fix(quantizers): use the field names the server actually reads

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

@@ -29,6 +29,7 @@
 import io.weaviate.client6.v1.api.collections.config.ShardStatus;
 import io.weaviate.client6.v1.api.collections.generative.DummyGenerative;
 import io.weaviate.client6.v1.api.collections.query.BaseQueryOptions;
+import io.weaviate.client6.v1.api.collections.quantizers.RQ;
 import io.weaviate.client6.v1.api.collections.vectorindex.Hnsw;
 import io.weaviate.client6.v1.api.collections.vectorizers.SelfProvidedVectorizer;
 import io.weaviate.containers.Container;
@@ -266,6 +267,37 @@ public void test_updateQuantization_uncompressed() throws IOException {
         .returns(Quantization.Kind.BQ, Quantization::_kind);
   }
 
+  /**
+   * The quantizer settings have to survive a round trip through the server.
+   *
+   * <p>
+   * They used to be sent under snake_case names ({@code rescore_limit},
+   * {@code training_limit}, ...) that Weaviate looks up verbatim and therefore
+   * never read, so every one of them was dropped on write and came back null.
+   * Asserting on {@code enabled} alone did not catch it.
+   */
+  @Test
+  public void test_quantizerSettingsRoundTrip() throws IOException {
+    // Arrange
+    var nsThings = ns("Things");
+
+    var things = client.collections.create(nsThings,
+        c -> c.vectorConfig(VectorConfig.selfProvided(
+            self -> self.quantization(Quantization.rq(rq -> rq.rescoreLimit(42).bits(8))))));
+
+    // Act
+    var config = things.config.get();
+
+    // Assert
+    Assertions.assertThat(config).get()
+        .extracting(CollectionConfig::vectors)
+        .extracting("default", InstanceOfAssertFactories.type(VectorConfig.class))
+        .extracting(VectorConfig::quantization)
+        .asInstanceOf(InstanceOfAssertFactories.type(RQ.class))
+        .returns(42, RQ::rescoreLimit)
+        .returns(8, RQ::bits);
+  }
+
   @Test
   public void test_updateGenerative() throws IOException {
     // Arrange

src/main/java/io/weaviate/client6/v1/api/collections/quantizers/BQ.java

@@ -9,7 +9,7 @@
 
 public record BQ(
     @SerializedName("enabled") boolean enabled,
-    @SerializedName("rescore_limit") Integer rescoreLimit,
+    @SerializedName("rescoreLimit") Integer rescoreLimit,
     @SerializedName("cache") Boolean cache) implements Quantization {
 
   @Override

src/main/java/io/weaviate/client6/v1/api/collections/quantizers/PQ.java

@@ -11,10 +11,28 @@ public record PQ(
     @SerializedName("enabled") boolean enabled,
     @SerializedName("centroids") Integer centroids,
     @SerializedName("segments") Integer segments,
-    @SerializedName("encoder_type") EncoderType encoderType,
-    @SerializedName("encoder_distribution") EncoderDistribution encoderDistribution,
-    @SerializedName("training_limit") Integer trainingLimit,
-    @SerializedName("bit_compression") Boolean bitCompression) implements Quantization {
+    /**
+     * Encoder settings, which the server nests one level deeper as
+     * {@code encoder: {type, distribution}}.
+     */
+    @SerializedName("encoder") Encoder encoder,
+    @SerializedName("trainingLimit") Integer trainingLimit,
+    @SerializedName("bitCompression") Boolean bitCompression) implements Quantization {
+
+  /** Type of the encoder, or {@code null} if it was left at the server default. */
+  public EncoderType encoderType() {
+    return encoder != null ? encoder.type() : null;
+  }
+
+  /** Encoder distribution, or {@code null} if left at the server default. */
+  public EncoderDistribution encoderDistribution() {
+    return encoder != null ? encoder.distribution() : null;
+  }
+
+  public record Encoder(
+      @SerializedName("type") EncoderType type,
+      @SerializedName("distribution") EncoderDistribution distribution) {
+  }
 
   public enum EncoderType {
     @SerializedName("kmeans")
@@ -53,8 +71,9 @@ public PQ(Builder builder) {
         builder.enabled,
         builder.centroids,
         builder.segments,
-        builder.encoderType,
-        builder.encoderDistribution,
+        builder.encoderType == null && builder.encoderDistribution == null
+            ? null
+            : new Encoder(builder.encoderType, builder.encoderDistribution),
         builder.trainingLimit,
         builder.bitCompression);
   }

src/main/java/io/weaviate/client6/v1/api/collections/quantizers/RQ.java

@@ -9,7 +9,7 @@
 
 public record RQ(
     @SerializedName("enabled") boolean enabled,
-    @SerializedName("rescore_limit") Integer rescoreLimit,
+    @SerializedName("rescoreLimit") Integer rescoreLimit,
     @SerializedName("bits") Integer bits,
     @SerializedName("cache") Boolean cache) implements Quantization {
 

src/main/java/io/weaviate/client6/v1/api/collections/quantizers/SQ.java

@@ -9,8 +9,8 @@
 
 public record SQ(
     @SerializedName("enabled") boolean enabled,
-    @SerializedName("rescore_limit") Integer rescoreLimit,
-    @SerializedName("training_limit") Integer trainingLimit,
+    @SerializedName("rescoreLimit") Integer rescoreLimit,
+    @SerializedName("trainingLimit") Integer trainingLimit,
     @SerializedName("cache") Boolean cache) implements Quantization {
 
   @Override

src/test/java/io/weaviate/client6/v1/internal/json/JSONTest.java

@@ -1206,11 +1206,13 @@ public static Object[][] testCases() {
                     "pq": {
                       "enabled": true,
                       "centroids": 8,
-                      "encoder_distribution": "normal",
-                      "encoder_type": "tile",
+                      "encoder": {
+                        "type": "tile",
+                        "distribution": "normal"
+                      },
                       "segments": 16,
-                      "training_limit": 1024,
-                      "bit_compression": true
+                      "trainingLimit": 1024,
+                      "bitCompression": true
                     }
                   }
                 }
@@ -1230,8 +1232,8 @@ public static Object[][] testCases() {
                   "vectorIndexConfig": {
                     "sq": {
                       "enabled": true,
-                      "rescore_limit": 10,
-                      "training_limit": 1024,
+                      "rescoreLimit": 10,
+                      "trainingLimit": 1024,
                       "cache": true
                     }
                   }
@@ -1251,7 +1253,7 @@ public static Object[][] testCases() {
                   "vectorIndexConfig": {
                     "rq": {
                       "enabled": true,
-                      "rescore_limit": 10,
+                      "rescoreLimit": 10,
                       "bits": 8
                     }
                   }
@@ -1271,7 +1273,7 @@ public static Object[][] testCases() {
                   "vectorIndexConfig": {
                     "bq": {
                       "enabled": true,
-                      "rescore_limit": 10,
+                      "rescoreLimit": 10,
                       "cache": true
                     }
                   }