如何同时进行SQLAlchemy 4查询？

Question

im试图同时执行4次插入。我现在正在尝试以下操作：

params = [
    [1, market_currency_id, add_party1, db],
    [1, pair_currency_id, - subs_party1, db],
    [2, market_currency_id, -subs_party2, db],
    [2, pair_currency_id, add_party2, db]
]  

cpu_count = os.cpu_count()  
with Pool( cpu_count ) as p:
    pu.db
    p.map(calculateBalances, params, 1)

def calculateBalances(params):
    user_id = params[0]
    currency_id = params[1]
    amount = params[2]
    db = params[3]
    _balance = Balance(user_id=user_id, currency_id= currency_id, amount=amount)
    db.add(_balance)

但是，出现以下错误： Can't pickle <class 'sqlalchemy.orm.session.Session'>: it's not the same object as sqlalchemy.orm.session.Session