Move the DagRun-TaskInstance relationship to TaskInstance #17016
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uranusjr
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ashb,
kaxil,
turbaszek and
XD-DENG
as code owners
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according the sqla document, backref in dag_run or task_instance has same resullt, maybe change it to back_populates. and delete dag_run need also delete related task_instance, maybe the relationship is needed by dag_run |
A relationship implies cascading behavior when a row is deleted in SQLAlchemy. Defining the relationship on DagRun means the TaskInstance becomes a "parent" to DagRun, thus deleting a TaskInstance automatically clears its associating DagRun's foreign key fields, which is not what we want. The relationship should be the other way around -- deleting a DagRun should clear its associating TaskInstance row's foreign key fields, so we move the relationship to the other side.
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ashb
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Jul 16, 2021
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| TaskInstance.dag_run = relationship(DagRun) |
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The primary reason for having this was to help with code-completion, so maybe we should keep the relationship on dagrun and change backref to back_populates as suggested
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Any update on this? I have to change the code by myself to avoid the delete dag issue after migrate airflow. Is it possible fixed it in 2.1.3? |
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I’m not actively working on this right now. Feel free to submit a superceding PR. |
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Closing in favour of #17719 |
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@ashb I think this is what’s needed?
Fix #16896, close #16960.
DagRun.task_instancesis not actually used in Airflow anywhere, so the static check hack is not needed for the new relationship’s backref. But the backref itself is kept for compatibility.String reference is used instead to avoid circular imports.
Not sure how this should be tested.