Hello Derek,
There's no setting but this is controlled by the allows_auto_pk_0 feature
flag [0].
Database feature are set to the default database configurations so Django
can
minimized the number of introspection queries required to work appropriately
each time a connection is opened.
In order to override it I suggest you create a subclass of
django.db.backends.mysql.base.DatabaseWrapper in
a custom foo.bar.base module and set feature_class to a
.features.DatabaseFeatures[1]
subclass that sets the allows_auto_pk_0 flag to True.
e.g.
#foo/bar/base.py
from django.db.backends.mysql.base import DatabaseWrapper as
BaseDatabaseWrapper
from django.db.backends.mysql.features import DatabaseFeatures as
BaseDatabaseFeatures
class DatabaseFeatures(BaseDatabaseFeatures):
allows_auto_pk_0 = True
class DatabaseWrapper(BaseDatabaseWrapper):
features_class = DatabaseFeatures
Then you'll want to point your DATABASES.ENGINE to 'foo.bar' instead of
'django.db.backends.mysql'.
Keep in mind that Django expects
1. A .base submodule [2]
2. A class named DatabaseWrapper [3]
The foo.bar module path can be renamed to whatever you want.
Cheers,
[0]
https://github.com/django/django/blob/e817ae74da0e515db31907ebcb2d00bcf7c3f5bc/django/db/backends/mysql/features.py#L27
[1]
https://github.com/django/django/blob/e817ae74da0e515db31907ebcb2d00bcf7c3f5bc/django/db/backends/mysql/base.py#L184
[2]
https://github.com/django/django/blob/e817ae74da0e515db31907ebcb2d00bcf7c3f5bc/django/db/utils.py#L110
[3]
https://github.com/django/django/blob/e817ae74da0e515db31907ebcb2d00bcf7c3f5bc/django/db/utils.py#L203
Le vendredi 28 décembre 2018 07:47:31 UTC-5, Derek a écrit :
>
> I am working with some legacy data and need to preserve the existing
> record ID's which, in some tables, include the value of 0 for their
> auto-increment field.
>
> I have updated the configuration file for MySQL such that the sql_mode is
> set to include 'NO_AUTO_VALUE_ON_ZERO'.
>
> I can check that this works by running the following test inside the MySQL
> shell:
>
> create table number (number int not null auto_increment primary key);
> insert into number(number) values (0); select * from number; drop table
> number;
>
> +--------+
> | number |
> +--------+
> | 0 |
> +--------+
> 1 row in set (0,00 sec)
>
> However, when I try this approach with one of my existing models (in the
> Django shell) I get an error:
>
> from myapp.models import MyModel
> MyModel.objects.create(pk=0, direction=1, code='UNK')
>
> Traceback (most recent call last):
> File "<console>", line 1, in <module>
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/manager.py",
>
> line 157, in create
> return self.get_queryset().create(**kwargs)
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/query.py",
>
> line 322, in create
> obj.save(force_insert=True, using=self.db)
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/base.py",
>
> line 545, in save
> force_update=force_update, update_fields=update_fields)
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/base.py",
>
> line 573, in save_base
> updated = self._save_table(raw, cls, force_insert, force_update,
> using, update_fields)
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/base.py",
>
> line 654, in _save_table
> result = self._do_insert(cls._base_manager, using, fields, update_pk,
> raw)
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/base.py",
>
> line 687, in _do_insert
> using=using, raw=raw)
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/manager.py",
>
> line 232, in _insert
> return insert_query(self.model, objs, fields, **kwargs)
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/query.py",
>
> line 1514, in insert_query
> return query.get_compiler(using=using).execute_sql(return_id)
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py",
>
> line 902, in execute_sql
> for sql, params in self.as_sql():
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py",
>
> line 860, in as_sql
> for obj in self.query.objs
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/fields/__init__.py",
>
> line 350, in get_db_prep_save
> prepared=False)
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/models/fields/__init__.py",
>
> line 607, in get_db_prep_value
> value = connection.ops.validate_autopk_value(value)
> File
> "/home/gamesbook/,virtualenvs/proj/local/lib/python2.7/site-packages/django/db/backends/mysql/base.py",
>
> line 336, in validate_autopk_value
> raise ValueError('The database backend does not accept 0 as a '
> ValueError: The database backend does not accept 0 as a value for
> AutoField.
>
> Is there a setting I need to change such that Django does not raise this
> error and allows the PK to be zero?
>
> Thanks
> Derek
>
>
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