As you pointed out, to guarantee strong consistency you need to use an Ancestor query, or retrieve an Entity by its Key value. In both cases, the data store should roll-forward any commits that have not yet been applied.
I am a little confused because it *looks *like you are retrieving the Entity by Key in your sample code, but I assume you are really saying that a (non-Ancestor) query down the line is returning inconsistent results. That is the expected behavior, and you have to design around it. The latency is usually a few seconds, although even that is not guaranteed. While you are correct that 30,000 Entities in one group sounds like a lot, you *may *be able to get away with it if the Contacts are not updated frequently or concurrently. In other words, if only that single User can update his/her own contacts one at a time, there will never be any update contention within the Entity Group, which (AFAIK) is the main reason to limit Entity group size. On Wednesday, May 9, 2012 2:03:33 PM UTC-4, savilak wrote: > > I use JDO and I update an Entity like this: > > pm.currentTransaction().begin(); > Contact c = (Contact) > pm.getObjectById(Contact.class, > encodedKey); > //JDOHelper.makeDirty(c, "groups");//Make a > field dirty -- > Comment 1 > c.setGroups(groupsNew); > pm.makePersistent(c); > pm.currentTransaction().commit(); > // Contact c1 = (Contact) > pm.getObjectById(Contact.class, encodedKey); -- Comment 2: This is > making the read consistent > > then I use Request Factory to read this Entity. 50% of the times I get > the Old value and not the New one. > > I know that is due to the High Replication Datastore (HRD). How can I > force the read always to be consistent? > > One way I managed to do it is by adding an extra read of the entity > right after its update. I do not like this approach. Why exactly is > this happening? > I also noticed that the makeDirty approach does not resolve the issue > (see Comment 1). > > I believe that forcing all the entities in the same entity group will > not be a good solution for my context either > (as it is described here > > https://developers.google.com/appengine/docs/java/datastore/structuring_for_strong_consistency). > > > I have User Accounts one User Account might have up to 30.000 > contacts. A typical query would be fetch a range of 100 contacts for a > specific User Account. > Entity Group will move parsing from Datastore to my application (since > I have no join facility in datastore). Is this correct? > > I would much appreciate some input from an HRD guru or anyone who has/ > d a similar issue. > > Thanks > Savilak > > > > > -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-appengine/-/4YnQRtdthSEJ. To post to this group, send email to google-appengine@googlegroups.com. To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
