operator class

Hello

I have just started with postgreSQL.

I have a file with the following commands :

CREATE TYPE t_cod_t_activ AS (

      cod_t_activ       CHAR(10)

      );

CREATE TABLE tip_activ (

      id_tip_activ            t_cod_t_activ,

      des_t_activ             t_des_t_activ

      );

CREATE INDEX i_tip_activ ON tip_activ (id_tip_activ bpchar_pattern_ops);

When the CREATE INDEX is executed, this error shows:

ERROR:  operator class "bpchar_pattern_ops" does not accept data type t_cod_t_activ

Does it mean that I cannot create an index on a field wich is of a type defined by the user?

I need that id_tip_activ be PRIMARY KEY.

Thanks and best regards

Miguel Ibáñez