Andrew Dunstan <andrew@xxxxxxxxxxxx> writes: > On 01/22/2013 09:21 AM, rudi wrote: >> The query is pretty simple and standard, the behaviour (and the plan) >> is totally different when it comes to a partitioned table. >> >> Partioned table query => explain analyze SELECT "sb_logs".* FROM >> "sb_logs" WHERE (device_id = 901 AND date_taken = (SELECT >> MAX(date_taken) FROM sb_logs WHERE device_id = 901)); > And there you have it. Constraint exclusion does not work in cases like > this. It only works with static expressions (such as a literal date in > this case). This isn't about constraint exclusion I think. The main problem is in the sub-select: 9.0 isn't able to index-optimize a MAX() across a partitioned table, for lack of MergeAppend, so you end up scanning lots of rows there. 9.1 or 9.2 should be better. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
