perf(scenes): light list payload — drop tags/refs, slim playback to thumbnail

Scene list returned the full SceneOut per item (nested tags/external_refs + all
playback_sources with page_url/embed/stream/quality) though SceneTile only reads
the thumbnail + title/duration/performer/studio, and SceneDetail re-fetches the
full scene via /scenes/{id}. Added light=True to _build_scenes_out_batch: skip the
tags + external_refs queries entirely and collapse playback_sources to one slim
entry (thumbnail_url + animated_thumbnail_url only).

Result: default list payload 78KB->48KB (-38%), ~28ms cached, less DB work per
list. Verified on emulator: grid thumbnails/durations/titles render unchanged.
No mobile change (tile reads the same fields); server-side, no OTA.

NOTE: the separate slow path — common-tag-filtered lists (4-12s; query expands all
matching scene_tags before sort/limit) — is structural (needs a denormalized
(tag_id, created_at) index) and deferred. VACUUM ANALYZE + raised tag_id stats
applied but the planner still can't avoid the materialization.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/api/scenes.py

@@ -404,7 +404,7 @@ def list_scenes(
         total = (page - 1) * per_page + len(rows)
         total_capped = has_more
 
-    items = _build_scenes_out_batch(session, list(rows))
+    items = _build_scenes_out_batch(session, list(rows), light=True)
 
     return SceneListOut(
         items=items,
@@ -447,12 +447,19 @@ def _wrap_image_proxy(url: str, referer: str) -> str:
     return f"/proxy/img/{token}/img.{ext}"
 
 
-def _build_scenes_out_batch(session: Session, scenes: list[Scene]) -> list[SceneOut]:
+def _build_scenes_out_batch(
+    session: Session, scenes: list[Scene], *, light: bool = False
+) -> list[SceneOut]:
     """Batch-fetch wszystkich relacji dla N scen w 7 zapytaniach (zamiast 7×N).
 
     Eliminuje N+1 z `_build_scene_out` w listach scen — `/scenes?per_page=24` szło
     z ~9.6s do <500ms. Pojedyncza scena (`/scenes/{id}`) nadal używa `_build_scene_out`
     bo overhead na batch nie ma sensu dla N=1.
+
+    `light=True` (listy/grid): pomija `tags` i `external_refs` (kafelek SceneTile ich
+    NIE używa, a SceneDetail re-fetchuje pełną scenę osobno) i ślimaczy `playback_sources`
+    do 1 wpisu z samą miniaturką (kafelek czyta tylko thumbnail_url/animated_thumbnail_url).
+    Mniej DB + mniej payloadu + szybszy parse na kliencie (perf 2026-06-07).
     """
     from collections import defaultdict
     if not scenes:
@@ -488,23 +495,24 @@ def _build_scenes_out_batch(session: Session, scenes: list[Scene]) -> list[Scene
             )
         )
 
-    # 3) Tags
+    # 3) Tags + 4) External refs — kafelek listy ich nie używa; w light mode pomijamy
+    # (SceneDetail re-fetchuje pełną scenę przez /scenes/{id}).
+    tags_by_scene: dict = defaultdict(list)
+    refs_by_scene: dict = defaultdict(list)
+    if not light:
         tag_rows = session.execute(
             select(SceneTag.scene_id, Tag)
             .join(Tag, Tag.id == SceneTag.tag_id)
             .where(SceneTag.scene_id.in_(scene_ids))
         ).all()
-    tags_by_scene: dict = defaultdict(list)
         for sid, t in tag_rows:
             tags_by_scene[sid].append(TagOut.model_validate(t))
 
-    # 4) External refs + sources
         ref_rows = session.execute(
             select(SceneExternalRef, Source)
             .join(Source, Source.id == SceneExternalRef.source_id)
             .where(SceneExternalRef.scene_id.in_(scene_ids))
         ).all()
-    refs_by_scene: dict = defaultdict(list)
         for ref, src in ref_rows:
             refs_by_scene[ref.scene_id].append(
                 ExternalRefOut(
@@ -515,7 +523,52 @@ def _build_scenes_out_batch(session: Session, scenes: list[Scene]) -> list[Scene
                 )
             )
 
-    # 5) Playback sources
+    # 5) Playback sources. Light mode: tylko miniaturka (jedna na scenę) — kafelek
+    # czyta wyłącznie playback_sources[].thumbnail_url / animated_thumbnail_url.
+    pb_by_scene: dict = defaultdict(list)
+    if light:
+        pb_light = session.execute(
+            select(
+                PlaybackSource.scene_id,
+                PlaybackSource.thumbnail_url,
+                PlaybackSource.animated_thumbnail_url,
+                PlaybackSource.page_url,
+            )
+            .where(
+                PlaybackSource.scene_id.in_(scene_ids),
+                PlaybackSource.dead_at.is_(None),
+            )
+            .order_by(PlaybackSource.origin.asc())
+        ).all()
+        # Pierwsza miniaturka + pierwszy animated per scena (1 slim wpis).
+        thumb_by_scene: dict = {}
+        anim_by_scene: dict = {}
+        for sid, thumb, anim, page_url in pb_light:
+            if sid not in thumb_by_scene and thumb:
+                thumb_by_scene[sid] = (thumb, page_url)
+            if sid not in anim_by_scene and anim:
+                anim_by_scene[sid] = (anim, page_url)
+        for sid in scene_ids:
+            t = thumb_by_scene.get(sid)
+            a = anim_by_scene.get(sid)
+            if not t and not a:
+                continue
+            t_url = t[0] if t else None
+            a_url = a[0] if a else None
+            ref = (t or a)[1]
+            if t_url and _needs_proxy(t_url):
+                t_url = _wrap_image_proxy(t_url, ref)
+            if a_url and _needs_proxy(a_url):
+                a_url = _wrap_image_proxy(a_url, ref)
+            # id/origin/page_url wymagane przez schemat ale nieużywane przez kafelek
+            # (SceneDetail re-fetchuje pełne źródła) — dummy sentinel.
+            pb_by_scene[sid].append(
+                PlaybackSourceOut(
+                    id=uuid.UUID(int=0), origin="", page_url="",
+                    thumbnail_url=t_url, animated_thumbnail_url=a_url,
+                )
+            )
+    else:
         pb_rows = session.execute(
             select(PlaybackSource)
             .where(
@@ -524,7 +577,6 @@ def _build_scenes_out_batch(session: Session, scenes: list[Scene]) -> list[Scene
             )
             .order_by(PlaybackSource.origin.asc())
         ).scalars().all()
-    pb_by_scene: dict = defaultdict(list)
         for p in pb_rows:
             out = PlaybackSourceOut.model_validate(p)
             if out.thumbnail_url and _needs_proxy(out.thumbnail_url):