Currently Truncate Table (or Partition) is implemented using FileSystem.delete and then recreate the directory, so
1. it does not support HDFS Trash
2. if the table/partition directory is initially encryption protected, after being deleted and recreated, it is no more protected.
The new implementation is to clean the contents of directory using multi-threaded trashFiles. If Trash is enabled and has a lower encryption level than the data directory, the files under it will be deleted. Otherwise, they will be Trashed