[jira] [Resolved] (AIRFLOW-6170) BranchPythonOperator does not do XCom push of returned value

["Jarek Potiuk (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/AIRFLOW-6170?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jarek Potiuk resolved AIRFLOW-6170.
-----------------------------------
    Resolution: Fixed

> BranchPythonOperator does not do XCom push of returned value
> ------------------------------------------------------------
>
>                 Key: AIRFLOW-6170
>                 URL: https://issues.apache.org/jira/browse/AIRFLOW-6170
>             Project: Apache Airflow
>          Issue Type: Bug
>          Components: operators
>    Affects Versions: 1.10.6
>            Reporter: Bjorn Olsen
>            Assignee: Bjorn Olsen
>            Priority: Minor
>             Fix For: 2.0.0
>
>
> BranchPythonOperator subclasses PythonOperator, and after it has selected a branch we get a message like this in the task log:
> [2019-12-04 08:39:59,960] \{python_operator.py:114} INFO - Done. Returned value was: <chosen_task>
>  This returned value is from the execute() method.
> A user would expect the returned value from this to be pushed to an XCOM; but this does not happen due to no return value from the BranchPythonOperator's execute method.
>   
> {code:java}
>      def execute(self, context: Dict):
>          branch = super().execute(context)
>          self.skip_all_except(context['ti'], branch)
>  {code}
>  
> If we do an XCOM push of the result then we can use the decision made by BranchPythonOperator in downstream tasks.
> Eg consider this dependency chain:
>  get >> branch >>   [ create, update ]>> join >> execute
> The 'execute' task might need to know whether the 'branch' decided to create a new thing to run, or whether to use the existing one from the 'get'. Without an XCOM push from the branch return value, it is difficult to pick up the correct value later on.



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