On Nov 2, 2007, at 12:41 AM, Bruza wrote:
> > I am quite baffled by the "deferred loading" behavior on a class > member in the following code (see below). Looks like if I create an > object (t1) with some field (c2) having None as value, then after I > save, commit, and closed the object in a SQLAlchemy session, I cannot > update the c2 field. It will give me an InvalidRequestError error. > > However, if I loaded the same object (into t2) from DB (even though > t2.c2 field and attribute still having None as value), I can modify > t2.c2 field even after I commit, and close the session that associated > with t2. So, is this very confusing, or did I miss some of the reasons > in this behavior? what youre not showing me here, that is the most crucial part of this, is what kind of column "c2" is. from what I can see, it appears that you have a SQL-side default set up on c2. when the object is inserted into the DB and you havent set a non-None value on "c2", the default will generate inline with the INSERT statement; SA then marks the column as "deferred" so that when next accessed, it will load the newly generated value. in the second case, you've loaded the object from the DB so "c2" just populates just like "c1" and its immediately available without a second SQL statement. If you get the latest trunk or wait for version 0.4.1 (possibly this weekend), the behavior of "deferred" column attributes has changed such that you can set a new value without forcing a load of the previous value, so this particular error won't occur (trying to read "c1" when its deferred and theres no Session will still raise an error, however). --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
