sqlalchemy session.merge()

作者：花生_TL007 | 2024-05-02 03:10:11

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 1 from sqlalchemy import *
 2 from sqlalchemy.orm import *
 3 
 4 metadata = MetaData()
 5 
 6 t = Table(
 7     't', metadata,
 8     Column('id', Integer, primary_key=True),
 9     Column('state', String(10)),
10 )
11 
12 class Model(object): pass
13 
14 mapper(Model, t)
15 
16 engine = create_engine('sqlite://')
17 metadata.create_all(engine)
18 
19 session = sessionmaker(bind=engine)()
20 
21 obj1 = Model()
22 obj1.state = 'value1'
23 session.add(obj1)
24 session.commit()
25 obj_id = obj1.id
26 
27 obj2 = Model()
28 obj2.id = obj_id
29 obj2.state = 'value2'
30 obj3 = session.merge(obj2)
31 session.commit()
32 print obj3 is obj1, obj3 is obj2
33 print obj3.state

结果：

True False
value2

 1 from sqlalchemy import *
 2 from sqlalchemy.orm import *
 3 
 4 metadata = MetaData()
 5 
 6 t = Table(
 7     't', metadata,
 8     Column('id', Integer, primary_key=True),
 9     Column('state1', String(10)),
10     Column('state2', String(10)),
11 )
12 
13 class Model(object): pass
14 
15 mapper(Model, t)
16 
17 engine = create_engine('sqlite://')
18 metadata.create_all(engine)
19 
20 session = sessionmaker(bind=engine)()
21 
22 obj1 = Model()
23 obj1.state1 = 'value1-1'
24 obj1.state2 = 'value2-1'
25 session.add(obj1)
26 session.commit()
27 obj_id = obj1.id
28 session.expunge_all()
29 
30 obj2 = Model()
31 obj2.id = obj_id
32 obj2.state1 = 'value1-2'
33 obj3 = session.merge(obj2)
34 session.commit()
35 print obj3 is obj1, obj3 is obj2
36 print obj3.state1, obj3.state2

结果：
False False
value1-2 value2-1

转载于:https://www.cnblogs.com/haojinming/archive/2013/04/16/3024936.html

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