The typical use of a JDOQL query is to translate it into the native query language of the datastore and return objects matched by the query. For many datastores it is simply impossible to support the full JDOQL syntax in the datastore native query language and so it is necessary to evaluate the query in-memory. This means that we evaluate as much as we can in the datastore and then instantiate those objects and evaluate further in-memory. Here we document the current capabilities of in-memory evaluation in DataNucleus.

• Query methods Collection.contains , Map.containsKey , Map.containsValue and Map.get are not supported currently
• Only simple subqueries are supported currently

To enable evaluation in memory you specify the query extension datanucleus.query.evaluateInMemory to true as follows

query.addExtension("datanucleus.query.evaluateInMemory","true");

This is also useful where you have a Collection of (persisted) objects and want to run a query over the Collection. Simply turn on in-memory evaluation, and supply the candidate collection to the query, and no communication with the datastore will be needed.