An index manager is a component responsible for how and when changes are applied to a Lucene index. It coordinates the optimization strategy, the directory provider, and worker back ends (seen later in this chapter), and various other low-level components.
Hibernate Search includes two index manager implementations out of the box. The default is
directory-based, and is a very sensible choice in most situations.
The other built-in alternative is
near-real-time. It is a subclass inheriting from the directory-based index manager, but is designed for low-latency index writes. Rather than performing adds or deletes on the disk right away, this implementation queues them in the memory so they may be written more efficiently in ...