About support ORC Filter pushdown

[Shen, Xiangxiang]

Hi all，

               In arrow dataset, Filter pushdown can improve reading files 
performance greatly. We notice parquet has implemented, 
https://github.com/apache/arrow/blob/35b3567e73423420a99dbe6116f000e3c77d2a4c/cpp/src/arrow/dataset/file_parquet.cc#L465-L484.
               But ORC fileformat has not supported Filter pushdown. It ignores 
the "filter" of  ScanOptions now.
               Would you have plans to support ORC Filter pushdown?


Thanks!