Support Rollup/Cube/GroupingSets
revert the unnecessary changes
Add GroupingExpression to replace the Seq[Expression]
Optimization about reduce memory costs during the HashOuterJoin
Add BroadcastHashOuterJoin
remove commented old codes
add comment
add testsuite
optimize some codes
change testsuite
Merge branch 'master' of https://github.com/apache/spark into SPARK-4485
remove commented codes
fix spell bug
fix bug: missing output when the join-key is null.
add BroadcastLeftSemiJoinHash
add testsuite
performance optimization
add throw and style
change import
window function