@Override
  public String getDisplayString(String[] children) {
    return getStandardDisplayString("cardinality_violation", children, ",");
  }
Function intended to fail. It is used in query parts which should not return anything, and thus mark the problem.
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDFCardinalityViolation.java