On Mar 27, 2014, at 10:08 AM, Josh Kuhn <deontologic...@gmail.com> wrote:
> I have a situation where I need to produce a select object, and then later, > one of the fields needs to be "zeroed" out conditionally. > > so something like: > > def select_ab(param): > from_obj = join(A, B, A.c.b == B.c.b) > return select([A.c.a, B.c.b, B.c.d], from_obj=from_obj).where(A.c.a == > param) > > ... > > sql_query = select_ab(34) > > # Would like to do something like this: > if some_condition: > sql_query = sql_query.replace_column(B.c.d, literal(0)) > > engine.execute(sql_query) > > > I tried to hack together a "replace_column" function using > Select.with_only_columns, but as the documentation indicates, I need the > original list of columns in order to really do what I want to do, I can't > take the select's columns. And in my case, the original select's columns are > trapped inside the function select_ab. I'd like to be able to replace a > column on any arbitrary select if the column exists in the select. > > Is there a way to do what I'm trying to do? Or do I just need to keep the > original columns around? the original columns are in the select() object. They're first in their original form in a list called _raw_columns, that is, if you had select([sometable, somecol, someothercol]) it would be literally those three elements, and then there is a public accessor called inner_columns which is derived directly from _raw_columns, it just expands a selectable (e.g. something with a .c. collection) into individual columns. So it should be feasible to say something equivalent to: select.with_only_columns([(literal(0) if c is my_special_thing else c) for c in select.inner_columns]) -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
