Sith/counter/migrations/0025_alter_studentcard_customer.py

# Generated by Django 4.2.16 on 2024-11-15 12:34
from __future__ import annotations

from operator import attrgetter
from typing import TYPE_CHECKING

import django.db.models.deletion
from django.db import migrations, models
from django.db.models import Count

if TYPE_CHECKING:
    from django.db.backends.postgresql.schema import DatabaseSchemaEditor
    from django.db.migrations.state import StateApps


def delete_duplicates(apps: StateApps, schema_editor: DatabaseSchemaEditor):
    """Delete cards of users with more than one student cards.

    For all users who have more than one registered student card, all
    the cards except the last one are deleted.
    """
    Customer = apps.get_model("counter", "Customer")
    StudentCard = apps.get_model("counter", "StudentCard")
    customers = (
        Customer.objects.annotate(nb_cards=Count("student_cards"))
        .filter(nb_cards__gt=1)
        .prefetch_related("student_cards")
    )
    to_delete = [
        card.id
        for customer in customers
        for card in sorted(customer.student_cards.all(), key=attrgetter("id"))[:-1]
    ]
    StudentCard.objects.filter(id__in=to_delete).delete()


class Migration(migrations.Migration):
    dependencies = [("counter", "0024_accountdump_accountdump_unique_ongoing_dump")]

    operations = [
        migrations.RunPython(delete_duplicates, migrations.RunPython.noop),
        migrations.AlterField(
            model_name="studentcard",
            name="customer",
            field=models.OneToOneField(
                on_delete=django.db.models.deletion.CASCADE,
                related_name="student_card",
                to="counter.customer",
                verbose_name="student card",
            ),
        ),
    ]