http://code.google.com/appengine/docs/python/datastore/hr/overview.html see:
However, in the High Replication datastore, queries across entity groups (in other words, non-ancestor queries) may return stale results. In order to return strongly consistent query results in the High Replication environment, you need to query over a single entity group. This type of query is called an ancestor query<http://code.google.com/appengine/docs/python/datastore/queries.html#Ancestor_Queries> . Ancestor queries work because entity groups are a unit of consistency: all operations are applied to the entire group. Ancestor queries won't return data until the entire entity group is up to date. Thus, the data returned from ancestor queries on entity groups is strongly consistent. 2011/4/13 PT <[email protected]> > Hello, > I'm trying to wrap my head around the Appengine and its cloud > architecture. > > So if I have a program based on this large database where a multitude of > users around the world edit and update lets say a city map. > As I understand it right now peoples actions are applied not to the > database itself (as in being the sole one) but to "clones" of it > distributed around the world and which are synchronized realitively > quickely. > > So taking my example, what happens if a person in France adds a building on > the map while an other edits its color and someone else changes its name all > of this while an other group of people in Australia (thus working on an > other clone of the DB) at the very same time edit different information on > the very same grid coordinates, and then imagine 5 other groups around the > world doing the same thing. What would actually happen ? > > I'm asking this as I've read in other threads about the Appengine that even > it has a strong integrity of its information it comes at a cost of its real > time handling of events. So is this true and how much so ? > > Thanks for any answers ;) > > -- > 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. > -- Gr, Wim den Ouden <https://profiles.google.com/wdenouden>, Offline web application developer based on Javascript<https://developer.mozilla.org/en/javascript> , Html <http://en.wikipedia.org/wiki/HTML5>, Css<http://en.wikipedia.org/wiki/CSS>, Python <http://www.python.org/>, Google app engine<http://code.google.com/intl/nl/appengine/> , Buuring <http://buuring.appspot.com>, developer tips<http://code.google.com/p/relat/wiki/gaetips> -- 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.
