Send empty vector index type on new Weavaite versions

weaviate/collections/classes/config.py

@@ -2473,7 +2473,7 @@ def __add_to_module_config(
         else:
             return_dict["moduleConfig"][addition_key] = addition_val
 
-    def _to_dict(self) -> Dict[str, Any]:
+    def _to_dict(self, *, emit_default_vector_index_type: bool = True) -> Dict[str, Any]:
         ret_dict: Dict[str, Any] = {}
 
         for cls_field in type(self).model_fields:
@@ -2494,14 +2494,23 @@ def _to_dict(self) -> Dict[str, Any]:
                 ret_dict["vectorIndexType"] = val.vector_index_type().value
                 ret_dict[cls_field] = val._to_dict()
             elif isinstance(val, _VectorConfigCreate):
-                ret_dict["vectorConfig"] = {val.name or "default": val._to_dict()}
+                ret_dict["vectorConfig"] = {
+                    val.name or "default": val._to_dict(
+                        emit_default_vector_index_type=emit_default_vector_index_type
+                    )
+                }
             elif (
                 isinstance(val, list)
                 and len(val) > 0
                 and all(isinstance(item, _NamedVectorConfigCreate) for item in val)
             ):
                 val = cast(List[_NamedVectorConfigCreate], val)
-                ret_dict["vectorConfig"] = {item.name: item._to_dict() for item in val}
+                ret_dict["vectorConfig"] = {
+                    item.name: item._to_dict(
+                        emit_default_vector_index_type=emit_default_vector_index_type
+                    )
+                    for item in val
+                }
             elif (
                 isinstance(val, list)
                 and len(val) > 0
@@ -2514,11 +2523,17 @@ def _to_dict(self) -> Dict[str, Any]:
                         raise WeaviateInvalidInputError(
                             "Vector config name must be set when specifying multiple vectors"
                         )
-                    ret_dict["vectorConfig"][item.name] = item._to_dict()
+                    ret_dict["vectorConfig"][item.name] = item._to_dict(
+                        emit_default_vector_index_type=emit_default_vector_index_type
+                    )
             else:
                 assert isinstance(val, _ConfigCreateModel)
                 ret_dict[cls_field] = val._to_dict()
-        if self.vectorIndexConfig is None and "vectorConfig" not in ret_dict:
+        if (
+            self.vectorIndexConfig is None
+            and "vectorConfig" not in ret_dict
+            and emit_default_vector_index_type
+        ):
             ret_dict["vectorIndexType"] = VectorIndexType.HNSW
 
         ret_dict["class"] = self.name

weaviate/collections/classes/config_named_vectors.py

@@ -77,12 +77,12 @@ class _NamedVectorConfigCreate(_ConfigCreateModel):
         default=None, alias="vector_index_config"
     )
 
-    def _to_dict(self) -> Dict[str, Any]:
+    def _to_dict(self, *, emit_default_vector_index_type: bool = True) -> Dict[str, Any]:
         ret_dict: Dict[str, Any] = self.__parse_vectorizer()
         if self.vectorIndexConfig is not None:
             ret_dict["vectorIndexType"] = self.vectorIndexConfig.vector_index_type().value
             ret_dict["vectorIndexConfig"] = self.vectorIndexConfig._to_dict()
-        else:
+        elif emit_default_vector_index_type:
             ret_dict["vectorIndexType"] = self.vectorIndexType.value
         return ret_dict
 

weaviate/collections/classes/config_vectors.py

@@ -87,12 +87,12 @@ class _VectorConfigCreate(_ConfigCreateModel):
         default=None, alias="vector_index_config"
     )
 
-    def _to_dict(self) -> Dict[str, Any]:
+    def _to_dict(self, *, emit_default_vector_index_type: bool = True) -> Dict[str, Any]:
         ret_dict: Dict[str, Any] = self.__parse_vectorizer()
         if self.vectorIndexConfig is not None:
             ret_dict["vectorIndexType"] = self.vectorIndexConfig.vector_index_type().value
             ret_dict["vectorIndexConfig"] = self.vectorIndexConfig._to_dict()
-        else:
+        elif emit_default_vector_index_type:
             ret_dict["vectorIndexType"] = self.vectorIndexType.value
         return ret_dict
 

weaviate/collections/collections/executor.py

@@ -253,8 +253,16 @@ def create(
                 f"Invalid collection config create parameters: {e}"
             ) from e
 
+        # Servers >= 1.37.4 apply DEFAULT_VECTOR_INDEX_TYPE to named-vector
+        # configs that omit `vectorIndexType`; older servers reject the empty
+        # field, so for them we keep emitting the client-side HNSW default.
+        emit_default_vector_index_type = not self._connection._weaviate_version.is_at_least(
+            1, 37, 4
+        )
         return self.__create(
-            config=config._to_dict(),
+            config=config._to_dict(
+                emit_default_vector_index_type=emit_default_vector_index_type,
+            ),
             data_model_properties=data_model_properties,
             data_model_references=data_model_references,
             skip_argument_validation=skip_argument_validation,