public function get_action_sql() {
        global $DB;

        // In new logs we have a field to pick, and in legacy try get this from action.
        if ($this->filterparams->logreader instanceof logstore_legacy\log\store) {
            $action = $this->get_legacy_crud_action($this->filterparams->action);
            $firstletter = substr($action, 0, 1);
            if ($firstletter == '-') {
                $sql = $DB->sql_like('action', ':action', false, true, true);
                $params['action'] = '%'.substr($action, 1).'%';
            } else {
                $sql = $DB->sql_like('action', ':action', false);
                $params['action'] = '%'.$action.'%';
            }
        } else if (!empty($this->filterparams->action)) {
             list($sql, $params) = $DB->get_in_or_equal(str_split($this->filterparams->action),
                    SQL_PARAMS_NAMED, 'crud');
            $sql = "crud " . $sql;
        } else {
            // Add condition for all possible values of crud (to use db index).
            list($sql, $params) = $DB->get_in_or_equal(array('c', 'r', 'u', 'd'),
                    SQL_PARAMS_NAMED, 'crud');
            $sql = "crud ".$sql;
        }
        return array($sql, $params);
    }