Lucene - The First Parameter of the Index Writer

[JiaPei Jen]

I am constructing a web site. I am learning the Lucene so that I can use it to search the database. I started with reading the "Introdution In Text Indexing with Jakarta Apache Lucene" at http://www.onjava.com/pub/a/onjava/2003/01/15/lucene.html
and in the example given, it looks that I have to specify a directory for the first parameter of the IndexWriter (see below).

   String indexDir = System.getProperty
       ("java.io.tmpdir", "tmp") + System.getProperty
       ("file.separator") + "index-1";
   Analyzer analyzer = new StandardAnalyzer();
   boolean createFlag = true;
   IndexWriter writer = new IndexWriter(indexDir, 
                                analyzer, createFlag);

I have a record created and stored in a table in my database whenever a user submits his/her inputs. And I want to index that record. What should be the indexDir in my case? Should I follow the above example and use "java.io.tmpdir"? I sort of doubt it. Please advise.