Add support for search using the "fields" parameter with knn_vector field

CHANGELOG.md

@@ -20,6 +20,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Introduced a writing layer in native engines where relies on the writing interface to process IO. (#2241)[https://github.com/opensearch-project/k-NN/pull/2241]
 ### Bug Fixes
 * Fixing the bug when a segment has no vector field present for disk based vector search (#2282)[https://github.com/opensearch-project/k-NN/pull/2282]
+* Fixing the bug where search fails with "fields" parameter for an index with a knn_vector field (#2314)[https://github.com/opensearch-project/k-NN/pull/2314]
 ### Infrastructure
 * Updated C++ version in JNI from c++11 to c++17 [#2259](https://github.com/opensearch-project/k-NN/pull/2259)
 * Upgrade bytebuddy and objenesis version to match OpenSearch core and, update github ci runner for macos [#2279](https://github.com/opensearch-project/k-NN/pull/2279)

src/main/java/org/opensearch/knn/index/mapper/KNNVectorFieldType.java

@@ -11,6 +11,7 @@
 import org.apache.lucene.util.BytesRef;
 import org.opensearch.index.fielddata.IndexFieldData;
 import org.opensearch.index.mapper.MappedFieldType;
+import org.opensearch.index.mapper.ArraySourceValueFetcher;
 import org.opensearch.index.mapper.TextSearchInfo;
 import org.opensearch.index.mapper.ValueFetcher;
 import org.opensearch.index.query.QueryShardContext;
@@ -51,7 +52,12 @@ public KNNVectorFieldType(String name, Map<String, String> metadata, VectorDataT
 
     @Override
     public ValueFetcher valueFetcher(QueryShardContext context, SearchLookup searchLookup, String format) {
-        throw new UnsupportedOperationException("KNN Vector do not support fields search");
+        return new ArraySourceValueFetcher(name(), context) {
+            @Override
+            protected Object parseSourceValue(Object value) {
+                return value;
+            }
+        };
     }
 
     @Override

src/test/java/org/opensearch/knn/index/OpenSearchIT.java

@@ -13,7 +13,7 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.primitives.Floats;
-import java.util.Locale;
+
 import lombok.SneakyThrows;
 import org.apache.hc.core5.http.ParseException;
 import org.junit.BeforeClass;
@@ -39,6 +39,7 @@
 import java.net.URL;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.TreeMap;
 
@@ -900,6 +901,136 @@ public void testKNNIndex_whenBuildVectorGraphThresholdIsProvidedEndToEnd_thenBui
         deleteKNNIndex(indexName);
     }
 
