com.google.cloud.datastore.QueryResults Java Examples

/**
 * Removes all deleted blobs tracked in this index.
 *
 */
void removeData() {
  log.warn("removing all entries in the index of soft-deleted blobs...");
  Query<Entity> query = Query.newEntityQueryBuilder()
      .setNamespace(namespace)
      .setKind(DELETED_BLOBS)
      .build();
  QueryResults<Entity> results = gcsDatastore.run(query);
  List<Key> keys = StreamSupport.stream(
      Spliterators.spliteratorUnknownSize(results, Spliterator.ORDERED),
      false).map(entity -> entity.getKey()).collect(Collectors.toList());

  // datastore has a hard limit of 500 keys in a single delete
  List<List<Key>> partitions = Lists.partition(keys, 500);
  partitions.stream().forEach(partition -> gcsDatastore.delete(partition.toArray(new Key[partition.size()])) );

  log.warn("deleted {} blobIds from the soft-deleted blob index", keys.size());
}
 

@Override
public Result<Book> listBooks(String startCursorString) {
  Cursor startCursor = null;
  if (startCursorString != null && !startCursorString.equals("")) {
    startCursor = Cursor.fromUrlSafe(startCursorString);    // Where we left off
  }
  Query<Entity> query = Query.newEntityQueryBuilder()       // Build the Query
      .setKind("Book5")                                     // We only care about Books
      .setLimit(10)                                         // Only show 10 at a time
      .setStartCursor(startCursor)                          // Where we left off
      .setOrderBy(OrderBy.asc(Book.TITLE))                  // Use default Index "title"
      .build();
  QueryResults<Entity> resultList = datastore.run(query);   // Run the query
  List<Book> resultBooks = entitiesToBooks(resultList);     // Retrieve and convert Entities
  Cursor cursor = resultList.getCursorAfter();              // Where to start next time
  if (cursor != null && resultBooks.size() == 10) {         // Are we paging? Save Cursor
    String cursorString = cursor.toUrlSafe();               // Cursors are WebSafe
    return new Result<>(resultBooks, cursorString);
  } else {
    return new Result<>(resultBooks);
  }
}
 

public static void wipeDatastore() {
  Datastore datastore = getDatastore();
  QueryResults<Key> guestbooks =
      datastore.run(Query.newKeyQueryBuilder().setKind("Greeting").build());
  ArrayList<Key> keys = Lists.newArrayList(guestbooks);

  if (!keys.isEmpty()) {
    datastore.delete(keys.toArray(new Key[keys.size()]));
  }
}
 

@Override
public List<String> retrieveClaims(int limit) {
  // Get claim saved in Datastore
  Datastore datastore = getDatastoreInstance();
  Query<Entity> query = Query.newEntityQueryBuilder().setKind(claimsKind).setLimit(limit).build();
  QueryResults<Entity> results = datastore.run(query);

  List<String> claims = new ArrayList<>();
  while (results.hasNext()) {
    Entity entity = results.next();
    String claim = entity.getString("claim");
    if (claim != null) {
      claims.add(claim);
    }
  }
  return claims;
}
 

@Test
public void testNamespaceRunQuery() {
  setUpQueryTests();
  // [START datastore_namespace_run_query]
  KeyFactory keyFactory = datastore.newKeyFactory().setKind("__namespace__");
  Key startNamespace = keyFactory.newKey("g");
  Key endNamespace = keyFactory.newKey("h");
  Query<Key> query = Query.newKeyQueryBuilder()
      .setKind("__namespace__")
      .setFilter(CompositeFilter.and(
          PropertyFilter.gt("__key__", startNamespace),
          PropertyFilter.lt("__key__", endNamespace)))
      .build();
  List<String> namespaces = new ArrayList<>();
  QueryResults<Key> results = datastore.run(query);
  while (results.hasNext()) {
    namespaces.add(results.next().getName());
  }
  // [END datastore_namespace_run_query]
  assertEquals(ImmutableList.of("ghijklmnop"), namespaces);
}
 

public List<Greeting> getGreetings() {
  // This query requires the index defined in index.yaml to work because of the orderBy on date.
  EntityQuery query =
      Query.newEntityQueryBuilder()
          .setKind("Greeting")
          .setFilter(hasAncestor(key))
          .setOrderBy(desc("date"))
          .setLimit(5)
          .build();

  QueryResults<Entity> results = getDatastore().run(query);

