@Override
    public RelDistribution getDistribution(HiveJoin join) {
      return HiveAlgorithmsUtil.getJoinRedistribution(join.getJoinPredicateInfo());
    }
BUCKET_JOIN is a hash joins where one bucket of the non streaming tables
is kept in memory at the time.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/cost/HiveOnTezCostModel.java