On Friday 29 January 2010 08:53:26 Oleg Broytman wrote:
> On Thu, Jan 28, 2010 at 09:35:50PM -0300, Juan Manuel Santos wrote:
> > class File(InheritableSQLObject):
> > name = StringCol()
> > root = ForeignKey("Directory", default=None)
> >
> > class Directory(File):
> > dirs = MultipleJoin("Directory", joinColumn="root_id")
> > files = MultipleJoin("File", joinColumn="root_id")
> >
> > sqlobject.dberrors.OperationalError: no such column: root_id
> >
> > 1/QueryR : SELECT id FROM directory WHERE root_id = (1)
>
> Table 'directory' doesn't have root_id, only 'file' as it.
>
> The problem is that InheritableSQLObject is rather limited thing. These
> limitations are documented:
> http://sqlobject.org/Inheritance.html#limitations-and-notes
> The problem you are stumbled upon is "Inheritance works in two stages -
> first it draws the IDs from the parent table and then it draws the rows
> from the children tables. The first stage could fail if you try to do
> complex things. For example, Children.select(orderBy=Children.q.column,
> distinct=True) could fail because at the first stage inheritance generates
> a SELECT query for the parent table with ORDER BY the column from the
> children table."
> Your code choked on the first stage while trying to SELECT IDs from the
> child table using a column that only exists in the parent.
>
> You can try simple Python inheritance instead:
>
> class File(SQLObject):
> name = StringCol()
> root = ForeignKey("Directory", default=None)
>
> class Directory(File):
> dirs = MultipleJoin("Directory", joinColumn="root_id")
> files = MultipleJoin("File", joinColumn="root_id")
>
> This works by copying all parent columns to the child table.
>
> Oleg.
>
Yes, that's what I ended up doing, after I thought it might be a limitation.
But well, it works fine for the rest of the classes.
Thanks :)
Juan Manuel
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