  Builder<Greeting> resultListBuilder = ImmutableList.builder();
  while (results.hasNext()) {
    resultListBuilder.add(new Greeting(results.next()));
  }

  return resultListBuilder.build();
}
 

/**
 * Finds the ID of the first {@link PortabilityJob} in state {@code jobState} in Datastore, or
 * null if none found.
 *
 * <p>TODO(rtannenbaum): Order by creation time so we can process jobs in a FIFO manner. Trying to
 * OrderBy.asc("created") currently fails because we don't yet have an index set up.
 */
@Override
public UUID findFirst(JobAuthorization.State jobState) {
  Query<Key> query =
      Query.newKeyQueryBuilder()
          .setKind(JOB_KIND)
          .setFilter(PropertyFilter.eq(PortabilityJob.AUTHORIZATION_STATE, jobState.name()))
          // .setOrderBy(OrderBy.asc("created"))
          .setLimit(1)
          .build();
  QueryResults<Key> results = datastore.run(query);
  if (!results.hasNext()) {
    return null;
  }
  Key key = results.next();
  return UUID.fromString(key.getName());
}
 

@Test
public void deleteAllTest() {
	QueryResults<Key> queryResults = mock(QueryResults.class);
	when(queryResults.getResultClass()).thenReturn((Class) Key.class);
	doAnswer((invocation) -> {
		Arrays.asList(this.key1, this.key2).iterator()
				.forEachRemaining(invocation.getArgument(0));
		return null;
	}).when(queryResults).forEachRemaining(any());
	when(this.datastore
			.run(eq(Query.newKeyQueryBuilder().setKind("custom_test_kind").build())))
					.thenReturn(queryResults);

	verifyBeforeAndAfterEvents(
			new BeforeDeleteEvent(new Key[] { this.key1, this.key2 }, TestEntity.class, null, null),
			new AfterDeleteEvent(new Key[] { this.key1, this.key2 }, TestEntity.class, null, null),
			() -> assertThat(this.datastoreTemplate.deleteAll(TestEntity.class)).isEqualTo(2),
			x -> x.verify(this.datastore, times(1)).delete(same(this.key1), same(this.key2)));
}
 

/** Example of running a query to find all entities with an ancestor. */
// [TARGET run(Query)]
// [VARIABLE "my_parent_key_name"]
public List<Entity> run(String parentKeyName) {
  Datastore datastore = transaction.getDatastore();
  // [START run]
  KeyFactory keyFactory = datastore.newKeyFactory().setKind("ParentKind");
  Key parentKey = keyFactory.newKey(parentKeyName);
  // Build a query
  Query<Entity> query =
      Query.newEntityQueryBuilder()
          .setKind("MyKind")
          .setFilter(PropertyFilter.hasAncestor(parentKey))
          .build();
  QueryResults<Entity> results = transaction.run(query);
  List<Entity> entities = Lists.newArrayList();
  while (results.hasNext()) {
    Entity result = results.next();
    // do something with result
    entities.add(result);
  }
  transaction.commit();
  // [END run]
  return entities;
}
 

private Cursor cursorPaging(int pageSize, Cursor pageCursor) {
  // [START datastore_cursor_paging]
  EntityQuery.Builder queryBuilder = Query.newEntityQueryBuilder().setKind("Task")
      .setLimit(pageSize);
  if (pageCursor != null) {
    queryBuilder.setStartCursor(pageCursor);
  }
  QueryResults<Entity> tasks = datastore.run(queryBuilder.build());
  while (tasks.hasNext()) {
    Entity task = tasks.next();
    // do something with the task
  }
  Cursor nextPageCursor = tasks.getCursorAfter();
  // [END datastore_cursor_paging]
  return nextPageCursor;
}
 

@Test
public void testPropertyRunQuery() {
  setUpQueryTests();
  // [START datastore_property_run_query]
  Query<Key> query = Query.newKeyQueryBuilder().setKind("__property__").build();
  QueryResults<Key> keys = datastore.run(query);
  Map<String, Collection<String>> propertiesByKind = new HashMap<>();
  while (keys.hasNext()) {
    Key key = keys.next();
    String kind = key.getParent().getName();
    String propertyName = key.getName();
    Collection<String> properties = propertiesByKind.get(kind);
    if (properties == null) {
      properties = new HashSet<>();
      propertiesByKind.put(kind, properties);
    }
    properties.add(propertyName);
  }
  // [END datastore_property_run_query]
  Map<String, ImmutableSet<String>> expected = ImmutableMap.of("Task", ImmutableSet.of(
      "done", "category", "done", "completed", "priority", "created", "percent_complete", "tag"));
  assertEquals(expected, propertiesByKind);
}
 

