#25678: migrate scalar to array field in PostrgreSQL fails
-----------------------------+---------------------------------------------
Reporter: mikofski | Owner: nobody
Type: | Status: new
Uncategorized |
Component: Migrations | Version: 1.8
Severity: Normal | Keywords: PostgreSQL, migrate, ArrayField
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
-----------------------------+---------------------------------------------
Django-1.8.5
Python 2.7.10
PostgreSQL-9.4
Problem: Scalar type might not be cast to array of same type explicitly
with `USING` SQL command?
Solution: Use psql to migrate fields manually
{{{
dev=# ALTER TABLE my_app_mymodel ALTER COLUMN "my_field" TYPE double
precision [] USING array["my_field"]::double precision[];
ALTER TABLE
}}}
== Details ==
given an initial model:
{{{
class MyModel(models.Model):
my_field = models.FloatField()
}}}
change this to `ArrayField`
{{{
class MyModel(models.Model):
my_field = ArrayField(
base_field=models.FloatField(),
default=list
)
}}}
then make migrations and migrate
{{{
$ ./manage.py makemigrations
$ ./manage.py migrate
}}}
returns the following traceback:
{{{
Operations to perform:
Synchronize unmigrated apps: staticfiles, messages
Apply all migrations: admin, contenttypes, my_app, auth, sessions
Synchronizing apps without migrations:
Creating tables...
Running deferred SQL...
Installing custom SQL...
Running migrations:
Rendering model states... DONE
Applying my_app.0XYZ_auto_YYYYMMDD_hhmm...Traceback (most recent call
last):
File "./manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "C:\Python27\lib\site-packages\django\core\management\__init__.py",
line 351, in execute_from_command_line
utility.execute()
File "C:\Python27\lib\site-packages\django\core\management\__init__.py",
line 343, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "C:\Python27\lib\site-packages\django\core\management\base.py",
line 394, in run_from_argv
self.execute(*args, **cmd_options)
File "C:\Python27\lib\site-packages\django\core\management\base.py",
line 445, in execute
output = self.handle(*args, **options)
File "C:\Python27\lib\site-
packages\django\core\management\commands\migrate.py", line 222, in handle
executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
File "C:\Python27\lib\site-packages\django\db\migrations\executor.py",
line 110, in migrate
self.apply_migration(states[migration], migration, fake=fake,
fake_initial=fake_initial)
File "C:\Python27\lib\site-packages\django\db\migrations\executor.py",
line 148, in apply_migration
state = migration.apply(state, schema_editor)
File "C:\Python27\lib\site-packages\django\db\migrations\migration.py",
line 115, in apply
operation.database_forwards(self.app_label, schema_editor, old_state,
project_state)
File "C:\Python27\lib\site-
packages\django\db\migrations\operations\fields.py", line 201, in
database_forwards
schema_editor.alter_field(from_model, from_field, to_field)
File "C:\Python27\lib\site-packages\django\db\backends\base\schema.py",
line 484, in alter_field
old_db_params, new_db_params, strict)
File "C:\Python27\lib\site-packages\django\db\backends\base\schema.py",
line 636, in _alter_field
params,
File "C:\Python27\lib\site-packages\django\db\backends\base\schema.py",
line 111, in execute
cursor.execute(sql, params)
File "C:\Python27\lib\site-packages\django\db\backends\utils.py", line
79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "C:\Python27\lib\site-packages\django\db\backends\utils.py", line
64, in execute
return self.cursor.execute(sql, params)
File "C:\Python27\lib\site-packages\django\db\utils.py", line 97, in
__exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "C:\Python27\lib\site-packages\django\db\backends\utils.py", line
64, in execute
return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: column "my_field " cannot be cast
automatically to type double precision[]
HINT: Specify a USING expression to perform the conversion.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/25678>
Django <https://code.djangoproject.com/>
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