fix: facet keys always use full relation chain (#190)

docs/module/crud.md

@@ -474,7 +474,7 @@ The distinct values are returned in the `filter_attributes` field of [`Paginated
   "filter_attributes": {
     "status": ["active", "inactive"],
     "country": ["DE", "FR", "US"],
-    "name": ["admin", "editor", "viewer"]
+    "role__name": ["admin", "editor", "viewer"]
   }
 }
 ```
@@ -482,7 +482,7 @@ The distinct values are returned in the `filter_attributes` field of [`Paginated
 Use `filter_by` to pass the client's chosen filter values directly — no need to build SQLAlchemy conditions by hand. Any unknown key raises [`InvalidFacetFilterError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.InvalidFacetFilterError).
 
 !!! info "The keys in `filter_by` are the same keys the client received in `filter_attributes`."
-    Keys are normally the terminal `column.key` (e.g. `"name"` for `Role.name`). When two facet fields share the same column key (e.g. `(Build.project, Project.name)` and `(Build.os, Os.name)`), the relationship name is prepended automatically: `"project__name"` and `"os__name"`.
+    Keys use `__` as a separator for the full relationship chain. A direct column `User.status` produces `"status"`. A relationship tuple `(User.role, Role.name)` produces `"role__name"`. A deeper chain `(User.role, Role.permission, Permission.name)` produces `"role__permission__name"`.
 
 `filter_by` and `filters` can be combined — both are applied with AND logic.
 
@@ -517,7 +517,7 @@ Both single-value and multi-value query parameters work:
 ```
 GET /users?status=active                      → filter_by={"status": ["active"]}
 GET /users?status=active&country=FR           → filter_by={"status": ["active"], "country": ["FR"]}
-GET /users?role=admin&role=editor     → filter_by={"role": ["admin", "editor"]}  (IN clause)
+GET /users?role__name=admin&role__name=editor → filter_by={"role__name": ["admin", "editor"]}  (IN clause)
 ```
 
 ## Sorting

src/fastapi_toolsets/crud/search.py

@@ -2,7 +2,6 @@
 
 import asyncio
 import functools
-from collections import Counter
 from collections.abc import Sequence
 from dataclasses import dataclass, replace
 from typing import TYPE_CHECKING, Any, Literal
@@ -151,7 +150,7 @@ def build_search_filters(
 
 
 def facet_keys(facet_fields: Sequence[FacetFieldType]) -> list[str]:
-    """Return a key for each facet field, disambiguating duplicate column keys.
+    """Return a key for each facet field.
 
     Args:
         facet_fields: Sequence of facet fields — either direct columns or
@@ -160,22 +159,12 @@ def facet_keys(facet_fields: Sequence[FacetFieldType]) -> list[str]:
     Returns:
         A list of string keys, one per facet field, in the same order.
     """
-    raw: list[tuple[str, str | None]] = []
+    keys: list[str] = []
     for field in facet_fields:
         if isinstance(field, tuple):
-            rel = field[-2]
+            keys.append("__".join(el.key for el in field))
-            column = field[-1]
-            raw.append((column.key, rel.key))
         else:
-            raw.append((field.key, None))
+            keys.append(field.key)
-
-    counts = Counter(col_key for col_key, _ in raw)
-    keys: list[str] = []
-    for col_key, rel_key in raw:
-        if counts[col_key] > 1 and rel_key is not None:
-            keys.append(f"{rel_key}__{col_key}")
-        else:
-            keys.append(col_key)
     return keys
 
 

tests/test_crud_search.py

@@ -646,7 +646,7 @@ class TestFacetsRelationship:
         result = await UserRelFacetCrud.offset_paginate(db_session, schema=UserRead)
 
         assert result.filter_attributes is not None
-        assert set(result.filter_attributes["name"]) == {"admin", "editor"}
+        assert set(result.filter_attributes["role__name"]) == {"admin", "editor"}
 
     @pytest.mark.anyio
     async def test_relationship_facet_none_excluded(self, db_session: AsyncSession):
@@ -661,7 +661,7 @@ class TestFacetsRelationship:
         result = await UserRelFacetCrud.offset_paginate(db_session, schema=UserRead)
 
         assert result.filter_attributes is not None
-        assert result.filter_attributes["name"] == []
+        assert result.filter_attributes["role__name"] == []
 
     @pytest.mark.anyio
     async def test_relationship_facet_deduplicates_join_with_search(
@@ -689,7 +689,7 @@ class TestFacetsRelationship:
         )
 
         assert result.filter_attributes is not None
-        assert result.filter_attributes["name"] == ["admin"]
+        assert result.filter_attributes["role__name"] == ["admin"]
 
 
 class TestFilterBy:
@@ -755,7 +755,7 @@ class TestFilterBy:
         )
 
         result = await UserRelFacetCrud.offset_paginate(
-            db_session, filter_by={"name": "admin"}, schema=UserRead
+            db_session, filter_by={"role__name": "admin"}, schema=UserRead
         )
 
         assert isinstance(result.pagination, OffsetPagination)
@@ -824,7 +824,7 @@ class TestFilterBy:
 
         result = await UserRoleFacetCrud.offset_paginate(
             db_session,
-            filter_by={"name": "admin", "id": str(admin.id)},
+            filter_by={"role__name": "admin", "role__id": str(admin.id)},
             schema=UserRead,
         )
 
@@ -916,15 +916,15 @@ class TestFilterParamsSchema:
         param_names = set(inspect.signature(dep).parameters)
         assert param_names == {"username", "email"}
 
-    def test_relationship_facet_uses_column_key(self):
+    def test_relationship_facet_uses_full_chain_key(self):
-        """Relationship tuple uses the terminal column's key."""
+        """Relationship tuple uses the full chain joined by __ as the key."""
         import inspect
 
         UserRoleCrud = CrudFactory(User, facet_fields=[(User.role, Role.name)])
         dep = UserRoleCrud.filter_params()
 
         param_names = set(inspect.signature(dep).parameters)
-        assert param_names == {"name"}
+        assert param_names == {"role__name"}
 
     def test_raises_when_no_facet_fields(self):
         """ValueError raised when no facet_fields are configured or provided."""
@@ -978,6 +978,22 @@ class TestFilterParamsSchema:
         keys = facet_keys([(rel_a, col_a), (rel_b, col_b)])
         assert keys == ["project__name", "os__name"]
 
+    def test_deep_chain_joins_all_segments(self):
+        """Three-element tuple produces all relation segments joined by __."""
+        from unittest.mock import MagicMock
+
+        from fastapi_toolsets.crud.search import facet_keys
+
+        rel_a = MagicMock()
+        rel_a.key = "role"
+        rel_b = MagicMock()
+        rel_b.key = "permission"
+        col = MagicMock()
+        col.key = "name"
+
+        keys = facet_keys([(rel_a, rel_b, col)])
+        assert keys == ["role__permission__name"]
+
     def test_unique_column_keys_kept_plain(self):
         """Fields with unique column keys are not prefixed."""
         from fastapi_toolsets.crud.search import facet_keys

tests/test_example_pagination_search.py

@@ -182,8 +182,7 @@ class TestOffsetPagination:
         body = resp.json()
         fa = body["filter_attributes"]
         assert set(fa["status"]) == {"draft", "published"}
-        # "name" is unique across all facet fields — no prefix needed
+        assert set(fa["category__name"]) == {"backend", "python"}
-        assert set(fa["name"]) == {"backend", "python"}
 
     @pytest.mark.anyio
     async def test_filter_attributes_scoped_to_filter(