-- Function: merge_db(integer, text)

-- DROP FUNCTION merge_db(integer, text);

CREATE OR REPLACE FUNCTION merge_db(key integer, data text)
  RETURNS void AS
$BODY$CREATE FUNCTION merge_db(key INT, data TEXT) RETURNS VOID AS
$$
BEGIN
    LOOP
        -- first try to update the key
        UPDATE db SET b = data WHERE a = key;
        IF found THEN
            RETURN;
        END IF;
        -- not there, so try to insert the key
        -- if someone else inserts the same key concurrently,
        -- we could get a unique-key failure
        BEGIN
            INSERT INTO db(a,b) VALUES (key, data);
            RETURN;
        EXCEPTION WHEN unique_violation THEN
            -- do nothing, and loop to try the UPDATE again
        END;
    END LOOP;
END;
$$
LANGUAGE plpgsql;
$BODY$
  LANGUAGE 'sql' VOLATILE
  COST 100;
ALTER FUNCTION merge_db(integer, text) OWNER TO postgres;