Postgres in-query debug messages

postgres-debug.sql

/*
example:

#

WITH RECURSIVE t(n) AS (
                        VALUES (debug('init: ' || 1,1))
                        UNION ALL
                        SELECT debug('recursion: ' || n+1 ,n+1)
                        FROM t
                        WHERE n < 100)
SELECT sum(n),
       debug('final query')
FROM t;

NOTICE:  Debug: init: 1
NOTICE:  Debug: recursion: 2
NOTICE:  Debug: recursion: 3
NOTICE:  Debug: recursion: 4
NOTICE:  Debug: recursion: 5
NOTICE:  Debug: recursion: 6
NOTICE:  Debug: recursion: 7
NOTICE:  Debug: recursion: 8
NOTICE:  Debug: recursion: 9
NOTICE:  Debug: recursion: 10
NOTICE:  Debug: final query
 sum | debug
-----+-------
  55 |
(1 row)
*/



CREATE FUNCTION debug(msg TEXT) RETURNS void AS $$
BEGIN
    RAISE NOTICE 'Debug: %', msg;
    RETURN;
END;
$$ LANGUAGE plpgsql;


CREATE FUNCTION debug(msg TEXT, value ANYELEMENT) RETURNS ANYELEMENT AS $$
BEGIN
    RAISE NOTICE 'Debug: %', msg;
    RETURN value;
END;
$$ LANGUAGE plpgsql;