snapshot of https://github.com/zulip/zulip.git @ 48c69911c7dd4e03b20552eb3bd77ad8151c1357 (2026-09-15)

zerver/migrations/0074_fix_duplicate_attachments.py

@@ -0,0 +1,52 @@
+# Generated by Django 1.10.5 on 2017-04-13 22:12
+from django.db import migrations
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
+from django.db.migrations.state import StateApps
+from django.db.models import Count
+
+
+def fix_duplicate_attachments(apps: StateApps, schema_editor: BaseDatabaseSchemaEditor) -> None:
+    """Migration 0041 had a bug, where if multiple messages referenced the
+    same attachment, rather than creating a single attachment object
+    for all of them, we would incorrectly create one for each message.
+    This results in exceptions looking up the Attachment object
+    corresponding to a file that was used in multiple messages that
+    predate migration 0041.
+
+    This migration fixes this by removing the duplicates, moving their
+    messages onto a single canonical Attachment object (per path_id).
+    """
+    Attachment = apps.get_model("zerver", "Attachment")
+    # Loop through all groups of Attachment objects with the same `path_id`
+    for group in (
+        Attachment.objects.values("path_id")
+        .annotate(Count("id"))
+        .order_by()
+        .filter(id__count__gt=1)
+    ):
+        # Sort by the minimum message ID, to find the first attachment
+        attachments = sorted(
+            Attachment.objects.filter(path_id=group["path_id"]).order_by("id"),
+            key=lambda x: min(x.messages.all().values_list("id")[0]),
+        )
+        surviving = attachments[0]
+        to_cleanup = attachments[1:]
+        for a in to_cleanup:
+            # For each duplicate attachment, we transfer its messages
+            # to the canonical attachment object for that path, and
+            # then delete the original attachment.
+            for msg in a.messages.all():
+                surviving.messages.add(msg)
+            surviving.is_realm_public = surviving.is_realm_public or a.is_realm_public
+            surviving.save()
+            a.delete()
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("zerver", "0073_custom_profile_fields"),
+    ]
+
+    operations = [
+        migrations.RunPython(fix_duplicate_attachments, elidable=True),
+    ]