perf(core): cache _create_subset_model results with lru_cache

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

libs/core/langchain_core/utils/pydantic.py

@@ -199,18 +199,21 @@ class _IgnoreUnserializable(GenerateJsonSchema):
         return {}
 
 
+@lru_cache(maxsize=256)
 def _create_subset_model_v1(
     name: str,
     model: type[BaseModelV1],
-    field_names: list,
+    field_names: tuple[str, ...],
     *,
-    descriptions: dict | None = None,
+    descriptions: tuple[tuple[str, str], ...] | None = None,
     fn_description: str | None = None,
 ) -> type[BaseModelV1]:
     """Create a Pydantic model with only a subset of model's fields."""
+    descriptions_ = dict(descriptions) if descriptions else {}
+    field_names_list = list(field_names)
     fields = {}
 
-    for field_name in field_names:
+    for field_name in field_names_list:
         # Using pydantic v1 so can access __fields__ as a dict.
         field = model.__fields__[field_name]
         t = (
@@ -219,8 +222,8 @@ def _create_subset_model_v1(
             if field.required and not field.allow_none
             else field.outer_type_ | None
         )
-        if descriptions and field_name in descriptions:
-            field.field_info.description = descriptions[field_name]
+        if descriptions_ and field_name in descriptions_:
+            field.field_info.description = descriptions_[field_name]
         fields[field_name] = (t, field.field_info)
 
     rtn = cast("type[BaseModelV1]", create_model_v1(name, **fields))  # type: ignore[call-overload]
@@ -228,18 +231,20 @@ def _create_subset_model_v1(
     return rtn
 
 
+@lru_cache(maxsize=256)
 def _create_subset_model_v2(
     name: str,
     model: type[BaseModel],
-    field_names: list[str],
+    field_names: tuple[str, ...],
     *,
-    descriptions: dict | None = None,
+    descriptions: tuple[tuple[str, str], ...] | None = None,
     fn_description: str | None = None,
 ) -> type[BaseModel]:
     """Create a Pydantic model with a subset of the model fields."""
-    descriptions_ = descriptions or {}
+    descriptions_ = dict(descriptions) if descriptions else {}
+    field_names_list = list(field_names)
     fields = {}
-    for field_name in field_names:
+    for field_name in field_names_list:
         field = model.model_fields[field_name]
         description = descriptions_.get(field_name, field.description)
         field_kwargs: dict[str, Any] = {"description": description}
@@ -291,19 +296,20 @@ def _create_subset_model(
     Returns:
         The created subset model.
     """
+    descriptions_tuple = tuple(descriptions.items()) if descriptions else None
     if issubclass(model, BaseModelV1):
         return _create_subset_model_v1(
             name,
             model,
-            field_names,
-            descriptions=descriptions,
+            tuple(field_names),
+            descriptions=descriptions_tuple,
             fn_description=fn_description,
         )
     return _create_subset_model_v2(
         name,
         model,
-        field_names,
-        descriptions=descriptions,
+        tuple(field_names),
+        descriptions=descriptions_tuple,
         fn_description=fn_description,
     )
 

libs/core/tests/unit_tests/utils/test_pydantic.py

@@ -115,7 +115,7 @@ def test_with_field_metadata() -> None:
             description="List of integers", min_length=10, max_length=15
         )
 
-    subset_model = _create_subset_model_v2("Foo", Foo, ["x"])
+    subset_model = _create_subset_model_v2("Foo", Foo, ("x",))
     assert subset_model.model_json_schema() == {
         "properties": {
             "x": {
@@ -199,7 +199,7 @@ def test_create_subset_model_v2_preserves_default_factory() -> None:
     subset = _create_subset_model_v2(
         "Subset",
         Original,
-        ["required_field", "names", "mapping"],
+        ("required_field", "names", "mapping"),
     )
     schema = subset.model_json_schema()
     assert schema.get("required") == ["required_field"]