On Mon, Jan 14, 2019 at 2:22 PM <matthew.mahow...@freenome.com> wrote:
>
> Hello,
>
> Our data model for a structure named PlateWell in our software utilizes a
> singly linked-list structure with a field for a parent PlateWell. We are
> adding another field pointing to the root PlateWell of the link list to
> improve runtime of certain important operations, however the relationships
> are not loading. Here is the abridged model.
>
> class PlateWell(db.Model):
> __tablename__ = 'plate_wells'
>
> id = db.Column(db.Integer, primary_key=True)
> parent_well_id = db.Column(db.Integer, db.ForeignKey('plate_wells.id'),
> index=True)
> root_well_id = db.Column(db.Integer, db.ForeignKey('plate_wells.id'),
> index=True)
>
> parent_well = db.relationship(
> 'PlateWell', uselist=False, lazy='noload', remote_side=[id],
> foreign_keys=[parent_well_id])
> root_well = db.relationship(
> 'PlateWell', uselist=False, lazy='noload', remote_side=[id],
> foreign_keys=[root_well_id])
>
> At the root entry, the root_well_id is equal to id and parent_well_id is set
> to None.
>
> Prior to adding the root relationship, the model loaded the parent_well
> relationship without the foreign_keys kwarg. This relationship was fully
> functional.
>
> Now, any time a plate well is loaded via a query like
>
> well = PlateWell.query.filter(PlateWell.id == well.plate_well_id).one()
>
> both parent_well and root_well are set to None, despite both foreign key id
> fields containing an id that does relate to another entry. We've attempted
> adding explicit primaryjoin kwargs, expiring the session to clear the cache,
> but neither seems to work. Is there a trick to loading multiple
> self-referential relationships or some other change we can make to properly
> load these relationships?
I haven't tried your model but the "lazy='noload'" doesn't seem like
what you want to be doing there, that loader option explicitly
indicates you want nothing to load so that would likely be where
"None" is coming from. Removing that option will likely allow it to
work.
>
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