Implemented the memory-bounded HashGroupby and HashJoin for BigObject
It contains both hash grouby and hash join changes.
The main change is
1. update the ExternalGroupby to Hash-based groupby
2. update the Join operators to use the Buffermanager.
The buffer manager part is moved from the Sort package to upper
level so that it can be shared by all the operators.
Change-Id: I248f3a374fdacad7d57e49cf18d8233745e55460
Reviewed-on: https://asterix-gerrit.ics.uci.edu/398
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Yingyi Bu <buyingyi@gmail.com>
128 files changed
