Safer Background Reindex: slice batches + checkpoints

                  class Search::ReindexSnipsJob < ApplicationJob
  queue_as :search

  def perform(batch_size: 500)
    checkpoint = ReindexCheckpoint.find_or_create_by!(name: 'snips') { |c| c.last_id = 0 }

    Snip.where('id > ?', checkpoint.last_id).order(id: :asc).limit(batch_size).each do |snip|
      SearchIndex.upsert(document_id: snip.id, body: { title: snip.title })
      checkpoint.update!(last_id: snip.id)
    end
  end
end