KeyValueDataSource.keys() will not work as intended

[SergioDemianLerner]

The method is defined as : public Set<byte[]> keys();
A java byte[] does not implement hashCode() and therefore the resulting map will not support the contains() method (only iteration).

The resulting type should be Set.

[SergioDemianLerner]

For example, LevelDbDataSource.java returns a HashSet.

[SergioDemianLerner]

It's also possible to change it to a Collection, with potential duplicates.