gistfile1.aw

<?php

    function calculate_row_id($log_id) {
        if ($this->get_autoinc_type() == self::AUTOINC_ODD_EVEN) {
            $row_id = ceil($log_id / 2) % $this->get_max_rows();
        }
        elseif ($this->get_autoinc_type() == self::AUTOINC_NORMAL) {
            $row_id = ($log_id - 1) % $this->get_max_rows() + 1;
        }
        return $row_id;
    }

    protected function _get_invariant_columns() {

        if ($this->get_autoinc_type() == self::AUTOINC_NORMAL) {

            $ddb_expression = '(SELECT COALESCE(MAX('.$this->get_log_id_column().'), 0) ' .
                                    '% '.$this->get_max_rows().' + 1 ' .
                                    'FROM '.$this->get_table_name().' AS t)';
        }
        elseif ($this->get_autoinc_type() == self::AUTOINC_ODD_EVEN) {

            $ddb_expression = '(SELECT CEIL(COALESCE(MAX('.$this->get_log_id_column().'), -1) + 2 / 2)' .
                                    '% '.$this->get_max_rows() .
                                    'FROM '.$this->get_table_name().' AS t)';
        }

        return array($this->get_row_id_column() => DDBExpression($ddb_expression));
    }