duplicate key despite form.is_valid()

Using Django Mystery Errors
1

I get exception reports from a Django app that I created, that I do not understand how it is possible they even get raised:

IntegrityError at /abonnenten/create/
duplicate key value violates unique constraint “abonnenten_abonnent_abonummer_key”
DETAIL: Key (abonummer)=(000056001266) already exists.

My code runs form.save() only after validating the form via form.is_valid() checking before persisting the data, if the PK is available. The only thing that I could imagine would cause this is that another request is being made by another ASGI worker adding this unique key in the exact same time, specifically between the form.is_valid() and form.save() which I find highly unlikely since the app is used by maybe 40 people, of which most use it only 2-3 days a month. But maybe there’s something I’m just not seeing so I wanted to ask in the forum if anyone could point me to somewhere.

This is the trace. I emphasized the relevant part with blank lines.

The above exception (duplicate key value violates unique constraint "abonnenten_abonnent_abonummer_key"
DETAIL:  Key (abonummer)=(000056001266) already exists.) was the direct cause of the following exception:
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/core/handlers/exception.py", line 55, in inner
    response = get_response(request)
               ^^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/core/handlers/base.py", line 197, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/contrib/auth/decorators.py", line 59, in _view_wrapper
    return view_func(request, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^



  File "/srv/myapp/app/abonnenten/views.py", line 369, in abonnent_create_or_update
    abonnent = form.save()
               ^^^^^^^^^^^
  File "/srv/myapp/app/abonnenten/forms.py", line 86, in save
    return super().save(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/forms/models.py", line 554, in save
    self.instance.save()
    ^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/app/abonnenten/models.py", line 319, in save
    super().save(*args, **kwargs)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^



  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/models/base.py", line 902, in save
    self.save_base(
    ^
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/models/base.py", line 1008, in save_base
    updated = self._save_table(

  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/models/base.py", line 1169, in _save_table
    results = self._do_insert(

  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/models/base.py", line 1210, in _do_insert
    return manager._insert(

  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/models/query.py", line 1868, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/models/sql/compiler.py", line 1882, in execute_sql
    cursor.execute(sql, params)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/backends/utils.py", line 79, in execute
    return self._execute_with_wrappers(

  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/backends/utils.py", line 92, in _execute_with_wrappers
    return executor(sql, params, many, context)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/backends/utils.py", line 100, in _execute
    with self.db.wrap_database_errors:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/utils.py", line 91, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/venv/lib/python3.12/site-packages/django/db/backends/utils.py", line 105, in _execute
    return self.cursor.execute(sql, params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/myapp/venv/lib/python3.12/site-packages/psycopg/cursor.py", line 97, in execute
    raise ex.with_traceback(None)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

views.py L368-369:

    if request.method == "POST" and form.is_valid():
        abonnent = form.save()

models.py L317-319:

    def save(self, *args, **kwargs):
        self.adressliste = self.verein.adressliste_set.first()
        super().save(*args, **kwargs)
2

Please post the complete from, view, and model being saved here.

3

Sorry, I cannot do that. AFAIK, it does not matter. Is_valid has only two outcomes and only one of these outcomes leads to a save, the other one doesn’t, eg when theres a duplicate key found during the validation within is valid.

4

If you want help with code, you’ll need to post the code.

If you can’t post this specific code for some reason, then you might want to create a separate minimal example that demonstrates the problem which you can share. This process is often a good way of discovering the error yourself.

5

If I could reproduce the issue, I would not needed to have asked here.