Also the sensitiviy would be an issue. How many consecutive letters would there have to be before a match is made? 3? 4?
Too high and it would miss some posts and too low it would give many false positives which would dilute the results.
It would vary considerably depending on the search.
Unless the match sensitivity was based on the size of the search word, that I could see as a possible solution.
But I agree, it would be pretty hard on the server for sure. The search is already quite intensive as is.