lucene的写索引的操作问题

lucene的写操作，默认的时候writer = new IndexWriter(indexDir, analyzer, override);当override为TRUE的时候，lucene将进行重写操作，override为FALSE的时候将是增量索引的过程，对于重复的文章仍旧重复索引的。

if (writer == null) {   try {    writer = new IndexWriter(indexDir, analyzer, override);   } catch (IOException ioe) {    throw new RuntimeException(ioe);   }

   if (writer != null) {    writer.setMaxMergeDocs(25);    writer.setMaxBufferedDocs(25);   }  }