Phase 6: Update database layer identifier documentation

- Updated AnimeSeries model docstring to clarify key is primary identifier
- Updated folder field to indicate metadata-only usage
- Updated AnimeSeriesService docstring and get_by_key method
- Updated infrastructure.md with database identifier documentation
- All 996 tests passing

infrastructure.md

@@ -132,6 +132,20 @@ All series-related WebSocket events include `key` as the primary identifier in t
 
 **Mixins**: `TimestampMixin` (created_at, updated_at), `SoftDeleteMixin`
 
+### AnimeSeries Identifier Fields
+
+| Field  | Type        | Purpose                                           |
+| ------ | ----------- | ------------------------------------------------- |
+| `id`   | Primary Key | Internal database key for relationships           |
+| `key`  | Unique, Indexed | **PRIMARY IDENTIFIER** for all lookups       |
+| `folder` | String    | Filesystem metadata only (not for identification) |
+
+**Database Service Methods:**
+
+-   `AnimeSeriesService.get_by_key(key)` - **Primary lookup method**
+-   `AnimeSeriesService.get_by_id(id)` - Internal lookup by database ID
+-   No `get_by_folder()` method exists - folder is never used for lookups
+
 ## Core Services
 
 ### SeriesApp (`src/core/SeriesApp.py`)

instructions.md

@@ -156,88 +156,12 @@ All API layer tasks completed.
 
 ### Phase 5: Frontend ✅ (Completed November 28, 2025)
 
-All frontend tasks completed:
 
--   **Task 5.1: Update Frontend JavaScript** ✅
-    -   Updated `app.js` to use `key` as primary series identifier
-    -   `selectedSeries` Set now uses `key` instead of `folder`
-    -   `createSerieCard()` uses `data-key` attribute for identification
-    -   `toggleSerieSelection()` uses `key` for lookups
-    -   All selection and download operations use `key`
-    
--   **Task 5.2: Update WebSocket Events** ✅
-    -   WebSocket service already has proper documentation for `key` usage
-    -   Updated tests to include `key` and `folder` in broadcast data
-    -   Tests verify both fields are included in messages
-    
--   **Task 5.3: Update Additional Frontend JavaScript Files** ✅
-    -   Reviewed `queue.js`, `websocket_client.js`, and utility files
-    -   No changes needed - these files use download item IDs correctly
-    -   Series identification is handled in `app.js`
-    
--   **Task 5.4: Update HTML Templates** ✅
-    -   Reviewed all templates (`index.html`, `queue.html`, etc.)
-    -   No changes needed - series cards are rendered dynamically in JavaScript
-    -   Static templates don't contain series data attributes
+### Phase 6: Database Layer ✅ (Completed November 28, 2025)
 
----
-
-### Phase 6: Database Layer
-
-#### Task 6.1: Verify Database Models Use Key Correctly
-
-**File:** [`src/server/database/models.py`](src/server/database/models.py)
-
-**Objective:** Verify and document that database models correctly use `key` as unique identifier.
-
-**Steps:**
-
-1. Open [`src/server/database/models.py`](src/server/database/models.py)
-2. Verify `AnimeSeries.key` is unique and indexed
-3. Verify `AnimeSeries.folder` is not used for lookups
-4. Update docstrings to clarify identifier usage
-5. Ensure all relationships use `id` (primary key) not `key` or `folder`
-
-**Success Criteria:**
-
--   [ ] `key` is unique and indexed
--   [ ] `folder` is metadata only
--   [ ] Docstrings are clear
--   [ ] All database model tests pass
-
-**Test Command:**
-
-```bash
-conda run -n AniWorld python -m pytest tests/unit/test_database_models.py -v
-```
-
----
-
-#### Task 6.2: Update Database Services to Use Key
-
-**File:** [`src/server/database/service.py`](src/server/database/service.py)
-
-**Objective:** Ensure all database service methods use `key` for series lookup.
-
-**Steps:**
-
-1. Open [`src/server/database/service.py`](src/server/database/service.py)
-2. Verify `AnimeSeriesService.get_by_key()` is used for lookups
-3. Verify no methods use `folder` for identification
-4. Update any methods that incorrectly use `folder` for lookups
-5. Add migration helper if needed to update existing data
-
-**Success Criteria:**
-
--   [ ] All service methods use `key` for lookups
--   [ ] `folder` never used as identifier
--   [ ] All database service tests pass
-
-**Test Command:**
-
-```bash
-conda run -n AniWorld python -m pytest tests/unit/test_database_service.py -v
-```
+All database layer tasks completed:
+- Task 6.1: Verified `AnimeSeries.key` is unique and indexed, `folder` is metadata only, updated docstrings
+- Task 6.2: Verified all service methods use `key` for lookups, no folder-based identification
 
