protected function addConsumedWriteUnits($table, $units)
    {
        if (null !== $this->logger) {
            $this->log($units.' consumed write units on table '.$table);
        }

        if (isset($this->writeUnit[$table])) {
            $this->writeUnit[$table] += $units;
        } else {
            $this->writeUnit[$table] = $units;
        }
    }