More Like This: Fix correct use of size and from parameters

More Like This API would not take into account 'size' and 'from' in request body parameters.
Instead these values would always be overriden by the default values of REST parameters
'search_size' and 'search_from'.

Closes #5981

src/main/java/org/elasticsearch/action/mlt/TransportMoreLikeThisAction.java

@@ -45,6 +45,7 @@
 import org.elasticsearch.index.query.BoolQueryBuilder;
 import org.elasticsearch.index.query.MoreLikeThisFieldQueryBuilder;
 import org.elasticsearch.indices.IndicesService;
+import org.elasticsearch.search.builder.SearchSourceBuilder;
 import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.*;
 
@@ -196,22 +197,25 @@ public void onResponse(GetResponse getResponse) {
                 if (searchTypes == null) {
                     searchTypes = new String[]{request.type()};
                 }
-                int size = request.searchSize() != 0 ? request.searchSize() : 10;
-                int from = request.searchFrom() != 0 ? request.searchFrom() : 0;
                 SearchRequest searchRequest = searchRequest(searchIndices)
                         .types(searchTypes)
                         .searchType(request.searchType())
                         .scroll(request.searchScroll())
-                        .extraSource(searchSource()
-                                .query(boolBuilder)
-                                .from(from)
-                                .size(size)
-                        )
                         .listenerThreaded(request.listenerThreaded());
 
+                SearchSourceBuilder extraSource = searchSource().query(boolBuilder);
+                if (request.searchFrom() != 0) {
+                    extraSource.from(request.searchFrom());
+                }
+                if (request.searchSize() != 0) {
+                    extraSource.size(request.searchSize());
+                }
+                searchRequest.extraSource(extraSource);
+
                 if (request.searchSource() != null) {
                     searchRequest.source(request.searchSource(), request.searchSourceUnsafe());
                 }
+
                 searchAction.execute(searchRequest, new ActionListener<SearchResponse>() {
                     @Override
                     public void onResponse(SearchResponse response) {

src/test/java/org/elasticsearch/mlt/MoreLikeThisActionTests.java

@@ -20,14 +20,19 @@
 package org.elasticsearch.mlt;
 
 import org.elasticsearch.action.admin.cluster.health.ClusterHealthStatus;
+import org.elasticsearch.action.index.IndexRequestBuilder;
 import org.elasticsearch.action.search.SearchPhaseExecutionException;
 import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.client.Client;
 import org.elasticsearch.common.settings.ImmutableSettings;
 import org.elasticsearch.common.xcontent.XContentFactory;
+import org.elasticsearch.search.builder.SearchSourceBuilder;
 import org.elasticsearch.test.ElasticsearchIntegrationTest;
 import org.junit.Test;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import static org.elasticsearch.client.Requests.*;
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_REPLICAS;
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_SHARDS;
@@ -292,4 +297,48 @@ public void testSimpleMoreLikeInclude() throws Exception {
         assertSearchHits(mltResponse, "2");
     }
 
+    @Test
+    public void testMoreLikeThisBodyFromSize() throws Exception {
+        logger.info("Creating index test");
+        assertAcked(prepareCreate("test").addMapping("type1",
+                jsonBuilder().startObject().startObject("type1").startObject("properties")
+                        .startObject("text").field("type", "string").endObject()
+                        .endObject().endObject().endObject()));
+
+        logger.info("Running Cluster Health");
+        assertThat(ensureGreen(), equalTo(ClusterHealthStatus.GREEN));
+
+        logger.info("Indexing...");
+        List<IndexRequestBuilder> builders = new ArrayList<>(10);
+        for (int i = 1; i <= 10; i++) {
+            builders.add(client().prepareIndex("test", "type1").setSource("text", "lucene").setId(String.valueOf(i)));
+        }
+        indexRandom(true, builders);
+
+        logger.info("'size' set but 'search_from' and 'search_size' kept to defaults");
+        SearchResponse mltResponse = client().moreLikeThis(
+                moreLikeThisRequest("test").type("type1").id("1").minTermFreq(1).minDocFreq(1).include(true)
+                        .searchSource(SearchSourceBuilder.searchSource().size(5)))
+                .actionGet();
+        assertSearchResponse(mltResponse);
+        assertEquals(mltResponse.getHits().hits().length, 5);
+
+        logger.info("'from' set but 'search_from' and 'search_size' kept to defaults");
+        mltResponse = client().moreLikeThis(
+                moreLikeThisRequest("test").type("type1").id("1").minTermFreq(1).minDocFreq(1).include(true)
+                        .searchSource(SearchSourceBuilder.searchSource().from(5)))
+                .actionGet();
+        assertSearchResponse(mltResponse);
+        assertEquals(mltResponse.getHits().hits().length, 5);
+
+        logger.info("When set, 'search_from' and 'search_size' should override 'from' and 'size'");
+        mltResponse = client().moreLikeThis(
+                moreLikeThisRequest("test").type("type1").id("1").minTermFreq(1).minDocFreq(1).include(true)
+                        .searchSize(10).searchFrom(2)
+                        .searchSource(SearchSourceBuilder.searchSource().size(1).from(1)))
+                .actionGet();
+        assertSearchResponse(mltResponse);
+        assertEquals(mltResponse.getHits().hits().length, 8);
+    }
+
 }