2009/7/17 Hitoshi Harada <umi.tan...@gmail.com>: > 2009/7/17 Pavel Stehule <pavel.steh...@gmail.com>: >> Hello >> >> look on: >> postgres=# explain select count(*) over () from x; >> QUERY PLAN >> ------------------------------------------------------------- >> WindowAgg (cost=0.00..265.00 rows=10000 width=0) >> -> Seq Scan on x (cost=0.00..140.00 rows=10000 width=0) >> (2 rows) >> >> Time: 1,473 ms >> postgres=# explain select count(*) over (order by a) from x; >> QUERY PLAN >> ------------------------------------------------------------------------ >> WindowAgg (cost=0.00..556.25 rows=10000 width=4) >> -> Index Scan using gg on x (cost=0.00..406.25 rows=10000 width=4) >> (2 rows) >> >> but >> query1: 160ms >> query2: 72ms > > Well, how about "select a from x order by a"? > I wonder if index scan affects more than windowagg. >
select a from x -> 42ms select a from x order by a -> 50ms all data are from cache. > -- > Hitoshi Harada > -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
