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fix(spanner-django): db_returning should only be overridden for Spanner #16111

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Merged
olavloite merged 1 commit into from
Mar 16, 2026
Merged

fix(spanner-django): db_returning should only be overridden for Spanner #16111

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8 changes: 2 additions & 6 deletions packages/django-google-spanner/django_spanner/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -84,19 +84,15 @@ def autofield_init(self, *args, **kwargs):
== "true"
):
self.default = gen_rand_int64
self.db_returning = False
self.validators = []
break


AutoField.__init__ = autofield_init
AutoField.db_returning = False
AutoField.validators = []

SmallAutoField.__init__ = autofield_init
BigAutoField.__init__ = autofield_init
SmallAutoField.db_returning = False
BigAutoField.db_returning = False
SmallAutoField.validators = []
BigAutoField.validators = []


def get_prep_value(self, value):
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16 changes: 16 additions & 0 deletions packages/django-google-spanner/tests/unit/django_spanner/test_schema.py
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Original file line number Diff line number Diff line change
Expand Up @@ -408,19 +408,27 @@ def test_autofield_no_default(self):
"""Spanner, default is not provided."""
field = AutoField(name="field_name")
assert gen_rand_int64 == field.default
# db_returning must be explicitly False because Spanner is handling ID generation client-side
assert getattr(field, "db_returning", True) is False
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@gemini-code-assist gemini-code-assist bot Mar 16, 2026

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medium

For consistency and clarity, it's better to access the db_returning attribute directly. The AutoField class defines this attribute, so it will always be present on the field instance. Using getattr with a default is unnecessary and makes the assertion slightly harder to read compared to a direct access.

Suggested change
assert getattr(field, "db_returning", True) is False
assert field.db_returning is False


def test_autofield_default(self):
"""Spanner, default provided."""
mock_func = mock.Mock()
field = AutoField(name="field_name", default=mock_func)
assert gen_rand_int64 != field.default
assert mock_func == field.default
# A default was already provided, so Spanner does not generate random IDs client-side.
# Therefore, db_returning does not need to be overridden to False.
assert field.db_returning is True

def test_autofield_not_spanner(self):
"""Not Spanner, default not provided."""
connection.settings_dict["ENGINE"] = "another_db"
field = AutoField(name="field_name")
assert gen_rand_int64 != field.default
# db_returning should remain untouched (implicitly True) for non-Spanner databases
# so that Django retrieves the auto-increment ID correctly.
assert field.db_returning is True
connection.settings_dict["ENGINE"] = "django_spanner"

def test_autofield_not_spanner_w_default(self):
Expand All @@ -430,6 +438,8 @@ def test_autofield_not_spanner_w_default(self):
field = AutoField(name="field_name", default=mock_func)
assert gen_rand_int64 != field.default
assert mock_func == field.default
# Because it's not a Spanner database, the behavior shouldn't be altered in any way.
assert field.db_returning is True
connection.settings_dict["ENGINE"] = "django_spanner"

def test_autofield_spanner_as_non_default_db_random_generation_enabled(
Expand All @@ -441,6 +451,9 @@ def test_autofield_spanner_as_non_default_db_random_generation_enabled(
connections.settings["secondary"]["RANDOM_ID_GENERATION_ENABLED"] = "true"
field = AutoField(name="field_name")
assert gen_rand_int64 == field.default
# Since this specific connection explicitly enables client-side random generation,
# we must tell Django not to attempt retrieving the DB's returned ID.
assert getattr(field, "db_returning", True) is False
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medium

Similar to my other comment, direct attribute access is preferred here for better readability and consistency. Since db_returning is a standard attribute of AutoField, getattr is not needed.

Suggested change
assert getattr(field, "db_returning", True) is False
assert field.db_returning is False

connections.settings["default"]["ENGINE"] = "django_spanner"
connections.settings["secondary"]["ENGINE"] = "django_spanner"
del connections.settings["secondary"]["RANDOM_ID_GENERATION_ENABLED"]
Expand All @@ -450,4 +463,7 @@ def test_autofield_random_generation_disabled(self):
connections.settings["default"]["RANDOM_ID_GENERATION_ENABLED"] = "false"
field = AutoField(name="field_name")
assert gen_rand_int64 != field.default
# Because we're delegating ID generation back to the database backend,
# Django needs to be able to retrieve the assigned ID.
assert field.db_returning is True
del connections.settings["default"]["RANDOM_ID_GENERATION_ENABLED"]
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