akkoma/priv/repo/migrations/20190115085500_create_user_fts_index.exs

defmodule Pleroma.Repo.Migrations.CreateUserFtsIndex do
  use Ecto.Migration

  def change do
    create_if_not_exists index(
             :users,
             [
               """
               (setweight(to_tsvector('simple', regexp_replace(nickname, '\\W', ' ', 'g')), 'A') ||
               setweight(to_tsvector('simple', regexp_replace(coalesce(name, ''), '\\W', ' ', 'g')), 'B'))
               """
             ],
             name: :users_fts_index,
             using: :gin
           )
  end
end