There are 2 main differences: 1. Indexes. You probably want to mark most of the items as unindexed to lower the cost of a datastore write and datastore storage. 2. Possible serialization/deserialization time. Items are stored as protocol buffers (http://code.google.com/p/protobuf/). I don't know off the top of my head how this performs with large arrays versus individual properties. My suspicion is that there shouldn't be a real world difference, but I haven't verified this with my own testing, and I don't know how many properties you have in mind.
The documentation talks about query speed vs. get by key because that's where the bulk of the time will be spent (cross machine RPCs). -- Ikai Lan Developer Programs Engineer, Google App Engine plus.ikailan.com | twitter.com/ikai On Wed, Dec 14, 2011 at 8:19 AM, Miguel <[email protected]> wrote: > I am designing the model of an app that needs a lot of values to be > stored and I am thinking about which is the best in terms of > retrieving-time: > - define an array with all of them inside > - define a property for each of them > > My fear is that in the second case I will have a lot of "column" in > the datastore: which are the differences in terms of retrieving an > "Entity" with a lot of property or an entity with just 1 array? > I read a lot of documentation but it talks only about the difference > between the get and the query and not about the properties' number. > > Thank you > Michele > > -- > 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 > [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-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 [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-java?hl=en.
