SQLAlchemy (1.0.8) On Friday, September 15, 2017 at 12:14:33 PM UTC-4, Conferency wrote: > > class Paper(db.Model): > __tablename__ = 'papers' > reviewers = db.relationship('User', secondary=paper_reviewer, > backref=db.backref('papers_reviewed', > lazy='dynamic'), > lazy='dynamic') > > paper_reviewer = db.Table('paper_reviewer', > db.Column('user_id', db.Integer, > db.ForeignKey('users.id'), > primary_key=True), > db.Column('paper_id', db.Integer, > db.ForeignKey('papers.id'), > primary_key=True) > ) > @event.listens_for(Paper.reviewers, 'append')def > paper_reviewers_append(target, value, initiator): > # select queries... > > > > paper.reviewers.append(usr) > db.session.add(paper) > db.session.commit() > > The listener is fired before the execution of paper.reviewers.append(usr). > The execution of append makes two insertions into paper_reviewer table. The > second one causes IntegrityError: UNIQUE constraint failed. > > I tried different operations in the listener. If the operation in listener > triggered any query, the IntegrityError would be caused while the commit() > was executed. Not sure why listener could cause this error. Can anyone give > me some details? Plz > >
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