#28431: Default value for BinaryField in reverse migration
----------------------------+--------------------------------------
Reporter: sg-james | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.10
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+--------------------------------------
Description changed by sg-james:
Old description:
> == Description ==
> Initial migration has a default value {{{''}}} for BinaryField.
> Later, change default value to {{{b''}}} and migrate.
> Trying to undo this migration fails. It seems like {{{''}}} is allowed
> during migration, but not in reverse migration.
>
> == Related issue ==
> #22851 Default value for BinaryField
>
> == Reproduce ==
> Python 3.6.0, Django 1.10.6, Postgres 9.5.4
>
> 1. startproject djangoproject
> 2. startapp firstapp
> 3. firstapp/models.py:
>
> {{{
> class TableOne(models.Model):
> field1 = models.BinaryField(default = '')
> }}}
>
> 4. makemigrations firstapp
> 5. migrate firstapp 0001
> 5. Modify firstapp/models.py
>
> {{{
> class TableOne(models.Model):
> field1 = models.BinaryField(default = b'')
> }}}
>
> 6. migrate firstapp 0002
> 7. migrate firstapp 0001
>
> Error: TypeError: can't escape str to binary
>
> {{{
> Traceback (most recent call last):
> File "manage.py", line 22, in <module>
> execute_from_command_line(sys.argv)
> File "C:\Py\py3_64\lib\site-
> packages\django\core\management\__init__.py", line 367, in
> execute_from_command_line
> utility.execute()
> File "C:\Py\py3_64\lib\site-
> packages\django\core\management\__init__.py", line 359, in execute
> self.fetch_command(subcommand).run_from_argv(self.argv)
> File "C:\Py\py3_64\lib\site-packages\django\core\management\base.py",
> line 294, in run_from_argv
> self.execute(*args, **cmd_options)
> File "C:\Py\py3_64\lib\site-packages\django\core\management\base.py",
> line 345, in execute
> output = self.handle(*args, **options)
> File "C:\Py\py3_64\lib\site-
> packages\django\core\management\commands\migrate.py", line 204, in handle
> fake_initial=fake_initial,
> File "C:\Py\py3_64\lib\site-packages\django\db\migrations\executor.py",
> line 119, in migrate
> state = self._migrate_all_backwards(plan, full_plan, fake=fake)
> File "C:\Py\py3_64\lib\site-packages\django\db\migrations\executor.py",
> line 194, in _migrate_all_backwards
> self.unapply_migration(states[migration], migration, fake=fake)
> File "C:\Py\py3_64\lib\site-packages\django\db\migrations\executor.py",
> line 264, in unapply_migration
> state = migration.unapply(state, schema_editor)
> File "C:\Py\py3_64\lib\site-
> packages\django\db\migrations\migration.py", line 178, in unapply
> operation.database_backwards(self.app_label, schema_editor,
> from_state, to_state)
> File "C:\Py\py3_64\lib\site-
> packages\django\db\migrations\operations\fields.py", line 210, in
> database_backwards
> self.database_forwards(app_label, schema_editor, from_state,
> to_state)
> File "C:\Py\py3_64\lib\site-
> packages\django\db\migrations\operations\fields.py", line 205, in
> database_forwards
> schema_editor.alter_field(from_model, from_field, to_field)
> File "C:\Py\py3_64\lib\site-
> packages\django\db\backends\base\schema.py", line 506, in alter_field
> old_db_params, new_db_params, strict)
> File "C:\Py\py3_64\lib\site-
> packages\django\db\backends\postgresql\schema.py", line 118, in
> _alter_field
> new_db_params, strict,
> File "C:\Py\py3_64\lib\site-
> packages\django\db\backends\base\schema.py", line 660, in _alter_field
> params,
> File "C:\Py\py3_64\lib\site-
> packages\django\db\backends\base\schema.py", line 112, in execute
> cursor.execute(sql, params)
> File "C:\Py\py3_64\lib\site-packages\django\db\backends\utils.py", line
> 80, in execute
> return super(CursorDebugWrapper, self).execute(sql, params)
> File "C:\Py\py3_64\lib\site-packages\django\db\backends\utils.py", line
> 65, in execute
> return self.cursor.execute(sql, params)
> TypeError: can't escape str to binary
> }}}
New description:
== Description ==
Initial migration has a default value {{{''}}} for BinaryField.
