change linked orderpositions to many-to-many

src/pretix/base/migrations/0297_add_reusablemedium_secret.py

@@ -0,0 +1,30 @@
+# Generated by Django 4.2.26 on 2025-11-24 11:32
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("pretixbase", "0296_invoice_invoice_from_state"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="reusablemedium",
+            name="secret",
+            field=models.CharField(max_length=200, null=True),
+        ),
+        # use temporary related_name "linked_mediums" for ManyToManyField, so we can migrate existing data
+        migrations.AddField(
+            model_name="reusablemedium",
+            name="linked_orderpositions",
+            field=models.ManyToManyField(
+                related_name="linked_mediums", to="pretixbase.orderposition"
+            ),
+        ),
+        migrations.RunSQL(
+            sql="INSERT INTO pretixbase_reusablemedium_linked_orderpositions (reusablemedium_id, orderposition_id) SELECT id, linked_orderposition_id FROM pretixbase_reusablemedium;",
+            reverse_sql="DELETE FROM pretixbase_reusablemedium_linked_orderpositions;",
+        ),
+    ]

src/pretix/base/migrations/0298_reusablemedium_remove_orderposition.py

@@ -0,0 +1,46 @@
+# Generated by Django 4.2.26 on 2025-11-24 11:32
+
+from django.db import migrations, models
+
+
+def reverse(apps, schema_editor):
+    ReusableMedium = apps.get_model('pretixbase', 'ReusableMedium')
+
+    qs = ReusableMedium.linked_orderpositions.through.objects
+    objs = []
+    # get last added orderposition from linked_orderpositions
+    for rm_id, op_id in qs.filter(id__in=qs.values("reusablemedium_id").annotate(max_id=models.Max('id')).values('max_id')).values_list("reusablemedium_id", "orderposition_id"):
+        #obj = ReusableMedium.objects.get(id=rm_id)
+        #obj.linked_orderposition_id = op_id
+        obj = ReusableMedium(
+            id=rm_id,
+            linked_orderposition_id=op_id,
+        )
+        objs.append(obj)
+
+    ReusableMedium.objects.bulk_update(objs, ['linked_orderposition_id'])
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("pretixbase", "0297_add_reusablemedium_secret"),
+    ]
+
+    operations = [
+        # according to the docs, UPDATE FROM should run similarly on sqlite and postgres, but I could not get it to work
+        # so roll back the data migration with code before deleting data from through-table in 0297
+        migrations.RunPython(migrations.RunPython.noop, reverse),
+        migrations.RemoveField(
+            model_name="reusablemedium",
+            name="linked_orderposition",
+        ),
+        # change related_name for new ManyToManyField to previously used linked_media
+        migrations.AlterField(
+            model_name="reusablemedium",
+            name="linked_orderpositions",
+            field=models.ManyToManyField(
+                related_name="linked_media", to="pretixbase.orderposition"
+            ),
+        ),
+    ]

src/pretix/base/models/media.py

@@ -72,6 +72,11 @@ class ReusableMedium(LoggedModel):
         max_length=200,
         verbose_name=pgettext_lazy('reusable_medium', 'Identifier'),
     )
+    secret = models.CharField(
+        max_length=200,
+        verbose_name=pgettext_lazy('reusable_medium', 'Secret'),
+        null=True, blank=True
+    )
 
     active = models.BooleanField(
         verbose_name=_('Active'),
@@ -89,12 +94,10 @@ class ReusableMedium(LoggedModel):
         on_delete=models.SET_NULL,
         verbose_name=_('Customer account'),
     )
-    linked_orderposition = models.ForeignKey(
+    linked_orderpositions = models.ManyToManyField(
         OrderPosition,
-        null=True, blank=True,
         related_name='linked_media',
-        on_delete=models.SET_NULL,
-        verbose_name=_('Linked ticket'),
+        verbose_name=_('Linked tickets'),
     )
     linked_giftcard = models.ForeignKey(
         GiftCard,
@@ -111,6 +114,11 @@ class ReusableMedium(LoggedModel):
 
     objects = ReusableMediumQuerySetManager()
 
+    @cached_property
+    def linked_orderposition(self):
+        # always return last added linked_orderposition to make it behave backwardscompatible
+        return self.linked_orderpositions.order_by('pk').last()
+
     @cached_property
     def media_type(self):
         return MEDIA_TYPES[self.type]