DATAREDIS-551 - Fix pageable query execution when derived criteria is empty.

We now make sure to count records without using criteria when derived criteria is empty. This allows usage of declared query methods using `Pageable` without criteria like `findBy(Pageable page)`.

Original Pull Request: #220

Author: mp911de

src/main/java/org/springframework/data/redis/core/RedisQueryEngine.java

@@ -40,6 +40,7 @@
  * Redis specific {@link QueryEngine} implementation.
  * 
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 1.7
  */
 class RedisQueryEngine extends QueryEngine<RedisKeyValueAdapter, RedisOperationChain, Comparator<?>> {
@@ -156,6 +157,10 @@ public Collection<?> execute(final RedisOperationChain criteria, Comparator<?> s
 	@Override
 	public long count(final RedisOperationChain criteria, final Serializable keyspace) {
 
+		if(criteria == null) {
+			return this.getAdapter().count(keyspace);
+		}
+
 		return this.getAdapter().execute(new RedisCallback<Long>() {
 
 			@Override

src/test/java/org/springframework/data/redis/repository/RedisRepositoryIntegrationTestBase.java

@@ -222,6 +222,24 @@ public void shouldApplyPageableCorrectlyWhenUsingFindAll() {
  		assertThat(repo.findAll(firstPage.nextPageable()).getContent(), hasSize(1));
 	}
 
+	/**
+	 * @see DATAREDIS-551
+	 */
+	@Test
+	public void shouldApplyPageableCorrectlyWhenUsingFindByWithoutCriteria() {
+
+		Person eddard = new Person("eddard", "stark");
+		Person robb = new Person("robb", "stark");
+		Person jon = new Person("jon", "snow");
+
+		repo.save(Arrays.asList(eddard, robb, jon));
+
+		Page<Person> firstPage = repo.findBy(new PageRequest(0, 2));
+ 		assertThat(firstPage.getContent(), hasSize(2));
+ 		assertThat(firstPage.getTotalElements(), is(equalTo(3L)));
+ 		assertThat(repo.findBy(firstPage.nextPageable()).getContent(), hasSize(1));
+	}
+
 	/**
 	 * @see DATAREDIS-547
 	 */
@@ -317,6 +335,8 @@ public static interface PersonRepository extends PagingAndSortingRepository<Pers
 		List<Person> findTop2By();
 
 		List<Person> findTop2ByLastname(String lastname);
+
+		Page<Person> findBy(Pageable page);
 	}
 
 	/**