Hi there, can anyone from Google shines some light on the issue I
posted last week? I just need to find out if it is a major limitation
on google's part with no workaround so that I can move forward
accordingly. Thanks a lot.
On Oct 23, 11:01 am, king <kingalpha...@gmail.com> wrote:
> Thanks so much for the feedback. I actually tried to extend the Key
> CONTAINS concept to other fields but ran into a big wall right away.
> It would be great to get your 2 cents. Here is the root of my
> problem:
>
> I have a student object, it has a number of qualifying attributes, for
> example:
> int gpa: 1 = 0 to 2.0, 2 = 2.0 to 3.0, 3 = 3.0 to 4.0
> int ageGroup: 1 = 0 to 17, 2 = 18 to 30, 3 = 30 to 65, 4 = 65+
> ArrayList schoolPreference: [0] = 'MIT', [1] = 'Stanford', [2] =
> 'Harvard', [3] = 'Yale'
>
> Now, I need to create a query to find out all the students where (gpa
> = 2 or gpa = 3) AND (age group = 3 or age group = 4) AND
> (schoolPreference contains MIT or Yale, or both)
>
> As far as I know, GAE doesn't support OR operator in a query, so the
> only way I can get the query above to work is to have multiple sub-
> queries and do a manual join on all the datastore resultsets to
> artificially create a union. If so, big problem arises:
>
> Since I have so many OR sub-conditions, if every OR translates into a
> separate sub-query, literally speaking, I need to do a full
> permutation of all the conditions (full product of all the OR and AND
> conditions) in all my sub-queries to achieve my goal, which doesn't
> make any sense if I keep adding more value types (such as more schools
> being selected in the student preference criteria) into my attributes,
> not to mention adding more attributes to my student object. Is there
> any way to accomplish this query in GAE? Your help is greatly
> appreciated because this can be the deal breaker of whether my whole
> project can migrate to GAE or not. Thanks a lot in advance.
>
> On Oct 23, 1:51 am, Yasuo Higa <higaya...@gmail.com> wrote:
>
>
>
> > Hi Andy,
>
> > >> query.setFilter("key == :keyList");
> > >> List<Master> list = (List<Master>) query.execute(keyList);
>
> > > I'd like to know if that works with GAE/J, because it is illegal JDOQL
> > > syntax and would be a bug. JDOQL is supposed to follow Java syntax,
> > > and you simply cannot do
> > > Key == List<Key>
> > > and get success in Java.
>
> > You are right, but unfortunately the above query works on GAE/J.
>
> > I should have recommended the following query:
>
> > List<Key> keys = ...;
> > List<Object> ids = new ArrayList<Object>();
> > for (Key key : keys) {
> > ids.add(pm.newObjectIdInstance(Master.class, key));}
>
> > List<Master> list = (List<Master>) pm.getObjectsById(ids);
>
> > Thanks,
>
> > Yasuo Higa
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