[appengine-java] Re: Retrieving the number of entities into the DS

[Patrizio Munzi]

Hi, I thought of only keys queries but since I've got to use encoded keys I don't know if they work. However, I'll try it! thanks Yasuo Higa wrote: Hi Patrizio, what's the best way to know the number of entities of a specific kind saved into the DS? Of course I'd like to know the optimized way, without retrieving all the objects. If you have less than or equal to 1000 entities for a specific kind, the following codes are efficient. Low level API: DatastoreService ds = DatastoreServiceFactory.getDatastoreService(); int count = ds.prepare(new Queue("your kind").setKeysOnly()).countEntities(); JDO: PersistenceManager pm = PMF.get().getPersistenceManager(); Query query = pm.newQuery(Xxx.class); query.setResult("count(this)"); int count = (Integer) query.exeucte(); If you have more than 1000 entities for a specific kind, the following codes are efficient. Low level API: DatastoreService ds = DatastoreServiceFactory.getDatastoreService(); int count = ds.prepare(new Query("your kind").setKeysOnly()) .asList(FetchOptions.Builder.withOffset(0)).size(); JDO: PersistenceManager pm = PMF.get().getPersistenceManager(); Query query = pm.newQuery(Xxx.class); query.setResult("key");// "key" is a name of primary key field int count = ((List) query.exeucte()).size(); Hope this helps, Yasuo higa -- Patrizio Munzi Product Specialist Viale Bruno Buozzi, 19 - 00197 Roma (Italy) tel: +39 06 4543 3540 fax: +39 06 4543 3587 mobile: +39 393 7195 164 mail: patrizio.mu...@eris4.com web: http://www.eris4.com skype: eris4_munzi --~--~---------~--~----~------------~-------~--~----~ 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-java@googlegroups.com To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en -~----------~----~----~----~------~----~------~--~---