Thanks Michael for your answer. Shame on me, that I did not find this
point in documentation.
But such behaviour seems strange to me. Why should I specify these
parameters in anchestors, specify anchestors in a child class and then
explicitly describe my arguments once more in a child class? I would
prefer if __mapper_args__ would be merged automatically in the
standard inheritance order.
On 13 фев, 23:30, Michael Bayer <mike...@zzzcomputing.com> wrote:
> On Feb 13, 2011, at 1:39 PM, Andrey Gladilin wrote:
>
>
>
> > I am trying to create a version column which would use values from a
> > single postgresql sequence.
>
> > record_versions_id_seq = Sequence('record_versions_id_seq')
>
> > class TimestampMixin(object):
> > created_at = Column(DateTime, default=func.now())
> > record_version = Column(Integer, nullable=False,
> > default=func.nextval("record_versions_id_seq"))
>
> > __mapper_args__ = {
> > 'version_id_col': record_version,
> > 'version_id_generator': lambda v:
> > func.nextval("record_versions_id_seq")
> > }
>
> > class Team(Base, NameMixin, TimestampMixin):
> > __tablename__ = 'teams'
> > id = Column(Integer, primary_key=True)
>
> > There are other tables like Team inheriting TimestampMixin. And here I
> > have two problems:
>
> > 1. Decribed code does not work for update. I.e when I update the
> > record from Team, the record_version column value is not getting
> > changed. So to workaround this problem I have to explicitly specify
> > __mapper_args__ in Team class.
>
> if Base or NameMixin is also modifying __mapper_args__, those will override
> what TimestampMixin returns. The __mapper_args__ from different mixins need
> to be combined manually for the final product. Some background
> athttp://www.sqlalchemy.org/docs/orm/extensions/declarative.html#combin...
>
> > 2. Code lambda v: func.nextval("record_versions_id_seq") does not
> > work. I guess this code is incorrect, so could you help me to create a
> > correct one please?
>
> you'd need to execute the function through a connection, and you can use the
> Sequence object directly:
>
> lambda v: some_engine.execute(record_versions_id_seq)
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