On Wed, Apr 30, 2008 at 9:44 PM, Michael Bayer <[EMAIL PROTECTED]> wrote:
>
>
> On Apr 30, 2008, at 3:23 PM, Eric Lemoine wrote:
>
> >
> > Yes, the sequence is my table's PK. What I want to know is the PK
> > value of the line I'm going to insert (or I've just inserted). So I
> > guess this is indeed INSERT RETURNING.
>
> if you pre-execute the sequence, the number you get back from it is
> yours to keep and will never come up again (unless the sequence is
> manually manipulated). Its safe to use for a primary key value at
> any time regardless of concurrent threads which also use that sequence.
>
> SQLAlchemy does this process for you automatically, so if you just set
> the Sequence() on your table's primary key Column, you can safely save
> and flush your instances without assigning any identifier, and the
> newly generated id is present on the corresponding class attributes,
> i.e.:
>
> mytable = Table('mytable', metadata, Column('id', Sequence('my_seq'),
> primary_key=True), ...)
>
> mapper(MyClass, mytable, ...)
>
> x = MyClass()
> session.save(x)
> session.flush()
>
> newly_inserted_id = x.id
>
> no threading issues to worry about. Same thing happens with raw
> inserts, if you leave the "id" column out of the values list:
>
> result = engine.execute(mytable.insert())
> newly_inserted_id = result.last_inserted_ids()[0]
Great! Thanks,
--
Eric
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