Question

Assuming I have the following (simplified) models in a GAE Java application:

Entity project = new Entity("Project")
project.setProperty("name", "test");

and

Entity task = new Entity("Task");
task.setProperty("name", "test");
task.setProperty("project", project.getKey());

How do I get all Tasks that have a reference to a specific Project?

I’ve tried

    Query q = new Query("Task");
    Query.FilterPredicate projectFilter =
            new Query.FilterPredicate("project",
                    Query.FilterOperator.EQUAL,
                    project.getKey()
                    );
    q.setFilter(projectFilter);

But to no avail.
I’ve check the actual data with the Datastore viewer and everything is in place.
Tasks have a proper Key to a project and all of the properties are indexed.

The only thing that seems out of the ordinary, is the fact that (considering my app supports multi-tenancy), that Project key as a namespace prefix on the viewer.

Could that be the problem, and is there any solution?

Many thanks in advance.

Answer 1

try to use project.getKey().getId() instead,

or use the special key filter: Entity.KEY_RESERVED_PROPERTY

which is described here:

https://developers.google.com/appengine/docs/java/datastore/queries#Key_Filters