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📝 Docs: 数据库最佳实践 (#2545)
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Ju4tCode <42488585+yanyongyu@users.noreply.github.com>
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website/docs/best-practice/database/developer/dependency.md
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240
website/docs/best-practice/database/developer/dependency.md
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---
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sidebar_position: 3
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description: 依赖注入
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---
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# 依赖注入
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`nonebot-plugin-orm` 提供了强大且灵活的依赖注入，可以方便地帮助你获取数据库会话和查询数据。
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## 数据库会话
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### AsyncSession
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新数据库会话，常用于有独立的数据库操作逻辑的插件。
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```python {13,26}
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from nonebot import on_message
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from nonebot.params import Depends
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from nonebot_plugin_orm import AsyncSession, Model, async_scoped_session
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from sqlalchemy.orm import Mapped, mapped_column
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message = on_message()
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class Message(Model):
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id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
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async def get_message(session: AsyncSession) -> Message:
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# 等价于 session = get_session()
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async with session:
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msg = Message()
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session.add(msg)
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await session.commit()
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await session.refresh(msg)
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return msg
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@message.handle()
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async def _(session: async_scoped_session, msg: Message = Depends(get_message)):
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await session.rollback() # 无法回退 get_message() 中的更改
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await message.send(str(msg.id)) # msg 被存储，msg.id 递增
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```
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### async_scoped_session
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数据库作用域会话，常用于事件响应器和有与响应逻辑相关的数据库操作逻辑的插件。
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```python {13，26}
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from nonebot import on_message
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from nonebot.params import Depends
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from nonebot_plugin_orm import Model, async_scoped_session
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from sqlalchemy.orm import Mapped, mapped_column
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message = on_message()
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class Message(Model):
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id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
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async def get_message(session: async_scoped_session) -> Message:
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# 等价于 session = get_scoped_session()
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msg = Message()
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session.add(msg)
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await session.flush()
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await session.refresh(msg)
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return msg
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@message.handle()
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async def _(session: async_scoped_session, msg: Message = Depends(get_message)):
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await session.rollback() # 可以回退 get_message() 中的更改
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await message.send(str(msg.id)) # msg 没有被存储，msg.id 不变
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```
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## 查询数据
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### Model
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支持类作为依赖。
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```python
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from typing import Annotated
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from nonebot.params import Depends
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from nonebot_plugin_orm import Model
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from sqlalchemy.orm import Mapped, mapped_column
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def get_id() -> int: ...
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class Message(Model):
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id: Annotated[Mapped[int], Depends(get_id)] = mapped_column(
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primary_key=True, autoincrement=True
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)
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async def _(msg: Message):
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# 等价于 msg = (
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# await (await session.stream(select(Message).where(Message.id == get_id())))
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# .scalars()
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# .one_or_none()
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# )
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...
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```
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### SQLDepends
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参数为一个 SQL 语句，决定依赖注入的内容，SQL 语句中可以使用子依赖。
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```python {11-13}
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from nonebot.params import Depends
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from nonebot_plugin_orm import Model, SQLDepends
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from sqlalchemy import select
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def get_id() -> int: ...
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async def _(
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model: Model = SQLDepends(select(Model).where(Model.id == Depends(get_id))),
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): ...
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```
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参数可以是任意 SQL 语句，但不建议使用 `select` 以外的语句，因为语句可能没有返回值（`returning` 除外），而且代码不清晰。
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### 类型标注
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类型标注决定依赖注入的数据结构，主要影响以下几个层面：
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- 迭代器（`session.execute()`）或异步迭代器（`session.stream()`）
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- 标量（`session.execute().scalars()`）或元组（`session.execute()`）
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- 一个（`session.execute().one_or_none()`，注意 `None` 时可能触发 [重载](../../../appendices/overload#重载)）或全部（`session.execute()` / `session.execute().all()`）
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- 连续（`session().execute()`）或分块（`session.execute().partitions()`）
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具体如下（可以使用父类型作为类型标注）：
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- ```python
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async def _(rows_partitions: AsyncIterator[Sequence[Tuple[Model, ...]]]):
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# 等价于 rows_partitions = await (await session.stream(sql).partitions())
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async for partition in rows_partitions:
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for row in partition:
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print(row[0], row[1], ...)
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```
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- ```python
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async def _(model_partitions: AsyncIterator[Sequence[Model]]):
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# 等价于 model_partitions = await (await session.stream(sql).scalars().partitions())
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async for partition in model_partitions:
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for model in partition:
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print(model)
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```
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- ```python
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async def _(row_partitions: Iterator[Sequence[Tuple[Model, ...]]]):
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# 等价于 row_partitions = await session.execute(sql).partitions()
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for partition in rows_partitions:
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for row in partition:
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print(row[0], row[1], ...)
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```
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- ```python
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async def _(model_partitions: Iterator[Sequence[Model]]):
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# 等价于 model_partitions = await (await session.execute(sql).scalars().partitions())
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for partition in model_partitions:
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for model in partition:
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print(model)
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```
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- ```python
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async def _(rows: sa_async.AsyncResult[Tuple[Model, ...]]):
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# 等价于 rows = await session.stream(sql)
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async for row in rows:
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print(row[0], row[1], ...)
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```
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- ```python
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async def _(models: sa_async.AsyncScalarResult[Model]):
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# 等价于 models = await session.stream(sql).scalars()
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async for model in models:
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print(model)
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```
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- ```python
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async def _(rows: sa.Result[Tuple[Model, ...]]):
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# 等价于 rows = await session.execute(sql)
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for row in rows:
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print(row[0], row[1], ...)
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```
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- ```python
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async def _(models: sa.ScalarResult[Model]):
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# 等价于 models = await session.execute(sql).scalars()
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for model in models:
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print(model)
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```
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- ```python
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async def _(rows: Sequence[Tuple[Model, ...]]):
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# 等价于 rows = await (await session.stream(sql).all())
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for row in rows:
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print(row[0], row[1], ...)
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```
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- ```python
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async def _(models: Sequence[Model]):
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# 等价于 models = await (await session.stream(sql).scalars().all())
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for model in models:
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print(model)
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```
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- ```python
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async def _(row: Tuple[Model, ...]):
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# 等价于 row = await (await session.stream(sql).one_or_none())
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print(row[0], row[1], ...)
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```
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- ```python
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async def _(model: Model):
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# 等价于 model = await (await session.stream(sql).scalars().one_or_none())
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print(model)
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```
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