code: func (b *lowBuilder) oldDBNames(of dbname) string {
  	switch of {
  	case dbIndex:
  		return "camlistore_index"
  	case dbBlobpackedIndex:
  		return "blobpacked_index"
  	case "queue-sync-to-index":
  		return "sync_index_queue"
  	case dbUIThumbcache:
  		return "ui_thumbmeta_cache"
  	}
  	return ""
  }
docs: // As of rev 7eda9fd5027fda88166d6c03b6490cffbf2de5fb, we changed how the
  // databases names were defined. But we wanted the existing GCE instances to keep
  // on working with the old names, so that nothing would break for existing users,
  // without any intervention needed. Through the help of the perkeep-config-version
  // variable, set by the GCE launcher, we can know whether an instance is such an
  // "old" one, and in that case we keep on using the old database names. oldDBNames
  // returns these names.