Thank you Michael
On May 22, 12:37 pm, Michael Bayer <[EMAIL PROTECTED]> wrote:
> On May 22, 2008, at 12:23 PM, askel wrote:
>
>
>
>
>
> > Hello everybody,
>
> > I'm having hard time figuring out how or whether it is possible at all
> > to use select statement that can access record to be inserted as
> > column's default value.
>
> > groups = Table('groups', meta,
> > Column('id', Integer, primary_key=True),
> > Column('prefix', String(32), nullable=False, unique=True)
> > )
>
> > accounts = Table('accounts', meta,
> > Column('number', String(32), primary_key=True),
> > Column('group_id', Integer, ForeignKey('groups.id'),
> > nullable=False,
> > default=select([groups.c.id], groups.c.prefix ==
> > somefunc(current_accounts_record)))
> > )
>
> > Basically, what I need is to be able to access record/values to be
> > inserted into accounts table to build correct select clause. I know
> > how to do that on ORM level using MapperExtension but I want to
> > enforce this on table level instead. And I realize that I can
> > explicitly call my function to assign value to group_id at the time
> > accounts.insert is executed but that doesn't smell good.
>
> > Any help is greatly appreciated.
>
> the function you pass to default can take an optional "context"
> parameter which contains the current ExecutionContext. so write it
> like this:
>
> def my_default(ctx):
> current_accounts_record = ctx.parameters['some_parameter']
> return ctx.connection.scalar(select([groups.c.id],
> groups.c.prefix ==somefunc(current_accounts_record)))
>
> ...
>
> Column('mycolumn', Integer, default=my_default)
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