Major Description
When run TPCDS Q3 [1] with lots predicates to filter out the partitions, the optimizer rule BooleanSimplification take about 2 seconds (it use lots of sematicsEqual, which require copy the whole tree).
It will great if we could speedup it.
[1] https://github.com/cloudera/impala-tpcds-kit/blob/master/queries/q3.sql
cc marmbrus