@Test
public void testGetKindNs_Namespace_KindName() {
  final String namespace = "junit";
  final String kindName = "StringField";
  StatKindNs statEntity = stats.getKindNs(namespace, kindName);
  Query query = Query.newEntityQueryBuilder().setNamespace(namespace)
      .setKind(StatConstants.STAT_KIND_NS)
      .setFilter(StructuredQuery.PropertyFilter.eq(StatConstants.PROP_KIND_NAME, kindName))
      .build();
  QueryResults<com.google.cloud.datastore.Entity> results = datastore.run(query);
  com.google.cloud.datastore.Entity nativeEntity = null;
  if (results.hasNext()) {
    nativeEntity = results.next();
  }
  assertTrue(equals(statEntity, nativeEntity));
}
 

protected void deleteSessionWithValue(String varName, String varValue) {
  Transaction transaction = datastore.newTransaction();
  try {
    Query<Entity> query = Query.newEntityQueryBuilder()
        .setKind("SessionVariable")
        .setFilter(PropertyFilter.eq(varName, varValue))
        .build();
    QueryResults<Entity> resultList = transaction.run(query);
    while (resultList.hasNext()) {
      Entity stateEntity = resultList.next();
      transaction.delete(stateEntity.getKey());
    }
    transaction.commit();
  } finally {
    if (transaction.isActive()) {
      transaction.rollback();
    }
  }
}
 

@Override
public void init(FilterConfig config) throws ServletException {
  // initialize local copy of datastore session variables

  datastore = DatastoreOptions.getDefaultInstance().getService();
  keyFactory = datastore.newKeyFactory().setKind("SessionVariable");
  // Delete all sessions unmodified for over two days
  DateTime dt = DateTime.now(DateTimeZone.UTC);
  Query<Entity> query = Query.newEntityQueryBuilder()
      .setKind("SessionVariable")
      .setFilter(PropertyFilter.le("lastModified", dt.minusDays(2).toString(dtf)))
      .build();
  QueryResults<Entity> resultList = datastore.run(query);
  while (resultList.hasNext()) {
    Entity stateEntity = resultList.next();
    datastore.delete(stateEntity.getKey());
  }
}
 

@Override
public Result<Book> listBooksByUser(String userId, String startCursorString) {
  Cursor startCursor = null;
  if (startCursorString != null && !startCursorString.equals("")) {
    startCursor = Cursor.fromUrlSafe(startCursorString);    // Where we left off
  }
  Query<Entity> query = Query.newEntityQueryBuilder()          // Build the Query
      .setKind("Book4")                                        // We only care about Books
      .setFilter(PropertyFilter.eq(Book.CREATED_BY_ID, userId))// Only for this user
      .setLimit(10)                                            // Only show 10 at a time
      .setStartCursor(startCursor)                             // Where we left off
      // a custom datastore index is required since you are filtering by one property
      // but ordering by another
      .setOrderBy(OrderBy.asc(Book.TITLE))
      .build();
  QueryResults<Entity> resultList = datastore.run(query);   // Run the Query
  List<Book> resultBooks = entitiesToBooks(resultList);     // Retrieve and convert Entities
  Cursor cursor = resultList.getCursorAfter();              // Where to start next time
  if (cursor != null && resultBooks.size() == 10) {         // Are we paging? Save Cursor
    String cursorString = cursor.toUrlSafe();               // Cursors are WebSafe
    return new Result<>(resultBooks, cursorString);
  } else {
    return new Result<>(resultBooks);
  }
}
 

@Override
public Result<Book> listBooks(String startCursorString) {
  Cursor startCursor = null;
  if (startCursorString != null && !startCursorString.equals("")) {
    startCursor = Cursor.fromUrlSafe(startCursorString);    // Where we left off
  }
  Query<Entity> query = Query.newEntityQueryBuilder()       // Build the Query
      .setKind("Book4")                                     // We only care about Books
      .setLimit(10)                                         // Only show 10 at a time
      .setStartCursor(startCursor)                          // Where we left off
      .setOrderBy(OrderBy.asc(Book.TITLE))                  // Use default Index "title"
      .build();
  QueryResults<Entity> resultList = datastore.run(query);   // Run the query
  List<Book> resultBooks = entitiesToBooks(resultList);     // Retrieve and convert Entities
  Cursor cursor = resultList.getCursorAfter();              // Where to start next time
  if (cursor != null && resultBooks.size() == 10) {         // Are we paging? Save Cursor
    String cursorString = cursor.toUrlSafe();               // Cursors are WebSafe
    return new Result<>(resultBooks, cursorString);
  } else {
    return new Result<>(resultBooks);
  }
}
 

