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該代碼是從sqlahcmey的orm tutorial的分步拷貝,除了最後一行, 我打算在查詢後刪除所有表格。但受阻上Base.metadata.drop_all(bind=engine)
該程序,下面是MySQL的當時的狀態(從MySQL工作臺截取):SQLAlchemy在丟失表格時被阻止
作爲標記行顯示,刪除表過程由於 table metadata lock
上吊,我建議元數據鎖定是由於result = session.query(User).all()
引起的,因爲如果該行被刪除,程序沒有被阻止, ,但我仍然不知道原因。所以我的問題是:爲什麼會出現這種情況,如何避免阻塞
#!/usr/bin/env python
# -*- coding: utf-8 -*-
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
Base = declarative_base()
class User(Base):
__tablename__ = 'users'
id = Column(Integer, primary_key=True)
name = Column(String(16))
fullname = Column(String(16))
password = Column(String(16))
def __init__(self, name, fullname, password):
self.name = name
self.fullname = fullname
self.password = password
def __repr__(self):
return "<User('%s','%s', '%s')>" % (self.name, self.fullname, self.password)
uri = 'mysql://root:[email protected]/test_sa'
engine = create_engine(uri, echo=False)
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()
user = User('ed', 'Ed Jones', 'edspassword')
session.add(user)
session.commit()
result = session.query(User).all()
print len(result)
Base.metadata.drop_all(bind=engine)
謝謝,我明白了! [本頁](http://dev.mysql.com/doc/refman/5.5/en/metadata-locking.html)是否解釋了我遇到過的同樣的事情? – Reorx
是的(填滿15個字符) – zzzeek