Hello Derek,
Not sure of your custom module structure but you'll want to point ENGINE to
'custom'
and not 'custom.base' just like you were pointing to
'django.db.backends.mysql' and
not 'django.db.backends.mysql.base'.
Cheers,
Simon
Le dimanche 30 décembre 2018 04:01:59 UTC-5, Derek a écrit :
>
> Hi Simon
>
> Much appreciated.
>
> However, I am obviously doing something wrong. If I save that code into a
> file called "base.py" stored in my 'custom' app, and then change my
> settings file to have:
>
> DATABASES = {
> 'default': {
> 'ENGINE': 'custom.base', # WAS: 'django.db.backends.mysql',
> 'NAME': DB_NAME,
> 'USER': DB_USER,
> 'PASSWORD': DB_PWORD,
> 'HOST': '',
> 'PORT': '',
> }
> }
>
> Then I get this error on startup:
>
> Traceback (most recent call last):
> File "manage.py", line 14, in <module>
> execute_from_command_line(sys.argv)
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/core/management/__init__.py",
>
> line 399, in execute_from_command_line
> utility.execute()
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/core/management/__init__.py",
>
> line 392, in execute
> self.fetch_command(subcommand).run_from_argv(self.argv)
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/core/management/base.py",
>
> line 242, in run_from_argv
> self.execute(*args, **options.__dict__)
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/core/management/base.py",
>
> line 280, in execute
> translation.activate('en-us')
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/utils/translation/__init__.py",
>
> line 130, in activate
> return _trans.activate(language)
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/utils/translation/trans_real.py",
>
> line 188, in activate
> _active.value = translation(language)
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/utils/translation/trans_real.py",
>
> line 177, in translation
> default_translation = _fetch(settings.LANGUAGE_CODE)
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/utils/translation/trans_real.py",
>
> line 159, in _fetch
> app = import_module(appname)
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/utils/importlib.py",
>
> line 40, in import_module
> __import__(name)
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/massadmin/__init__.py",
>
> line 28, in <module>
> from django.contrib import admin
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/contrib/admin/__init__.py",
>
> line 6, in <module>
> from django.contrib.admin.sites import AdminSite, site
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/contrib/admin/sites.py",
>
> line 4, in <module>
> from django.contrib.admin.forms import AdminAuthenticationForm
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/contrib/admin/forms.py",
>
> line 6, in <module>
> from django.contrib.auth.forms import AuthenticationForm
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/contrib/auth/forms.py",
>
> line 17, in <module>
> from django.contrib.auth.models import User
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/contrib/auth/models.py",
>
> line 48, in <module>
> class Permission(models.Model):
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/db/models/base.py",
>
> line 96, in __new__
> new_class.add_to_class('_meta', Options(meta, **kwargs))
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/db/models/base.py",
>
> line 264, in add_to_class
> value.contribute_to_class(cls, name)
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/db/models/options.py",
>
> line 124, in contribute_to_class
> self.db_table = truncate_name(self.db_table,
> connection.ops.max_name_length())
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/db/__init__.py",
>
> line 34, in __getattr__
> return getattr(connections[DEFAULT_DB_ALIAS], item)
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/db/utils.py",
>
> line 198, in __getitem__
> backend = load_backend(db['ENGINE'])
> File
> "/home/gamesbook/.virtualenvs/s2s/local/lib/python2.7/site-packages/django/db/utils.py",
>
> line 131, in load_backend
> raise ImproperlyConfigured(error_msg)
> django.core.exceptions.ImproperlyConfigured: 'custom.base' isn't an
> available database backend.
> Try using 'django.db.backends.XXX', where XXX is one of:
> u'mysql', u'oracle', u'postgresql_psycopg2', u'sqlite3'
>
> Any idea what I have missed?
>
> Thanks
> Derek
>
>
> On Friday, 28 December 2018 16:20:33 UTC+2, Simon Charette wrote:
>>
>> 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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