Did u try Cursors?
http://code.google.com/appengine/docs/java/datastore/queries.html#Query_Cursors
On Thu, Sep 15, 2011 at 1:20 PM, cghersi <cristiano.ghe...@gmail.com> wrote:
> Hi all,
>
> I'm facing a little problem of scalability. I'm using JDO to query my
> datastore.
> I need to retrieve all the keys of a given entity (such keys are of
> type Long). Given that in my datastore such entity has 1.000.000 of
> records, I need to get them in a very efficient way, in order to loop
> over this set in a background task.
>
> Which is the most efficient way to do this?
>
> And what if I need not only the key, but also another field? Let's say
> I've got an entity called TPImage:
> Long idPic; //this is my key
> String title; //this is the field I want to retrieve together with the
> key
> ... // other properties
>
> How may I retrieve both idPic and title in a single efficient query?
> Something like
> Query q = new Query("select idPic, title from " +
> TPImage.class.getName());
> but more efficient?
>
> Thank you very much!
>
> Bye
> cghersi
>
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