On Aug 4, 2010, at 10:07 AM, Richard Kuesters wrote:
> hi all,
>
> in a polymorphic query, after a 'print' command i realized that SA generates
> some columns named 'anon_X', which can be helpful for me.
>
> the question is:
>
> 1. is it safe to use those anon_X columns to refine my query?
> --- regarding this, my concern is that once the polymorphic query is done by
> SA, will it anytime change it's name, or anything else in future releases?
it's not. When anonymous aliases are generated within the orm Query against
some entity that you've given it explicitly, you use the column attributes on
that entity to reference those columns, not strings. Never use strings except
for those that you've named explicitly, and at the same level as where you
named it.
For example, you might use a string if you wanted to ORDER BY some expression
that's named in the columns clause:
q = sess.query(func.myfunction(...).label('bar')).order_by('bar')
However, once you nest "q" as a subquery, it gains a .c. collection, and now
you use that .c. collection for all future references to 'bar':
q = q.subquery()
q2 = sess.query(MyEntity).join((q, q.c.bar==MyEntity.bar))
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