Migrations

Since Django 1.7

New In Django 1.7

Commands

  • Makemigrations

    python manage.py makemigrations
    
  • Migrate

    python manage.py migrate
    
  • Forwards/Backwards

    • Database and Django_migrations Both Change

      python manage.py migrate app_name 0001
      
    • Database Not and Django_migrations Change

      python manage.py migrate app_name 0001 --fake
      

Problems

  • ValueError: Cannot serialize:

    • Models

      uid = models.CharField(_(u'uid'), max_length=255, default=shortuuid.uuid, help_text=u'User UUID', db_index=True)
      
    • Description

      ValueError: Cannot serialize: <bound method ShortUUID.uuid of <shortuuid.main.ShortUUID object at 0x1025eab90>>
      There are some values Django cannot serialize into migration files.
      For more, see https://docs.djangoproject.com/en/1.8/topics/migrations/#migration-serializing
      
    • Solution

      • Use ShortUUIDField

      • Installation

        pip install django-shortuuidfield
        
      • ​Usage

        from shortuuidfield import ShortUUIDField
        
        uid = ShortUUIDField(_(u'uid'), max_length=255, help_text=u'User UUID', db_index=True)
        
  • No changes detected

    • python manage.py makemigrations - No changes detected
    • python manage.py makemigrations app_name - Changes detected

South

  • Conflict

    There is no South database module 'south.db.mysql' for your database. Please either choose a supported database, check for SOUTH_DATABASE_ADAPTER[S] settings, or remove South from INSTALLED_APPS.
    

Before Django 1.7

South

  • Install

    pip install south
    

Commands

  • Initial

    python manage.py schemamigration app_name --initial
    
  • Add-On Field

    python manage.py schemamigration app_name --auto
    
  • Exists Projects Convert to Use South

    python manage.py syncdb  # Syncdb has already changed by South, to create table ``south_migrationhistory`` in Database
    python manage.py convert_to_south app_name  # create 0001_initial.py, insert record in table ``south_migrationhistory``
    
  • Forwards/Backwards

    • Database and South_migrationhistory Both Change

      python manage.py migrate app_name 0001
      
    • Database Not and South_migrationhistory Change

      python manage.py migrate app_name 0001 --fake
      

Problems

  • Multiple Branches

    • Suppose app_name developed in two branches(master and branch2) from 0004

    • At the time of merge, mater is 0007 and branch2 is 0008, and they don't add the same field

    • Solve multiple branches merge

      • Exec command in master branch

        git merge branch2
        
      • Solve conflict

      • south_migrationhistory back to 004

        python manage.py migrate app_name 0004 --fake
        
      • delete migrations after 0004

      • create new migration

        python manage.py schemamigration app_name --auto
        
      • south_migrationhistory back to 0005

        python manage.py migrate app_name 0005 --fake
        

Problems

  • Problem after Migrate
    django.db.utils.OperationalError: (1366, "Incorrect string value: '\\xE6\\x95\\xB0\\xE6\\x8D\\xAE...' for column 'name' at row 1")
    

References

[1] [email protected], There is no South database module 'south.db.postgresql_psycopg2' for your database

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