+    public void testKNNIndexSearchFieldsParameter() throws Exception {
+        createKnnIndex(INDEX_NAME, createKnnIndexMapping(Arrays.asList("vector1", "vector2", "vector3"), Arrays.asList(2, 3, 5)));
+        for (int i = 1; i <= 10; i++) {
+            Float[] vector1 = { (float) i, (float) (i + 1) };
+            Float[] vector2 = { (float) i, (float) (i + 1), (float) (i + 2) };
+            Float[] vector3 = { (float) i, (float) (i + 1), (float) (i + 2), (float) (i + 3), (float) (i + 4) };
+            addKnnDoc(
+                INDEX_NAME,
+                Integer.toString(i),
+                Arrays.asList("vector1", "vector2", "vector3"),
+                Arrays.asList(vector1, vector2, vector3)
+            );
+        }
+        int k = 100; // nearest 100 neighbors
+
+        // Create search body, all fields
+        XContentBuilder builder = XContentFactory.jsonBuilder()
+            .startObject()
+            .field("fields", new String[] { "*" })
+            .startObject("query")
+            .startObject("match_all")
+            .endObject()
+            .endObject()
+            .endObject();
+        Response response = searchKNNIndex(INDEX_NAME, builder, k);
+        List<KNNResult> resultsField1 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "vector1");
+        List<KNNResult> resultsField2 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "vector2");
+        List<KNNResult> resultsField3 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "vector3");
+        assertEquals(10, resultsField1.size());
+        assertEquals(10, resultsField2.size());
+        assertEquals(10, resultsField3.size());
+
+        // Create search body, some fields
+        builder = XContentFactory.jsonBuilder()
+            .startObject()
+            .field("fields", new String[] { "vector1", "vector2" })
+            .startObject("query")
+            .startObject("match_all")
+            .endObject()
+            .endObject()
+            .endObject();
+        Response response2 = searchKNNIndex(INDEX_NAME, builder, k);
+        resultsField1 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "vector1");
+        resultsField2 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "vector2");
+        expectThrows(
+            NullPointerException.class,
+            () -> parseSearchResponseScriptFields(EntityUtils.toString(response2.getEntity()), "vector3")
+        );
+        assertEquals(10, resultsField1.size());
+        assertEquals(10, resultsField2.size());
+    }
+
+    public void testKNNIndexSearchFieldsParameterWithOtherFields() throws Exception {
+        XContentBuilder xContentBuilder = XContentFactory.jsonBuilder()
+            .startObject()
+            .startObject("properties")
+            .startObject("vector1")
+            .field("type", "knn_vector")
+            .field("dimension", "2")
+            .endObject()
+            .startObject("vector2")
+            .field("type", "knn_vector")
+            .field("dimension", "3")
+            .endObject()
+            .startObject("float1")
+            .field("type", "float")
+            .endObject()
+            .startObject("float2")
+            .field("type", "float")
+            .endObject()
+            .endObject()
+            .endObject();
+        createKnnIndex(INDEX_NAME, xContentBuilder.toString());
+        for (int i = 1; i <= 10; i++) {
+            Float[] vector1 = { (float) i, (float) (i + 1) };
+            Float[] vector2 = { (float) i, (float) (i + 1), (float) (i + 2) };
+            Float[] text1 = { (float) i };
+            Float[] text2 = { (float) (i + 1) };
+            addKnnDoc(
+                INDEX_NAME,
+                Integer.toString(i),
+                Arrays.asList("vector1", "vector2", "float1", "float2"),
+                Arrays.asList(vector1, vector2, text1, text2)
+            );
+        }
+        int k = 100; // nearest 100 neighbors
+
+        // Create search body, all fields
+        XContentBuilder builder = XContentFactory.jsonBuilder()
+            .startObject()
+            .field("fields", new String[] { "*" })
+            .startObject("query")
+            .startObject("match_all")
+            .endObject()
+            .endObject()
+            .endObject();
+        Response response = searchKNNIndex(INDEX_NAME, builder, k);
+        List<KNNResult> resultsField1 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "vector1");
+        List<KNNResult> resultsField2 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "vector2");
+        List<KNNResult> resultsField3 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "float1");
+        List<KNNResult> resultsField4 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "float2");
+        assertEquals(10, resultsField1.size());
+        assertEquals(10, resultsField2.size());
+        assertEquals(10, resultsField3.size());
+        assertEquals(10, resultsField4.size());
+
+        // Create search body, some fields
+        builder = XContentFactory.jsonBuilder()
+            .startObject()
+            .field("fields", new String[] { "vector1", "float2" })
+            .startObject("query")
+            .startObject("match_all")
+            .endObject()
+            .endObject()
+            .endObject();
+        Response response2 = searchKNNIndex(INDEX_NAME, builder, k);
+        resultsField1 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "vector1");
+        expectThrows(
+            NullPointerException.class,
+            () -> parseSearchResponseScriptFields(EntityUtils.toString(response2.getEntity()), "vector2")
+        );
+        expectThrows(
+            NullPointerException.class,
+            () -> parseSearchResponseScriptFields(EntityUtils.toString(response2.getEntity()), "float1")
+        );
+        resultsField4 = parseSearchResponseScriptFields(EntityUtils.toString(response.getEntity()), "float2");
+        assertEquals(10, resultsField1.size());
+        assertEquals(10, resultsField4.size());
+    }
+
     private List<KNNResult> getResults(final String indexName, final String fieldName, final float[] vector, final int k)
         throws IOException, ParseException {
         final Response searchResponseField = searchKNNIndex(indexName, new KNNQueryBuilder(fieldName, vector, k), k);