public int getTagLength() {
    int tagLength = -1;
    for (byte tag : getExprs().keySet()) {
      tagLength = Math.max(tagLength, tag + 1);
    }
    return tagLength;
  }
@param skewKeysValuesTables
         set the table desc for storing skew keys and their corresponding
         value;
ql/src/java/org/apache/hadoop/hive/ql/plan/JoinDesc.java