#25417: decimal.InvalidOperation caused by Migrations and DecimalField()
-------------------------------------+-------------------------------------
Reporter: avorio | Owner: nobody
Type: Bug | Status: closed
Component: Migrations | Version: 1.8
Severity: Release blocker | Resolution: needsinfo
Keywords: decimal, | Triage Stage:
InvalidOperation, migrations | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by avorio):
I just reproduced this error again on a fresh new Django project using
Python 3.4.3 and Django 1.8.4. I followed exactly the same steps using
`django.db.backends.postgresql_psycopg2` as the database backend instead.
Just to clarify, the only change in the field is from `max_digits=3` to
`max_digits=5`. The default value continues the same `default=20.00`
(which, by the way, would not be compatible with the first `max_digits`
value).
Here's the first migration:
{{{
# -*- coding: utf-8 -*-
from __future__ import unicode_literals
from django.db import models, migrations
class Migration(migrations.Migration):
dependencies = [
]
operations = [
migrations.CreateModel(
name='Item',
fields=[
('id', models.AutoField(auto_created=True,
primary_key=True, verbose_name='ID', serialize=False)),
('tax_rate', models.DecimalField(help_text='VAT rate',
decimal_places=2, blank=True, null=True, max_digits=3, default=20.0,
verbose_name='tax rate (%)')),
],
),
]
}}}
And here's the second:
{{{
# -*- coding: utf-8 -*-
from __future__ import unicode_literals
from django.db import models, migrations
class Migration(migrations.Migration):
dependencies = [
('testapp', '0001_initial'),
]
operations = [
migrations.AlterField(
model_name='item',
name='tax_rate',
field=models.DecimalField(decimal_places=2, help_text='VAT
rate', verbose_name='tax rate (%)', default=20.0, max_digits=5,
blank=True, null=True),
),
]
}}}
And here's the output of migrations:
{{{
(.venv)➜ mysite python manage.py makemigrations
Migrations for 'testapp':
0001_initial.py:
- Create model Item
(.venv)➜ mysite python manage.py migrate
Operations to perform:
Synchronize unmigrated apps: messages, staticfiles
Apply all migrations: apython manage.py migratein, auth, contenttypes,
sessions, testapp
Synchronizing apps without migrations:
Creating tables...
Running deferred SQL...
Installing custom SQL...
Running migrations:
Rendering model states... DONE
Applying testapp.0001_initial... OK
(.venv)➜ mysite python manage.py makemigrations
Migrations for 'testapp':
0002_auto_20150917_0951.py:
- Alter field tax_rate on item
(.venv)➜ mysite python manage.py migrate
Operations to perform:
Synchronize unmigrated apps: messages, staticfiles
Apply all migrations: testapp, contenttypes, auth, sessions, apython
manage.py migratein
Synchronizing apps without migrations:
Creating tables...
Running deferred SQL...
Installing custom SQL...
Running migrations:
Rendering model states... DONE
Applying testapp.0002_auto_20150917_0951...Traceback (most recent call
last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/core/management/__init__.py", line 338, in
execute_from_command_line
utility.execute()
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/core/management/__init__.py", line 330, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/core/management/base.py", line 393, in run_from_argv
self.execute(*args, **cmd_options)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/core/management/base.py", line 444, in execute
output = self.handle(*args, **options)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/core/management/commands/migrate.py", line 222, in handle
executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/db/migrations/executor.py", line 110, in migrate
self.apply_migration(states[migration], migration, fake=fake,
fake_initial=fake_initial)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/db/migrations/executor.py", line 148, in apply_migration
state = migration.apply(state, schema_editor)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/db/migrations/migration.py", line 115, in apply
operation.database_forwards(self.app_label, schema_editor, old_state,
project_state)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/db/migrations/operations/fields.py", line 201, in
database_forwards
schema_editor.alter_field(from_model, from_field, to_field)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/db/backends/base/schema.py", line 484, in alter_field
old_db_params, new_db_params, strict)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/db/backends/base/schema.py", line 566, in _alter_field
old_default = self.effective_default(old_field)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/db/backends/base/schema.py", line 211, in
effective_default
default = field.get_db_prep_save(default, self.connection)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/db/models/fields/__init__.py", line 1627, in
get_db_prep_save
self.max_digits, self.decimal_places)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/db/backends/base/operations.py", line 477, in
value_to_db_decimal
return utils.format_number(value, max_digits, decimal_places)
File "/new-django-project/.venv/lib/python3.4/site-
packages/django/db/backends/utils.py", line 200, in format_number
value = value.quantize(decimal.Decimal(".1") ** decimal_places,
context=context)
decimal.InvalidOperation: [<class 'decimal.InvalidOperation'>]
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/25417#comment:5>
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