pydantic resolve解决嵌套数据结构生成痛点分析

[
  {
    "id": 1,
    "post": "v2ex",
    "author": {
      "name": "tangkikodo",
      "id": 1
    }
  },
  {
    "id": 2,
    "post": "v3ex",
    "author": {
      "name": "tangkikodo2",
      "id": 1
    }
  }
]

[
  {
    "id": 1,
    "post": "v2ex",
    "author": {
      "name": "tangkikodo",
      "recent_views": [
        {
          "id": 2,
          "post": "v3ex"
        },
        {
          "id": 3,
          "post": "v4ex"
        }
      ]
    }
  }
]

# posts query
posts = query_all_posts()
# authors query
authors_ids = fetch_unique_author_id(posts)  
authors = query_author(author_ids)
recent_view_posts = fetch_recent_review_posts(author_ids)  # 新需求
recent_view_maps = calc_view_mapping(recent_view_posts)    # 新需求
# authors attach
authors = [attach_posts(a, recent_view_maps) for a in authors]
author_map = calc_author_mapping(authors)
# posts attach
posts = [attach_author(p, author_map) for p in posts]

class AuthorLoader(DataLoader):
    async def batch_load_fn(self, author_ids):
        async with async_session() as session:
            # query authors
            res = await session.execute(select(Author).where(Author.id.in_(author_ids)))
            rows = res.scalars().all()
            # transform into pydantic object
            dct = defaultdict(dict)
            for row in rows:
                dct[row.author_id] = AuthorSchema.from_orm(row)
            # order by author_id
            return [dct.get(k, None) for k in author_ids]
class RecentViewPostLoader(DataLoader):
    async def batch_load_fn(self, view_ids):
        async with async_session() as session:
            res = await session.execute(select(Post, PostVisit.visitor_id)  # join 浏览中间表
                .join(PostVist, PostVisit.post_id == Post.id)
                .where(PostVisit.user_id.in_(view_ids)
                .where(PostVisit.created_at < some_timestamp)))
            rows = res.scalars().all()
            dct = defaultdict(list)
            for row in rows:
                dct[row.visitor_id].append(PostSchema.from_orm(row))  # group 到 visitor
            return [dct.get(k, []) for k in view_ids]

class RecentPostSchema(BaseModel):
    id: int
    name: str
    class Config:
        orm_mode = True
class AuthorSchema(BaseModel):
    id: int
    name: str
    img_url: str
    recent_views: Tuple[RecentPostSchema, ...] = tuple()
    def resolve_recent_views(self, loader=LoaderDepend(RecentViewPostLoader)):  
        return loader.load(self.id)
    class Config:
        orm_mode = True
class PostSchema(BaseModel):
    id: int
    author_id: int
    name: str
    author: Optional[AuthorSchema] = None
    def resolve_author(self, loader=LoaderDepend(AuthorLoader)):
         return loader.load(self.author_id)
    class Config:
        orm_mode = True

posts = (await session.execute(select(Post))).scalars().all()
posts = [PostSchema.from_orm(p) for p in posts]
results = await Resolver().resolve(posts)