Queries in Lucene are executed on an IndexReader. Hibernate Search caches all index readers to maximize performance. Your code can access this cached resources, but you have to follow some "good citizen" rules.

DirectoryProvider orderProvider = searchFactory.getDirectoryProviders(Order.class)[0];
DirectoryProvider clientProvider = searchFactory.getDirectoryProviders(Client.class)[0];

ReaderProvider readerProvider = searchFactory.getReaderProvider();
IndexReader reader = readerProvider.openReader(orderProvider, clientProvider);

try {
    //do read-only operations on the reader
}
finally {
    readerProvider.closeReader(reader);
}

The ReaderProvider (described in Reader strategy), will open an IndexReader on top of the index(es) referenced by the directory providers. Because this IndexReader is shared amongst several clients, you must adhere to the following rules:

Aside from those rules, you can use the IndexReader freely, especially to do native queries. Using the shared IndexReaders will make most queries more efficient.