1.5

backend/app/services/moment_service.py

@@ -82,7 +82,7 @@ class MomentService:
         unique.sort(key=lambda x: x.created_at, reverse=True)
         unique = unique[:limit]
 
-        return [await self._moment_to_dict(m, user_id) for m in unique]
+        return await self._moments_to_dicts(unique, user_id)
 
     async def get_user_moments(self, user_id: str, viewer_id: str | None = None,
                                 cursor: str | None = None, limit: int = 20) -> list[dict]:
@@ -116,7 +116,7 @@ class MomentService:
                 if viewer_id == user_id:
                     filtered.append(m)
 
-        return [await self._moment_to_dict(m, viewer_id) for m in filtered]
+        return await self._moments_to_dicts(filtered, viewer_id)
 
     async def delete_moment(self, moment_id: str, user_id: str):
         """删除动态（仅作者）"""
@@ -243,56 +243,70 @@ class MomentService:
             raise ValueError("只能删除自己的评论")
         await self.db.delete(comment)
 
-    async def _moment_to_dict(self, moment: Moment, viewer_id: str | None) -> dict:
-        """将 Moment ORM 对象转为前端需要的字典"""
-        user_result = await self.db.execute(select(User).where(User.id == moment.user_id))
-        user = user_result.scalars().first()
+    async def _moments_to_dicts(self, moments: list[Moment], viewer_id: str | None) -> list[dict]:
+        """批量将 Moment ORM 对象转为前端需要的字典（优化 N+1 查询）"""
+        if not moments:
+            return []
 
-        # 点赞数
-        like_count_result = await self.db.execute(
-            select(func.count(MomentLike.id)).where(MomentLike.moment_id == moment.id)
+        moment_ids = [m.id for m in moments]
+        user_ids = list(set(m.user_id for m in moments))
+
+        # 批量获取所有作者
+        users_result = await self.db.execute(select(User).where(User.id.in_(user_ids)))
+        users_map = {u.id: u for u in users_result.scalars().all()}
+
+        # 批量获取点赞数
+        like_counts_result = await self.db.execute(
+            select(MomentLike.moment_id, func.count(MomentLike.id))
+            .where(MomentLike.moment_id.in_(moment_ids))
+            .group_by(MomentLike.moment_id)
         )
-        like_count = like_count_result.scalar() or 0
+        like_counts_map = dict(like_counts_result.all())
 
-        # 是否已点赞
-        is_liked = False
+        # 批量获取评论数
+        comment_counts_result = await self.db.execute(
+            select(MomentComment.moment_id, func.count(MomentComment.id))
+            .where(MomentComment.moment_id.in_(moment_ids))
+            .group_by(MomentComment.moment_id)
+        )
+        comment_counts_map = dict(comment_counts_result.all())
+
+        # 批量获取当前用户的点赞状态
+        liked_moment_ids = set()
         if viewer_id:
-            like_result = await self.db.execute(
-                select(MomentLike).where(
-                    MomentLike.moment_id == moment.id,
+            liked_result = await self.db.execute(
+                select(MomentLike.moment_id).where(
+                    MomentLike.moment_id.in_(moment_ids),
                     MomentLike.user_id == viewer_id,
                 )
             )
-            is_liked = like_result.scalars().first() is not None
+            liked_moment_ids = {r[0] for r in liked_result.all()}
 
-        # 评论数
-        comment_count_result = await self.db.execute(
-            select(func.count(MomentComment.id)).where(MomentComment.moment_id == moment.id)
-        )
-        comment_count = comment_count_result.scalar() or 0
+        result = []
+        for moment in moments:
+            user = users_map.get(moment.user_id)
+            images = []
+            if moment.images:
+                try:
+                    images = json.loads(moment.images)
+                except Exception:
+                    pass
 
-        # 解析图片
-        images = []
-        if moment.images:
-            try:
-                images = json.loads(moment.images)
-            except:
-                pass
-
-        return {
-            "id": moment.id,
-            "user_id": moment.user_id,
-            "username": user.username if user else "未知",
-            "nickname": user.nickname if user else None,
-            "avatar_url": user.avatar_url if user else None,
-            "content": moment.content,
-            "images": images,
-            "visibility": moment.visibility,
-            "like_count": like_count,
-            "is_liked": is_liked,
-            "comment_count": comment_count,
-            "created_at": moment.created_at,
-        }
+            result.append({
+                "id": moment.id,
+                "user_id": moment.user_id,
+                "username": user.username if user else "未知",
+                "nickname": user.nickname if user else None,
+                "avatar_url": user.avatar_url if user else None,
+                "content": moment.content,
+                "images": images,
+                "visibility": moment.visibility,
+                "like_count": like_counts_map.get(moment.id, 0),
+                "is_liked": moment.id in liked_moment_ids,
+                "comment_count": comment_counts_map.get(moment.id, 0),
+                "created_at": moment.created_at,
+            })
+        return result
 
     async def _get_friend_ids(self, user_id: str) -> list[str]:
         """获取好友ID列表"""