On Thu, Mar 31, 2011 at 11:33 PM, Kevin Grittner <kevin.gritt...@wicourts.gov> wrote: > Greg Stark <gsst...@mit.edu> wrote: > >> your query does require reading all the data. > > Huh? It requires reading all the data from at least *one* of the > tables.
The query he posted a plan for was: EXPLAIN ANALYZE select oi.id from order_items oi inner join clients_orders co on oi.order_id = co.id; And the plan for it looks like it's optimal to me: 'Hash Join (cost=780.55..1908023.16 rows=1027457 width=4) (actual time=63.506..85607.003 rows=33768 loops=1)' ' Hash Cond: (oi.order_id = co.id)' ' -> Seq Scan on order_items oi (cost=0.00..1558536.52 rows=33843152 width=8) (actual time=0.005..69718.563 rows=33909137 loops=1)' ' -> Hash (cost=480.80..480.80 rows=23980 width=4) (actual time=13.072..13.072 rows=23980 loops=1)' ' Buckets: 4096 Batches: 1 Memory Usage: 844kB' ' -> Seq Scan on clients_orders co (cost=0.00..480.80 rows=23980 width=4) (actual time=0.006..6.570 rows=23980 loops=1)' 'Total runtime: 85613.391 ms' -- greg -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
