There won't be an index with both the full text search and the id in, so MySQL will have to create a temporary table with the results and sort that and do the l

There won't be an index with both the full text search and the id in, so MySQL will have to create a temporary table with the results and sort that and do the limit. If you have a TEXT or a BLOB column or it's too big, MySQL will do that on disk rather than in memory, so it's slow. I'd suggest using "EXPLAIN EXTENDED" before your "SELECT" to see what it's doing and to consider specifying the columns, though in general I'd do what you did.