This is an old revision of the document!
SELECT split_part(substr(LINES, 1+POSITION(E'\n'||FIELD IN LINES), 200), E'\n', 1) AS ct, COUNT(*) FROM header, (VALUES ('X-Priority'), ('Importance'), ('Precedence'), ('Priority'), ('X-MSMail-Priority'), ('X-MS-Priority')) AS h(FIELD) WHERE POSITION(E'\n'||FIELD IN LINES)>0 GROUP BY split_part(substr(LINES, 1+POSITION(E'\n'||FIELD IN LINES), 200), E'\n', 1)