On 8/25/15 10:05 AM, Jakub Bąk wrote:
I just came across a solution to this problem.
Adding 'with_polymorphic': '*' to __mapper_args__ on the Node model
was enough.
|
classNode(db.Model):
id =db.Column(db.Integer,primary_key=True)
type =db.Column(db.String(20))
name =db.Column(db.String(30),nullable=False)
date_added =db.Column(db.DateTime,default=datetime.now())
parent_id =db.Column(db.Integer,db.ForeignKey('node.id
<http://node.id/>'),nullable=True)
path =db.Column(db.String(200),default='')
__mapper_args__ ={'polymorphic_on':type,
'with_polymorphic':'*'}
|
OK, yeah that's a funny problem you have. The with_polymorphic in all
cases is going to lead to heavier queries, because there's the join but
also if you already have joins between Node classes, you'll start to see
some very long queries with lots of joins / sub-joins.
A more portable solution would be to also implement before_delete(),
where you either ensure that the Image columns are loaded, or you add
the files to be deleted to some kind of collection; then you'd actually
delete the files using a safer event like after_commit(), so that way if
your transaction fails, the files are preserved.
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