Django migration system creates migrations for existing constraints

Using Django Using the ORM
1

I’ve created constraints by myself in migration because one of our servers have old postgres version and it works quite good, but every time I run makemigrations django creates new migration for this app with this constraints, and then it fails because it’s already here. Here is the code of my hand-written constraints migration for understanding

from django.db import migrations, models, utils, transaction


def add_constraint_if_not_exists(
        apps,
        schema_editor,
        condition,
        fields,
        constraint_name
    ):
    MyModel = apps.get_model(...)

    with transaction.atomic():
        try:
            constraint = models.UniqueConstraint(
                condition=condition,
                fields=fields,
                name=constraint_name
            )
            schema_editor.add_constraint(MyModel, constraint)
        except utils.ProgrammingError:
            transaction.set_rollback(True)


def add_unique_..._constraint(apps, schema_editor):
    condition = models.Q(('field', True))
    fields = ('...', '...', '...')
    add_constraint_if_not_exists(
        apps,
        schema_editor,
        condition,
        fields,
        'unique_fields'
    )


def add_unique_field_constraint(apps, schema_editor):
    condition = models.Q(('field', False))
    fields = ('field',)
    add_constraint_if_not_exists(
        apps,
        schema_editor,
        condition,
        fields,
        'unique_field'
    )


class Migration(migrations.Migration):

    dependencies = [
        ('app_name', '...'),
    ]

    operations = [
        migrations.RunPython(
            add_unique_..._constraint, migrations.RunPython.noop),
        migrations.RunPython(add_unique_field_constraint, migrations.RunPython.noop),
    ]

And when I’m running makemigrations it creates this migration:

from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('app_name', '...'),
    ]

    operations = [
        migrations.AddConstraint(
            model_name='mymodel',
            constraint=models.UniqueConstraint(condition=models.Q(('field', True)), fields=('...', '...', '...'), name='unique_...'),
        ),
        migrations.AddConstraint(
            model_name='mymodel',
            constraint=models.UniqueConstraint(condition=models.Q(('field', False)), fields=('field',), name='unique_field'),
        ),
    ]

What can I do to tell migration system that there is already constraints?

2

Could you please share your model definition? Do you have the constraint defined in the models’ Meta?