migrations: Switch to AddIndexConcurrently.

zerver/migrations/0510_add_realmauditlog_realm_event_type_index.py

@@ -1,15 +1,18 @@
 # Generated by Django 4.2.12 on 2024-04-17 10:33
 
+from django.contrib.postgres.operations import AddIndexConcurrently
 from django.db import migrations, models
 
 
 class Migration(migrations.Migration):
+    atomic = False
+
     dependencies = [
         ("zerver", "0509_fix_emoji_metadata"),
     ]
 
     operations = [
-        migrations.AddIndex(
+        AddIndexConcurrently(
             model_name="realmauditlog",
             index=models.Index(
                 fields=["realm", "event_type", "event_time"],