django_migrate&--fake: 迁移回滚/重新执行某一次迁移/伪回滚迁移(不执行相应的sql操作,仅修改执行状态标记)

文章目录

• migrate&--fake: 迁移回滚/重新执行某一次迁移/伪回滚迁移(不执行相应的sql操作,仅修改执行状态标记)
• • • 模型重置可能遇到的问题
    • 细节&步骤
    • 撤销最近一次成功的迁移
    • • 场景实例(当前迁移情况)
      • 回退效果
  • 逆向fake
  • • 实操
  • migrate 子命令手册
  • • fake&fake-initial

migrate&–fake: 迁移回滚/重新执行某一次迁移/伪回滚迁移(不执行相应的sql操作,仅修改执行状态标记)

• python - Rolling back to a previous migration in django - Stack Overflow

模型重置可能遇到的问题

如果您的其他代码已经引用了需要被重置的模型,这会稍微棘手一些,因为在您执行makemigrations的时候,会检查各个代码的依赖等是否正常,如果简单的删除模型,可能导致makemigrations无法完整执行
这样,就需要一步步将所有相关代码都注释掉,等到模型重置后,再将这些代码恢复(撤销屏蔽)
可能出现的地方有(将DRF一同考虑)

• urls.py

• serializer.py

• views.py

• 可以将这些文件都全部注释掉,模型重置完毕后,再解开注释

细节&步骤

• 使用python manage.py showmigrations <appName>查看当前迁移执行情况
• 回滚前,不要删除已有的migration(回滚要依赖于这些已经执行过的文件
• 执行回滚命令不建议使用别名(直接使用全拼命令行,保证所有参数都能够正确被manage.py接收到)
  • python manage.py migrate <appName> <00xxx(replace it with your target migration file name code>
  • 重新使用showmigrations检查撤销情况
• 删除掉已经被撤销执行的migration.py文件
  • 重新使用showmigrations检查撤销情况
• 现在将最新的模型代码进行迁移
  • 执行python manage.py makemigrations <appName>
  • 以及python manage.py migrate <appName>
• 如果全部成功,那么再次查看数据库(建议使用命令行,可以最及时和准确的查看刚刚迁移完毕的数据库)

撤销最近一次成功的迁移

场景实例(当前迁移情况)

# 执行迁移情况查看(当前的应用(django app)是user应用)
python manage.py showmigrations user
 
 [X] 0013_alter_wordsearchhistory_spelling_and_more
 [X] 0014_testforeignkey
 [X] 0015_delete_wordstar
 [X] 0016_wordstar
 [X] 0017_alter_user_signupdate
 [X] 0018_user_openid
 [ ] 0019_alter_user_openid
 

• 现在,想要撤销掉最近一次成功的迁移(0018)
• 我们需要执行的是python manage.py migrate 0017
• 类似于git的代码版本控制回滚那样,将指针移动到了0017

🚀  python manage.py migrate user 0017
 
Operations to perform:
  Target specific migration: 0017_alter_user_signupdate, from user
Running migrations:
  Rendering model states... DONE
  Unapplying user.0018_user_openid... OK
 

回退效果

• 可见,django 提示我们,0018的那一次迁移操作被撤销了

 [X] 0016_wordstar
 [X] 0017_alter_user_signupdate
 [ ] 0018_user_openid
 [ ] 0019_alter_user_openid

逆向fake

• fake的反向操作
• 需要注意的是语法(参数&选项的先后位置),否则起不到作用!

实操

PS D:\repos\ELA\backEnd\ela> manage migrate scoreImprover 0001 --fake
Operations to perform:
  Target specific migration: 0001_initial, from scoreImprover
Running migrations:
  Rendering model states... DONE
  Unapplying scoreImprover.0002_alter_cet4study_wid_alter_cet6study_wid... FAKED

可以看到,0002那一次迁移被伪撤回了

PS D:\repos\ELA\backEnd\ela> pmg showmigrations scoreImprover
scoreImprover
 [X] 0001_initial
 [ ] 0002_alter_cet4study_wid_alter_cet6study_wid
 

migrate 子命令手册

PS D:\repos\ELA\backEnd\ela> .\manage.py migrate  --fake -h      
usage: manage.py migrate [-h] [--noinput] [--database DATABASE] [--fake] [--fake-initial] [--plan] [--run-syncdb]
                         [--check] [--version] [-v {0,1,2,3}] [--settings SETTINGS] [--pythonpath PYTHONPATH]
                         [--traceback] [--no-color] [--force-color] [--skip-checks]
                         [app_label] [migration_name]
 
Updates database schema. Manages both apps with migrations and those without.
 
positional arguments:
  app_label             App label of an application to synchronize the state.
  migration_name        Database state will be brought to the state after that migration. Use the name "zero" to
                        unapply all migrations.
 
options:
  -h, --help            show this help message and exit
  --noinput, --no-input
                        Tells Django to NOT prompt the user for input of any kind.
  --database DATABASE   Nominates a database to synchronize. Defaults to the "default" database.
  --fake                Mark migrations as run without actually running them.
  --fake-initial        Detect if tables already exist and fake-apply initial migrations if so. Make sure that     
                        the current database schema matches your initial migration before using this flag. Django  
                        will only check for an existing table name.
  --plan                Shows a list of the migration actions that will be performed.
  --run-syncdb          Creates tables for apps without migrations.
  --check               Exits with a non-zero status if unapplied migrations exist.
  --version             Show program's version number and exit.
  -v {0,1,2,3}, --verbosity {0,1,2,3}
                        Verbosity level; 0=minimal output, 1=normal output, 2=verbose output, 3=very verbose       
                        output
  --settings SETTINGS   The Python path to a settings module, e.g. "myproject.settings.main". If this isn't        
                        provided, the DJANGO_SETTINGS_MODULE environment variable will be used.
  --pythonpath PYTHONPATH
                        A directory to add to the Python path, e.g. "/home/djangoprojects/myproject".
  --traceback           Raise on CommandError exceptions.
  --no-color            Don't colorize the command output.
  --force-color         Force colorization of the command output.
  --skip-checks         Skip system checks.
 
 

fake&fake-initial

  --fake                Mark migrations as run without actually running them.
  --fake-initial        Detect if tables already exist and fake-apply initial migrations if so. Make sure that     
                        the current database schema matches your initial migration before using this flag. Django  

• First, to clear migrations table:(清理migrations 表,注意这里直接用的是migrate而非makemigrations)

  ./manage.py migrate --fake <app-name> zero

• Remove app-name/migrations/ folder or contents.

• Make the migrations:

  ./manage.py makemigrations <app-name>

• Finally tidy up(整理) your migrations without making other database changes:

  ./manage.py migrate --fake <app-name>