Leonardo Francalanci <m_li...@yahoo.it> writes: >> Cases with lots of irrelevant indexes. Zoltan's example had 4 indexes >> per child table, only one of which was relevant to the query. In your >> test case there are no irrelevant indexes, which is why the runtime >> didn't change.
> Mmh... I must be doing something wrong. It looks to me it's not just > the irrelevant indexes: it's the "order by" that counts. Ah, I oversimplified a bit: actually, if you don't have an ORDER BY or any mergejoinable join clauses, then the possibly_useful_pathkeys test in find_usable_indexes figures out that we aren't interested in the sort ordering of *any* indexes, so the whole thing gets short-circuited. You need at least the possibility of interest in sorted output from an indexscan before any of this code runs. regards, tom lane -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers