a related complaint here: http://archives.postgresql.org/pgsql-bugs/2005-10/msg00227.php If we were to change things so that the result of the UNION were still the domain, not plain bigint, then your example would be optimized the way you want. I'm unsure about what other side-effects that would have though. regards, tom lane
