You could definitely tokenize a string into three character overlapping chunks. One problem might be tracking the overlapping of strings. For example, if you had a string 'ABCDEF' and you searched for 'DEFABC', you would find 'ABC' and 'DEF'. You wouldn't find 'EFA' or 'FAB'. So your MATCH clause would probably need to be customized based on what you were searching for. So the FTS index could have all the trigrams, but matching would be a little more complex than a simple LIKE. However, it should be quite fast to find even with the more complicated query formatting, and probably much easier than adding actual trigram indexes to SQLite.