On 19 Jul 2000, at 14:30, Tom Lane wrote: > "Joel Burton" <[EMAIL PROTECTED]> writes: > > I have a function that always returns the same answer given the same > > input (no database lookups, etc.). The pg Users' Manual documents > > the attribute 'iscachable' as allowing the database to parse the > > results of the function and not keep looking it up. > > iscachable does not mean that the system will cache the results of the > function across queries, it just means that the function needn't be > re-evaluated multiple times for the same arguments within a single > query. For example, given > > SELECT * from table1 where col = foo(42); > > If foo() is marked cachable then it's evaluated once during query > planning; if not it's evaluated again for each row scanned in table1. Sounds reasonable. But does it work as advertised? CREATE FUNCTION foo(int) RETURNS int AS ' BEGIN RAISE NOTICE ''hi''; RETURN 1; END;' LANGUAGE 'plpgsql'; CREATE FUNCTION foocache(int) RETURNS int AS ' BEGIN RAISE NOTICE ''hi''; RETURN 1; END;' LANGUAGE 'plpgsql' WITH (iscachable); SELECT foo(1),foo(1),foo(1) gives us 3 NOTICEs, as does SELECT foocache(1), foocache(1), foocache(1) So is it running the cached version a second time? Thanks, -- Joel Burton, Director of Information Systems -*- [EMAIL PROTECTED] Support Center of Washington (www.scw.org)