/** Example of running a query to find all entities of one kind. */
// [TARGET run(Query, ReadOption...)]
// [VARIABLE "my_kind"]
public List<Entity> runQuery(String kind) {
  // TODO change so that it's not necessary to hold the entities in a list for integration testing
  // [START runQuery]
  StructuredQuery<Entity> query = Query.newEntityQueryBuilder().setKind(kind).build();
  QueryResults<Entity> results = datastore.run(query);
  List<Entity> entities = Lists.newArrayList();
  while (results.hasNext()) {
    Entity result = results.next();
    // do something with result
    entities.add(result);
  }
  // [END runQuery]
  return entities;
}
 

@Before
public void setUp() throws Exception {
  MockitoAnnotations.initMocks(this);
  store = new DatastoreStore();
  KeyFactory keyFactory = new KeyFactory("project").setKind("kind");
  key = keyFactory.newKey(keyId);
  attributeKey = keyFactory.newKey("attribute");
  QueryResults<Key> keyQueryResults = new IteratorQueryResults<>(ImmutableList.of(key).iterator());

  when(datastore.newKeyFactory()).thenAnswer((invocation) -> new KeyFactory("project"));
  when(datastore.run(any(KeyQuery.class))).thenReturn(keyQueryResults);

  when(manager.getContext()).thenReturn(new StandardContext());
  when(manager.willAttributeDistribute(anyString(), any())).thenReturn(true);
  when(manager.createEmptySession()).thenReturn(new DatastoreSession(manager));

  store.setDatastore(datastore);
  store.setClock(clock);
  store.setSessionKind("kind");
  store.setManager(manager);
}
 

protected void deleteSessionWithValue(String varName, String varValue) {
  Transaction transaction = datastore.newTransaction();
  try {
    Query<Entity> query = Query.newEntityQueryBuilder()
        .setKind("SessionVariable")
        .setFilter(PropertyFilter.eq(varName, varValue))
        .build();
    QueryResults<Entity> resultList = transaction.run(query);
    while (resultList.hasNext()) {
      Entity stateEntity = resultList.next();
      transaction.delete(stateEntity.getKey());
    }
    transaction.commit();
  } finally {
    if (transaction.isActive()) {
      transaction.rollback();
    }
  }
}
 

@Test
public void shouldIncrementCounter() throws IOException {
  // init counter
  assertEquals(0, shardedCounter.getCounter(COUNTER_ID1));

  //increment counter by 1
  updateCounterInTransaction(COUNTER_ID1, 1L);

  QueryResults<Entity> results = datastore.run(EntityQuery.newEntityQueryBuilder()
      .setKind(KIND_COUNTER_SHARD)
      .setFilter(CompositeFilter.and(PropertyFilter.eq(PROPERTY_COUNTER_ID, COUNTER_ID1),
          PropertyFilter.eq(PROPERTY_SHARD_VALUE,1)))
      .build());
  // assert there's one and only one shard with the value set to 1
  assertEquals(1L, results.next().getLong(PROPERTY_SHARD_VALUE));
  assertFalse(results.hasNext());

  // assert the correct value is fetched after cache expiry
  shardedCounter.inMemSnapshot.invalidate(COUNTER_ID1);
  assertEquals(1L, shardedCounter.getCounter(COUNTER_ID1));
}
 

@Override
public void init(FilterConfig config) throws ServletException {
  // initialize local copy of datastore session variables

  datastore = DatastoreOptions.getDefaultInstance().getService();
  keyFactory = datastore.newKeyFactory().setKind("SessionVariable");
  // Delete all sessions unmodified for over two days
  DateTime dt = DateTime.now(DateTimeZone.UTC);
  Query<Entity> query = Query.newEntityQueryBuilder()
      .setKind("SessionVariable")
      .setFilter(PropertyFilter.le("lastModified", dt.minusDays(2).toString(dtf)))
      .build();
  QueryResults<Entity> resultList = datastore.run(query);
  while (resultList.hasNext()) {
    Entity stateEntity = resultList.next();
    datastore.delete(stateEntity.getKey());
  }
}
 

