Assuming "user_id" is a surrogate primary key, I dont see any need for
onupdate="CASCADE" to be used here. Additionally, ondelete="CASCADE"
on your hat.user_id column implies that "hat" will be deleted when a
"user" entry is deleted - however your relation has this set up on the
many-to-one side indicating that a "user" would be deleted when a
"hat" is deleted.
I think this is the full setup you're looking for:
users_table = Table('tg_user', metadata,
Column('user_id', Integer, primary_key=True),
Column('user_name', Unicode(16), unique=True),
Column('created', DateTime, default=datetime.now),
mysql_engine='InnoDB',
)
hat_table = Table('hat', metadata,
Column('id', Integer, primary_key=True),
Column('name', Unicode(100)),
Column('user_id', Integer, ForeignKey('tg_user.user_id',
ondelete='CASCADE')),
mysql_engine='InnoDB',
)
class User(object):
pass
class Hat(object):
pass
mapper(User, users_table)
mapper(Hat, hat_table,
properties = {
'user': relation(User,
backref=backref("hats", cascade="all, delete, delete-orphan",
passive_deletes=True)
),
}
)
On Dec 5, 2008, at 1:42 PM, James wrote:
>
> Thanks for your quick response! Unfortunately I made the changes you
> suggest and I still get the UPDATE commands being sent to the children
> before the DELETE on the parent. My model is now:
>
> users_table = Table('tg_user', metadata,
> Column('user_id', Integer, primary_key=True),
> Column('user_name', Unicode(16), unique=True),
> Column('created', DateTime, default=datetime.now),
> mysql_engine='InnoDB',
> )
>
> hat_table = Table('hat', metadata,
> Column('id', Integer, primary_key=True),
> Column('name', Unicode(100)),
> Column('user_id', Integer, ForeignKey('tg_user.user_id',
> onupdate='CASCADE', ondelete='CASCADE')),
> mysql_engine='InnoDB',
> )
>
> class User(object):
> pass
>
> class Hat(object):
> pass
>
> mapper(User, users_table)
>
> mapper(Hat, hat_table,
> properties = {
> 'user': relation(User, backref="hats", cascade="all, delete,
> delete-orphan", passive_updates=True, passive_deletes=True),
> }
> )
>
> And I get the same pattern in the log:
> BEGIN
> UPDATE hat SET user_id=%s WHERE hat.id = %s
> [None, 1L]
> DELETE FROM tg_user WHERE tg_user.user_id = %s
> [1L]
> COMMIT
>
> The ondelete and cascade arguments I have should be working in this
> situation, right?
>
> Thanks again,
> James
>
> On Dec 5, 11:36 am, Michael Bayer <[EMAIL PROTECTED]> wrote:
>> actually, use passive_deletes=True, not 'all'. It will issue
>> DELETEs
>> only for collections that are already loaded, this doesn't break
>> anything and prevents unnecessary SELECTs of unloaded collections.
>> The True setting is needed so that the session can update the state
>> of
>> those collections during the flush process.
>>
>> On Dec 5, 2008, at 12:29 PM, Michael Bayer wrote:
>>
>>> use the "passive_updates=True, passive_deletes='all'" flags. These
>>> are described
>>> athttp://www.sqlalchemy.org/docs/05/sqlalchemy_orm.html#docstrings_sqla
>>> ...
>>> .
>>
>>> On Dec 5, 2008, at 11:42 AM, James Brady wrote:
>>
>>>> Hi all,
>>>> I'm trying to get deletes and updates cascaded down from a parent
>>>> object to the child objects (connected by ForeignKey).
>>
>>>> It all seems pretty simple in the docs, but I can't get it to work!
>>>> I'm using MySQL with the InnoDB engine, and have played with all
>>>> the variation of the onupdate, ondelete and cascade arguments I can
>>>> think of.
>>
>>>> The problem is that immediately before the DELETE command is sent
>>>> to MySQL, there are UPDATE commands nulling out the foreign key
>>>> references of the child objects, so MySQL doesn't trigger it's ON
>>>> DELETE CASCADE action, and for some reason cascade="all, delete-
>>>> orphan" doesn't clean up the children with NULL FKs.
>>
>>>> Here's a simplified model:
>>>> users_table = Table('tg_user', metadata,
>>>> Column('user_id', Integer, primary_key=True),
>>>> Column('created', DateTime, default=datetime.now),
>>>> mysql_engine='InnoDB',
>>>> )
>>
>>>> hat_table = Table('hat', metadata,
>>>> Column('id', Integer, primary_key=True),
>>>> Column('name', Unicode(100)),
>>>> Column('user_id', Integer, ForeignKey('tg_user.user_id'),
>>>> onupdate='CASCADE', ondelete='CASCADE'),
>>>> mysql_engine='InnoDB',
>>>> )
>>
>>>> class User(object):
>>>> pass
>>
>>>> class Hat(object):
>>>> pass
>>
>>>> mapper(User, users_table)
>>
>>>> mapper(Hat, hat_table,
>>>> properties = {
>>>> 'user': relation(User, backref="hats", cascade="all,
>>>> delete, delete-orphan"),
>>>> }
>>>> )
>>
>>>> And the log from SA when I do a User.delete:
>>>> BEGIN
>>>> UPDATE hat SET user_id=%s WHERE hat.id = %s
>>>> [None, 1L]
>>>> DELETE FROM tg_user WHERE tg_user.user_id = %s
>>>> [1L]
>>>> COMMIT
>>
>>>> Any help would be much appreciated!
>>
>>>> James
> >
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