tree a8e1f10756c1487b6d7a32cdb7e80b333a769b3b
parent c20aa64af7e850d6c2c791d3a2aa05b8cb634759
author Jianfeng Jia <jianfeng.jia@gmail.com> 1456453700 -0800
committer Jianfeng Jia <jianfeng.jia@gmail.com> 1456465727 -0800

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>