On Wed, Sep 2, 2009 at 4:15 PM, Kenneth Cox<kenstir@xxxxxxxxx> wrote: > With postgresql-8.3.6, I have many partitions inheriting a table. SELECT > min() on the parent performs a Seq Scan, but SELECT min() on a child uses > the index. Is this another case where the planner is not aware enough to > come up with the best plan? I tried creating an index on the parent table > to no avail. Is there a way to formulate the query so that it uses the > index? Here is the general flavor: > > create table calls (caller text, ts timestamptz); > create table calls_partition_2009_08 (check (ts >= '2009-08-01' and ts < > '2009-09-01')) inherits (calls); > create index calls_partition_2009_08_ts on calls_partition_2009_08 (ts); > insert into calls_partition_2009_08 (ts) > select to_timestamp(unix_time) > from generate_series(extract(epoch from '2009-08-01'::timestamptz)::int, > extract(epoch from '2009-08-31 > 23:59'::timestamptz)::int, 60) as unix_time; > analyze calls_partition_2009_08; > explain select min(ts) from calls; ATM, constraint exclusion mainly only supports queries of the form: SELECT ... WHERE 'x', with x being an expression in the check constraint. Table partitioning unfortunately is not a free lunch, you have to be aware of it at all times when writing queries vs your partitioned tables. merlin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
