Merge pull request #140 from DoiiarX/fix-db-module

修复缺失的文件

+"""
+通用数据库工具（异步）
+
+此模块提供基于 SQLAlchemy 2.x 异步引擎的数据库访问封装，支持 MySQL 与 PostgreSQL。
+数据模型定义位置：
+- 无（本模块仅提供连接与查询工具，不定义数据模型）
+"""
+
+from __future__ import annotations
+
+import asyncio
+import os
+from typing import Any, Dict, Iterable, List, Optional, Union
+
+from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession, create_async_engine
+from sqlalchemy import text
+from InsightEngine.utils.config import settings
+
+__all__ = [
+    "get_async_engine",
+    "fetch_all",
+]
+
+
+_engine: Optional[AsyncEngine] = None
+
+
+def _build_database_url() -> str:
+    dialect: str = (settings.DB_DIALECT or "mysql").lower()
+    host: str = settings.DB_HOST or ""
+    port: str = str(settings.DB_PORT or "")
+    user: str = settings.DB_USER or ""
+    password: str = settings.DB_PASSWORD or ""
+    db_name: str = settings.DB_NAME or ""
+
+    if os.getenv("DATABASE_URL"):
+        return os.getenv("DATABASE_URL")  # 直接使用外部提供的完整URL
+
+    if dialect in ("postgresql", "postgres"):
+        # PostgreSQL 使用 asyncpg 驱动
+        return f"postgresql+asyncpg://{user}:{password}@{host}:{port}/{db_name}"
+
+    # 默认 MySQL 使用 aiomysql 驱动
+    return f"mysql+aiomysql://{user}:{password}@{host}:{port}/{db_name}"
+
+
+def get_async_engine() -> AsyncEngine:
+    global _engine
+    if _engine is None:
+        database_url: str = _build_database_url()
+        _engine = create_async_engine(
+            database_url,
+            pool_pre_ping=True,
+            pool_recycle=1800,
+        )
+    return _engine
+
+
+async def fetch_all(query: str, params: Optional[Union[Iterable[Any], Dict[str, Any]]] = None) -> List[Dict[str, Any]]:
+    """
+    执行只读查询并返回字典列表。
+    """
+    engine: AsyncEngine = get_async_engine()
+    async with engine.connect() as conn:
+        result = await conn.execute(text(query), params or {})
+        rows = result.mappings().all()
+        # 将 RowMapping 转换为普通字典
+        return [dict(row) for row in rows]
+
+