An Extent is a logical view of all persistent instances of a given persistence-capable class, possibly including subclasses. Extents are obtained from PersistenceManagers, and are usually used to specify the candidate objects to a Query.

The Extent interface is straightforward. The getCandidateClass method returns the persistence-capable class of the Extent's instances. The hasSubclasses method indicates whether instances of subclasses are also included.

You can obtain an iterator over every object in an Extent using the iterator method. The iterators used by some implementations might consume data store resources; therefore, you should always close an Extent's iterators as soon as you are done with them. You can close an individual iterator by passing it to the close method, or you can close all open iterators at once with closeAll.