Adds a new query option DEFAULT_JOIN_DISTRIBUTION_MODE to
control which join distribution mode is chosen when the join
inputs have an unknown cardinality (e.g., missing stats) or when
the expected costs of the different strategies are equal.
Values for DEFAULT_JOIN_DISTRIBUTION_MODE: [BROADCAST, SHUFFLE]
Default: BROADCAST
Note that this change effectively undoes IMPALA-5120.
Testing:
- Added new planner tests
- Core/hdfs run passed
Change-Id: Ibd34442f422129d53bef5493fc9cbe7375a0765c
Reviewed-on: http://gerrit.cloudera.org:8080/7059
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Tested-by: Impala Public Jenkins
ecda49f3e3