refactor(dry-B2): ImportSettings.load()/load_sync() classmethods for the singleton row

The `select(ImportSettings).where(id == 1)).scalar_one()` singleton load was
repeated 15× across services, API, and 5 task modules. Added async load() +
sync load_sync() classmethods on the model and migrated all 15 full-row sites
(callers already imported ImportSettings, so no new imports; dropped download's
now-orphaned select import). Left maintenance.py's deliberate column-select
(import_scan_path only) as-is.

Rest of the service layer was already adequately DRY — the Record/to_dict
pattern is only 2 instances and the savepoint find-or-create recovery is
correctly per-entity, so neither was forced into a shared abstraction.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/api/import_admin.py

@@ -159,9 +159,7 @@ def _refetch_task_sync(session, task_id: int) -> dict:
         return {"status": "not_found"}
     if task.status != "failed":
         return {"status": "not_failed"}
-    settings = session.execute(
+    settings = ImportSettings.load_sync(session)
-        select(ImportSettings).where(ImportSettings.id == 1)
-    ).scalar_one()
     return attempt_refetch(session, task, Path(settings.import_scan_path))
 
 

backend/app/api/settings.py

@@ -31,9 +31,7 @@ _EDITABLE_FIELDS = (
 @settings_bp.route("/settings/import", methods=["GET"])
 async def get_import_settings():
     async with get_session() as session:
-        row = (
+        row = await ImportSettings.load(session)
-            await session.execute(select(ImportSettings).where(ImportSettings.id == 1))
-        ).scalar_one()
     return jsonify({
         "min_width": row.min_width,
         "min_height": row.min_height,
@@ -99,9 +97,7 @@ async def update_import_settings():
             return _bad_int("download_failure_warning_threshold", 1, 100)
 
     async with get_session() as session:
-        row = (
+        row = await ImportSettings.load(session)
-            await session.execute(select(ImportSettings).where(ImportSettings.id == 1))
-        ).scalar_one()
         for field in _EDITABLE_FIELDS:
             if field in body:
                 setattr(row, field, body[field])

backend/app/api/system_backup.py

@@ -227,9 +227,7 @@ async def delete_run(run_id: int):
 @system_backup_bp.route("/settings", methods=["GET"])
 async def get_settings():
     async with get_session() as session:
-        row = (await session.execute(
+        row = await ImportSettings.load(session)
-            select(ImportSettings).where(ImportSettings.id == 1)
-        )).scalar_one()
     return jsonify({
         "backup_db_nightly_enabled": row.backup_db_nightly_enabled,
         "backup_db_nightly_hour_utc": row.backup_db_nightly_hour_utc,
@@ -249,9 +247,7 @@ async def patch_settings():
         return err
 
     async with get_session() as session:
-        row = (await session.execute(
+        row = await ImportSettings.load(session)
-            select(ImportSettings).where(ImportSettings.id == 1)
-        )).scalar_one()
         for field in _BACKUP_SETTINGS_FIELDS:
             if field in body:
                 setattr(row, field, body[field])

backend/app/models/import_settings.py

@@ -4,7 +4,7 @@ Enforced as a single row via a CHECK (id = 1) constraint. The application
 always SELECTs id=1 and never inserts/deletes after the initial migration.
 """
 
-from sqlalchemy import Boolean, CheckConstraint, Float, Integer, Text
+from sqlalchemy import Boolean, CheckConstraint, Float, Integer, Text, select
 from sqlalchemy.orm import Mapped, mapped_column
 
 from .base import Base
@@ -63,3 +63,13 @@ class ImportSettings(Base):
     backup_images_keep_last_n: Mapped[int] = mapped_column(
         Integer, nullable=False, default=3,
     )
+
+    @classmethod
+    async def load(cls, session) -> "ImportSettings":
+        """The singleton settings row (id=1), via an async session."""
+        return (await session.execute(select(cls).where(cls.id == 1))).scalar_one()
+
+    @classmethod
+    def load_sync(cls, session) -> "ImportSettings":
+        """The singleton settings row (id=1), via a sync session."""
+        return session.execute(select(cls).where(cls.id == 1)).scalar_one()

backend/app/services/scheduler_service.py

@@ -58,9 +58,7 @@ async def select_due_sources(session: AsyncSession) -> list[Source]:
         .where(Artist.auto_check.is_(True))
     )).scalars().all()
 
