How does Apache Drill work on top of Hive? Does it execute MapReduce to query, or is it something like how Tez works? Thanks.
Neither. The storage plugin integrates Drill with Hive metadata. Drill does not invoke the Hive execution engine for any requests as stated in the Drill docs. You can use Drill to read Hive data, not to write. The Hive Storage Plugin section has more info.