Index elasticsearch_indexed_namespaces created_at

For find latest inserted records to rollback

db/migrate/20191225071320_add_index_to_elasticsearch_indexed_namespaces.rb

+# frozen_string_literal: true
+
+class AddIndexToElasticsearchIndexedNamespaces < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index(:elasticsearch_indexed_namespaces, :created_at)
+  end
+
+  def down
+    remove_concurrent_index(:elasticsearch_indexed_namespaces, :created_at)
+  end
+end

db/schema.rb

@@ -1460,6 +1460,7 @@ ActiveRecord::Schema.define(version: 2020_01_02_170221) do
     t.datetime_with_timezone "created_at", null: false
     t.datetime_with_timezone "updated_at", null: false
     t.integer "namespace_id"
+    t.index ["created_at"], name: "index_elasticsearch_indexed_namespaces_on_created_at"
     t.index ["namespace_id"], name: "index_elasticsearch_indexed_namespaces_on_namespace_id", unique: true
   end