Question

I want to delete a document in lucene 2.4 with java. My code is

  Directory directory = FSDirectory.getDirectory("c:/index");
  IndexReader indexReader = IndexReader.open(directory);
  System.out.println("num="+indexReader.maxDoc());
  indexReader.deleteDocuments(new Term("name","1"));
  System.out.println("num="+indexReader.maxDoc());

 output 
         num=1
         num=1     

Answer 1

In my opinion it is best to use Indexwriter to delete the documents, since Indexreader buffers the deletions and does not write changes to the index until close() is called on.; unless you use the same reference for search.

The Lucene wiki states

Generally it’s best to use IndexWriter
for deletions, unless

you must delete by document number

you need your searches to
immediately reflect the deletions or

you must know how many documents
were deleted for a given
deleteDocuments invocation

I can see you want the maxdoc value for the document in memory so its a better approach to use Indexwriter

so the answer for your question is

you should close the Indexreader object or use Indexwriter for deletions