Add "filter" to neural query

CHANGELOG.md

@@ -57,6 +57,7 @@ This section is for maintaining a changelog for all breaking changes for the cli
 - Support weight function in function score query ([#880](https://github.com/opensearch-project/opensearch-java/pull/880))
 - Fix pattern replace by making flag and replacement optional as on api  ([#895](https://github.com/opensearch-project/opensearch-java/pull/895))
 - Client with Java 8 runtime and Apache HttpClient 5 Transport fails with java.lang.NoSuchMethodError: java.nio.ByteBuffer.flip()Ljava/nio/ByteBuffer ([#920](https://github.com/opensearch-project/opensearch-java/pull/920)) 
+- Add missed field  "filter" to NeuralQuery model class
 
 ### Security
 
@@ -364,4 +365,4 @@ This section is for maintaining a changelog for all breaking changes for the cli
 [2.5.0]: https://github.com/opensearch-project/opensearch-java/compare/v2.4.0...v2.5.0
 [2.4.0]: https://github.com/opensearch-project/opensearch-java/compare/v2.3.0...v2.4.0
 [2.3.0]: https://github.com/opensearch-project/opensearch-java/compare/v2.2.0...v2.3.0
-[2.2.0]: https://github.com/opensearch-project/opensearch-java/compare/v2.1.0...v2.2.0
+[2.2.0]: https://github.com/opensearch-project/opensearch-java/compare/v2.1.0...v2.2.0

java-client/src/main/java/org/opensearch/client/opensearch/_types/query_dsl/NeuralQuery.java

@@ -27,6 +27,8 @@ public class NeuralQuery extends QueryBase implements QueryVariant {
     private final int k;
     @Nullable
     private final String modelId;
+    @Nullable
+    private final Query filter;
 
     private NeuralQuery(NeuralQuery.Builder builder) {
         super(builder);
@@ -35,6 +37,7 @@ private NeuralQuery(NeuralQuery.Builder builder) {
         this.queryText = ApiTypeHelper.requireNonNull(builder.queryText, this, "queryText");
         this.k = ApiTypeHelper.requireNonNull(builder.k, this, "k");
         this.modelId = builder.modelId;
+        this.filter = builder.filter;
     }
 
     public static NeuralQuery of(Function<NeuralQuery.Builder, ObjectBuilder<NeuralQuery>> fn) {
@@ -93,6 +96,16 @@ public final String modelId() {
         return this.modelId;
     }
 
+    /**
+     * Optional - A query to filter the results of the query.
+     *
+     * @return The filter query.
+     */
+    @Nullable
+    public final Query filter() {
+        return this.filter;
+    }
+
     @Override
     protected void serializeInternal(JsonGenerator generator, JsonpMapper mapper) {
         generator.writeStartObject(this.field);
@@ -107,11 +120,16 @@ protected void serializeInternal(JsonGenerator generator, JsonpMapper mapper) {
 
         generator.write("k", this.k);
 
+        if (this.filter != null) {
+            generator.writeKey("filter");
+            this.filter.serialize(generator, mapper);
+        }
+
         generator.writeEnd();
     }
 
     public Builder toBuilder() {
-        return new Builder().field(field).queryText(queryText).k(k).modelId(modelId);
+        return new Builder().field(field).queryText(queryText).k(k).modelId(modelId).filter(filter);
     }
 
     /**
@@ -123,6 +141,8 @@ public static class Builder extends QueryBase.AbstractBuilder<NeuralQuery.Builde
         private Integer k;
         @Nullable
         private String modelId;
+        @Nullable
+        private Query filter;
 
         /**
          * Required - The target field.
@@ -169,6 +189,17 @@ public NeuralQuery.Builder k(@Nullable Integer k) {
             return this;
         }
 
+        /**
+         * Optional - A query to filter the results of the knn query.
+         *
+         * @param filter The filter query.
+         * @return This builder.
+         */
+        public NeuralQuery.Builder filter(@Nullable Query filter) {
+            this.filter = filter;
+            return this;
+        }
+
         @Override
         protected NeuralQuery.Builder self() {
             return this;
@@ -198,6 +229,7 @@ protected static void setupNeuralQueryDeserializer(ObjectDeserializer<NeuralQuer
         op.add(NeuralQuery.Builder::queryText, JsonpDeserializer.stringDeserializer(), "query_text");
         op.add(NeuralQuery.Builder::modelId, JsonpDeserializer.stringDeserializer(), "model_id");
         op.add(NeuralQuery.Builder::k, JsonpDeserializer.integerDeserializer(), "k");
+        op.add(NeuralQuery.Builder::filter, Query._DESERIALIZER, "filter");
 
         op.setKey(NeuralQuery.Builder::field, JsonpDeserializer.stringDeserializer());
     }

java-client/src/test/java/org/opensearch/client/opensearch/_types/query_dsl/NeuralQueryTest.java

@@ -6,7 +6,11 @@
 public class NeuralQueryTest extends ModelTestCase {
     @Test
     public void toBuilder() {
-        NeuralQuery origin = new NeuralQuery.Builder().field("field").queryText("queryText").k(1).build();
+        NeuralQuery origin = new NeuralQuery.Builder().field("field")
+            .queryText("queryText")
+            .k(1)
+            .filter(IdsQuery.of(builder -> builder.values("Some_ID")).toQuery())
+            .build();
         NeuralQuery copied = origin.toBuilder().build();
 
         assertEquals(toJson(copied), toJson(origin));