Add index on group_id column concurrently

This fixes previously added migration which caused timeouts on
big events table.

1 files changed, 12 insertions, 2 deletions

diff --git a/db/migrate/20190826100605_add_group_column_to_events.rb b/db/migrate/20190826100605_add_group_column_to_events.rb
index cd7b2b1d96a..dfc9d8cbdf1 100644
--- a/db/migrate/20190826100605_add_group_column_to_events.rb
+++ b/db/migrate/20190826100605_add_group_column_to_events.rb
@@ -1,9 +1,19 @@
 # frozen_string_literal: true
 
 class AddGroupColumnToEvents < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
   DOWNTIME = false
 
-  def change
-    add_reference :events, :group, index: true, foreign_key: { to_table: :namespaces, on_delete: :cascade }
+  disable_ddl_transaction!
+
+  def up
+    add_column(:events, :group_id, :bigint) unless column_exists?(:events, :group_id)
+    add_concurrent_index(:events, :group_id)
+    add_concurrent_foreign_key(:events, :namespaces, column: :group_id, on_delete: :cascade)
+  end
+
+  def down
+    remove_column(:events, :group_id) if column_exists?(:events, :group_id)
   end
 end