2009/4/18 Heikki Linnakangas <heikki.linnakan...@enterprisedb.com>: > Grzegorz Jaśkiewicz wrote: >> >> Can correlation be negative ? > > Yes, if the data in the column are in descending order. For example: > > postgres=# CREATE TABLE foo(id int4); > CREATE TABLE > postgres=# INSERT INTO foo SELECT 1000 - generate_series(1, 1000); > INSERT 0 1000 > postgres=# ANALYZE foo; > ANALYZE > postgres=# SELECT attname, correlation FROM pg_stats WHERE tablename='foo'; > attname | correlation > ---------+------------- > id | -1 > (1 row)
aye, thanks. -- GJ -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
