chore: initialize insar management system v2

backend/app/database.py

@@ -0,0 +1,71 @@
+import os
+from typing import AsyncGenerator
+from urllib.parse import urlparse
+from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, AsyncSession
+from sqlalchemy.orm import declarative_base
+
+# --- 全局变量，将在应用启动时被初始化 ---
+engine = None
+AsyncSessionLocal = None
+_CURRENT_DB_URL = None
+Base = declarative_base()
+
+def init_db(db_url: str = None):
+    """
+    初始化 PostgreSQL 数据库连接。
+    """
+    global engine, AsyncSessionLocal, _CURRENT_DB_URL
+
+    # 1. 确定数据库 URL
+    database_url = db_url or os.environ.get('DATABASE_URL')
+    
+    if not database_url:
+        raise RuntimeError("未设置 DATABASE_URL 环境变量。请配置 PostgreSQL 连接字符串 (postgresql+asyncpg://...)。")
+
+    if engine is not None and AsyncSessionLocal is not None:
+        if db_url is None or _CURRENT_DB_URL == database_url:
+            return
+        raise RuntimeError("数据库连接已初始化，且 DATABASE_URL 不一致。请重启服务以应用新的配置。")
+
+    if "postgresql" not in database_url:
+        raise ValueError("仅支持 PostgreSQL 数据库。")
+
+    print(f"数据库正在初始化，连接至: {urlparse(database_url).hostname}")
+
+    # 2. 创建异步引擎
+    # 配置高性能连接池
+    engine = create_async_engine(
+        database_url,
+        echo=False,
+        future=True,
+        pool_size=20,
+        max_overflow=10,
+        pool_recycle=3600,
+        pool_pre_ping=True
+    )
+    
+    AsyncSessionLocal = async_sessionmaker(
+        autocommit=False,
+        autoflush=False,
+        bind=engine,
+        class_=AsyncSession,
+        expire_on_commit=False,
+    )
+    _CURRENT_DB_URL = database_url
+
+# 创建一个 FastAPI 依赖项，用于在每个请求中获取数据库会话
+async def get_db() -> AsyncGenerator[AsyncSession, None]:
+    """
+    FastAPI dependency that provides a database session for a single request.
+    """
+    if AsyncSessionLocal is None:
+        raise RuntimeError("数据库未初始化。请在应用启动时调用 init_db()。")
+
+    async with AsyncSessionLocal() as session:
+        try:
+            yield session
+        except Exception:
+            await session.rollback()
+            raise
+        finally:
+            await session.close()