Yes, that was what I searched for. My Solution now is to use pythons
introspection like this:
for dataClass in Master.__subclasses__():
table = sqlalchemy.orm.class_mapper(dataClass).local_table
delete_query = table.delete(). \
where(...)
session.execute(delete_query, dict(...))
I was searching for something in sqlalchemy, that does the same by
calling something like:
Master.deleteAll().where(...) or similar
Thanks for the help!
On 10 Nov., 15:43, Michael Bayer <mike...@zzzcomputing.com> wrote:
> On Nov 10, 2010, at 8:00 AM, Mene wrote:
>
> > Yes, I definitely want to emit a DELETE statement. The Problem is that
> > calling master.delete() only gives an delete statement for the master
> > table. However, I need n querys: DELETE child1... , DELETE child2 and
> > so on.
>
> OK, so I think there's another question that you mean to be asking here,
> since I'm sure its obvious that to emit a DELETE statement for child1,
> child2, etc., you do the same thing for those Table objects:
>
> child1.delete().where(...)
> child2.delete().where(...)
> child3.delete().where(...)
> ... etc
>
> I think the question you want here is "how do I get at all the Table objects
> in an inheritance hierarchy given only the base class?"
>
> for mapper in master_mapper.polymorphic_iterator():
> Session.execute(mapper.local_table.delete().where(...))
>
> Note that concrete inheritance is the least wieldy inheritance scheme. If
> you were using joined table inheritance, you could configure ON DELETE
> CASCADE on all your tables and you could then emit a single DELETE just for
> the master table that would automatically delete from all related tables.
>
>
>
>
>
> > On 8 Nov., 20:31, Michael Bayer <mike...@zzzcomputing.com> wrote:
> >> On Nov 8, 2010, at 11:02 AM, Mene wrote:
>
> >>> Hi all,
> >>> I have some 'child' tables which inherit from the same 'master' table,
> >>> now I'd like to delete some entries from all tables. The 'where'-part
> >>> comes solely from the master table.
> >>> I have decided to use Concrete Table Inheritance since I don't need
> >>> the inheritance at points other than deleting, but I expect the tables
> >>> to have a lot of entries and at the moment I don't know how many child
> >>> tables I will have in the future. Also the delete process won't occur
> >>> often.
>
> >>> Each table has a compound primary key of user and room.
> >>> I use version 0.4.8 (and I can't change this)
>
> >>> I need a delete statement that deletes according to user_id and the
> >>> length of the room identifier.
> >>> Also master is only an abstract class, so I don't need to have a table
> >>> in my database (AFAIK).
>
> >> There's only two choices here, you can either load the objects with the
> >> ORM and individually pass them to session.delete(), or you can emit DELETE
> >> statements against the tables directly using SQL expressions or strings.
> >> The SQL expression would be along the lines of
> >> Session.execute(master.delete().where(...)).
>
> >>> master = Table('master', metadata,
> >>> Column('user_id', Integer, ForeignKey('user.user_id',
> >>> ondelete='CASCADE'), primary_key=True),
> >>> Column('room', Unicode(16), ForeignKey('room.id'),
> >>> primary_key=True)
> >>> )
>
> >>> child1 = Table('child1', metadata,
> >>> Column('user_id', Integer, ForeignKey('user.user_id',
> >>> ondelete='CASCADE'), primary_key=True),
> >>> Column('room', Unicode(16), ForeignKey('room.id'),
> >>> primary_key=True),
> >>> Column('child1_data', Unicode(16))
> >>> )
>
> >>> child2 = Table('child2', metadata,
> >>> Column('user_id', Integer, ForeignKey('user.user_id',
> >>> ondelete='CASCADE'), primary_key=True),
> >>> Column('room', Unicode(16), ForeignKey('room.id'),
> >>> primary_key=True),
> >>> Column('child2_data', Unicode(16))
> >>> )
>
> >>> join = polymorphic_union({
> >>> 'master': master,
> >>> 'child1': child1,
> >>> 'child2': child2
> >>> }, 'type', 'pjoin')
>
> >>> master_mapper = mapper(Master, master, with_polymorphic=('*',
> >>> vote_join), \
> >>> polymorphic_on=vote_join.c.type, polymorphic_identity='vote_data')
>
> >>> child1_mapper = mapper(Child1, child1, inherits=master, \
> >>> concrete=True, polymorphic_identity='child1')
>
> >>> child2_mapper = mapper(Child2, child2, inherits=master, \
> >>> concrete=True, polymorphic_identity='child2')
>
> >>> Thanks for your time,
> >>> Mene
>
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