#33331: Improve exception handling with `cursor.close()` after errors
-------------------------------------+-------------------------------------
Reporter: Daniel | Owner: nobody
Hahler |
Type: | Status: new
Cleanup/optimization |
Component: Database | Version: 3.2
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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`cursor.close()` is explicitly after Exceptions with `cursor.execute()`,
and has a comment already that it might fail:
https://github.com/django/django/blob/322a1a037d4d2f18744c5d1a1efc2e84d4c5e94b/django/db/models/sql/compiler.py#L1210-L1215
{{{
try:
cursor.execute(sql, params)
except Exception:
# Might fail for server-side cursors (e.g. connection closed)
cursor.close()
}}}
The code there was changed to ignore any exception in
https://github.com/django/django/commit/6b6be692fcd102436c7abef1d7b3fa1d37ad4bdf
(Refs #16614), but then changed to the current code in
https://github.com/django/django/commit/d170c63351944fd91b2206d10f89e7ff75b53b76
(https://github.com/django/django/commit/d170c63351944fd91b2206d10f89e7ff75b53b76
#diff-f58de2deaccecd2d53199c5ca29e3e1050ec2adb80fb057cdfc0b4e6accdf14f).
The current approach however will create a chained exception always, and
especially will add it as context, and not as cause (see
https://blog.ram.rachum.com/post/621791438475296768/improving-python-
exception-chaining-with).
I suggest that exceptions in `cursor.close()` should get ignored as being
expected in a lot / most cased, and it being done only to ensure the
connection gets closed really, and should get `raised from` otherwise.
The main motivation here is that it makes it hard/confusing to see the
real error, e.g. when running tests or doing development, and the DB is
out of sync.
--
Ticket URL: <https://code.djangoproject.com/ticket/33331>
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