potiuk opened a new pull request, #33309:
URL: https://github.com/apache/airflow/pull/33309
The `render_template_fields` method of mapped operator needs to use database
session object to render mapped fields, but it cannot get the session passed by
@provide_session decorator, because it is used in derived classes and we cannot
change the signature without impacting those classes.
So far it was done by creating new session in mapped_operator, but it has
the drawback of creating an extra session while one is already created
(remnder_template_fields is always run in the context of task run and it always
has a session created already in _run_raw_task). It also causes problems in our
tests where two opened database session accessed database at the same time and
it cases sqlite exception on concurrent access and mysql error on running
operations out of sync - likely when the same object was modified in both
sessions.
This PR changes the approach - rather than creating a new session in the
mapped_operator, we are retrieving the session from one stored by the
_run_raw_task. It is done by context manager and adequate protection has been
added to make sure that:
a) the call is made within the context manager
b) context manageer is never initialized twice in the same
call stack
After this change, resources used by running task will be smaller, and
mapped tasks will not always open 2 DB sesions.
Fixes: #33178
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