Hello app engine team,
I'd like to have a search form, which allows user to search next if more
result available by using a Cursor.
My issue is, in the last chunk, I am not able to detect if it's.
Therefore, I will need to execute one additional query to test if more data.
Can you please advise if other approach, without using the 2nd query.
Thanks.
By document, CursorHelper.getCursor(List<?>) will return a Cursor which
points to the last element in the list.
The code is below (correct according to doc)
import com.google.appengine.api.datastore.Cursor;
EntityManager em = ...
Query query = em.createQuery(queryString);
query.setMaxResults(20);
em.getTransaction().begin();
List<TestEntity> testEntities = query.getResultList();
Cursor cursor = JPACursorHelper.getCursor(testEntities);
em.getTransaction().rollback();
Then I will need to invoke one more call later, to check a null cursor
returned indicates no more data available
query.setMaxResults(1);
query.setHint(JPACursorHelper.CURSOR_HINT, cursor);
em.getTransaction().begin();
List<TestEntity> testEntities = query.getResultList();
Cursor cursor = JPACursorHelper.getCursor(testEntities);
em.getTransaction().rollback();
By curiosity (please correct me if I'm wrong), I looked into
org.datanucleus.store.appengine.query
and found that StreamingQueryResult returned by DatastoreQuery,
which was in fact constructed from
com.google.appengine.api.datastore.QueryResultList.
The document say return a cursor that points to the result immediately after
the last one in this list.
http://code.google.com/appengine/docs/java/javadoc/com/google/appengine/api/datastore/QueryResultList.html#getCursor()
So I wonder if CursorHelper.getCursor(List<?>) can have something similar?
Thank you.
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