从标准 sqlite 更改为 postgres 数据库答案

【问题标题】：Changing from standard sqlite to postgres database从标准 sqlite 更改为 postgres 数据库
【发布时间】：2018-06-06 15:41:43
【问题描述】：

我正在尝试在我的 Django 项目中从标准 sqlite 数据库更改为 postgresql。这是我到目前为止所做的：

已安装 postgresql
创建了一个数据库和一个具有写入权限的用户

在 settings.py 中更改数据库设置：

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'workout',
        'USER': 'admin',
        'PASSWORD': 'admin',
        'HOST': 'localhost',
        'PORT': '5432',
    }
}

然后，当我尝试迁移时，会发生这种情况（长错误跟踪警告）：

(workout) Sahands-MBP:workout sahandzarrinkoub$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sessions, workoutcal
Running migrations:
  Applying contenttypes.0001_initial... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0001_initial... OK
  Applying auth.0002_alter_permission_name_max_length... OK
  Applying auth.0003_alter_user_email_max_length... OK
  Applying auth.0004_alter_user_username_opts... OK
  Applying auth.0005_alter_user_last_login_null... OK
  Applying auth.0006_require_contenttypes_0002... OK
  Applying auth.0007_alter_validators_add_error_messages... OK
  Applying auth.0008_alter_user_username_max_length... OK
  Applying workoutcal.0001_initial... OK
  Applying admin.0001_initial... OK
  Applying admin.0002_logentry_remove_auto_add... OK
  Applying sessions.0001_initial... OK
  Applying workoutcal.0002_auto_20171215_1102... OK
  Applying workoutcal.0003_auto_20171215_1153...Traceback (most recent call last):
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
psycopg2.ProgrammingError: multiple default values specified for column "id" of table "workoutcal_user"


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 204, in handle
    fake_initial=fake_initial,
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/executor.py", line 115, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/migration.py", line 129, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/operations/fields.py", line 87, in database_forwards
    field,
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 429, in add_field
    self.execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 120, in execute
    cursor.execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 80, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: multiple default values specified for column "id" of table "workoutcal_user"

(workout) Sahands-MBP:workout sahandzarrinkoub$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sessions, workoutcal
Running migrations:
  Applying workoutcal.0003_auto_20171215_1153...Traceback (most recent call last):
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
psycopg2.ProgrammingError: multiple default values specified for column "id" of table "workoutcal_user"


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 204, in handle
    fake_initial=fake_initial,
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/executor.py", line 115, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/migration.py", line 129, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/operations/fields.py", line 87, in database_forwards
    field,
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 429, in add_field
    self.execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 120, in execute
    cursor.execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 80, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: multiple default values specified for column "id" of table "workoutcal_user"

(workout) Sahands-MBP:workout sahandzarrinkoub$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sessions, workoutcal
Running migrations:
  Applying workoutcal.0003_auto_20171215_1153...Traceback (most recent call last):
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
psycopg2.ProgrammingError: multiple default values specified for column "id" of table "workoutcal_user"


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 204, in handle
    fake_initial=fake_initial,
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/executor.py", line 115, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/migration.py", line 129, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/operations/fields.py", line 87, in database_forwards
    field,
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 429, in add_field
    self.execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 120, in execute
    cursor.execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 80, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: multiple default values specified for column "id" of table "workoutcal_user"

因此，锻炼cal_user 似乎存在某种错误。我不确定 django 是如何命名表的，但我在 workoutcal/models.py 中定义的唯一模型就是这个：

class User(AbstractUser):
    REQUIRED_FIELDS = []
    USERNAME_FIELD = 'email'
    email = models.EmailField(
        _('email address'),
        max_length=150,
        unique=True,
        help_text=_('Required. 150 characters or fewer. Must be a valid email address.'),
        error_messages={
            'unique':_("A user with that email address already exists."),
        },
    )

我猜这是导致问题的模型。我的问题很明显，为什么？为这个模型的id 字段指定了多个默认值是什么意思？我怎样才能让它们只有一个？

编辑：

按照 Daniel Roseman 的要求，失败的迁移 0003_auto_20171215_1153.py：

# -*- coding: utf-8 -*-
# Generated by Django 1.11.5 on 2017-12-15 11:53
from __future__ import unicode_literals

from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('workoutcal', '0002_auto_20171215_1102'),
    ]

    operations = [
        migrations.AddField(
            model_name='user',
            name='id',
            field=models.AutoField(auto_created=True, default=1, primary_key=True, serialize=False, verbose_name='ID'),
            preserve_default=False,
        ),
        migrations.AlterField(
            model_name='user',
            name='email',
            field=models.EmailField(error_messages={'unique': 'A user with that email address already exists.'}, help_text='Required. 150 characters of fewer. Must be a valid email address.', max_length=150, unique=True, verbose_name='email address'),
        ),
    ]

编辑 2：

我听从了 cezar 的指示。到达最后一步并尝试迁移时，出现此错误。

(workout) Sahands-MBP:workout sahandzarrinkoub$ python manage.py migrate workoutcal
Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 86, in handle
    executor.loader.check_consistent_history(connection)
  File "/Users/sahandzarrinkoub/Documents/Programming/Web/Django/workout/lib/python3.6/site-packages/django/db/migrations/loader.py", line 298, in check_consistent_history
    connection.alias,
django.db.migrations.exceptions.InconsistentMigrationHistory: Migration admin.0001_initial is applied before its dependency workoutcal.0001_initial on database 'default'.

其他迁移是什么？如何彻底清除迁移历史记录？

编辑 3：在使用 DROP TABLE 'tablename' CASCADE; 删除数据库中的每个表后，删除锻炼/迁移中的所有文件并再次运行 makemigrations 和 migrate，它工作了。

【问题讨论】：

已更改。同样的问题仍然存在。
展示你的模特workoutcal_user
已经在问题中了。我想不出任何其他模型，这是我定义的唯一模型。
如何删除为它指定的默认值？
您应该显示迁移失败的代码，workoutcal.0003_auto_20171215_1153。

标签： python django postgresql sqlite

【解决方案1】：

问题出在下面一行：

field=models.AutoField(auto_created=True, <b>default=1</b>, primary_key=True, serialize=False, verbose_name='ID'),

id 字段必须是唯一的，因为它是主键。这意味着它不能有一个在许多条目中重复的默认值。

我建议一个快速而肮脏的解决方案。直接转到您的 PosgreSQL 命令行。删除应用程序workoutcal 的表django_migrations 中的所有条目：

DELETE FROM django_migrations WHERE app = 'workoutcal';

在你的应用程序workoutcal中删除目录migrations的内容：

rm -rf workoutcal/migrations/*

然后生成新的迁移：

python manage.py makemigrations workoutcal

这应该会创建新的初始迁移。之后的命令：

python manage.py migrate workoutcal

应该没有任何问题地填充数据库。

编辑：

迁移admin.0001_initial 依赖于workoutcal.0001_initial。我无法解释这种依赖性。您可以使用 django 命令行工具还原 admin 的迁移：

python manage.py migrate admin zero

使用zero 选项，您可以告诉 django 恢复所有迁移并在初始迁移运行之前建立状态。您可以指定迁移的编号，而不是 zero。但是，在您的特定情况下，您需要使用 zero 恢复到初始状态。

之后运行 workoutcal 和 admin 的迁移：

python manage.py migrate workoutcal
python manage.py migrate admin

【讨论】：

谢谢@cezar。不幸的是，当我尝试您的解决方案时出现错误。你能看看 EDIT 2 吗？