EDIT Taking COST 100 out made the command go through, however, I'm still unable to run my query because it yields this error:

ERROR:  function group_concat(character) does not exist
HINT:  No function matches the given name and argument types. You may need to add explicit type casts.

The query I'm running is this:

select tpid, group_concat(z) as z,                                                                                                                                                    
    group_concat(cast(r as char(2))) as r,                                                                                                                                   
    group_concat(to_char(datecreated,'DD-Mon-YYYY HH12:MI am')) as datecreated,                                                                                                        
    group_concat(to_char(datemodified,'DD-Mon-YYYY HH12:MI am')) as datemodified                                                                                                       
    from tpids group by tpid order by tpid, zip

This function seems to work fine locally, but moving it online yields this error... Is there something I'm missing?

CREATE OR REPLACE FUNCTION group_concat(text, text)
  RETURNS text AS
$BODY$
SELECT CASE
WHEN $2 IS NULL THEN $1
WHEN $1 IS NULL THEN $2
ELSE $1 operator(pg_catalog.||) ',' operator(pg_catalog.||) $2
END
$BODY$
  LANGUAGE 'sql' IMMUTABLE
  COST 100;
ALTER FUNCTION group_concat(text, text) OWNER TO j76dd3;