[kmike]

Thinking about two post tables idea, it could go really well along with mysql replication.
Idea: set up second mysql server (even on the same physical machine), set it up to replicate post table from main forums db. All updates to that second mysql server will be handled by only one slave thread, and it could be locked freely without any effect on first mysql server perfomance.
Since JohnWoo's hack uses two tables in the main query, it appears that thread table need to be replicated along with post table.
Changes to current hack code would be really small: initialize another db connection and fire query to a second db instead of main one.

I don't plan to implement this any time soon, though accidentally we have workng replication of our forum db to another server. I'm polishing a vb2-like hack of this (JohnWoo's) hack . It eliminates LEFT JOIN and always searches IN BOOLEAN MODE. Had to drop search by relevance though, I highly doubt someone used it even once though.