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

zerver/migrations/0287_clear_duplicate_reactions.py

@@ -0,0 +1,38 @@
+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 clear_duplicate_reactions(apps: StateApps, schema_editor: BaseDatabaseSchemaEditor) -> None:
+    """Zulip's data model for reactions has enforced via code,
+    nontransactionally, that they can only react with one emoji_code
+    for a given reaction_type.  This fixes any that were stored in the
+    database via a race; the next migration will add the appropriate
+    database-level unique constraint.
+    """
+    Reaction = apps.get_model("zerver", "Reaction")
+
+    duplicate_reactions = (
+        Reaction.objects.all()
+        .values("user_profile_id", "message_id", "reaction_type", "emoji_code")
+        .annotate(Count("id"))
+        .filter(id__count__gt=1)
+    )
+    for duplicate_reaction in duplicate_reactions:
+        duplicate_reaction.pop("id__count")
+        to_cleanup = Reaction.objects.filter(**duplicate_reaction)[1:]
+        for reaction in to_cleanup:
+            reaction.delete()
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("zerver", "0286_merge_0260_0285"),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            clear_duplicate_reactions, reverse_code=migrations.RunPython.noop, elidable=True
+        ),
+    ]