CREATE TYPE md5hash;

-- input/output function
CREATE FUNCTION md5_in(cstring)           RETURNS md5hash AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION md5_out(md5hash)          RETURNS cstring AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;

-- functions backing operators (and btree opclass)
CREATE FUNCTION md5_eq(md5hash, md5hash)  RETURNS boolean AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION md5_neq(md5hash, md5hash) RETURNS boolean AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION md5_leq(md5hash, md5hash) RETURNS boolean AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION md5_lt(md5hash, md5hash)  RETURNS boolean AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION md5_geq(md5hash, md5hash) RETURNS boolean AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION md5_gt(md5hash, md5hash)  RETURNS boolean AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION md5_cmp(md5hash, md5hash) RETURNS int     AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;

CREATE FUNCTION md5_recv(internal)        RETURNS md5hash AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION md5_send(md5hash)         RETURNS bytea   AS 'md5hash' LANGUAGE C IMMUTABLE STRICT;

CREATE TYPE md5hash (
    INPUT = md5_in,
    OUTPUT = md5_out,
    INTERNALLENGTH = 16,
    SEND = md5_send,
    RECEIVE = md5_recv
);

-- some basic support for implicit casts
CREATE CAST (md5hash AS text) WITH INOUT AS IMPLICIT;
CREATE CAST (text AS md5hash) WITH INOUT AS IMPLICIT;

CREATE OPERATOR = (
    PROCEDURE = md5_eq,
    LEFTARG = md5hash,
    RIGHTARG = md5hash,
    COMMUTATOR = =,
    NEGATOR = <>,
    RESTRICT = eqsel,
    JOIN = eqjoinsel,
    MERGES,
    HASHES
);

CREATE OPERATOR <> (
    PROCEDURE = md5_neq,
    LEFTARG = md5hash,
    RIGHTARG = md5hash,
    COMMUTATOR = <>,
    NEGATOR = =,
    RESTRICT = neqsel,
    JOIN = neqjoinsel
);

CREATE OPERATOR < (
    PROCEDURE = md5_lt,
    LEFTARG = md5hash,
    RIGHTARG = md5hash,
    COMMUTATOR = >,
    NEGATOR = >=,
    RESTRICT = scalarltsel,
    JOIN = scalarltjoinsel
);

CREATE OPERATOR > (
    PROCEDURE = md5_gt,
    LEFTARG = md5hash,
    RIGHTARG = md5hash,
    COMMUTATOR = <,
    NEGATOR = <=,
    RESTRICT = scalargtsel,
    JOIN = scalargtjoinsel
);

CREATE OPERATOR <= (
    PROCEDURE = md5_leq,
    LEFTARG = md5hash,
    RIGHTARG = md5hash,
    COMMUTATOR = >=,
    NEGATOR = >,
    RESTRICT = scalarltsel,
    JOIN = scalarltjoinsel
);

CREATE OPERATOR >= (
    PROCEDURE = md5_geq,
    LEFTARG = md5hash,
    RIGHTARG = md5hash,
    COMMUTATOR = <=,
    NEGATOR = <,
    RESTRICT = scalargtsel,
    JOIN = scalargtjoinsel
);

CREATE OPERATOR CLASS btree_md5_ops
DEFAULT FOR TYPE md5hash USING btree
AS
        OPERATOR        1       <,
        OPERATOR        2       <=,
        OPERATOR        3       =,
        OPERATOR        4       >= ,
        OPERATOR        5       > ,
        FUNCTION        1       md5_cmp(md5hash, md5hash);