DEV: Make recent creation of chat index idempotent (#19603)

plugins/chat/db/migrate/20221219082223_add_index_to_chat_messages.rb

@@ -3,7 +3,20 @@
 class AddIndexToChatMessages < ActiveRecord::Migration[7.0]
   disable_ddl_transaction!
 
-  def change
-    add_index :chat_messages, [:chat_channel_id, :id], where: "deleted_at IS NULL", algorithm: :concurrently
+  def up
+    # Transaction has been disabled so we need to clean up the invalid index if index creation timeout
+    execute <<~SQL
+    DROP INDEX CONCURRENTLY IF EXISTS index_chat_messages_on_chat_channel_id_and_id
+    SQL
+
+    execute <<~SQL
+    CREATE INDEX CONCURRENTLY index_chat_messages_on_chat_channel_id_and_id
+    ON chat_messages (chat_channel_id,id)
+    WHERE deleted_at IS NOT NULL
+    SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
   end
 end