wolfdn opened a new pull request, #55559:
URL: https://github.com/apache/airflow/pull/55559
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## Description
We noticed that when using a comparison like the one below for a KEDA query
there is an issue with *null* values. Comparisons using '!=' will not return
any rows which are *null*.
https://modern-sql.com/caniuse/is-distinct-from
This becomes a problem if there are tasks in the task_instance table which
have not explicitly set an *executor* (so they just use the default one). So
the issue occurs if the CeleryExecutor is set as default executor and the
Kubernetes executor is set as additional (non-default) executor.
Then task instances which are up to be executed by the Celery executor will
not be considered by the KEDA query and KEDA will scale down the worker count
to 0 - which means that tasks waiting to be executed by the Celery executor
never be executed.
The SQL comparison using "IS DISTINCT FROM" *includes* null values. Like
this the KEDA query also works if the Celery Executor is set as default
executor and tasks do not explicitly set the Executor field.
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