Enhancement: Add Support for Custom Sortable Field Mapping in SQLAlchemy ModelView (#328)

* Enhancement: Add Support for Custom Sortable Field Mapping in SQLAlchemy ModelView

* Fix linting

* Add changelog

Author: jowilf

docs/changelog/index.md

@@ -9,6 +9,26 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### Added
 
+* Add Support for Custom Sortable Field Mapping in SQLAlchemy ModelView by [@jowilf](https://github.com/jowilf)
+  in [#328](https://github.com/jowilf/starlette-admin/pull/328)
+
+!!! usage
+    ```python
+    class Post(Base):
+        __tablename__ = "post"
+
+        id: Mapped[int] = mapped_column(primary_key=True)
+        title: Mapped[str] = mapped_column()
+        user_id: Mapped[int] = mapped_column(ForeignKey("user.id"))
+        user: Mapped[User] = relationship(back_populates="posts")
+
+    class PostView(ModelView):
+        sortable_field = ["id", "title", "user"]
+        sortable_field_mapping = {
+            "user": User.age,  # Sort by the age of the related user
+        }
+    ```
+
 * Add support for datatables [state saving](https://datatables.net/examples/basic_init/state_save.html)
 
 !!! usage

starlette_admin/contrib/sqla/helpers.py

@@ -1,4 +1,4 @@
-from typing import Any, Callable, Dict, List, Optional, Sequence
+from typing import Any, Callable, Dict, Optional, Sequence
 
 from sqlalchemy import Column, String, and_, cast, false, not_, or_, true
 from sqlalchemy.orm import (
@@ -58,16 +58,6 @@ def build_query(
     return and_(True)
 
 
-def build_order_clauses(order_list: List[str], model: Any) -> Any:
-    clauses = []
-    for value in order_list:
-        attr_key, order = value.strip().split(maxsplit=1)
-        attr = getattr(model, attr_key, None)
-        if attr is not None:
-            clauses.append(attr.desc() if order.lower() == "desc" else attr)
-    return clauses
-
-
 def normalize_list(
     arr: Optional[Sequence[Any]], is_default_sort_list: bool = False
 ) -> Optional[Sequence[str]]:

starlette_admin/contrib/sqla/view.py

@@ -1,4 +1,4 @@
-from typing import Any, Dict, List, Optional, Sequence, Type, Union
+from typing import Any, ClassVar, Dict, List, Optional, Sequence, Type, Union
 
 import anyio.to_thread
 from sqlalchemy import Column, String, cast, func, inspect, or_, select
@@ -20,7 +20,6 @@
 )
 from starlette_admin.contrib.sqla.exceptions import InvalidModelError
 from starlette_admin.contrib.sqla.helpers import (
-    build_order_clauses,
     build_query,
     extract_column_python_type,
     normalize_list,
@@ -41,6 +40,30 @@
 
 
 class ModelView(BaseModelView):
+    """A view for managing SQLAlchemy models."""
+
+    sortable_field_mapping: ClassVar[Dict[str, InstrumentedAttribute]] = {}
+    """A dictionary for overriding the default model attribute used for sorting.
+
+    Example:
+        ```python
+        class Post(Base):
+            __tablename__ = "post"
+
+            id: Mapped[int] = mapped_column(primary_key=True)
+            title: Mapped[str] = mapped_column()
+            user_id: Mapped[int] = mapped_column(ForeignKey("user.id"))
+            user: Mapped[User] = relationship(back_populates="posts")
+
+
+        class PostView(ModelView):
+            sortable_field = ["id", "title", "user"]
+            sortable_field_mapping = {
+                "user": User.age,  # Sort by the age of the related user
+            }
+        ```
+    """
+
     def __init__(
         self,
         model: Type[Any],
@@ -231,10 +254,14 @@ async def find_all(
                     request, where, self.model
                 )
             stmt = stmt.where(where)  # type: ignore
-        stmt = stmt.order_by(*build_order_clauses(order_by or [], self.model))
+        stmt = stmt.order_by(
+            *self.build_order_clauses(request, order_by or [], self.model)
+        )
         for field in self.get_fields_list(request, RequestAction.LIST):
             if isinstance(field, RelationField):
-                stmt = stmt.options(joinedload(getattr(self.model, field.name)))
+                stmt = stmt.outerjoin(getattr(self.model, field.name)).options(
+                    joinedload(getattr(self.model, field.name))
+                )
         if isinstance(session, AsyncSession):
             return (await session.execute(stmt)).scalars().unique().all()
         return (
@@ -417,6 +444,19 @@ async def build_full_text_search_query(
     ) -> Any:
         return self.get_search_query(request, term)
 
+    def build_order_clauses(
+        self, request: Request, order_list: List[str], model: Any
+    ) -> Any:
+        clauses = []
+        for value in order_list:
+            attr_key, order = value.strip().split(maxsplit=1)
+            attr = self.sortable_field_mapping.get(
+                attr_key, getattr(model, attr_key, None)
+            )
+            if attr is not None:
+                clauses.append(attr.desc() if order.lower() == "desc" else attr)
+        return clauses
+
     def handle_exception(self, exc: Exception) -> None:
         try:
             """Automatically handle sqlalchemy_file error"""