Hi

I think 0.9.0 introduced regression where ByteBuffers comparison has changed.
This likely is a result of a change in #199
where custom comparator for byte[] and ByteBuffer has been swapped for Arrays.compare(o1, o2);

It seems original implementation was always using unsigned bytes.
Now default implementation uses unsigned bytes.
As far as I understand this can be modified by passing MDB_INTEGERKEY to _env.openDb and this is a setting persisted in Db.
This was never a requirement in previous versions so it seems existing databases are not compatible unless the flag is added in the code.

When I try to add that flag my tests still fail unable to either get key/value or iterate through them (iterator is empty).

This is likely related to
#228