1 files changed, 29 insertions, 0 deletions
diff --git a/db/post_migrate/20200128132510_add_temporary_index_for_notes_with_mentions.rb b/db/post_migrate/20200128132510_add_temporary_index_for_notes_with_mentions.rb
new file mode 100644
index 00000000000..bd55485f871
--- /dev/null
+++ b/db/post_migrate/20200128132510_add_temporary_index_for_notes_with_mentions.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+class AddTemporaryIndexForNotesWithMentions < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  INDEX_CONDITION = "note LIKE '%@%'::text"
+  INDEX_NAME = 'note_mentions_temp_index'
+
+  EPIC_MENTIONS_INDEX_NAME = 'epic_mentions_temp_index'
+  DESIGN_MENTIONS_INDEX_NAME = 'design_mentions_temp_index'
+
+  def up
+    # create temporary index for notes with mentions, may take well over 1h
+    add_concurrent_index(:notes, [:id, :noteable_type], where: INDEX_CONDITION, name: INDEX_NAME)
+
+    # cleanup previous temporary indexes, as we'll be usig the single one
+    remove_concurrent_index(:notes, :id, name: EPIC_MENTIONS_INDEX_NAME)
+    remove_concurrent_index(:notes, :id, name: DESIGN_MENTIONS_INDEX_NAME)
+  end
+
+  def down
+    remove_concurrent_index(:notes, :id, name: INDEX_NAME)
+
+    add_concurrent_index(:notes, :id, where: "#{INDEX_CONDITION} AND noteable_type='Epic'", name: EPIC_MENTIONS_INDEX_NAME)
+    add_concurrent_index(:notes, :id, where: "#{INDEX_CONDITION} AND noteable_type='DesignManagement::Design'", name: DESIGN_MENTIONS_INDEX_NAME)
+  end
+end