Great news! I'm currently having some problems with second level cache and JPA, so a nice alternative like SimpleDS is a good idea. Just one question: does SimpleDS support query caching too? I've some very popular queries and want to cache their results in a 2nd level cache (not only its entities)
Thanks and congratulation for the release Sérgio Lopes http://www.caelum.com.br On May 4, 6:31 am, Nacho Coloma <icol...@gmail.com> wrote: > We are really excited with this release, which is the first feature- > complete release of SimpleDS. Lots of things have been included in so > little time. > > Getting up-to-date with AppEngine > ============================ > > It's hard to keep up the pace with these guys. This release includes: > > * Unindexed attributes. > * Cursors support. > * IN and != clauses. > > Cache > ===== > > We have included a great Level 1 and Level 2 cache [1]. If you come > from JDO/JPA, you may already know how it works: > > * Level 1 cache: This is basically a Map bound to the current thread. > Until the end of the current request, any get() invocation will check > this cache first. If a match is found, no invocation will be > propagated to GAE. > * Level 2 cache: Datastore entities are also stored in memcache, which > is a second chance to get a positive match. > > Cacheable entities must be marked with @Cacheable, with an optional > expiration time. This feature will work with single and batch get(), > and the cache entries are updated with put() and delete() > invocations. > > // Invoke memcache or the datastore > List<MyData> data = entityManager.get(key1, key2, key3); > > // this does not invoke anything (resolved by the Level 1 cache) > MyData d2 = entityManager.get(key1); > > Functions > ======== > > We are going extremely functional these days [2]. This release > includes a package with functions to transform collections and > PagedList instances, which can be combined with batch get() to get > even better performance results. This is a simple example, equivalent > to a common situation with relationships: > > // n + 1 requests to the datastore > List<MyData> data = entityManager.find(query); > Collection<Parent> parents = > Lists.newArrayListwithCapacity(data.size()); > for (MyData d : data) { > parents.add(entityManager.get(d.getKey().getParent()); > > } > > // Transformations: 2 requests > List<MyData> data = entityManager.find(query); > Collection<Key> parentKeys = Collections2.transform(data, new > EntityToParentKeyFunction(MyData.class)); > Collection<Parent> parents = entityManager.get(parentKeys); > > That's all it takes to get all entities and their parents, and store > them in the Level 1 cache so any request by PK will not hit memcache > or the datastore. This release includes functions to retrieve parent > and foreign keys, and also works with PagedList. We have taken two > real-world snapshots with just this optimization (transformation + > cacheable), applied to a single loop: > > Before:http://www.flickr.com/photos/koliseocom/4575062969/sizes/l/ > After:http://www.flickr.com/photos/koliseocom/4575696456/sizes/o > > Notice that requests "before" are targeted to the datastore, while > most of the "after" are memcache requests. > > Background tasks > ============== > > I know that background tasks [3] are in the roadmap for AppEngine, but > we needed these today. This started as an exercise to upgrade the > datastore schema (add properties, delete entities, etc) and ended up > as a full reusable implementation of tasks that I expect to deprecate > once that AppEngine includes its own, probably better, implementation. > > Background tasks require adding a servlet to web.xml (and optionally > appengine-web.xml as an admin-console entry) and configuring the tasks > on application start using plain Java. Tasks can be invoked directly > by cron triggers, queues or by POST requests. > > public class WriteBehindCacheTask extends IterableTask<MyClass> { > > protected WriteBehindCacheTask() { > super("my-task-id"); > } > > @Override > protected SimpleQuery createQuery(TaskRequest request) { > return entityManager.createQuery(MyClass.class); > } > > @Override > protected void process(MyClass entity, TaskRequest request) { > // ...modify entity... > entityManager.put(entity); > } > > } > > Query cursors and execution deferral will be done transparently (no > need to limit or handle cursors). There are some implementation > superclasses depending on what you need to do, and some of them just > use the raw AppEngine datastore and don't even require SimpleDS to > work. > > This is the first feature-complete release of SimpleDS. Next on the > roadmap: cached queries and we may be revisiting relations. > > As always, all kind of feedback is welcome. > > Nacho. > > [1]http://code.google.com/p/simpleds/wiki/Cache > [2]http://code.google.com/p/simpleds/wiki/Functions > [3]http://code.google.com/p/simpleds/wiki/BackgroundTasks > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine for Java" group. > To post to this group, send email to google-appengine-j...@googlegroups.com. > To unsubscribe from this group, send email to > google-appengine-java+unsubscr...@googlegroups.com. > For more options, visit this group > athttp://groups.google.com/group/google-appengine-java?hl=en. -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to google-appengine-j...@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. 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