@Test
public void shouldDeleteOnlySpecifiedCounterAndLimit() throws IOException {
  //init counter
  assertEquals(0L, shardedCounter.getCounter(COUNTER_ID1));
  assertEquals(0L, shardedCounter.getCounter(COUNTER_ID2));

  // create limit
  storage.runInTransactionWithRetries(transaction -> {
    shardedCounter.updateLimit(transaction, COUNTER_ID1, 10);
    shardedCounter.updateLimit(transaction, COUNTER_ID2, 10);
    return null;
  });

  storage.deleteResource(COUNTER_ID1);

  QueryResults<Entity> shardsCounter1 = getShardsForCounter(COUNTER_ID1);
  QueryResults<Entity> shardsCounter2 = getShardsForCounter(COUNTER_ID2);

  assertFalse(shardsCounter1.hasNext());
  assertNull(getLimitFromStorage(COUNTER_ID1));

  assertTrue(shardsCounter2.hasNext());
  assertNotNull(getLimitFromStorage(COUNTER_ID2));
}
 

@Override
public Result<Book> listBooks(String startCursorString) {
  Cursor startCursor = null;
  if (startCursorString != null && !startCursorString.equals("")) {
    startCursor = Cursor.fromUrlSafe(startCursorString);    // Where we left off
  }
  Query<Entity> query = Query.newEntityQueryBuilder()       // Build the Query
      .setKind("Book3")                                     // We only care about Books
      .setLimit(10)                                         // Only show 10 at a time
      .setStartCursor(startCursor)                          // Where we left off
      .setOrderBy(OrderBy.asc(Book.TITLE))                  // Use default Index "title"
      .build();
  QueryResults<Entity> resultList = datastore.run(query);   // Run the query
  List<Book> resultBooks = entitiesToBooks(resultList);     // Retrieve and convert Entities
  Cursor cursor = resultList.getCursorAfter();              // Where to start next time
  if (cursor != null && resultBooks.size() == 10) {         // Are we paging? Save Cursor
    String cursorString = cursor.toUrlSafe();               // Cursors are WebSafe
    return new Result<>(resultBooks, cursorString);
  } else {
    return new Result<>(resultBooks);
  }
}
 

private <T extends BaseEntity<?>> void testInstrumentedQueryResults(QueryResults<T> instrumented,
    QueryResults<T> delegate) {
  when(delegate.hasNext()).thenReturn(true);
  when(delegate.next()).thenReturn((T) entity);
  when(delegate.getSkippedResults()).thenReturn(17);
  when(delegate.getMoreResults()).thenReturn(MORE_RESULTS_AFTER_CURSOR);
  assertThat(instrumented.hasNext(), is(true));
  verify(delegate).hasNext();
  assertThat(instrumented.next(), is(entity));
  verify(delegate).next();
  assertThat(instrumented.getSkippedResults(), is(17));
  assertThat(instrumented.getMoreResults(), is(MORE_RESULTS_AFTER_CURSOR));
  verify(delegate).getSkippedResults();
  verify(delegate).getMoreResults();
  verify(stats).recordDatastoreEntityReads(TEST_KIND, 1);
}
 

protected void deleteSessionWithValue(String varName, String varValue) {
  Transaction transaction = datastore.newTransaction();
  try {
    Query<Entity> query = Query.newEntityQueryBuilder()
        .setKind("SessionVariable")
        .setFilter(PropertyFilter.eq(varName, varValue))
        .build();
    QueryResults<Entity> resultList = transaction.run(query);
    while (resultList.hasNext()) {
      Entity stateEntity = resultList.next();
      transaction.delete(stateEntity.getKey());
    }
    transaction.commit();
  } finally {
    if (transaction.isActive()) {
      transaction.rollback();
    }
  }
}
 

private Long getCount(String fieldName) {
  Transaction txn = datastore.newTransaction(
      TransactionOptions.newBuilder()
          .setReadOnly(ReadOnly.newBuilder().build())
          .build()
  );

  QueryResults<ProjectionEntity> results;
  try {
    Query<ProjectionEntity> countQuery = Query.newProjectionEntityQueryBuilder()
        .setKind(SHARD)
        .setNamespace(namespace)
        .setProjection(fieldName)
        .build();

    results = datastore.run(countQuery);
    return StreamSupport.stream(Spliterators.spliteratorUnknownSize(results, Spliterator.NONNULL), false)
        .map(entity -> Long.valueOf(entity.getLong(fieldName)))
        .reduce(0L, (valueA, valueB) -> valueA + valueB);
  } finally {
    if (txn.isActive()) {
      txn.rollback();
    }
  }
}
 