 ---
 
@@ -543,9 +467,9 @@ conda run -n AniWorld python -m pytest tests/integration/test_identifier_consist
     -   [x] Task 5.2: Update WebSocket Events
     -   [x] Task 5.3: Update Additional Frontend JavaScript Files
     -   [x] Task 5.4: Update HTML Templates
--   [ ] Phase 6: Database Layer
-    -   [ ] Task 6.1: Verify Database Models
-    -   [ ] Task 6.2: Update Database Services
+-   [x] Phase 6: Database Layer ✅ **Completed November 28, 2025**
+    -   [x] Task 6.1: Verify Database Models
+    -   [x] Task 6.2: Update Database Services
 -   [ ] Phase 7: Testing and Validation
     -   [ ] Task 7.1: Update Test Fixtures
     -   [ ] Task 7.2: Add Integration Tests

src/server/database/models.py

@@ -38,20 +38,31 @@ class AnimeSeries(Base, TimestampMixin):
     Represents an anime series with metadata, provider information,
     and links to episodes. Corresponds to the core Serie class.
     
+    Series Identifier Convention:
+        - `key`: PRIMARY IDENTIFIER - Unique, provider-assigned, URL-safe
+          (e.g., "attack-on-titan"). Used for all lookups and operations.
+        - `folder`: METADATA ONLY - Filesystem folder name for display
+          (e.g., "Attack on Titan (2013)"). Never used for identification.
+        - `id`: Internal database primary key for relationships.
+    
     Attributes:
-        id: Primary key
-        key: Unique identifier used by provider
-        name: Series name
+        id: Database primary key (internal use for relationships)
+        key: Unique provider key - PRIMARY IDENTIFIER for all lookups
+        name: Display name of the series
         site: Provider site URL
-        folder: Local filesystem path
+        folder: Filesystem folder name (metadata only, not for lookups)
         description: Optional series description
         status: Current status (ongoing, completed, etc.)
         total_episodes: Total number of episodes
         cover_url: URL to series cover image
-        episodes: Relationship to Episode models
-        download_items: Relationship to DownloadQueueItem models
+        episodes: Relationship to Episode models (via id foreign key)
+        download_items: Relationship to DownloadQueueItem models (via id foreign key)
         created_at: Creation timestamp (from TimestampMixin)
         updated_at: Last update timestamp (from TimestampMixin)
+    
+    Note:
+        All database relationships use `id` (primary key), not `key` or `folder`.
+        Use `get_by_key()` in AnimeSeriesService for lookups.
     """
     __tablename__ = "anime_series"
     
@@ -63,7 +74,7 @@ class AnimeSeries(Base, TimestampMixin):
     # Core identification
     key: Mapped[str] = mapped_column(
         String(255), unique=True, nullable=False, index=True,
-        doc="Unique provider key"
+        doc="Unique provider key - PRIMARY IDENTIFIER for all lookups"
     )
     name: Mapped[str] = mapped_column(
         String(500), nullable=False, index=True,
@@ -75,7 +86,7 @@ class AnimeSeries(Base, TimestampMixin):
     )
     folder: Mapped[str] = mapped_column(
         String(1000), nullable=False,
-        doc="Local filesystem path"
+        doc="Filesystem folder name - METADATA ONLY, not for lookups"
     )
     
     # Metadata

src/server/database/service.py

@@ -43,6 +43,11 @@ class AnimeSeriesService:
     
     Provides methods for creating, reading, updating, and deleting anime series
     with support for both async and sync database sessions.
+    
+    Series Identifier Convention:
+        - Use `get_by_key()` for lookups by provider key (primary identifier)
+        - Use `get_by_id()` for lookups by database primary key (internal)
+        - Never use `folder` for identification - it's metadata only
     """
     
     @staticmethod
@@ -115,12 +120,19 @@ class AnimeSeriesService:
     async def get_by_key(db: AsyncSession, key: str) -> Optional[AnimeSeries]:
         """Get anime series by provider key.
         
+        This is the PRIMARY lookup method for series identification.
+        Use this method instead of get_by_id() when looking up by
+        the provider-assigned unique key.
+        
         Args:
             db: Database session
-            key: Unique provider key
+            key: Unique provider key (e.g., "attack-on-titan")
         
         Returns:
             AnimeSeries instance or None if not found
+        
+        Note:
+            Do NOT use folder for lookups - it's metadata only.
         """
         result = await db.execute(
             select(AnimeSeries).where(AnimeSeries.key == key)