fix(query): allow rerank on every search operator

src/it/java/io/weaviate/integration/SearchITest.java

@@ -801,13 +801,56 @@ public void test_rerankQueries() throws IOException {
         Map.of("title", "Height-adjustable desk", "price", 349));
 
     // Act
-    var got = things.query.nearText(
-        "office supplies",
-        nt -> nt.rerank(Rerank.by("price",
-            rank -> rank.query("cheaper first"))));
+    var rerank = Rerank.by("price", rank -> rank.query("cheaper first"));
+    var got = things.query.nearText("office supplies", nt -> nt.rerank(rerank));
 
     // Assert: ranking not important really, just that the request was valid.
     Assertions.assertThat(got.objects()).hasSize(2);
+
+    // Assert: rerank is not exclusive to vector search -- BM25, hybrid and
+    // fetchObjects accept it too, and the server reranks for all of them.
+    Assertions.assertThat(things.query.bm25("chair", bm25 -> bm25.rerank(rerank)).objects())
+        .as("bm25").isNotEmpty().allSatisfy(SearchITest::assertReranked);
+    Assertions.assertThat(things.query.hybrid("chair", hybrid -> hybrid.rerank(rerank)).objects())
+        .as("hybrid").isNotEmpty().allSatisfy(SearchITest::assertReranked);
+    Assertions.assertThat(things.query.fetchObjects(fetch -> fetch.rerank(rerank)).objects())
+        .as("fetchObjects").hasSize(2).allSatisfy(SearchITest::assertReranked);
+  }
+
+  private static void assertReranked(WeaviateObject<Map<String, Object>> object) {
+    Assertions.assertThat(object.queryMetadata().rerankScore())
+        .as("rerank score of %s", object.uuid()).isNotNull();
+  }
+
+  @Test
+  public void test_rerankScoreIsReturned() throws IOException {
+    // Arrange
+    var nsThings = ns("Things");
+
+    var things = client.collections.create(nsThings,
+        c -> c
+            .properties(Property.text("title"), Property.integer("price"))
+            .vectorConfig(VectorConfig.text2vecModel2Vec(
+                t2v -> t2v.sourceProperties("title", "price")))
+            .rerankerModules(new DummyReranker()));
+
+    things.data.insertMany(
+        Map.of("title", "Ergonomic chair", "price", 269),
+        Map.of("title", "Height-adjustable desk", "price", 349));
+
+    // Act
+    var got = things.query.fetchObjects(
+        fetch -> fetch.rerank(Rerank.by("title", rank -> rank.query("chair"))));
+
+    // Assert: the score which produced the ordering is readable.
+    Assertions.assertThat(got.objects()).hasSize(2)
+        .allSatisfy(obj -> Assertions.assertThat(obj.queryMetadata().rerankScore())
+            .as("rerank score of %s", obj.uuid()).isNotNull());
+
+    // Assert: a query without rerank leaves the score unset.
+    Assertions.assertThat(things.query.fetchObjects().objects()).hasSize(2)
+        .allSatisfy(obj -> Assertions.assertThat(obj.queryMetadata().rerankScore())
+            .as("not reranked").isNull());
   }
 
   @Test

src/main/java/io/weaviate/client6/v1/api/collections/generate/GenerativeResponseGroup.java

@@ -2,7 +2,9 @@
 
 import java.util.List;
 
+import io.weaviate.client6.v1.api.collections.query.BaseQueryOptions;
 import io.weaviate.client6.v1.api.collections.query.QueryObjectGrouped;
+import io.weaviate.client6.v1.api.collections.query.Rerank;
 
 public record GenerativeResponseGroup<PropertiesT>(
     /** Group name. */
@@ -19,6 +21,14 @@ public record GenerativeResponseGroup<PropertiesT>(
     Float maxDistance,
     /** The size of the group. */
     long numberOfObjects,
+    /**
+     * Score assigned to this group by the reranker module.
+     *
+     * <p>
+     * Only present if the query requested reranking, see
+     * {@link BaseQueryOptions.Builder#rerank(Rerank)}.
+     */
+    Double rerankScore,
     /** Objects retrieved in the query. */
     List<QueryObjectGrouped<PropertiesT>> objects,
     /** Output of the summary task for this group. */

src/main/java/io/weaviate/client6/v1/api/collections/generate/GenerativeResponseGrouped.java

