Search is slow (non-Elasticsearch version)

We are apparently not prioritising the ability to enable ES on GitLab.com, but we have another problem: the non-ES search is really slow: https://performance.gitlab.net/dashboard/db/rails-controllers?orgId=1&from=now-6h&to=now&var-action=SearchController%23show&var-database=Production

Here's the dashboard: https://performance.gitlab.net/dashboard/db/rails-controllers?orgId=1&from=now-6h&to=now&var-action=SearchController%23show&var-database=Production

https://gitlab.com/gitlab-com/infrastructure/issues/3291 will set the statement timeout to 15s on 1 February, which means that this page will just start 500-ing.

We need to either work on this, or on getting ES ready for GitLab.com, or both.