Over here -> http://www.postgresql.org/message-id/6351.1404663...@sss.pgh.pa.us Tom noted that create_unique_path did not check for set returning functions.
Tom Wrote: > I notice that create_unique_path is not paying attention to the question > of whether the subselect's tlist contains SRFs or volatile functions. > It's possible that that's a pre-existing bug. I looked at this a bit and I can confirm that it does not behave as it should do. Take the following as an example: create table x (id int primary key); create table y (n int not null); insert into x values(1); insert into y values(1); select * from x where (id,id) in(select n,generate_series(1,2) / 10 + 1 g from y); id ---- 1 (1 row) select * from x where (id,id) in(select n,generate_series(1,2) / 10 + 1 g from y group by n); id ---- 1 1 (2 rows) The 2nd query does group by n, so query_is_distinct_for returns true, therefore the outer query think's it's ok to perform an INNER JOIN rather than a SEMI join, which is this case produces an extra record. I think we should probably include the logic to test for set returning functions into query_is_distinct_for. The attached fixes the problem. Regards David Rowley
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