It might make sense to flag in the metadata that an index might be needed; then again someone using SQLite will probably know very well which queries are being

It might make sense to flag in the metadata that an index might be needed; then again someone using SQLite will probably know very well which queries are being executed. Also, most of the time joins are made on foreign keys and these should always be indexed. So I guess this should be a rare occurrence if the database is properly thought-out.