65 lines
2.0 KiB
Python
65 lines
2.0 KiB
Python
"""数据库：async engine + session，SQLAlchemy 2.0 声明式基类。"""
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from datetime import datetime, timezone
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from sqlalchemy import event
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from sqlalchemy.ext.asyncio import (
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AsyncSession,
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async_sessionmaker,
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create_async_engine,
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)
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from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
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from app.config import settings
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_is_sqlite = settings.database_url.startswith("sqlite")
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# SQLite 需要 check_same_thread=False 以配合异步
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engine = create_async_engine(
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settings.database_url,
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echo=settings.debug,
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connect_args={"check_same_thread": False} if _is_sqlite else {},
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)
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if _is_sqlite:
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@event.listens_for(engine.sync_engine, "connect")
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def _sqlite_pragmas(dbapi_conn, _record):
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"""每个连接都要单独设置：WAL 让读写不再互斥，外键约束默认是关的。"""
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cur = dbapi_conn.cursor()
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cur.execute("PRAGMA journal_mode=WAL")
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cur.execute("PRAGMA synchronous=NORMAL")
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cur.execute("PRAGMA foreign_keys=ON")
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# 写锁等待，避免并发写直接报 database is locked
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cur.execute("PRAGMA busy_timeout=5000")
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cur.close()
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SessionLocal = async_sessionmaker(engine, expire_on_commit=False, class_=AsyncSession)
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class Base(DeclarativeBase):
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"""所有 ORM 模型的基类。"""
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def _utcnow() -> datetime:
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return datetime.now(timezone.utc)
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class TimestampMixin:
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"""通用时间戳字段。
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用 Python 侧的 datetime（带微秒）而非 SQL 的 now()：SQLite 的
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CURRENT_TIMESTAMP 只精确到秒，同一秒内的多条记录无法排出先后，
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会让"取最近一次作答"这类查询出错。
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"""
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created_at: Mapped[datetime] = mapped_column(default=_utcnow, nullable=False)
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updated_at: Mapped[datetime] = mapped_column(
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default=_utcnow, onupdate=_utcnow, nullable=False
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)
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async def get_db():
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"""FastAPI 依赖：提供一个请求级 session。"""
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async with SessionLocal() as session:
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yield session
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