wolfier commented on a change in pull request #15183:
URL: https://github.com/apache/airflow/pull/15183#discussion_r609136866
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File path: docs/apache-airflow/best-practices.rst
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@@ -54,6 +59,12 @@ Some of the ways you can avoid producing a different result -
You should define repetitive parameters such as ``connection_id`` or S3
paths in ``default_args`` rather than declaring them for each task.
The ``default_args`` help to avoid mistakes such as typographical errors.
+Creating a custom Operator
+---------------------------
+
+When implementing custom operators, do not make any expensive expensive
operations in their ``__init__``. They are
+going to be instantiated once per scheduler run per task using them, and
making database calls can significantly slow
+down scheduling and waste resources.
Review comment:
Got it!
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