DATAES-593 - Add support for field collapse function.

Original PR: #290

src/test/java/org/springframework/data/elasticsearch/core/ElasticsearchTemplateTests.java

@@ -105,6 +105,7 @@ import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
  * @author Ivan Greene
  * @author Dmitriy Yakovlev
  * @author Peter-Josef Meisch
+ * @author Martin Choraine
  * @author Farid Azaza
  */
 @RunWith(SpringJUnit4ClassRunner.class)
@@ -2825,6 +2826,36 @@ public class ElasticsearchTemplateTests {
 		assertThat(sampleEntities.get(2).getMessage()).isEqualTo(sampleEntity1.getMessage());
 	}
 
+	@Test // DATAES-593
+	public void shouldReturnDocumentWithCollapsedField() {
+
+		// given
+		SampleEntity sampleEntity = SampleEntity.builder().id(randomNumeric(5)).message("message 1").rate(1)
+				.version(System.currentTimeMillis()).build();
+		SampleEntity sampleEntity2 = SampleEntity.builder().id(randomNumeric(5)).message("message 2").rate(2)
+				.version(System.currentTimeMillis()).build();
+		SampleEntity sampleEntit3 = SampleEntity.builder().id(randomNumeric(5)).message("message 1").rate(1)
+				.version(System.currentTimeMillis()).build();
+
+		List<IndexQuery> indexQueries = getIndexQueries(Arrays.asList(sampleEntity, sampleEntity2, sampleEntit3));
+
+		elasticsearchTemplate.bulkIndex(indexQueries);
+		elasticsearchTemplate.refresh(SampleEntity.class);
+
+		SearchQuery searchQuery = new NativeSearchQueryBuilder().withQuery(matchAllQuery())
+				.withIndices(INDEX_NAME_SAMPLE_ENTITY).withTypes(TYPE_NAME).withCollapse("rate").build();
+
+		// when
+		Page<SampleEntity> page = elasticsearchTemplate.queryForPage(searchQuery, SampleEntity.class);
+
+		// then
+		assertThat(page).isNotNull();
+		assertThat(page.getTotalElements()).isEqualTo(3);
+		assertThat(page.getContent()).hasSize(2);
+		assertThat(page.getContent().get(0).getMessage()).isEqualTo("message 1");
+		assertThat(page.getContent().get(1).getMessage()).isEqualTo("message 2");
+	}
+
 	private IndexQuery getIndexQuery(SampleEntity sampleEntity) {
 		return new IndexQueryBuilder().withId(sampleEntity.getId()).withObject(sampleEntity)
 				.withVersion(sampleEntity.getVersion()).build();

src/test/java/org/springframework/data/elasticsearch/core/ReactiveElasticsearchTemplateTests.java

@@ -24,6 +24,8 @@ import lombok.Builder;
 import lombok.Data;
 import lombok.EqualsAndHashCode;
 import lombok.NoArgsConstructor;
+import org.springframework.data.domain.Page;
+import org.springframework.data.elasticsearch.core.query.NativeSearchQuery;
 import reactor.core.publisher.Mono;
 import reactor.test.StepVerifier;
 
@@ -76,6 +78,7 @@ import org.springframework.util.StringUtils;
  * @author Mark Paluch
  * @author Peter-Josef Meisch
  * @author Farid Azaza
+ * @author Martin Choraine
  * @currentRead Golden Fool - Robin Hobb
  */
 @RunWith(SpringRunner.class)
@@ -666,6 +669,30 @@ public class ReactiveElasticsearchTemplateTests {
 				.verifyComplete();
 	}
 
+	@Test // DATAES-593
+	public void shouldReturnDocumentWithCollapsedField() {
+
+		SampleEntity entity1 = randomEntity("test message");
+		entity1.setRate(1);
+		SampleEntity entity2 = randomEntity("test another message");
+		entity2.setRate(2);
+		SampleEntity entity3 = randomEntity("test message again");
+		entity3.setRate(1);
+		index(entity1, entity2, entity3);
+
+		SearchQuery query = new NativeSearchQueryBuilder()
+				.withIndices(DEFAULT_INDEX)
+				.withQuery(matchAllQuery())
+				.withCollapse("rate")
+				.withPageable(PageRequest.of(0, 25))
+				.build();
+
+		template.find(query, SampleEntity.class)
+				.as(StepVerifier::create)
+				.expectNextCount(2)
+				.verifyComplete();
+	}
+
 	@Data
 	@Document(indexName = "marvel", type = "characters")
 	static class Person {
@@ -733,6 +760,7 @@ public class ReactiveElasticsearchTemplateTests {
 
 		@Id private String id;
 		@Field(type = Text, store = true, fielddata = true) private String message;
+		private int rate;
 		@Version private Long version;
 		@Score private float score;
 	}