-    settings = (await session.execute(
+    settings = await ImportSettings.load(session)
-        select(ImportSettings).where(ImportSettings.id == 1)
-    )).scalar_one()
 
     now = datetime.now(UTC)
     due: list[Source] = []
@@ -121,9 +119,7 @@ async def scheduler_status(session: AsyncSession) -> dict:
         .where(Source.enabled.is_(True))
         .where(Artist.auto_check.is_(True))
     )).scalars().all()
-    settings = (await session.execute(
+    settings = await ImportSettings.load(session)
-        select(ImportSettings).where(ImportSettings.id == 1)
-    )).scalar_one()
 
     now = datetime.now(UTC)
     due_now = 0

backend/app/services/source_service.py

@@ -120,9 +120,7 @@ class SourceService:
         return config
 
     async def _load_settings(self) -> ImportSettings:
-        return (await self.session.execute(
+        return await ImportSettings.load(self.session)
-            select(ImportSettings).where(ImportSettings.id == 1)
-        )).scalar_one()
 
     def _build_record(
         self, source: Source, artist: Artist, settings: ImportSettings,

backend/app/tasks/backup.py

@@ -246,9 +246,7 @@ def prune_backups() -> dict:
     SessionLocal = _sync_session_factory()
     counts = {"db_deleted": 0, "images_deleted": 0, "files_unlinked": 0}
     with SessionLocal() as session:
-        s = session.execute(
+        s = ImportSettings.load_sync(session)
-            select(ImportSettings).where(ImportSettings.id == 1)
-        ).scalar_one()
         for kind, keep in (
             ("db", s.backup_db_keep_last_n),
             ("images", s.backup_images_keep_last_n),
@@ -286,9 +284,7 @@ def backup_db_nightly() -> dict:
     either {'skipped': '<reason>'} or {'dispatched': '<task_id>'}."""
     SessionLocal = _sync_session_factory()
     with SessionLocal() as session:
-        s = session.execute(
+        s = ImportSettings.load_sync(session)
-            select(ImportSettings).where(ImportSettings.id == 1)
-        ).scalar_one()
         nightly_enabled = s.backup_db_nightly_enabled
         configured_hour = s.backup_db_nightly_hour_utc
     if not nightly_enabled:

backend/app/tasks/download.py

@@ -3,7 +3,6 @@
 import asyncio
 from pathlib import Path
 
-from sqlalchemy import select
 from sqlalchemy.exc import DBAPIError, OperationalError
 
 from ..celery_app import celery
@@ -41,9 +40,7 @@ def download_source(self, source_id: int) -> int:
         SyncFactory = _sync_session_factory()
         try:
             with SyncFactory() as sync_session:
-                settings = sync_session.execute(
+                settings = ImportSettings.load_sync(sync_session)
-                    select(ImportSettings).where(ImportSettings.id == 1)
-                ).scalar_one()
                 rate_limit = settings.download_rate_limit_seconds
                 validate_files = settings.download_validate_files
 
@@ -57,9 +54,7 @@ def download_source(self, source_id: int) -> int:
             async with async_factory() as async_session:
                 cred_service = CredentialService(async_session, crypto)
                 with SyncFactory() as sync_session:
-                    sync_settings = sync_session.execute(
+                    sync_settings = ImportSettings.load_sync(sync_session)
-                        select(ImportSettings).where(ImportSettings.id == 1)
-                    ).scalar_one()
                     importer = Importer(
                         session=sync_session,
                         images_root=IMAGES_ROOT,

backend/app/tasks/import_file.py

@@ -167,9 +167,7 @@ def enqueue_import(task_id: int, task_type: str) -> None:
 
 def _do_import(session, task, import_task_id: int) -> dict:
     """Actual work, called from inside the resilience wrapper."""
-    settings = session.execute(
+    settings = ImportSettings.load_sync(session)
-        select(ImportSettings).where(ImportSettings.id == 1)
-    ).scalar_one()
     import_root = Path(settings.import_scan_path)
     batch = session.get(ImportBatch, task.batch_id)
     deep = bool(batch and batch.scan_mode == "deep")

backend/app/tasks/maintenance.py

@@ -460,9 +460,7 @@ def cleanup_old_download_events() -> int:
     """
     SessionLocal = _sync_session_factory()
     with SessionLocal() as session:
-        settings = session.execute(
+        settings = ImportSettings.load_sync(session)
-            select(ImportSettings).where(ImportSettings.id == 1)
-        ).scalar_one()
         retention_days = settings.download_event_retention_days
         cutoff = datetime.now(UTC) - timedelta(days=retention_days)
         result = session.execute(

backend/app/tasks/scan.py

@@ -44,9 +44,7 @@ def scan_directory(self, triggered_by: str = "manual",
     batch id."""
     SessionLocal = _sync_session_factory()
     with SessionLocal() as session:
-        settings = session.execute(
+        settings = ImportSettings.load_sync(session)
-            select(ImportSettings).where(ImportSettings.id == 1)
-        ).scalar_one()
         import_root = Path(settings.import_scan_path)
 
         batch = ImportBatch(