André Volpato <andre.volpato@xxxxxxxxxxxxxxxxxxxxx> writes: > And the query: > > # select j.i, t.t from jtest j inner join test t on t.i = j.i where (j.i*1.5) > between 3000000 and 4000000; > > Planner for [1]: > Nested Loop (cost=0.00..270192.02 rows=20000 width=41) (actual > Planner for [2]: > Hash Join (cost=176924.02..297518.03 rows=20000 width=38) (actual > Now, turning off hashing: > # set enable_hashjoin=off; > # set enable_hashagg=off; > > Again for [2]: > Merge Join (cost=178781.75..328370.60 rows=20000 width=38) (actual I think the answer is that if you have bad statistics you'll get a bad plan and which bad plan is going to be pretty much random. But I'm curious if you turn off mergejoin whether you can get a Nested Loop plan and what cost 8.3 gives it. It looks to me like 8.3 came up with a higher cost for Nested Loop than 8.1.9 (I think 8.1.10 came out with some planner fixes btw) and so it's deciding these other plans are better. And they might have been better for the imaginary scenario that the planner thinks is going on. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com Ask me about EnterpriseDB's Slony Replication support! ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to majordomo@xxxxxxxxxxxxxx so that your message can get through to the mailing list cleanly
