Resolution: Won't Fix
Affects Version/s: None
Fix Version/s: None
Parquet files's dictionary could be used for predicate pushdown
select * from table where column = 10;
could skip reading the whole row group if the dictionary for column has values [5, 11, 17, 20]
This could save IO and improve performance.
We implemented predicate pushdown using dictionary in Presto for parquet files, and benchmark shows up to 40X speedup for selective queries.
Need to add an api to ParquetFileReader, so that it returns dictionaries for requested columns.
If the column is not dictionary encoded in this row group, return null.
If the not all column pages are dictionary encoded in this row group, return null.