fix batch size during sort

Author: Davies Liu

python/pyspark/shuffle.py

@@ -512,9 +512,6 @@ def load(f):
                     f.close()
                 chunks.append(load(open(path, 'rb')))
                 current_chunk = []
-                gc.collect()
-                batch //= 2
-                limit = self._next_limit()
                 MemoryBytesSpilled += max(used_memory - get_used_memory(), 0) << 20
                 DiskBytesSpilled += os.path.getsize(path)
                 os.unlink(path)  # data will be deleted after close