hello ozwyzard,
On 09/17/2010 05:21 AM, ozwyzard wrote:
> Configuration: TG2, MySQL, SQLAlchemy
>
> The tg_user_group table uses onupdate='CASCADE', ondelete='CASCADE',
> and it is functional (when I delete a user, the associated entry in
> tg_user_group is deleted.
>
> However, when I use ondelete='CASCADE' from within a DeclarativeBase
> class as follows:
>
> class ABC(DeclarativeBase):
> __tablename__ = 'abc'
> id = Column(Integer, autoincrement=True, primary_key=True)
> created = Column(DateTime, default=datetime.now)
>
>
> class XYZ(DeclarativeBase):
> __tablename__ = 'xyz'
> id = Column(Integer, autoincrement=True, primary_key=True)
> abc = Column(ForeignKey('abc.id', onupdate='CASCADE',
> ondelete='CASCADE'))
>
to use ondelete cascade you need to create the onetomany part of the relation,
and give it the passive_deletes='all'.
> When a row in ABC table is deleted (via application), the associated
> row (ForeignKey) in XYZ table is not deleted, instead it has the 'abc'
> column set to NULL.
>
> The documentation @
> http://www.sqlalchemy.org/docs/core/schema.html#on-update-and-on-delete
> states the following:
> Note that these clauses are not supported on SQLite, and require
> InnoDB tables when
> used with MySQL. They may also not be supported on other
> databases.
>
> I do not setup any special config in MySQL nor in TG2 regarding
> InnoDB.
perharps this may be set by default?
> Question 1: Why does the ondelete='CASCADE' seem to work for the
> external tg_user_group (M-to-M relation), whereas it does not work for
> the above scenario, in the same application.
>
sa also offers cascading implementations through cascade='all,delete-orphan',
that may work even if cascading is not supported by the rdbms.
> Thanks!
>
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