private Operator invertOperator(Operator operator) {
    switch (operator) {
      case EQUALS:
        return Operator.NOTEQUALS;
      case NOTEQUALS:
      case NOTEQUALS2:
        return Operator.EQUALS;
      case GREATERTHAN:
        return Operator.LESSTHANOREQUALTO;
      case LESSTHAN:
        return Operator.GREATERTHANOREQUALTO;
      case GREATERTHANOREQUALTO:
        return Operator.LESSTHAN;
      case LESSTHANOREQUALTO:
        return Operator.GREATERTHAN;
      case LIKE:
        throw new UnsupportedOperationException("LIKE operator inversion is not supported.");
      default:
        throw new IllegalArgumentException("Unsupported operator for inversion: " + operator.getOp());
    }
  }
Override the default behavior for all visit methods. This will only return a non-null result
when the context has only one child. This is done because there is no generic method to
combine the results of the context children. In all other cases null is returned.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/parser/PartFilterVisitor.java