boothead wrote:
> Hi,
>
> I have a parent/superclass object in a polymorphic relationship which
> is mapped against a select. The select is a table and a coalesce
> function (the coalesce is to make up for the fact that the
> polymorphic_on column doesn't exist).
>
> All seems to be working fine on update, create etc but delete is
> coming a cropper here:
>
> /sqlalchemy/orm/mapper.pyc in _delete_obj(self, states,
> uowtransaction)
> 1459 mapper = table_to_mapper[table]
> 1460 clause = sql.and_()
> -> 1461 for col in mapper._pks_by_table[table]:
> 1462 clause.clauses.append(col == sql.bindparam
> (col.key, type_=col.type))
> 1463 if mapper.version_id_col and
> table.c.contains_column(mapper.version_id_col):
>
> KeyError: Table('map_table', MetaData
> (<sqlalchemy.engine.base.Connection object at 0x8751210>), Column
> (...), ....)
what version sqla you're on ? The line numbers aren't ordered that way
in 0.5.6. The dict lookup there should not be reachable as there's a
check for column present in the pks dict up above that would prevent the
delete collection from being populated. That code definitely needs a
little adjustment as its looping unnecessarily but still should be working
the way it is.
>
> In this instance map_table (names changed to protect the guilty) is
> our child table and I've just done:
>
> In [32]: q = ses.query(ChildClass)
>
> In [33]: h = q[0]
>
> In [34]: ses.delete(h)
>
> In [35]: ses.flush()
>
> At which point "kaboom".
>
> Interestingly the 'mapper' in question in the traceback is the mapper
> for a different child class i.e. NOT ChildClass in the ipython
> example above, but 'table' is the the table mapped to ChildClass.
>
> There are three of these child tables, all configured the same way and
> one of them actually works for deleting. The one type of child class
> that I can delete also belongs mapper in question when I get the above
> traceback when trying to delete instances of the other two children. I
> don't know if that's significant or not?
>
> The only columns in the map_table are a foreign key to the parent
> table / superclass and a foreign key to a related object (which are a
> composite primary key) and an additional column.
>
> I'm pretty sure that I'm doing something nasty, but the only really
> out of the ordinary thing (as compared with the documentation) is that
> the super class is mapped to something like:
>
> my_super_table = select([superclass_table, func.coalesce
> (<some_stuff>)]).alias('my_superclass_table')
>
> This is the gist of the SQL that
>
>>>> print select(my_super_table)
>
> gives:
>
> SELECT my_super_table.col1 ...
> FROM
> (SELECT h.col1 ...,
> coalesce(
> (SELECT 'C' FROM child1_map
> WHERE child1_map.holiday_id = h.holiday_id),
> (SELECT 'E' FROM dots.child2_map
> WHERE child2_map.holiday_id = h.holiday_id),
> (SELECT 'I' FROM child3_map
> WHERE child1_map.holiday_id = h.holiday_id)
> ) AS my_polymorphic_column
> FROM the_old_table h) my_super_table
>
> This is the sql I want, and as I mentioned update and select seems to
> be fine
>
> So, is this a problem with incorrectly configuring cascade rules, or
> have I found a corner case that should work but doesn't..?
>
> Cheers,
> Ben
>
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>
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