CREATE OR REPLACE FUNCTION ams_index (my_user_id VARCHAR, my_locidispid BIGINT, my_audio_latency INTEGER) RETURNS VOID STRICT VOLATILE AS $$
  BEGIN
    -- output table to hold tagged music sessions with latency
    CREATE TEMPORARY TABLE ams_music_session_tmp (music_session_id VARCHAR(64) NOT NULL, tag INTEGER, latency INTEGER) ON COMMIT DROP;

    -- populate ams_music_session_tmp as all music sessions
    INSERT INTO ams_music_session_tmp SELECT DISTINCT id, NULL::INTEGER AS tag, NULL::INTEGER AS latency
      FROM active_music_sessions;

    -- TODO worry about active music session where my_user_id is the creator?
    -- eh, maybe, but if the music session is active and you're the creator wouldn't you already be in it?
    -- so maybe you're on another computer, so why care? plus seth is talking about auto rsvp'ing the session
    -- for you, so maybe not a problem.

    -- tag accepted rsvp as 1
    UPDATE ams_music_session_tmp q SET tag = 1 FROM rsvp_slots s, rsvp_requests_rsvp_slots rrs, rsvp_requests r WHERE
      q.music_session_id = s.music_session_id AND
      s.id = rrs.rsvp_slot_id AND
      rrs.rsvp_request_id = r.id AND
      r.user_id = my_user_id AND
      rrs.chosen = TRUE AND
      q.tag is NULL;

    -- tag invitation as 2
    UPDATE ams_music_session_tmp q SET tag = 2 FROM invitations i WHERE
      q.music_session_id = i.music_session_id AND
      i.receiver_id = my_user_id AND
      q.tag IS NULL;

    -- musician access as 3
    UPDATE ams_music_session_tmp q SET tag = 3 FROM music_sessions m WHERE
      q.music_session_id = m.id AND
      m.musician_access = TRUE AND
      q.tag IS NULL;

    -- delete anything not tagged
    DELETE FROM ams_music_session_tmp WHERE tag IS NULL;

    -- output table to hold users involved in the ams_music_session_tmp sessions and their latency
    CREATE TEMPORARY TABLE ams_users_tmp (music_session_id VARCHAR(64) NOT NULL, user_id VARCHAR(64) NOT NULL, latency INTEGER NOT NULL) ON COMMIT DROP;

    -- populate ams_users_tmp as all musicians in the ams_music_session_tmp sessions with audio latency and score
    INSERT INTO ams_users_tmp SELECT c.music_session_id, c.user_id, (s.score+my_audio_latency+c.last_jam_audio_latency)/2 AS latency
      FROM ams_music_session_tmp q, connections c, current_scores s WHERE
        q.music_session_id = c.music_session_id AND
        c.locidispid = s.alocidispid AND
        s.blocidispid = my_locidispid AND
        c.last_jam_audio_latency IS NOT NULL;

    -- calculate the average latency
    UPDATE ams_music_session_tmp q SET latency = (select AVG(u.latency) FROM ams_users_tmp u WHERE
      q.music_session_id = u.music_session_id);

    RETURN;
  END;
$$ LANGUAGE plpgsql;