[GitHub] [airflow] Fokko opened a new pull request #6370: AIRFLOW-5701: Don't clear xcom explicitly before execution

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Fokko opened a new pull request #6370: AIRFLOW-5701: Don't clear xcom explicitly before execution
URL: https://github.com/apache/airflow/pull/6370
 
 
   Make sure you have checked _all_ steps below.
   
   - Don't clear the xcom upfront, but only when the job ran and new values are provided.
   - Remove the `id` column from the xcom table and make `(dag_id, task_id, execution_date, key)` the PK
   - Remove the commit in between of the delete and insert of the new xcom value. This would actually potentially lead to two values and violate the uniqueness constraint that we expect there (however until not this was implicit). If you would have two jobs running, they could do a DELETE at the same time, and then an INSERT at the same time, now this is atomic.
   
   ### Jira
   
   - [ ] My PR addresses the following [Airflow Jira](https://issues.apache.org/jira/browse/AIRFLOW/) issues and references them in the PR title. For example, "\[AIRFLOW-5701\] My Airflow PR"
     - https://issues.apache.org/jira/browse/AIRFLOW-5701
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     - In case you are proposing a fundamental code change, you need to create an Airflow Improvement Proposal ([AIP](https://cwiki.apache.org/confluence/display/AIRFLOW/Airflow+Improvements+Proposals)).
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   ### Description
   
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   ### Tests
   
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     1. Subject is separated from body by a blank line
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   ### Documentation
   
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     - All the public functions and the classes in the PR contain docstrings that explain what it does
     - If you implement backwards incompatible changes, please leave a note in the [Updating.md](https://github.com/apache/airflow/blob/master/UPDATING.md) so we can assign it to a appropriate release
   

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