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Fixed #28305 -- Fixed "Cannot change column 'x': used in a foreign key constraint" crash on MySQL with a sequence of AlterField or RenameField operations. 

Regression in 45ded053b1.
This commit is contained in:
Tim Graham 2017-06-30 14:51:08 -04:00
parent d6859a1489
commit c3e0adcad8
5 changed files with 113 additions and 8 deletions
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14
django/db/backends/base/schema.py
View File

@ -536,9 +536,15 @@ class BaseDatabaseSchemaEditor:
))
for constraint_name in constraint_names:
self.execute(self._delete_constraint_sql(self.sql_delete_unique, model, constraint_name))
# Drop incoming FK constraints if we're a primary key and things are going
# to change.
if old_field.primary_key and new_field.primary_key and old_type != new_type:
# Drop incoming FK constraints if the field is a primary key or unique,
# which might be a to_field target, and things are going to change.
drop_foreign_keys = (
(
(old_field.primary_key and new_field.primary_key) or
(old_field.unique and new_field.unique)
) and old_type != new_type
)
if drop_foreign_keys:
# '_meta.related_field' also contains M2M reverse fields, these
# will be filtered out
for _old_rel, new_rel in _related_non_m2m_objects(old_field, new_field):
@ -727,7 +733,7 @@ class BaseDatabaseSchemaEditor:
new_field.db_constraint):
self.execute(self._create_fk_sql(model, new_field, "_fk_%(to_table)s_%(to_column)s"))
# Rebuild FKs that pointed to us if we previously had to drop them
if old_field.primary_key and new_field.primary_key and old_type != new_type:
if drop_foreign_keys:
for rel in new_field.model._meta.related_objects:
if not rel.many_to_many and rel.field.db_constraint:
self.execute(self._create_fk_sql(rel.related_model, rel.field, "_fk"))

17
django/db/migrations/operations/fields.py
View File

@ -3,6 +3,7 @@ from django.db.models.fields import NOT_PROVIDED
from django.utils.functional import cached_property
from .base import Operation
from .utils import is_referenced_by_foreign_key
class FieldOperation(Operation):
@ -196,8 +197,12 @@ class AlterField(FieldOperation):
]
# TODO: investigate if old relational fields must be reloaded or if it's
# sufficient if the new field is (#27737).
# Delay rendering of relationships if it's not a relational field
delay = not field.is_relation
# Delay rendering of relationships if it's not a relational field and
# not referenced by a foreign key.
delay = (
not field.is_relation and
not is_referenced_by_foreign_key(state, self.model_name_lower, self.field, self.name)
)
state.reload_model(app_label, self.model_name_lower, delay=delay)
def database_forwards(self, app_label, schema_editor, from_state, to_state):
@ -268,8 +273,12 @@ class RenameField(FieldOperation):
for index, (name, field) in enumerate(fields):
if name == self.old_name:
fields[index] = (self.new_name, field)
# Delay rendering of relationships if it's not a relational field.
delay = not field.is_relation
# Delay rendering of relationships if it's not a relational
# field and not referenced by a foreign key.
delay = (
not field.is_relation and
not is_referenced_by_foreign_key(state, self.model_name_lower, field, self.name)
)
break
else:
raise FieldDoesNotExist(

9
django/db/migrations/operations/utils.py Normal file
View File

@ -0,0 +1,9 @@
def is_referenced_by_foreign_key(state, model_name_lower, field, field_name):
for state_app_label, state_model in state.models:
for _, f in state.models[state_app_label, state_model].fields:
if (f.related_model and
'%s.%s' % (state_app_label, model_name_lower) == f.related_model.lower() and
hasattr(f, 'to_fields')):
if (f.to_fields[0] is None and field.primary_key) or field_name in f.to_fields:
return True
return False

4
docs/releases/1.11.8.txt
View File

@ -30,3 +30,7 @@ Bugfixes
* Fixed a regression in caching of a ``GenericForeignKey`` when the referenced
model instance uses multi-table inheritance (:ticket:`28856`).
* Fixed "Cannot change column 'x': used in a foreign key constraint" crash on
MySQL with a sequence of ``AlterField`` and/or ``RenameField`` operations in
a migration (:ticket:`28305`).