@@ -58,6 +58,7 @@ static <PropertiesT> GenerativeResponseGrouped<PropertiesT> unmarshal(
               group.getMinDistance(),
               group.getMaxDistance(),
               group.getNumberOfObjects(),
+              group.hasRerank() ? group.getRerank().getScore() : null,
               objects,
               generative);
         })

src/main/java/io/weaviate/client6/v1/api/collections/query/BaseQueryOptions.java

@@ -21,6 +21,7 @@ public record BaseQueryOptions(
     ConsistencyLevel consistencyLevel,
     Filter filters,
     Boost boost,
+    Rerank rerank,
     GenerativeSearch generativeSearch,
     List<String> returnProperties,
     List<QueryReference> returnReferences,
@@ -40,6 +41,7 @@ private <T extends Object> BaseQueryOptions(Builder<? extends Builder<?, T>, T>
         builder.consistencyLevel,
         builder.filter,
         builder.boost,
+        builder.rerank,
         builder.generativeSearch,
         builder.returnProperties,
         builder.returnReferences,
@@ -57,6 +59,7 @@ public static abstract class Builder<SelfT extends Builder<SelfT, T>, T extends
     private ConsistencyLevel consistencyLevel;
     private Filter filter;
     private Boost boost;
+    private Rerank rerank;
     private GenerativeSearch generativeSearch;
     private List<String> returnProperties = new ArrayList<>();
     private List<QueryReference> returnReferences = new ArrayList<>();
@@ -152,6 +155,20 @@ public final SelfT boost(Boost boost) {
       return (SelfT) this;
     }
 
+    /**
+     * Control the ranking of the query results.
+     *
+     * <p>
+     * Reranking is applied by the server on top of the result set produced by the
+     * search operator, so it works with every operator: {@link NearText} and the
+     * other {@code near*} searches, {@link Bm25}, {@link Hybrid} and
+     * {@link FetchObjects}.
+     */
+    public final SelfT rerank(Rerank rerank) {
+      this.rerank = rerank;
+      return (SelfT) this;
+    }
+
     /** Select properties to include in the query result. */
     public final SelfT returnProperties(String... properties) {
       return returnProperties(Arrays.asList(properties));
@@ -243,6 +260,10 @@ final void appendTo(WeaviateProtoSearchGet.SearchRequest.Builder req) {
       req.setBoost(boost.toProto());
     }
 
+    if (rerank != null) {
+      rerank.appendTo(req);
+    }
+
     if (generativeSearch != null) {
       var generative = WeaviateProtoGenerative.GenerativeSearch.newBuilder();
       generativeSearch.appendTo(generative);

src/main/java/io/weaviate/client6/v1/api/collections/query/BaseVectorSearchBuilder.java

@@ -6,7 +6,6 @@ abstract class BaseVectorSearchBuilder<SelfT extends BaseVectorSearchBuilder<Sel
   // Optional query parameters.
   Float distance;
   Float certainty;
-  Rerank rerank;
   Diversity diversity;
 
   /**
@@ -38,15 +37,6 @@ public SelfT certainty(float certainty) {
     return (SelfT) this;
   }
 
-  /**
-   * Control the ranking of the query results.
-   */
-  @SuppressWarnings("unchecked")
-  public SelfT rerank(Rerank rerank) {
-    this.rerank = rerank;
-    return (SelfT) this;
-  }
-
   /**
    * Apply diversity selection to the query results.
    */

src/main/java/io/weaviate/client6/v1/api/collections/query/NearAudio.java

@@ -14,7 +14,6 @@ public record NearAudio(
     Target searchTarget,
     Float distance,
     Float certainty,
-    Rerank rerank,
     Diversity diversity,
     BaseQueryOptions common)
     implements QueryOperator, AggregateObjectFilter {
@@ -40,7 +39,6 @@ public NearAudio(Builder builder) {
         builder.media,
         builder.distance,
         builder.certainty,
-        builder.rerank,
         builder.diversity,
         builder.baseOptions());
   }

src/main/java/io/weaviate/client6/v1/api/collections/query/NearDepth.java

@@ -14,7 +14,6 @@ public record NearDepth(
     Target searchTarget,
     Float distance,
     Float certainty,
-    Rerank rerank,
     Diversity diversity,
     BaseQueryOptions common)
     implements QueryOperator, AggregateObjectFilter {
@@ -40,7 +39,6 @@ public NearDepth(Builder builder) {
         builder.media,
         builder.distance,
         builder.certainty,
-        builder.rerank,
         builder.diversity,
         builder.baseOptions());
   }

src/main/java/io/weaviate/client6/v1/api/collections/query/NearImage.java

@@ -14,7 +14,6 @@ public record NearImage(
     Target searchTarget,
     Float distance,
     Float certainty,
-    Rerank rerank,
     Diversity diversity,
     BaseQueryOptions common)
     implements QueryOperator, AggregateObjectFilter {
@@ -40,7 +39,6 @@ public NearImage(Builder builder) {
         builder.media,
         builder.distance,
         builder.certainty,
-        builder.rerank,
         builder.diversity,
         builder.baseOptions());
   }

src/main/java/io/weaviate/client6/v1/api/collections/query/NearImu.java

@@ -14,7 +14,6 @@ public record NearImu(
     Target searchTarget,
     Float distance,
     Float certainty,
-    Rerank rerank,
     Diversity diversity,
     BaseQueryOptions common)
     implements QueryOperator, AggregateObjectFilter {
@@ -40,7 +39,6 @@ public NearImu(Builder builder) {
         builder.media,
         builder.distance,
         builder.certainty,
-        builder.rerank,
         builder.diversity,
         builder.baseOptions());
   }

