Add database unique constraint to Subscribers email field

apps/web/migrations/0011_add_unique_constraint_to_subscribers_email.py

@@ -0,0 +1,50 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 2.2.20 on 2026-02-06 00:00
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+def remove_duplicate_subscribers(apps, schema_editor):
+    """
+    Remove duplicate subscriber entries before adding unique constraint.
+    Keep only the earliest entry for each email address.
+    """
+    Subscribers = apps.get_model("web", "Subscribers")
+    db_alias = schema_editor.connection.alias
+
+    # Get all emails that have duplicates
+    from django.db.models import Count
+    duplicate_emails = (
+        Subscribers.objects.using(db_alias)
+        .values("email")
+        .annotate(count=Count("id"))
+        .filter(count__gt=1)
+    )
+
+    # For each duplicate email, keep the oldest entry and delete the rest
+    for item in duplicate_emails:
+        email = item["email"]
+        subscribers = Subscribers.objects.using(db_alias).filter(email=email).order_by("created_at")
+        # Keep the first (oldest) entry, delete the rest
+        for subscriber in subscribers[1:]:
+            subscriber.delete()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [("web", "0010_add_verbose_name_plural_for_subscribers_model")]
+
+    operations = [
+        # First, remove any duplicate entries
+        migrations.RunPython(
+            remove_duplicate_subscribers,
+            reverse_code=migrations.RunPython.noop,
+        ),
+        # Then add the unique constraint
+        migrations.AlterField(
+            model_name="subscribers",
+            name="email",
+            field=models.EmailField(max_length=70, unique=True),
+        ),
+    ]

apps/web/models.py

@@ -29,7 +29,7 @@ class Meta:
 class Subscribers(TimeStampedModel):
     """Model representing subbscribed user's email"""
 
-    email = models.EmailField(max_length=70)
+    email = models.EmailField(max_length=70, unique=True)
 
     def __str__(self):
         return "{}".format(self.email)