Github user ravipesala commented on the issue:
https://github.com/apache/carbondata/pull/2207
@kunal642 The empty Fact folder is created because first the segment is
written inside this folder like the normal flow and in the end while creating
segment file it moves the data to the flat folder. We cannot simply delete the
folder as the write path for segment needs to be changed and it has lot of
impact on current code.---
