Neat trick to make sure plpgsql is installed as part of a schema

Hey,

I was puzzling over how to make sure a database has plpgsql
installed in it in pure SQL. I felt this would simplify the schema's
installation process since calling of extra binaries is no longer
neccessary. Here's what I came up with:

CREATE OR REPLACE FUNCTION make_plpgsql () RETURNS bool AS
'
CREATE TRUSTED LANGUAGE "plpgsql" HANDLER "plpgsql_call_handler"; --
SELECT true; --
' LANGUAGE SQL;

SELECT CASE WHEN
(SELECT COUNT(oid) > 0 FROM pg_language WHERE lanname = 'plpgsql')
THEN true ELSE
(SELECT make_plpgsql())
END
;

Cheers,
Tyler