关于用lucene不能删除索引的问题？谢谢！

最近用lucene做一个搜索，我的代码是这样的：
public synchronized void index(Message message) {
unIndex(message);
try {
Analyzer analyzer = luceneDocumentFactory.getAnalyzer();
IndexWriter writer = indexStore.createWriter(analyzer);
try {
Document doc = luceneDocumentFactory.createDocument(message);
writer.addDocument(doc);
writer.optimize();
} finally {
writer.close();
}
} catch (IOException e) {
throw new LuceneException("Cannot update index", e);
}
}

public synchronized void unIndex(Message message) {

try {
IndexReader reader = indexStore.createReader();
long toDelete = message.getId() ;
try {

Term t = new Term("id", Long.toString(toDelete));
int deleted =reader.delete(t);
System.out.println(deleted);//
} finally {
reader.close();
}
} catch (IOException e) {
throw new LuceneException("Cannot delete from index", e);
}
}
在对数据库操作时调用这两个方法，结果是总是不能正确删除索引，有谁知道吗？谢谢！！