python - Ordering SQLAlchemy relationship by another field, not by primary key -


i have following model using sqlalchemy in pyramid application:

class issue(base_iop):     __tablename__ = 'issues'     issueid = column(bigint, primary_key=true, name="issueid")     issuenum = column(varchar(20), name="issuenum")     status = column(varchar(32), name="status")     datetime = column(timestamp, name="issuetime")  class related(base_iop):     __tablename__ = 'related'     relationid = column(bigint, primary_key=true, name="rowstamp")     parent_num = column(varchar(20), foreignkey('issue.issuenum'),name="recordkey")     children_num = column(varchar(20), foreignkey('issue.issuenum'), name="relatedkey")     issues = relationship(iop, foreign_keys=[child_num])

i can related issues of issue fine using: issues attribute of related table:

for related in db.query(issue).all()[0].issues:     print related.status

however, didn't find solution order issues datetime attribute. if related had datetime attribute this, should pretty straightforward using order_by in relationship:

class issue(base_iop):     __tablename__ = 'issues'     issueid = column(bigint, primary_key=true, name="issueid")     issuenum = column(varchar(20), name="issuenum")     status = column(varchar(32), name="status")     datetime = column(timestamp, name="issuetime")     children =  relationship("related", foreign_keys="[related.parent_num]", backref="parent", order_by="[related.datetime]")  class related(base_iop):     __tablename__ = 'related'     relationid = column(bigint, primary_key=true, name="rowstamp")     parent_num = column(varchar(20), foreignkey('issue.issuenum'),name="recordkey")     children_num = column(varchar(20), foreignkey('issue.issuenum'), name="relatedkey")     datetime = column(timestamp, name="issuetime")     issues = relationship(iop, foreign_keys=[child_num])

how order related issues field, not primary key now?

relationship accept keyword argument order_by handle default ordering of relation. should somthing like:

issues = relationship(iop, foreign_keys=[child_num], order_by="issue.datetime")

note backref function has same keyword, if need handle that.

here can read more: http://docs.sqlalchemy.org/en/rel_1_0/orm/tutorial.html#building-a-relationship on topic


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