.net – Updating Lucene index from two different threads in a web application

According to this page,

Indexing and searching are not only thread safe, but process safe. What this means is that:

• Multiple index searchers can read the lucene index files at the same time.
• An index writer or reader can edit the lucene index files while searches are ongoing
• Multiple index writers or readers can try to edit the lucene index files at the same time (it's important for the index writer/reader to be closed so it will release the file lock). However, the query parser is not thread safe, so each thread using the index should have its own query parser.

The index writer however, is thread safe, so you can update the index while people are searching it. However, you then have to make sure that the threads with open index searchers close them and open new ones, to get the newly updated data.

Yes, Lucene can search from and write to an index at the same time as long as no more than 1 IndexWriter writes to it. If you want the new records visible ASAP, have the IndexWriter call the commit() function often (see IndexWriter's JavaDoc for details).

These Wiki pages might also help:

ImproveIndexingSpeed

ImproveSearchingSpeed