I vaguely remember seeing that PostgresSQL optimized selects on certain
UNION ALL statements, so that given:
CREATE VIEW orders AS
SELECT '2003-01' as period, * FROM orders_2003_01
UNION ALL
SELECT '2003-02' as period, * FROM orders_2003_02
then
SELECT * FROM orders WHERE period = '2003-01'
would do a full table scan only on the orders_2003_01 table.
But I didn't see this optimization while I was running some tests against
7.4.2.
Am I missing something now? Or am I just mis-remembering Postgres'
behavior?