Yes, that will be efficient for more than 30 receivers. It will check the indexes for a row with receivers = 'whatever' and return those keys, so the number of receivers is not an issue (at read-time). you might find the datastore articles useful: http://code.google.com/appengine/articles/datastore/overview.html
The limit you are referring to with the number '30' is because some queries actually require multiple queries to be executed. Read (at least) the first two sections the the Datastore Queries docs: http://code.google.com/appengine/docs/java/datastore/queries.html#Overview Also, you might find objectify a better for for App Engine's datastore. http://code.google.com/p/objectify-appengine/ Robert On Wed, Mar 23, 2011 at 16:15, AppEngineNoob <[email protected]> wrote: > For example, if I have: "List A" and a "String B" > > What is the difference, in JDO (AppEngine), between the following two > conditions in a query: B == A; and A.contains(B);? > > Also, does the query in Slides 23-25 of > http://dl.google.com/io/2009/pres/W_0415_Building_Scalable_Complex_App_Engines.pdf > work efficiently in AppEngine (JDO) for more than 30 receivers? How > so, especially since I read in AppEngine documentation that each > contains() query can have a maximum of 30 items in the list. Do I not > use a contains() query to imitate the above slides (written in > Python)? If not, then how can I achieve the same results in JDO? > > Finally, how does AppEngine limit the subqueries for a query like > this: > > Key A = "bla bla"; > Query query = pm.newQuery("select from Message" > " where keys.contains(:A) "); > ArrayList <Key> result = query.execute(A); > where keys is a list property in the datastore. > > Any suggestions/comments are highly welcome. > > Thanks. > > -- > 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. > > -- 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.
