from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

from app.core.config import settings

engine = create_engine(
    settings.DATABASE_URL,
    pool_pre_ping=True,
    pool_recycle=3600,
    echo=settings.DEBUG,
)

# 避免 commit 后 ORM 实例自动过期，导致读取字段时回表 SELECT（高频接口会显著拖慢）
SessionLocal = sessionmaker(autocommit=False, autoflush=False, expire_on_commit=False, bind=engine)

Base = declarative_base()


def get_db():
    """获取数据库会话"""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()