This is useful, e.g., with collections that have large fields which /// change rarely and small fields that change more frequently. The smaller /// fields may be re-indexed in a new index and both indexes may be searched /// together. /// ///
Warning: It is up to you to make sure all indexes /// are created and modified the same way. For example, if you add /// documents to one index, you need to add the same documents in the /// same order to the other indexes. Failure to do so will result in /// undefined behavior. ///
Note that all subreaders are closed if this ParallelReader is closed.
////// A re-opened instance might share one or more subreaders with the old /// instance. Index modification operations result in undefined behavior /// when performed before the old instance is closed. /// (see {@link IndexReader#Reopen()}). ///
/// If subreaders are shared, then the reference count of those /// readers is increased to ensure that the subreaders remain open /// until the last referring reader is closed. /// ///