Change migration to rename concurrently

In order to prevent downtime, rename columns concurrently

db/migrate/20190801193427_rename_application_settings_snowplow_collector_uri_column.rb

 # frozen_string_literal: true
 
-# See http://doc.gitlab.com/ce/development/migration_style_guide.html
-# for more information on how to write migrations for GitLab.
-
 class RenameApplicationSettingsSnowplowCollectorUriColumn < ActiveRecord::Migration[5.2]
   include Gitlab::Database::MigrationHelpers
 
   DOWNTIME = false
 
-  def change
-    rename_column :application_settings, :snowplow_collector_uri, :snowplow_collector_hostname
+  disable_ddl_transaction!
+
+  def up
+    rename_column_concurrently :application_settings, :snowplow_collector_uri, :snowplow_collector_hostname
+  end
+
+  def down
+    cleanup_concurrent_column_rename :application_settings, :snowplow_collector_hostname, :snowplow_collector_uri
   end
 end

db/post_migrate/20190802091750_cleanup_application_settings_snowplow_collector_uri_rename.rb

+# frozen_string_literal: true
+
+class CleanupApplicationSettingsSnowplowCollectorUriRename < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    cleanup_concurrent_column_rename :application_settings, :snowplow_collector_uri, :snowplow_collector_hostname
+  end
+
+  def down
+    rename_column_concurrently :application_settings, :snowplow_collector_hostname, :snowplow_collector_uri
+  end
+end