Merge pull request #1732 from mitodl/add-migration-to-delete-invalid-…

…redemptions

add migration to delete duplicate discount redemption

ecommerce/migrations/0035_delete_duplicate_discountredemption.py

@@ -0,0 +1,41 @@
+# Generated by Django 3.2.18 on 2023-07-07 15:13
+
+from django.db import migrations
+from django.db.models import Count
+
+
+def delete_duplicate_discountredemption(apps, schema_editor):
+    DiscountRedemption = apps.get_model("ecommerce", "DiscountRedemption")
+
+    duplicate_ids = (
+        DiscountRedemption.objects.values("redeemed_order_id")
+        .annotate(num_orders=Count("redeemed_order_id"))
+        .filter(num_orders__gt=1)
+        .values_list("redeemed_order_id", flat=True)
+    )
+
+    # sort duplicate DiscountRedemption so that the same orders group together with the most recent one on top
+    duplicate_redemptions = (
+        DiscountRedemption.objects.filter(redeemed_order_id__in=duplicate_ids)
+        .order_by("redeemed_order_id", "-created_on")
+        .all()
+    )
+
+    last_seen_order_id = 0
+    for row in duplicate_redemptions:
+        if row.redeemed_order_id == last_seen_order_id:
+            row.delete()
+        else:
+            last_seen_order_id = row.redeemed_order_id
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("ecommerce", "0034_add_bulk_field_to_discounts"),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            delete_duplicate_discountredemption, migrations.RunPython.noop
+        ),
+    ]