[GitHub] [airflow] deodeveloper opened a new pull request #5255: [AIRFLOW-4462] MSSQL backend broken

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deodeveloper opened a new pull request #5255: [AIRFLOW-4462] MSSQL backend broken
URL: https://github.com/apache/airflow/pull/5255
 
 
   - Airflow manual trigger/scheduled trigger doesn't always work on mssql(azure mssql, mssql 2017, other versions)
   
   * fixed mssql server as airflow backend. Applies only to sql server 2005  later versions and azure sql db where datetime2 datatype is available. Issue is with execution_date used as primary key in task_instance and a equality comparison column in dag_run. When comparing equality python microsecond precision to sql server, it returns false when the millisecond is non-zero,e.g, 2019-04-20T18:51:35.033. This change will make the execution_date from datetime to datetime(precision=6) matches with mysql precision. The date equality comparision works as desired. Microsoft also recommends to use datetime2.
   
   Without this fix, airflow is not usable in sql server and azure sql server db. This fix can also be applied to existing stable branches to make airflow work with mssql server
   
   Make sure you have checked _all_ steps below.
   
   ### Jira
   
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   ### Description
   
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   ### Documentation
   
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   ### Code Quality
   
   - [ ] Passes `flake8`
   

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