the key is this warning:
SAWarning: mapper Mapper|ApplicationSchedule|Select object creating an
alias for the given selectable - use Class attributes for queries.
so in this case the polymorphic_on column is no longer recognized
since its against the underlying selectable, which has been replaced.
change your selectable to:
select_application_schedules = select([table_application_schedules],
table_application_schedules.c.dateDeactivated == None).alias()
SQLA should be making a better choice here. Either not allow the auto-
alias() thing, or somehow figure out the right thing to do. The
latter is not trivial at the moment.
On Jan 5, 2009, at 2:06 PM, Eric R. Palakovich Carr wrote:
>
> Hello. SA newbie here.
>
> I'm using selectable in a mapper for the first time and I'm having
> problems. From what I understand, you can create a select object and
> use it in place of a Table object in a mapper. For example, if you
> have these two objects:
>
> schedTable = Table('schedule', metadata, Column('id', Integer,
> primary_key=True), Column('aDate', Date))
> schedSelect = select([schedTable])
>
> The following two mapper lines will result in a ScheduleClass that
> works exactly the same as the other:
>
> mapper(ScheduleClass, schedTable)
> mapper(ScheduleClass, schedSelect)
>
> Following this logic, I tried to update one of my mappings with a
> select object and received errors. To see what happened, I've wrote
> some simplified code that reproduces the problem and pasted it here:
>
> http://pastebin.com/d5467be2f
>
> When you run the code it succesfully creates the mapper and even
> inserts new objects correctly into the database, but when trying to
> retrieve data it throws the following error:
>
> sqlalchemy.exc.NoSuchColumnError: "Could not locate column in row for
> column 'scheduleType'"
>
> at the following line of code:
>
> schedules = session.query(ApplicationSchedule).all()
>
> What am I doing wrong / don't understand about SQLAlchemy?
>
> >
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