fix (migration): update to use an atomic migrateion

apps/inbox/migrations/0002_inboxreply_draft_lifecycle.py

@@ -21,6 +21,12 @@ def _mark_existing_sent(apps, schema_editor):
     for reply in InboxReply.objects.exclude(sent_at=None).iterator():
         InboxReply.objects.filter(pk=reply.pk).update(created_at=reply.sent_at)
 
+    if schema_editor.connection.vendor == "postgresql":
+        # AddField(db_index=True) queues CREATE INDEX until the schema editor
+        # exits. Drain the backfill's deferred FK checks before that DDL runs,
+        # keeping both the schema changes and backfill in one atomic migration.
+        schema_editor.execute("SET CONSTRAINTS ALL IMMEDIATE")
+
 
 def _noop(apps, schema_editor):
     pass

apps/inbox/tests/test_migration_0002.py

@@ -11,6 +11,8 @@
 from datetime import timedelta
 
 import pytest
+from django.db import connection
+from django.db.migrations.executor import MigrationExecutor
 from django.utils import timezone
 
 from apps.inbox.models import InboxMessage, InboxReply
@@ -58,8 +60,57 @@ def test_backfill_marks_existing_replies_sent(message):
         status=InboxReply.Status.DRAFT, sent_at=sent_at, created_at=timezone.now()
     )
 
-    migration_module._mark_existing_sent(global_apps, None)
+    migration_module._mark_existing_sent(global_apps, connection.schema_editor())
 
     reply.refresh_from_db()
     assert reply.status == InboxReply.Status.SENT
     assert reply.created_at == sent_at
+
+
+@pytest.mark.django_db(transaction=True)
+def test_upgrade_with_existing_replies_creates_status_index(message, user):
+    """Run the whole migration, including schema_editor's deferred CREATE INDEX.
+
+    Calling only the backfill misses PostgreSQL's pending-trigger failure when
+    existing rows are updated before the new status index is created.
+    """
+    before = [("inbox", "0001_initial")]
+    after = [("inbox", "0002_inboxreply_draft_lifecycle")]
+    executor = MigrationExecutor(connection)
+    latest = executor.loader.graph.leaf_nodes()
+    executor.migrate(before)
+    old_apps = executor.loader.project_state(before).apps
+    old_reply_model = old_apps.get_model("inbox", "InboxReply")
+    reply_ids = []
+    sent_at = timezone.now() - timedelta(days=7)
+    try:
+        for number in range(2):
+            reply = old_reply_model.objects.create(
+                inbox_message_id=message.pk,
+                author_id=user.pk,
+                body=f"Already delivered {number}",
+                platform_reply_id=f"platform-reply-{number}",
+            )
+            reply_ids.append(reply.pk)
+        old_reply_model.objects.filter(pk__in=reply_ids).update(sent_at=sent_at)
+
+        MigrationExecutor(connection).migrate(after)
+
+        for number, reply_id in enumerate(reply_ids):
+            reply = InboxReply.objects.get(pk=reply_id)
+            assert reply.status == InboxReply.Status.SENT
+            assert reply.created_at == reply.sent_at == sent_at
+            assert reply.body == f"Already delivered {number}"
+            assert reply.platform_reply_id == f"platform-reply-{number}"
+            assert reply.author_id == user.pk
+        with connection.cursor() as cursor:
+            indexes = connection.introspection.get_constraints(cursor, "inbox_reply")
+        assert any(index["index"] and index["columns"] == ["status"] for index in indexes.values())
+        draft = InboxReply.objects.create(inbox_message=message, body="New draft")
+        assert draft.status == InboxReply.Status.DRAFT
+        assert draft.sent_at is None
+        draft.delete()
+    finally:
+        # Restore the schema for the rest of the suite.
+        old_reply_model.objects.filter(pk__in=reply_ids).delete()
+        MigrationExecutor(connection).migrate(latest)