Lucene.NET-检查索引中是否存在文档 [英] Lucene.NET - check if document exists in index

问题描述

我想检查我的Lucene.NET(4.0)索引中是否已经存在一个文档.我试过使用这篇文章中的以下代码.

I want to check whether or not a document already exists in my Lucene.NET (4.0) index. I have tried using the following code from this post.

IndexReader reader;
Term indexTerm = new Term("filepath", "C:\\my\\path");
TermDocs docs = reader.TermDocs(indexTerm);
if (docs.Next())
{
    continue;
}

但是我收到一条错误消息，告诉我reader未分配.我已经在Google上进行了很多搜索，但是在Lucene.NET 4中找不到有效的答案，这应该是一件很容易的事情.

But I get an error telling me that reader is unassigned. I have Googled this a lot and cannot find a working answer in Lucene.NET 4 for what should be quite an easy task.

编辑:IndexReader是一个抽象类.在文档中说使用Lucene.Net.Store.Directory作为参数调用IndexReader.Open()，但是它本身是抽象的.我得到的代码示例好像没有使用它.而且，在与用户链接的帖子中，我说代码的第一段有效.

edit: IndexReader is an abstract class. In the documentation it says to call IndexReader.Open() with Lucene.Net.Store.Directory as a parameter, but it itself is abstract. Code samples that I get use it as if it were not. Moreover, in the post I linked to the user said the first segment of code worked.

EDIT2 :我现在有可编译的代码.在这里:

I now have code that compiles. Here it is:

bool exists = false;
IndexReader reader = IndexReader.Open(Lucene.Net.Store.FSDirectory.Open(lucenePath), false);
Term term = new Term("filepath", "\\myFile.PDF");
TermDocs docs = reader.TermDocs(term);
if (docs.Next())
{
   exists = true;
}

文件myFile.PDF确实存在，但始终以false返回.当我在调试中查看docs时，其Doc和Freq属性指出它们引发了类型'System.NullReferenceException'的异常.

The file myFile.PDF definitely exists, but it always comes back as false. When I look at docs in debug, its Doc and Freq properties state that they "threw an exception of type 'System.NullReferenceException'.

推荐答案

您尚未将reader设置为任何值.您需要先对其进行初始化，然后再使用它.您可以这样做是因为您使用以下方法获得了索引的路径:

You haven't set reader to be anything. You need to initialise it before using it. You can do this is you have the path of the index using:

IndexReader reader = IndexReader.Open(indexDirectoryPath);

或:

Directory directory = FSDirectory.Open(indexDirectoryPath);
IndexReader reader = IndexReader.Open(directory);

或:

DirectoryInfo directoryInfo = new DirectoryInfo(indexDirectoryPath);
Directory directory = FSDirectory.Open(directoryInfo);
IndexReader reader = IndexReader.Open(directory);

其中，在所有情况下，indexDirectoryPath是作为string的索引位置的完整路径.使用哪种方式取决于您使用的Lucene.Net版本.

where indexDirectoryPath in all cases is the full path of the index location as a string. Which way you use depends on which version of Lucene.Net you are using.

此外，请确保在完成阅读器的操作后将其关闭(通过调用reader.Close())，否则可能会遇到文件锁定问题.

Additionally, make sure that you close the reader when you have finished with it (by calling reader.Close()), otherwise you will likely get file locking issues.

这篇关于Lucene.NET-检查索引中是否存在文档的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！