On Nov 21, 2007, at 9:02 PM, Karlo Lozovina wrote:
>
> Hi guys, sorry for the vague subject, here is my problem. Let's say I
> have the following table:
>
> a = Table('aaa', meta,
> Column('id', Integer, primary_key=True),
> Column('id2', Integer))
>
> class A(object):
> pass
>
> mapper(A, a)
>
> I want the default value of A.id2 to be that of a A.id. So, for
> example, unless I modify it, I would like the A.id2 to be sort of a
> duplicate primary key. I know I can find out what is A.id after
> committing my object to database and then setting A.id2 accordingly,
> but I was wondering can SA do this automatically for me? Maybe some
> kind of a special `default=` construct in the Column call?
>
you can write a default function that does this ( i need to add docs
for column defaults that access the ExecutionContext):
def mydefault(ctx):
return ctx.compiled_parameters['id']
a = Table('aaa', meta, Column('id', Integer, primary_key=True),
Column('id2', Integer, default=mydefault))
now, the caveat: the 'id' parameter must be available before the
insert takes place. that means if you are using mysql or sqlite, and
relying upon auto-incrementing primary key columns, the 'id' column
will not be present in the bind parameters before the insert. if
thats the case then youd have to write some kind of trigger or do a
second UPDATE statement.
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