[GitHub] ubermen opened a new pull request #3874: [AIRFLOW-3001] Add task_instance table index 'ti_dag_date'

[GitBox <gi...@apache.org>]

ubermen opened a new pull request #3874: [AIRFLOW-3001] Add task_instance table index 'ti_dag_date'
URL: https://github.com/apache/incubator-airflow/pull/3874
 
 
   [ Description ]
   There was no index composed of dag_id and execution_date. So, when scheduler find all tis of dagrun like this "select * from task_instance where dag_id = 'some_id' and execution_date = '2018-09-01 ...'", this query will be using ti_dag_state index (I was testing it in mysql workbench. I was expecting 'ti_state_lkp' but, it was not that case). Perhaps there's no problem when range of execution_date is small (under 1000 dagrun), but I had experienced slow allocation of tis when the dag had 1000+ accumulative dagrun. So, now I was using airflow with adding new index ti_dag_date (dag_id, execution_date) on task_instance table. I have attached result of my test :)
   
   [ Test ]
   models.py > DAG.run
   jobs.py > BaseJob.run
   jobs.py > BackfillJob._execute
   jobs.py > BackfillJob._execute_for_run_dates
   jobs.py > BackfillJob._task_instances_for_dag_run
   models.py > DagRun.get_task_instances
   tis = session.query(TI).filter(
   TI.dag_id == self.dag_id,
   TI.execution_date == self.execution_date,
   )
   ![image](https://user-images.githubusercontent.com/6738941/45285016-fb9ecc00-b51c-11e8-945c-c28d81aece02.png)
   ![image](https://user-images.githubusercontent.com/6738941/45285019-fe012600-b51c-11e8-91fa-a66c2293ca5d.png)
   
   
   ### 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, "\[AIRFLOW-XXX\] My Airflow PR"
     - https://issues.apache.org/jira/browse/AIRFLOW-XXX
     - In case you are fixing a typo in the documentation you can prepend your commit with \[AIRFLOW-XXX\], code changes always need a Jira issue.
   
   ### Description
   
   - [ ] Here are some details about my PR, including screenshots of any UI changes:
   
   ### Tests
   
   - [ ] My PR adds the following unit tests __OR__ does not need testing for this extremely good reason:
   
   ### Commits
   
   - [ ] My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)":
     1. Subject is separated from body by a blank line
     1. Subject is limited to 50 characters (not including Jira issue reference)
     1. Subject does not end with a period
     1. Subject uses the imperative mood ("add", not "adding")
     1. Body wraps at 72 characters
     1. Body explains "what" and "why", not "how"
   
   ### Documentation
   
   - [ ] In case of new functionality, my PR adds documentation that describes how to use it.
     - When adding new operators/hooks/sensors, the autoclass documentation generation needs to be added.
   
   ### Code Quality
   
   - [ ] Passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
   

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