src/main/java/io/weaviate/client6/v1/api/collections/query/NearObject.java

@@ -12,7 +12,6 @@ public record NearObject(
     String uuid,
     Float distance,
     Float certainty,
-    Rerank rerank,
     Diversity diversity,
     BaseQueryOptions common)
     implements QueryOperator, AggregateObjectFilter {
@@ -30,7 +29,6 @@ public NearObject(Builder builder) {
         builder.uuid,
         builder.distance,
         builder.certainty,
-        builder.rerank,
         builder.diversity,
         builder.baseOptions());
   }

src/main/java/io/weaviate/client6/v1/api/collections/query/NearText.java

@@ -17,7 +17,6 @@ public record NearText(
     Target searchTarget,
     Float distance,
     Float certainty,
-    Rerank rerank,
     Move moveTo,
     Move moveAway,
     Diversity diversity,
@@ -44,7 +43,6 @@ public NearText(Builder builder) {
         builder.searchTarget,
         builder.distance,
         builder.certainty,
-        builder.rerank,
         builder.moveTo,
         builder.moveAway,
         builder.diversity,

src/main/java/io/weaviate/client6/v1/api/collections/query/NearThermal.java

@@ -13,7 +13,6 @@
 public record NearThermal(Target searchTarget,
     Float distance,
     Float certainty,
-    Rerank rerank,
     Diversity diversity,
     BaseQueryOptions common)
     implements QueryOperator, AggregateObjectFilter {
@@ -39,7 +38,6 @@ public NearThermal(Builder builder) {
         builder.media,
         builder.distance,
         builder.certainty,
-        builder.rerank,
         builder.diversity,
         builder.baseOptions());
   }

src/main/java/io/weaviate/client6/v1/api/collections/query/NearVector.java

@@ -11,7 +11,6 @@
 public record NearVector(NearVectorTarget searchTarget,
     Float distance,
     Float certainty,
-    Rerank rerank,
     Diversity diversity,
     BaseQueryOptions common)
     implements QueryOperator, AggregateObjectFilter {
@@ -44,7 +43,6 @@ public NearVector(Builder builder) {
     this(builder.searchTarget,
         builder.distance,
         builder.certainty,
-        builder.rerank,
         builder.diversity,
         builder.baseOptions());
   }

src/main/java/io/weaviate/client6/v1/api/collections/query/NearVideo.java

@@ -14,7 +14,6 @@ public record NearVideo(
     Target searchTarget,
     Float distance,
     Float certainty,
-    Rerank rerank,
     Diversity diversity,
     BaseQueryOptions common)
     implements QueryOperator, AggregateObjectFilter {
@@ -40,7 +39,6 @@ public NearVideo(Builder builder) {
         builder.media,
         builder.distance,
         builder.certainty,
-        builder.rerank,
         builder.diversity,
         builder.baseOptions());
   }

src/main/java/io/weaviate/client6/v1/api/collections/query/QueryMetadata.java

@@ -9,21 +9,31 @@ public record QueryMetadata(
     /** BM25 ranking score. */
     Float score,
     /** Components of the BM25 ranking score. */
-    String explainScore) {
+    String explainScore,
+    /**
+     * Score assigned by the reranker module.
+     *
+     * <p>
+     * Only present if the query requested reranking, see
+     * {@link BaseQueryOptions.Builder#rerank(Rerank)}.
+     */
+    Double rerankScore) {
 
   private QueryMetadata(Builder builder) {
     this(
         builder.distance,
         builder.certainty,
         builder.score,
-        builder.explainScore);
+        builder.explainScore,
+        builder.rerankScore);
   }
 
   static class Builder implements ObjectBuilder<QueryMetadata> {
     private Float distance;
     private Float certainty;
     private Float score;
     private String explainScore;
+    private Double rerankScore;
 
     final Builder distance(Float distance) {
       this.distance = distance;
@@ -45,6 +55,11 @@ final Builder explainScore(String explainScore) {
       return this;
     }
 
+    final Builder rerankScore(Double rerankScore) {
+      this.rerankScore = rerankScore;
+      return this;
+    }
+
     @Override
     public final QueryMetadata build() {
       return new QueryMetadata(this);

src/main/java/io/weaviate/client6/v1/api/collections/query/QueryOperator.java

@@ -7,8 +7,15 @@ default BaseQueryOptions common() {
     return null;
   }
 
+  /**
+   * Reranking requested for this query, if any.
+   *
+   * <p>
+   * Reranking is a common query option, so operators that carry
+   * {@link BaseQueryOptions} read it from there.
+   */
   default Rerank rerank() {
-    return null;
+    return common() != null ? common().rerank() : null;
   }
 
   /** Append QueryOperator to the request message. */

src/main/java/io/weaviate/client6/v1/api/collections/query/QueryRequest.java

@@ -33,9 +33,6 @@ public static <PropertiesT> WeaviateProtoSearchGet.SearchRequest marshal(
     if (request.operator.common() != null) {
       request.operator.common().appendTo(message);
     }
-    if (request.operator.rerank() != null) {
-      request.operator.rerank().appendTo(message);
-    }
     request.operator.appendTo(message);
 
     defaults.tenant().ifPresent(message::setTenant);