Why doesn`t work this query?
select table1.field1, func1.field2 from table1 left outer join func1(table1.field1) on true where func1.field3 in (20, 100);
The approach people usually use is:
SELECT
f1, (fn).field2
FROM
(
SELECT
field1 as f1, func1(field1) as fn
FROM
table1
OFFSET 0
) ss
WHERE
(fn).field3 IN (20, 100)
;
OFFSET 0 is there to prevent the function from getting called more than once. Also note that this will scan the whole table. There might be a way to avoid that by creating an index on ((func1(field1)).field3) and removing OFFSET 0, but only if the function is IMMUTABLE.
Regards,
Marko Tiikkaja
