Running the same query in SQLiteStudio, the query takes similar time (2 to 2.5 secs), but I keep getting a status of "[09:09:49] Query finished in 0.006 second(s).". Because of this, I am not sure how this is calculated though.
If it takes similar time in SQLiteStudio, it's not surprising it takes similar from Qt.
I do not have rights for asking changes in the database. But just out of curiosity, how do you add an index to a column?
I have never used SQLite. But CREATE INDEX in SQL creates an index. No idea whether SQLite will or will not take advantage of such an index if it exists, though...