How can I perform data migration using Django ORM?

How can I perform data migration using Django ORM?

You can perform data migration in Django ORM by using the migrations framework. First, create a migration file using python manage.py makemigrations, then apply it with python manage.py migrate. This will update your database schema.

What if I need to migrate data from one model to another?

You can create a custom migration file where you define the operations to copy data from one model to another. Use the RunPython operation to write a function that handles the data transfer.

Can you show me an example of a custom migration?

Sure! Here's a simple example:

from django.db import migrations

def copy_data(apps, schema_editor):
    OldModel = apps.get_model('app_name', 'OldModel')
    NewModel = apps.get_model('app_name', 'NewModel')
    for old_instance in OldModel.objects.all():
        NewModel.objects.create(field1=old_instance.field1, field2=old_instance.field2)

class Migration(migrations.Migration):
    dependencies = [
        ('app_name', 'previous_migration'),
    ]
    operations = [
        migrations.RunPython(copy_data),
    ]

What should I do if the migration fails?

If a migration fails, you can roll back the migration using python manage.py migrate app_name previous_migration. Check the error message for details and fix any issues before trying again.