@Override
public Result<Book> listBooksByUser(String userId, String startCursorString) {
  Cursor startCursor = null;
  if (startCursorString != null && !startCursorString.equals("")) {
    startCursor = Cursor.fromUrlSafe(startCursorString);    // Where we left off
  }
  Query<Entity> query = Query.newEntityQueryBuilder()          // Build the Query
      .setKind("Book5")                                        // We only care about Books
      .setFilter(PropertyFilter.eq(Book.CREATED_BY_ID, userId))// Only for this user
      .setLimit(10)                                            // Only show 10 at a time
      .setStartCursor(startCursor)                             // Where we left off
      // a custom datastore index is required since you are filtering by one property
      // but ordering by another
      .setOrderBy(OrderBy.asc(Book.TITLE))
      .build();
  QueryResults<Entity> resultList = datastore.run(query);   // Run the Query
  List<Book> resultBooks = entitiesToBooks(resultList);     // Retrieve and convert Entities
  Cursor cursor = resultList.getCursorAfter();              // Where to start next time
  if (cursor != null && resultBooks.size() == 10) {         // Are we paging? Save Cursor
    String cursorString = cursor.toUrlSafe();               // Cursors are WebSafe
    return new Result<>(resultBooks, cursorString);
  } else {
    return new Result<>(resultBooks);
  }
}
 

@Override
public void init(FilterConfig config) throws ServletException {
  // initialize local copy of datastore session variables

  datastore = DatastoreOptions.getDefaultInstance().getService();
  keyFactory = datastore.newKeyFactory().setKind("SessionVariable");
  // Delete all sessions unmodified for over two days
  DateTime dt = DateTime.now(DateTimeZone.UTC);
  Query<Entity> query = Query.newEntityQueryBuilder()
      .setKind("SessionVariable")
      .setFilter(PropertyFilter.le("lastModified", dt.minusDays(2).toString(dtf)))
      .build();
  QueryResults<Entity> resultList = datastore.run(query);
  while (resultList.hasNext()) {
    Entity stateEntity = resultList.next();
    datastore.delete(stateEntity.getKey());
  }
}
 

/** Example of running a query to find all entities with a matching property value. */
// [TARGET run(Query, ReadOption...)]
// [VARIABLE "my_kind"]
// [VARIABLE "my_property"]
// [VARIABLE "my_value"]
public List<Entity> runQueryOnProperty(String kind, String property, String value) {
  // TODO change so that it's not necessary to hold the entities in a list for integration testing
  // [START runQueryOnProperty]
  StructuredQuery<Entity> query =
      Query.newEntityQueryBuilder()
          .setKind(kind)
          .setFilter(PropertyFilter.eq(property, value))
          .build();
  QueryResults<Entity> results = datastore.run(query);
  List<Entity> entities = Lists.newArrayList();
  while (results.hasNext()) {
    Entity result = results.next();
    // do something with result
    entities.add(result);
  }
  // [END runQueryOnProperty]
  return entities;
}
 

@Override
public Result<Book> listBooks(String startCursorString) {
  Cursor startCursor = null;
  if (startCursorString != null && !startCursorString.equals("")) {
    startCursor = Cursor.fromUrlSafe(startCursorString);    // Where we left off
  }
  Query<Entity> query = Query.newEntityQueryBuilder()       // Build the Query
      .setKind("Book2")                                     // We only care about Books
      .setLimit(10)                                         // Only show 10 at a time
      .setStartCursor(startCursor)                          // Where we left off
      .setOrderBy(OrderBy.asc(Book.TITLE))                  // Use default Index "title"
      .build();
  QueryResults<Entity> resultList = datastore.run(query);   // Run the query
  List<Book> resultBooks = entitiesToBooks(resultList);     // Retrieve and convert Entities
  Cursor cursor = resultList.getCursorAfter();              // Where to start next time
  if (cursor != null && resultBooks.size() == 10) {         // Are we paging? Save Cursor
    String cursorString = cursor.toUrlSafe();               // Cursors are WebSafe
    return new Result<>(resultBooks, cursorString);
  } else {
    return new Result<>(resultBooks);
  }
}