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[1.8.x] Fixed #24757 -- Recreated MySQL index when needed during combined index removal 

Thanks Thomas Recouvreux for the report and Tim Graham for the tests and
review.
Backport of ae635cc36 from master.
This commit is contained in:
Claude Paroz 2015-05-13 17:40:57 +02:00
parent 30e5703844
commit 6a0d9f068f
4 changed files with 70 additions and 18 deletions
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31
django/db/backends/base/schema.py
View File

@ -317,15 +317,7 @@ class BaseDatabaseSchemaEditor(object):
news = set(tuple(fields) for fields in new_unique_together)
# Deleted uniques
for fields in olds.difference(news):
columns = [model._meta.get_field(field).column for field in fields]
constraint_names = self._constraint_names(model, columns, unique=True)
if len(constraint_names) != 1:
raise ValueError("Found wrong number (%s) of constraints for %s(%s)" % (
len(constraint_names),
model._meta.db_table,
", ".join(columns),
))
self.execute(self._delete_constraint_sql(self.sql_delete_unique, model, constraint_names[0]))
self._delete_composed_index(model, fields, {'unique': True}, self.sql_delete_unique)
# Created uniques
for fields in news.difference(olds):
columns = [model._meta.get_field(field).column for field in fields]
@ -341,20 +333,23 @@ class BaseDatabaseSchemaEditor(object):
news = set(tuple(fields) for fields in new_index_together)
# Deleted indexes
for fields in olds.difference(news):
columns = [model._meta.get_field(field).column for field in fields]
constraint_names = self._constraint_names(model, list(columns), index=True)
if len(constraint_names) != 1:
raise ValueError("Found wrong number (%s) of constraints for %s(%s)" % (
len(constraint_names),
model._meta.db_table,
", ".join(columns),
))
self.execute(self._delete_constraint_sql(self.sql_delete_index, model, constraint_names[0]))
self._delete_composed_index(model, fields, {'index': True}, self.sql_delete_index)
# Created indexes
for field_names in news.difference(olds):
fields = [model._meta.get_field(field) for field in field_names]
self.execute(self._create_index_sql(model, fields, suffix="_idx"))
def _delete_composed_index(self, model, fields, constraint_kwargs, sql):
columns = [model._meta.get_field(field).column for field in fields]
constraint_names = self._constraint_names(model, columns, **constraint_kwargs)
if len(constraint_names) != 1:
raise ValueError("Found wrong number (%s) of constraints for %s(%s)" % (
len(constraint_names),
model._meta.db_table,
", ".join(columns),
))
self.execute(self._delete_constraint_sql(sql, model, constraint_names[0]))
def alter_db_table(self, model, old_db_table, new_db_table):
"""
Renames the table a model points to.

18
django/db/backends/mysql/schema.py
View File

@ -62,6 +62,24 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
field.db_index = False
return super(DatabaseSchemaEditor, self)._model_indexes_sql(model)
def _delete_composed_index(self, model, fields, *args):
"""
MySQL can remove an implicit FK index on a field when that field is
covered by another index like a unique_together. "covered" here means
that the more complex index starts like the simpler one.
http://bugs.mysql.com/bug.php?id=37910 / Django ticket #24757
We check here before removing the [unique|index]_together if we have to
recreate a FK index.
"""
first_field = model._meta.get_field(fields[0])
if first_field.get_internal_type() == 'ForeignKey':
constraint_names = self._constraint_names(model, fields[0], index=True)
if not constraint_names:
self.execute(
self._create_index_sql(model, [model._meta.get_field(fields[0])], suffix="")
)
return super(DatabaseSchemaEditor, self)._delete_composed_index(model, fields, *args)
def _alter_column_type_sql(self, table, old_field, new_field, new_type):
# Keep null property of old field, if it has changed, it will be handled separately
if old_field.null:

3
docs/releases/1.8.2.txt
View File

@ -27,3 +27,6 @@ Bugfixes
:ticket:`24712`).
* Fixed ``isnull`` lookup for ``HStoreField`` (:ticket:`24751`).
* Fixed a MySQL crash when a migration removes a combined index (unique_together
or index_together) containing a foreign key (:ticket:`24757`).

36
tests/schema/tests.py
View File

@ -1084,6 +1084,24 @@ class SchemaTests(TransactionTestCase):
self.assertRaises(IntegrityError, UniqueTest.objects.create, year=2012, slug="foo")
UniqueTest.objects.all().delete()
def test_unique_together_with_fk(self):
"""
Tests removing and adding unique_together constraints that include
a foreign key.
"""
# Create the table
with connection.schema_editor() as editor:
editor.create_model(Author)
editor.create_model(Book)
# Ensure the fields are unique to begin with
self.assertEqual(Book._meta.unique_together, ())
# Add the unique_together constraint
with connection.schema_editor() as editor:
editor.alter_unique_together(Book, [], [['author', 'title']])
# Alter it back
with connection.schema_editor() as editor:
editor.alter_unique_together(Book, [['author', 'title']], [])
def test_index_together(self):
"""
Tests removing and adding index_together constraints on a model.
@ -1127,6 +1145,24 @@ class SchemaTests(TransactionTestCase):
),
)
def test_index_together_with_fk(self):
"""
Tests removing and adding index_together constraints that include
a foreign key.
"""
# Create the table
with connection.schema_editor() as editor:
editor.create_model(Author)
editor.create_model(Book)
# Ensure the fields are unique to begin with
self.assertEqual(Book._meta.index_together, ())
# Add the unique_together constraint
with connection.schema_editor() as editor:
editor.alter_index_together(Book, [], [['author', 'title']])
# Alter it back
with connection.schema_editor() as editor:
editor.alter_index_together(Book, [['author', 'title']], [])
def test_create_index_together(self):
"""
Tests creating models with index_together already defined