From d16c6085c935a8e5b1ac1560654c4af18ccb57a3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=A6=D0=B2=D1=8B=D0=BB=D0=B5=D0=B2=20=D0=90=D0=BB=D0=B5?=
 =?UTF-8?q?=D0=BA=D1=81=D0=B0=D0=BD=D0=B4=D1=80=20=D0=92=D0=B0=D0=B4=D0=B8?=
 =?UTF-8?q?=D0=BC=D0=BE=D0=B2=D0=B8=D1=87?= <Cvylev.A@prezident.ru>
Date: Wed, 29 Jul 2026 10:53:35 +0300
Subject: [PATCH] perf(reco): batch id->entity hydration

radio/similar resolved ids one get_by_id at a time (N round-trips). Add
TrackRepository.get_many and use it (plus ArtistRepository.get_many) to
hydrate in a single query, preserving requested order.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 app/application/recommendation_service.py              | 10 ++++++----
 app/domain/ports.py                                    |  5 +++++
 app/infrastructure/db/repositories/track_repository.py | 10 ++++++++++
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/app/application/recommendation_service.py b/app/application/recommendation_service.py
index 256de39..350a52b 100644
--- a/app/application/recommendation_service.py
+++ b/app/application/recommendation_service.py
@@ -82,8 +82,8 @@ class RecommendationService:
         if self._recommender.is_available():
             ids = await self._recommender.similar_artist_ids(artist_id, limit=limit)
             if ids is not None:
-                found = [a for i in ids if (a := await self._artists.get_by_id(i))]
-                return REASON_ML, found
+                by_id = {a.id: a for a in await self._artists.get_many(ids)}
+                return REASON_ML, [by_id[i] for i in ids if i in by_id]
 
         found = await self._artists.list_similar(artist_id=artist_id, limit=limit)
         return REASON_SIMILAR, found
@@ -183,5 +183,7 @@ class RecommendationService:
         return None, REASON_DISCOVER
 
     async def _hydrate_tracks(self, ids: list[uuid.UUID]) -> list[Track]:
-        """Resolve ids → tracks preserving order, skipping any that vanished."""
-        return [t for i in ids if (t := await self._tracks.get_by_id(i))]
+        """Resolve ids → tracks preserving order, skipping any that vanished.
+        One batched query rather than N per-id round-trips."""
+        by_id = {t.id: t for t in await self._tracks.get_many(ids)}
+        return [by_id[i] for i in ids if i in by_id]
diff --git a/app/domain/ports.py b/app/domain/ports.py
index 786de76..8b80e71 100644
--- a/app/domain/ports.py
+++ b/app/domain/ports.py
@@ -142,6 +142,11 @@ class ArtistRepository(Protocol):
 
 class TrackRepository(Protocol):
     async def get_by_id(self, track_id: uuid.UUID) -> Track | None: ...
+    async def get_many(self, ids: list[uuid.UUID]) -> list[Track]:
+        """Resolve multiple ids in one query (unordered) — batches the per-id
+        lookups radio/similar would otherwise fan out into N round-trips."""
+        ...
+
     async def get_by_source(self, source: str, source_id: str) -> Track | None: ...
     async def add(
         self,
diff --git a/app/infrastructure/db/repositories/track_repository.py b/app/infrastructure/db/repositories/track_repository.py
index 9b5cd59..0c250b4 100644
--- a/app/infrastructure/db/repositories/track_repository.py
+++ b/app/infrastructure/db/repositories/track_repository.py
@@ -46,6 +46,16 @@ class SqlAlchemyTrackRepository:
         row = await self._session.get(TrackModel, track_id)
         return _to_entity(row) if row is not None else None
 
+    async def get_many(self, ids: list[uuid.UUID]) -> list[Track]:
+        if not ids:
+            return []
+        rows = (
+            (await self._session.execute(select(TrackModel).where(TrackModel.id.in_(ids))))
+            .scalars()
+            .all()
+        )
+        return [_to_entity(r) for r in rows]
+
     async def get_by_source(self, source: str, source_id: str) -> Track | None:
         row = (
             await self._session.execute(