public function getOperators()
    {
        // Issue with Doctrine
        // -------------------
        // @see http://www.doctrine-project.org/jira/browse/DDC-1857
        // @see http://www.doctrine-project.org/jira/browse/DDC-1858
        if ($this->hasDQLFunction() && version_compare(DoctrineVersion::VERSION, '2.5') < 0) {
            return array_intersect($this->operators, [self::OPERATOR_EQ,
                self::OPERATOR_NEQ,
                self::OPERATOR_LT,
                self::OPERATOR_LTE,
                self::OPERATOR_GT,
                self::OPERATOR_GTE,
                self::OPERATOR_BTW,
                self::OPERATOR_BTWE, ]);
        }

        return $this->operators;
    }