domains.sql

--
-- Domain types.  A PL/php function sees a domain as its underlying base type
-- (scalar, array or composite), and a value returned into a domain result is
-- checked against the domain's constraints.
--
CREATE DOMAIN posint AS int CHECK (VALUE > 0);
CREATE DOMAIN shortstr AS text CHECK (length(VALUE) <= 5);
CREATE DOMAIN intvec AS int[] CHECK (cardinality(VALUE) > 0);

-- A scalar domain argument arrives as the base value; the CHECK on the input
-- has already been enforced by the caller.
CREATE FUNCTION dom_scalar(posint, shortstr) RETURNS text LANGUAGE plphp AS $$
    return $args[0] . "/" . strtoupper($args[1]);
$$;
SELECT dom_scalar(7, 'abc');

-- Returning into a scalar domain enforces its CHECK.
CREATE FUNCTION dom_double(int) RETURNS posint LANGUAGE plphp AS $$
    return $args[0] * 2;
$$;
SELECT dom_double(21);
SELECT dom_double(-1);   -- violates posint

-- A domain over an array arrives as a PHP array, and a PHP array can be
-- returned into it (the domain CHECK still applies).
CREATE FUNCTION dom_arr_in(intvec) RETURNS int LANGUAGE plphp AS $$
    return is_array($args[0]) ? array_sum($args[0]) : -1;
$$;
SELECT dom_arr_in('{10,20,30}');

CREATE FUNCTION dom_arr_out(int) RETURNS intvec LANGUAGE plphp AS $$
    $out = array();
    for ($i = 1; $i <= $args[0]; $i++)
        $out[] = $i * $i;
    return $out;
$$;
SELECT dom_arr_out(4);
SELECT dom_arr_out(0);   -- empty array violates intvec's CHECK

-- A domain used as a composite field is unwrapped there too.
CREATE TYPE drow AS (id posint, tag shortstr);
CREATE FUNCTION dom_field(drow) RETURNS text LANGUAGE plphp AS $$
    return $args[0]['id'] . ":" . $args[0]['tag'];
$$;
SELECT dom_field(ROW(3, 'ok')::drow);

DROP FUNCTION dom_scalar(posint, shortstr), dom_double(int),
    dom_arr_in(intvec), dom_arr_out(int), dom_field(drow);
DROP TYPE drow;
DROP DOMAIN posint, shortstr, intvec;