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https://issues.apache.org/jira/browse/AIRFLOW-3518?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16721536#comment-16721536
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ASF GitHub Bot commented on AIRFLOW-3518:
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NielsZeilemaker opened a new pull request #4322: [AIRFLOW-3518] Performance
fixes for topological_sort
URL: https://github.com/apache/incubator-airflow/pull/4322
For larger DAGs topological_sort was found to be very inefficient. Made
some small changes to the code to improve the datastructures used in the
method.
Make sure you have checked _all_ steps below.
### Jira
- [X] 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-3518
- 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
- [X] Here are some details about my PR, including screenshots of any UI
changes:
While running a larger DAG, topological_sort was found to be very slow. This
fixup improves the performance on my local machine from ~5-10 seconds to 0.01s.
Moreover, i've modified the __eq__ operators to have a shortcut for
dag_id/task_id. This should improve all other cases where equality is used.
### Tests
- [X] My PR adds the following unit tests __OR__ does not need testing for
this extremely good reason:
No tests, as I would expect topological_sort to be covered already.
### Commits
- [X] 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.
- All the public functions and the classes in the PR contain docstrings
that explain what it does
### Code Quality
- [X] Passes `flake8`
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> Toposort is very slow
> ---------------------
>
> Key: AIRFLOW-3518
> URL: https://issues.apache.org/jira/browse/AIRFLOW-3518
> Project: Apache Airflow
> Issue Type: New Feature
> Components: scheduler
> Reporter: Niels Zeilemaker
> Assignee: Niels Zeilemaker
> Priority: Major
>
> At a client we've discovered that for larger DAGs toposort is very slow.
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