77
tests/migrations/test_operations.py
View File

@ -1322,6 +1322,83 @@ class OperationTests(OperationTestBase):
operation.database_backwards("test_alflpkfk", editor, new_state, project_state)
assertIdTypeEqualsFkType()
def test_alter_field_reloads_state_on_fk_target_changes(self):
"""
If AlterField doesn't reload state appropriately, the second AlterField
crashes on MySQL due to not dropping the PonyRider.pony foreign key
constraint before modifying the column.
"""
app_label = 'alter_alter_field_reloads_state_on_fk_target_changes'
project_state = self.apply_operations(app_label, ProjectState(), operations=[
migrations.CreateModel('Rider', fields=[
('id', models.CharField(primary_key=True, max_length=100)),
]),
migrations.CreateModel('Pony', fields=[
('id', models.CharField(primary_key=True, max_length=100)),
('rider', models.ForeignKey('%s.Rider' % app_label, models.CASCADE)),
]),
migrations.CreateModel('PonyRider', fields=[
('id', models.AutoField(primary_key=True)),
('pony', models.ForeignKey('%s.Pony' % app_label, models.CASCADE)),
]),
])
project_state = self.apply_operations(app_label, project_state, operations=[
migrations.AlterField('Rider', 'id', models.CharField(primary_key=True, max_length=99)),
migrations.AlterField('Pony', 'id', models.CharField(primary_key=True, max_length=99)),
])
def test_alter_field_reloads_state_on_fk_with_to_field_target_changes(self):
"""
If AlterField doesn't reload state appropriately, the second AlterField
crashes on MySQL due to not dropping the PonyRider.pony foreign key
constraint before modifying the column.
"""
app_label = 'alter_alter_field_reloads_state_on_fk_with_to_field_target_changes'
project_state = self.apply_operations(app_label, ProjectState(), operations=[
migrations.CreateModel('Rider', fields=[
('id', models.CharField(primary_key=True, max_length=100)),
('slug', models.CharField(unique=True, max_length=100)),
]),
migrations.CreateModel('Pony', fields=[
('id', models.CharField(primary_key=True, max_length=100)),
('rider', models.ForeignKey('%s.Rider' % app_label, models.CASCADE, to_field='slug')),
('slug', models.CharField(unique=True, max_length=100)),
]),
migrations.CreateModel('PonyRider', fields=[
('id', models.AutoField(primary_key=True)),
('pony', models.ForeignKey('%s.Pony' % app_label, models.CASCADE, to_field='slug')),
]),
])
project_state = self.apply_operations(app_label, project_state, operations=[
migrations.AlterField('Rider', 'slug', models.CharField(unique=True, max_length=99)),
migrations.AlterField('Pony', 'slug', models.CharField(unique=True, max_length=99)),
])
def test_rename_field_reloads_state_on_fk_target_changes(self):
"""
If RenameField doesn't reload state appropriately, the AlterField
crashes on MySQL due to not dropping the PonyRider.pony foreign key
constraint before modifying the column.
"""
app_label = 'alter_rename_field_reloads_state_on_fk_target_changes'
project_state = self.apply_operations(app_label, ProjectState(), operations=[
migrations.CreateModel('Rider', fields=[
('id', models.CharField(primary_key=True, max_length=100)),
]),
migrations.CreateModel('Pony', fields=[
('id', models.CharField(primary_key=True, max_length=100)),
('rider', models.ForeignKey('%s.Rider' % app_label, models.CASCADE)),
]),
migrations.CreateModel('PonyRider', fields=[
('id', models.AutoField(primary_key=True)),
('pony', models.ForeignKey('%s.Pony' % app_label, models.CASCADE)),
]),
])
project_state = self.apply_operations(app_label, project_state, operations=[
migrations.RenameField('Rider', 'id', 'id2'),
migrations.AlterField('Pony', 'id', models.CharField(primary_key=True, max_length=99)),
])
def test_rename_field(self):
"""
Tests the RenameField operation.