@Override
  public int hashCode() {
    int superHashCode = super.hashCode();
    HashCodeBuilder builder = new HashCodeBuilder();
    builder.appendSuper(superHashCode);
    builder.append(column);
    builder.append(tabAlias);
    return builder.toHashCode();
  }
@param isSkewedCol the isSkewedCol to set
ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeColumnDesc.java