public static RowResolver getCombinedRR(RowResolver leftRR,
      RowResolver rightRR) throws SemanticException {
    RowResolver combinedRR = new RowResolver();
    IntRef outputColPos = new IntRef();
    if (!add(combinedRR, leftRR, outputColPos)) {
      LOG.warn("Duplicates detected when adding columns to RR: see previous message");
    }
    if (!add(combinedRR, rightRR, outputColPos)) {
      LOG.warn("Duplicates detected when adding columns to RR: see previous message");
    }
    return combinedRR;
  }
Return a new row resolver that is combination of left RR and right RR.
The schema will be schema of left, schema of right

@param leftRR
@param rightRR
@return
@throws SemanticException
ql/src/java/org/apache/hadoop/hive/ql/parse/RowResolver.java