public static JoinPredicateInfo constructJoinPredicateInfo(HiveMultiJoin mj) throws CalciteSemanticException {
      return constructJoinPredicateInfo(mj, mj.getCondition());
    }
NOTE: Join Schema = left Schema + (right Schema offset by
left.fieldcount). Hence its ok to return projections from left in child
schema.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/HiveCalciteUtil.java