[ALanJay]

Well that explains something - having done some more testing I can get results from the test programme now from ThreadIndex but not PostIndex which is very peculiar.

And this follows through on the actual vb search.php in that if you "search titmes only" it seems to work but "search entire posts"

One of my colleages was kind enough to compare the actual mySQL and the results from the different 3.0 and 3.6 databases and we discovered that there was a difference. It appears that after the upgrade (to 3.6) the index doesn't seem to be being correctly read so an explicit inclusion of - USE INDEX (threadid) - we thoguht might work:

                SELECT postid, forumid, post.threadid as threadid, IF(post.userid=0,99999999,post.userid) AS userid, IF(postuserid=0,99999999,postuserid) AS postuserid, post.
title, pagetext, post.dateline \
                FROM post \
                USE INDEX (threadid) \
                INNER JOIN thread AS thread ON(thread.threadid = post.threadid) \
                WHERE post.visible = 1 AND postid >= $start AND postid <= $end \
                        AND postid > ( SELECT max_doc_id FROM spy_forum.sph_counter WHERE counter_id = 1 );

Except that doesn't work when creating the sphinx index but does when using mysql directly.