Hi Peter, There is a very big difference. Strong consistency will ensure you are seeing the most recent version of the data in that entity group; if a strongly consistent request hits a server that does not have the most recent version of an entity group's data it will cause that server to 'catch up' before it returns the results. What this boils down to is that strong consistency means all reads are done in a transaction, which means one transaction for each entity group.
Eventual consistency means you'll get whatever data is on the datastore node the request hits. That data may be the latest or it might be out-of-date -- no guarantees are made. It also will not cause that node to catch up if it is out-of-date. Some things can tolerate eventual consistency, others can not. Up to you to decide if you'd prefer the faster reads. Robert On Tue, Jul 5, 2011 at 12:01, Peter Murray <[email protected]> wrote: > > Greetings folks, > It seems that entities load almost ten times faster when > using ReadPolicy.Consistency.EVENTUAL in the DatastoreServiceConfig. In my > little test, using the default of STRONG, loading 100 Entities by key (e.g. > ds.get(keys) ) takes around 500ms (plus or minus), but with EVENTUAL it > seems to be about 50ms. My question is, with the HR datastore, what are the > practical differences between STRONG and EVENTUAL when the entities are not > in a single entity-group anyway? I wonder why the big difference in lookup > by key performance between the two? Could it be that under HR most lookups > could be done with EVENTUAL read consistency? > Thanks! > -pete > > -- > 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/-/9x6eQ4EBia8J. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/google-appengine?hl=en. > -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
