fix: handle duplicates when applying CompontentType constraint

src/openedx_content/migrations/0004_componenttype_constraint.py

@@ -1,6 +1,35 @@
-# Generated by Django 5.2.11 on 2026-03-02 23:37
-
 from django.db import migrations, models
+from django.db.models import Count, Min
+
+
+def consolidate_duplicate_component_types(apps, schema_editor):
+    """
+    Older installations may have multiple ComponentType rows with the same
+    (namespace, name) due to a missing unique constraint.
+
+    Before we apply the constraint, we need to fix the data by removing the
+    duplicate entries. For each set of duplicates, keep the earliest row (lowest
+    ID), repoint any Components that referenced the duplicates to it, then
+    delete the duplicates so the new unique constraint can be applied cleanly.
+    """
+    ComponentType = apps.get_model("openedx_content", "ComponentType")
+    Component = apps.get_model("openedx_content", "Component")
+
+    duplicate_groups = (
+        ComponentType.objects.values("namespace", "name").annotate(num=Count("id"), keep_id=Min("id")).filter(num__gt=1)
+    )
+
+    for group in duplicate_groups:
+        keep_id = group["keep_id"]
+        duplicate_ids = list(
+            ComponentType.objects.filter(namespace=group["namespace"], name=group["name"])
+            .exclude(id=keep_id)
+            .values_list("id", flat=True)
+        )
+        Component.objects.filter(component_type_id__in=duplicate_ids).update(
+            component_type_id=keep_id,
+        )
+        ComponentType.objects.filter(id__in=duplicate_ids).delete()
 
 
 class Migration(migrations.Migration):
@@ -9,6 +38,10 @@ class Migration(migrations.Migration):
     ]
 
     operations = [
+        migrations.RunPython(
+            consolidate_duplicate_component_types,
+            reverse_code=migrations.RunPython.noop,
+        ),
         migrations.AddConstraint(
             model_name="componenttype",
             constraint=models.UniqueConstraint(fields=("namespace", "name"), name="oel_component_type_uniq_ns_n"),