gistfile1.sql

BEGIN;

CREATE FUNCTION put_item(collection_id_arg integer, key_arg bytea, value_arg bytea) RETURNS void
AS $$
    BEGIN
        LOOP
            UPDATE items
               SET value = value_arg
             WHERE collection_id = collection_id_arg
               AND key = key_arg;

            IF FOUND THEN
                RETURN;
            END IF;

            BEGIN
                INSERT INTO items
                    (collection_id, key, value)
                VALUES
                    (collection_id_arg, key_arg, value_arg);
                RETURN;
            EXCEPTION WHEN unique_violation THEN
                -- loop
            END;
        END LOOP;
    END;
$$ LANGUAGE plpgsql;

COMMIT;