id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
35712	CheckConstraint with RawSQL breaks ModelForm when inside transaction.atomic()	Alex Fischer	Alex Fischer	"When a model uses a `CheckConstraint` with `RawSQL`, trying to save a `ModelForm` for that model inside a `transaction.atomic()` block fails. 

== Project Setup
settings.py:
{{{

INSTALLED_APPS = [
    ""test_app"",
    ...
]
DATABASES = {
    ""default"": {
        ""ENGINE"": ""django.db.backends.postgresql"",
        ...
    }
}
}}}

test_app/models.py (''the Bar model has a CheckConstraint using RawSQL''):
{{{
from django.db import models
from django.db.models.expressions import ExpressionWrapper, RawSQL

class Bar(models.Model):
    a = models.IntegerField(null=True)

    class Meta:
        constraints = [
            models.CheckConstraint(
                name=""a_is_1"",
                check=ExpressionWrapper(
                    RawSQL( ""a = 1"", []),
                    output_field=models.BooleanField(),
                ),
            ),
        ]
}}}

test_app/management_commands/form_test.py (''a ModelForm is used to create a Bar instance''):
{{{
from django import forms
from django.core.management import BaseCommand
from django.db import transaction

from test_app.models import Bar

class BarForm(forms.ModelForm):
    class Meta:
        model = Bar
        fields = [""a""]

class Command(BaseCommand):
    def handle(self, **options):
        with transaction.atomic():
            form = BarForm({""a"": 1})
            form.save()
}}}

== Test Procedure

{{{
>>> python manage.py form_test
}}}

== Expected Outcome
The code runs without any exceptions, and a new Bar instance is created.

== Actual Outcome
`form.save()`  raises `django.db.utils.InternalError`
{{{
Traceback (most recent call last):
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/backends/utils.py"", line 105, in _execute
    return self.cursor.execute(sql, params)
psycopg2.errors.InFailedSqlTransaction: current transaction is aborted, commands ignored until end of transaction block


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File ""/Users/alex/projects/django_constraint_issue/manage.py"", line 22, in <module>
    main()
  File ""/Users/alex/projects/django_constraint_issue/manage.py"", line 18, in main
    execute_from_command_line(sys.argv)
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/core/management/__init__.py"", line 442, in execute_from_command_line
    utility.execute()
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/core/management/__init__.py"", line 436, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/core/management/base.py"", line 413, in run_from_argv
    self.execute(*args, **cmd_options)
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/core/management/base.py"", line 459, in execute
    output = self.handle(*args, **options)
  File ""/Users/alex/projects/django_constraint_issue/test_app/management/commands/form_test.py"", line 18, in handle
    form.save()
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/forms/models.py"", line 554, in save
    self.instance.save()
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/models/base.py"", line 891, in save
    self.save_base(
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/models/base.py"", line 997, in save_base
    updated = self._save_table(
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/models/base.py"", line 1160, in _save_table
    results = self._do_insert(
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/models/base.py"", line 1201, in _do_insert
    return manager._insert(
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/models/manager.py"", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/models/query.py"", line 1847, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/models/sql/compiler.py"", line 1836, in execute_sql
    cursor.execute(sql, params)
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/backends/utils.py"", line 122, in execute
    return super().execute(sql, params)
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/backends/utils.py"", line 79, in execute
    return self._execute_with_wrappers(
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/backends/utils.py"", line 92, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/backends/utils.py"", line 100, in _execute
    with self.db.wrap_database_errors:
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/utils.py"", line 91, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File ""/Users/alex/projects/django_constraint_issue/venv/lib/python3.10/site-packages/django/db/backends/utils.py"", line 105, in _execute
    return self.cursor.execute(sql, params)
django.db.utils.InternalError: current transaction is aborted, commands ignored until end of transaction block
}}}

== Notes

Whether you use an atomic transaction or not, Django _tries_ to validate the CheckConstraint before inserting the new Bar instance. This logs the following warning:
{{{
Got a database error calling check() on <Q: (AND: ExpressionWrapper(RawSQL(a = 1, [])))>: column ""a"" does not exist
LINE 1: SELECT 1 AS ""_check"" WHERE COALESCE(((a = 1)), true)
}}}
Django appears to log this warning and then carry on. If the connection is in auto-commit mode, this is not a problem. The next statement will be executed in a new transaction. In an atomic block, this causes the `InternalError`.

When you migrate, Django ''does'' warn about the CheckConstraint with RawSQL:

{{{
>>> python manage.py migrate
System check identified some issues:

WARNINGS:
test_app.Bar: (models.W045) Check constraint 'a_is_1' contains RawSQL() expression and won't be validated during the model full_clean().
	HINT: Silence this warning if you don't care about it.
}}}
It seems that rather than skipping the validation of this constraint, Django is still validating it and then ignoring/logging the error. And it doesn't handle transaction state properly.



"	Bug	closed	Database layer (models, ORM)	5.1	Normal	fixed			Ready for checkin	1	0	0	0	0	0