public function optimize()
    {
        if (Zend_Search_Lucene_LockManager::obtainOptimizationLock($this->_directory) === false) {
            return false;
        }

        // Update segments list to be sure all segments are not merged yet by another process
        //
        // Segment merging functionality is concentrated in this class and surrounded
        // by optimization lock obtaining/releasing.
        // _updateSegments() refreshes segments list from the latest index generation.
        // So only new segments can be added to the index while we are merging some already existing
        // segments.
        // Newly added segments will be also included into the index by the _updateSegments() call
        // either by another process or by the current process with the commit() call at the end of _mergeSegments() method.
        // That's guaranteed by the serialisation of _updateSegments() execution using exclusive locks.
        $this->_updateSegments();

        $this->_mergeSegments($this->_segmentInfos);

        Zend_Search_Lucene_LockManager::releaseOptimizationLock($this->_directory);

        return true;
    }