Function for generating name-based MD5 UUIDs (v3) on PostgreSQL

fn_uuid_name_based.sql

/**
 * Returns a name-based UUID v3 (MD5) 
 *
 * RFC-4122 compliant.
 *
 * Tags: uuid guid uuid-generator guid-generator generator name hash md5 sha1 rfc4122 rfc-4122
 *
 * @param p_name      a string
 * @param p_namespace a UUID string
 */
create or replace function fn_uuid_name_based(p_name varchar, p_namespace varchar) returns uuid as $$
declare
	v_bytes  bytea;
begin

	-- Decode name space UUID string to byte array
	v_bytes := decode(replace(p_namespace::varchar, '-', ''), 'hex');

	-- Calculate the MD5 of name space and name
	v_bytes := decode(md5((v_bytes::bytea || p_name::bytea)), 'hex');

	-- Set version bits (0011)
	v_bytes := set_bit(v_bytes, 55, 0);
	v_bytes := set_bit(v_bytes, 54, 0);
	v_bytes := set_bit(v_bytes, 53, 1);
	v_bytes := set_bit(v_bytes, 52, 1);

	-- Set variant bits (10xx)
	v_bytes := set_bit(v_bytes, 71, 1);
	v_bytes := set_bit(v_bytes, 70, 0);

	return encode(v_bytes, 'hex')::uuid;

end $$ language plpgsql;

/**
 * Returns a name-based UUID v3 (MD5)
 *
 * RFC-4122 compliant.
 *
 * Tags: uuid guid uuid-generator guid-generator generator name hash md5 sha1 rfc4122 rfc-4122
 *
 * @param p_name a string
 */
create or replace function fn_uuid_name_based(p_name varchar) returns uuid as $$
declare
begin
	return fn_uuid_name_based(p_name, ''::varchar);
end $$ language plpgsql;

-- EXAMPLE 1:
-- select fn_uuid_name_based('John Smith', '58988cc4-bbab-48a2-94f4-d23807e3b73c');

-- EXAMPLE 1 OUTPUT: 
-- d89c2dfb-96e1-3ce8-bee8-9cc44149c95f

-- EXAMPLE 2:
-- select fn_uuid_name_based('John Smith');

-- EXAMPLE 2 OUTPUT: 
-- 6117323d-2cab-3c17-944c-2b44587f682c