If the bulk load input files do not match the existing region boudaries, the files will be splitted.
In the unfornate cases where the files need to be splitted multiple times,
the process can consume unnecessary space and can even cause out of space.
Here is over-simplified example.
Orinal size of input files:
consumed space: size --> 300GB
After a round of splits:
consumed space: size + tmpspace1 --> 300GB + 300GB
After another round of splits:
consumded space: size + tmpspace1 + tmpspace2 --> 300GB + 300GB + 300GB
Currently we don't do any cleanup in the process. At least all the intermediate tmpspace (not the last one) can be deleted in the process.