Hello,
I have written a CMS which is, among other, based on the joined load
inheritance feature of SQLAlchemy.
It is quite simple: the user is able to add "objects" in "containers"
and can select the default polymorphic loading for a "container". In
gross it can dynamically select which tables will be joined. For that
I'm using the new orm.with_polymorphic() stuff of version 0.8.
It works well, and now I would also be able to let the user to set a
default ORDER BY, ... for a "container".
Basically I would like to be able to select a default ORDER BY from the
orm.with_polymorphic() join above.
For the moment I'm using a "bytea" (I'm using PostgreSQL) column, named
"default_order" which is mapped in a "PickleType" on the SQLAlchemy
side. This column is just a serialized list which looks like:
[{'column': 'starts', 'polymorphic_identity': 5, 'weight': 1, 'order':
'desc'},
{'column': 'weight', 'polymorphic_identity': None, 'weight': 2,
'order': 'asc'},
{'column': 'last_update', 'polymorphic_identity': None, 'weight': 3,
'order': 'asc'}]
So it tells which column from which primary mapper should be used and in
which order.
I'm using the following code http://pastie.org/6459613 to transform this
in an ORDER BY clause.
Not all columns should be selectable, so I used something like this in
my mapped classes:
Content.__order__ = [Content.weight, Content.last_update]
Event.__order__ = [Event.starts, Event.ends]
File.__order__ = [File.file_size]
I need some advices on how would you do to maintain the "consistency" of
everything. By consistency I mean that I would like to avoid cases where
the user select a column that doesn't exist or is not allowed, a
polymorphic_identity that doesn't exist, maintain the synchronization
between the polymorphic loading of a container and the serialized list, etc
Would you create a custom type based on PickleType or a simple
@validates() or .. ?
Thank you!
Julien
--
No trees were killed in the creation of this message.
However, many electrons were terribly inconvenienced.
--
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sqlalchemy+unsubscr...@googlegroups.com.
To post to this group, send email to sqlalchemy@googlegroups.com.
Visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
For more options, visit https://groups.google.com/groups/opt_out.
