This approach would require that the full results be enlisted in cache (i.e., traversed) prior to the EM being closed. That may or may not be what you're looking for.
If what you're looking for is to hold the cursor to the DB open across multiple requests, you'll need to create an extended-persistence-context EM (either via a stateful session bean or via using a non-JTA entity manager, obtained through an EMF), and then do the query in that EM and bind the query into session state somewhere. Of course, all the normal cautions about keeping database connections open across multiple requests apply. If you're just looking to page through results for a search-result-style listing, you might be interested in the JPA Query.setFirstResult() and Query.setMaxResults() calls -- these allow for efficient (but non-isolated) paging through queries. Don't forget to add an ordering to your query when you do this, of course. Oh, and OpenJPA is smart about using range data in the query cache. -Patrick -- Patrick Linskey BEA Systems, Inc. _______________________________________________________________________ Notice: This email message, together with any attachments, may contain information of BEA Systems, Inc., its subsidiaries and affiliated entities, that may be confidential, proprietary, copyrighted and/or legally privileged, and is intended solely for the use of the individual or entity named in this message. If you are not the intended recipient, and have received this message in error, please immediately return this by email and then delete it. > -----Original Message----- > From: Dain Sundstrom [mailto:[EMAIL PROTECTED] > Sent: Saturday, December 09, 2006 9:24 AM > To: open-jpa-dev@incubator.apache.org > Subject: Re: extending the life of a LRS query > > I am by no means an OpenJPA expert, but I did see something related > to this when reading the docs yesterday. OpenJPA has a > QueryResultsCache where it keeps the results of a query so if > you run > the query again you get the same results (I'm not sure if that is > what you want). Here is the code from the docs: > > OpenJPAEntityManagerFactory oemf = OpenJPAPersistence.cast(emf); > QueryResultCache qcache = oemf.getQueryResultCache(); > EntityManager em = emf.createEntityManager(); > > Query pinQuery = em.createQuery(...). > setParameter(0, paramVal0). > setParameter(1, paramVal1); > qcache.pin(pinQuery); > Query unpinQuery = em.createQuery(...). > setParameter(0, paramVal0). > setParameter(1, paramVal1); > qcache.unpin(unpinQuery); > > > Hope that helped. > > -dain > > On Dec 8, 2006, at 8:04 PM, roger.keays wrote: > > > > > Hi, > > > > I'm trying to use OpenJPA's fetch plan extensions to have a query > > return a > > large result set. It seems to work okay, except that the LRS gets > > closed / > > detached with the EntityManager, which only makes it useful > for one > > request. > > Is it possible to have the LRS stay open after the em has been > > disposed? > > > > Thanks, > > > > Roger > > -- > > View this message in context: http://www.nabble.com/extending-the- > > life-of-a-LRS-query-tf2784490.html#a7769269 > > Sent from the open-jpa-dev mailing list archive at Nabble.com. > >
