airflow/models/dagrun.py
def get_previous_dagrun(self, session=None):
        """The previous DagRun, if there is one"""

        return session.query(DagRun).filter(
            DagRun.dag_id == self.dag_id,
            DagRun.execution_date < self.execution_date
        ).order_by(
            DagRun.execution_date.desc()
        ).first()
def get_previous_dagrun(self, session=None):
        """The previous DagRun, if there is one"""

        return session.query(DagRun).filter(
            DagRun.dag_id == self.dag_id,
            DagRun.execution_date < self.execution_date
        ).order_by(
            DagRun.execution_date.desc()
        ).first()
The previous DagRun, if there is one