public function getModifyTableIndicesDDL(TableDiff $tableDiff)
    {
        $ret = '';

        foreach ($tableDiff->getRemovedIndices() as $index) {
            $ret .= $this->getDropIndexDDL($index);
        }

        foreach ($tableDiff->getAddedIndices() as $index) {
            $ret .= $this->getAddIndexDDL($index);
        }

        foreach ($tableDiff->getModifiedIndices() as $indexModification) {
            list($fromIndex, $toIndex) = $indexModification;
            $ret .= $this->getDropIndexDDL($fromIndex);
            $ret .= $this->getAddIndexDDL($toIndex);
        }

        return $ret;
    }