[Pgsql-ayuda] Cual es el error

[Edwin Quijada]

Tengo un error un poco extrano en esta funcion: Me da este error

WARNING:  Error occurred while executing PL/pgSQL function cortar_char
WARNING:  line 8 at select into variables

ERROR:  Unable to identify an operator '=' for types 'name' and 'character'
 You will have to retype this query using an explicit cast

--Este es el codigo de la funcion--
CREATE FUNCTION cortar_char(bpchar,bpchar,bpchar) RETURNS int4 AS '
DECLARE
     tabla ALIAS FOR $1;
     campo ALIAS FOR $2;
     dato ALIAS FOR $3;
     len int;
     reg record;
BEGIN
      select into reg b.atttypmod
      from  pg_class a, pg_attribute b, pg_type c
      where a.relname = tabla
      and  b.attrelid = a.relfilenode
      and  b.attname = campo
      and b.attnum >0
      and b.atttypid = c.oid;
  len:=reg.lon;
      return len;
END;'
LANGUAGE 'plpgsql';