Adding sort to Objectify query causes empty result

Question

I'm experimenting with App Engine, Datastore and Objectify 4. I have a working Objectify query that fetches all entities of a given kind from the Datastore. I'm trying to sort the result based on a date:

List<MyEntity> entities = OfyService.ofy().load().type(MyEntity.class).order("-createdDate").list();

But after I add order, the query returns 0 records. This is my entity class:

@Entity
public class MyEntity
{   
    @Id Long id;
    Long userID;
    @Ignore String username;
    @Index String name;
    String url;
    String description;
    @Index Date createdDate;
    @Index int viewCount;
}

I've tried to order by other data types with no success. Why does this happen?

It's hard to say without seeing the full code, but do you get results if you remove the - in the order() to return results in ascending order? According to the documentation, App Engine should automatically create an index for Queries with no filters and only one sort order on a property, either ascending or descending. — tx802
I get the same result when removing the "-" from order(). For some reason, none of the indexes defined in the entity class are stored in the datastore, please read the answer I just added — André

Vinh Vo Vinh Vo · Accepted Answer · 2014-07-11T20:32:40

We need to define index manually in WEB-INF/datastore-indexes.xml.

<?xml version="1.0" encoding="utf-8"?>
<datastore-indexes
  autoGenerate="true">
    <datastore-index kind="AppMedia" ancestor="false">
        <property name="createdDate" direction="desc" />
    </datastore-index>
</datastore-indexes>

Then the index is created properly and the query will work. Note : The query will only work with those rows added after the index is configured properly.

Adding sort to Objectify query causes empty result

2 Answers