Later, change default value to {{{b''}}} and migrate.
Trying to undo this migration fails. It seems like {{{''}}} is allowed
during migration, but not in reverse migration.
== Related issue ==
#22851 Default value for BinaryField
== Reproduce ==
Python 3.6.0, Django 1.10.6, Postgres 9.5.4
1. startproject djangoproject
2. startapp firstapp
3. firstapp/models.py:
{{{
class TableOne(models.Model):
field1 = models.BinaryField(default = '')
}}}
4. makemigrations firstapp
5. migrate firstapp 0001
5. Modify firstapp/models.py
{{{
class TableOne(models.Model):
field1 = models.BinaryField(default = b'')
}}}
6. migrate firstapp 0002
7. migrate firstapp 0001
Error: TypeError: can't escape str to binary
{{{
Traceback (most recent call last):
File "manage.py", line 22, in <module>
execute_from_command_line(sys.argv)
File "C:\Py\py3_64\lib\site-
packages\django\core\management\__init__.py", line 367, in
execute_from_command_line
utility.execute()
File "C:\Py\py3_64\lib\site-
packages\django\core\management\__init__.py", line 359, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "C:\Py\py3_64\lib\site-packages\django\core\management\base.py",
line 294, in run_from_argv
self.execute(*args, **cmd_options)
File "C:\Py\py3_64\lib\site-packages\django\core\management\base.py",
line 345, in execute
output = self.handle(*args, **options)
File "C:\Py\py3_64\lib\site-
packages\django\core\management\commands\migrate.py", line 204, in handle
fake_initial=fake_initial,
File "C:\Py\py3_64\lib\site-packages\django\db\migrations\executor.py",
line 119, in migrate
state = self._migrate_all_backwards(plan, full_plan, fake=fake)
File "C:\Py\py3_64\lib\site-packages\django\db\migrations\executor.py",
line 194, in _migrate_all_backwards
self.unapply_migration(states[migration], migration, fake=fake)
File "C:\Py\py3_64\lib\site-packages\django\db\migrations\executor.py",
line 264, in unapply_migration
state = migration.unapply(state, schema_editor)
File "C:\Py\py3_64\lib\site-packages\django\db\migrations\migration.py",
line 178, in unapply
operation.database_backwards(self.app_label, schema_editor,
from_state, to_state)
File "C:\Py\py3_64\lib\site-
packages\django\db\migrations\operations\fields.py", line 210, in
database_backwards
self.database_forwards(app_label, schema_editor, from_state, to_state)
File "C:\Py\py3_64\lib\site-
packages\django\db\migrations\operations\fields.py", line 205, in
database_forwards
schema_editor.alter_field(from_model, from_field, to_field)
File "C:\Py\py3_64\lib\site-packages\django\db\backends\base\schema.py",
line 506, in alter_field
old_db_params, new_db_params, strict)
File "C:\Py\py3_64\lib\site-
packages\django\db\backends\postgresql\schema.py", line 118, in
_alter_field
new_db_params, strict,
File "C:\Py\py3_64\lib\site-packages\django\db\backends\base\schema.py",
line 660, in _alter_field
params,
File "C:\Py\py3_64\lib\site-packages\django\db\backends\base\schema.py",
line 112, in execute
cursor.execute(sql, params)
File "C:\Py\py3_64\lib\site-packages\django\db\backends\utils.py", line
80, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "C:\Py\py3_64\lib\site-packages\django\db\backends\utils.py", line
65, in execute
return self.cursor.execute(sql, params)
TypeError: can't escape str to binary
}}}
== Notes ==
site-packages\django\db\backends\base\shema.py {{{ def
effective_default(self, field): }}}
determines default as an empty <class 'str'>, when {{{(default = '')}}}
== Possible Fix? ==
site-packages\django\db\backends\base\shema.py ~line 197
{{{
def effective_default(self, field):
if field.has_default():
default = field.get_default()
if field.get_internal_type() == "BinaryField" and not default:
default = six.binary_type()
elif not field.null and field.blank and
field.empty_strings_allowed:
if field.get_internal_type() == "BinaryField":
default = six.binary_type()
else:
default = six.text_type()
elif getattr(field, 'auto_now', False)
}}}
--
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Ticket URL: <https://code.djangoproject.com/ticket/28431#comment:1>
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