Datastore: Add skippedResults in QueryResults

google-cloud-clients/google-cloud-datastore/src/main/java/com/google/cloud/datastore/QueryResults.java

@@ -55,4 +55,19 @@ public interface QueryResults<V> extends Iterator<V> {
    * }</pre>
    */
   Cursor getCursorAfter();
+
+  /**
+   * Returns the number of results skipped, typically because of an offset.
+   *
+   * <p>A simple use case to count entities:
+   *
+   * <pre>{@code
+   * Query<Key> query = Query.newKeyQueryBuilder().setOffset(Integer.MAX_VALUE).build();
+   * QueryResults<Key> result = datasore.datastore.run(query);
+   * if (!result.hasNext()) {
+   *  int numberOfEntities = result.getSkippedResults();
+   * }
+   * }</pre>
+   */
+  int getSkippedResults();
 }

google-cloud-clients/google-cloud-datastore/src/main/java/com/google/cloud/datastore/QueryResultsImpl.java

@@ -114,4 +114,9 @@ public Class<?> getResultClass() {
   public Cursor getCursorAfter() {
     return new Cursor(cursor);
   }
+
+  @Override
+  public int getSkippedResults() {
+    return runQueryResponsePb.getBatch().getSkippedResults();
+  }
 }

google-cloud-clients/google-cloud-datastore/src/test/java/com/google/cloud/datastore/DatastoreTest.java

@@ -633,6 +633,13 @@ public void testQueryPaginationWithLimit() throws DatastoreException {
     EasyMock.verify(rpcFactoryMock, rpcMock);
   }
 
+  @Test
+  public void testRunKeyQueryWithOffset() {
+    Query<Key> query = Query.newKeyQueryBuilder().setOffset(Integer.MAX_VALUE).build();
+    int numberOfEntities = datastore.run(query).getSkippedResults();
+    assertEquals(2, numberOfEntities);
+  }
+
   private List<RunQueryResponse> buildResponsesForQueryPaginationWithLimit() {
     Entity entity4 = Entity.newBuilder(KEY4).set("value", StringValue.of("value")).build();
     Entity entity5 = Entity.newBuilder(KEY5).set("value", "value").build();

google-cloud-clients/google-cloud-datastore/src/test/java/com/google/cloud/datastore/it/ITDatastoreTest.java

@@ -851,4 +851,11 @@ public Integer run(DatastoreReaderWriter transaction) {
       assertEquals(3, ((DatastoreException) expected.getCause()).getCode());
     }
   }
+
+  @Test
+  public void testSkippedResults() {
+    Query<Key> query = Query.newKeyQueryBuilder().setOffset(Integer.MAX_VALUE).build();
+    int numberOfEntities = DATASTORE.run(query).getSkippedResults();
+    assertEquals(2, numberOfEntities);
+  }
 }