
-- another fix in the calculation of the tags_vn_bayesian.spoiler column

CREATE OR REPLACE FUNCTION tag_vn_calc() RETURNS void AS $$
BEGIN
  -- all votes for all tags
  CREATE OR REPLACE TEMPORARY VIEW tags_vn_all AS
    SELECT * FROM tags_vn UNION SELECT * FROM tag_vn_childs();
  -- grouped by (tag, vid, uid), so only one user votes on one parent tag per VN entry
  CREATE OR REPLACE TEMPORARY VIEW tags_vn_grouped AS
    SELECT tag, vid, uid, MAX(vote)::real AS vote, COALESCE(AVG(spoiler), 0)::real AS spoiler
    FROM tags_vn_all GROUP BY tag, vid, uid;
  -- grouped by (tag, vid) and serialized into a table
  DROP INDEX IF EXISTS tags_vn_bayesian_tag;
  TRUNCATE tags_vn_bayesian;
  INSERT INTO tags_vn_bayesian
      SELECT tag, vid, COUNT(uid) AS users, AVG(vote)::real AS rating,
          (CASE WHEN AVG(spoiler) < 0.7 THEN 0 WHEN AVG(spoiler) > 1.3 THEN 2 ELSE 1 END)::smallint AS spoiler
        FROM tags_vn_grouped
    GROUP BY tag, vid
      HAVING AVG(vote) > 0;
  CREATE INDEX tags_vn_bayesian_tag ON tags_vn_bayesian (tag);
  -- now perform the bayesian ranking calculation
  UPDATE tags_vn_bayesian tvs SET rating =
      ((SELECT AVG(users)::real * AVG(rating)::real FROM tags_vn_bayesian WHERE tag = tvs.tag) + users*rating)
    / ((SELECT AVG(users)::real FROM tags_vn_bayesian WHERE tag = tvs.tag) + users)::real;
  -- and update the VN count in the tags table as well
  UPDATE tags SET c_vns = (SELECT COUNT(*) FROM tags_vn_bayesian WHERE tag = id);
  RETURN;
END;
$$ LANGUAGE plpgsql;
SELECT tag_vn_calc();
