code: func warnMultipleDBs() {
  	// This is intentionally not using the known db types which depend
  	// on the database types compiled into the binary since we want to
  	// detect legacy db types as well.
  	dbTypes := []string{"ffldb", "leveldb", "sqlite"}
  	duplicateDbPaths := make([]string, 0, len(dbTypes)-1)
  	for _, dbType := range dbTypes {
  		if dbType == cfg.DbType {
  			continue
  		}
  
  		// Store db path as a duplicate db if it exists.
  		dbPath := blockDbPath(dbType)
  		if fileExists(dbPath) {
  			duplicateDbPaths = append(duplicateDbPaths, dbPath)
  		}
  	}
  
  	// Warn if there are extra databases.
  	if len(duplicateDbPaths) > 0 {
  		selectedDbPath := blockDbPath(cfg.DbType)
  		btcdLog.Warnf("WARNING: There are multiple block chain databases "+
  			"using different database types.\nYou probably don't "+
  			"want to waste disk space by having more than one.\n"+
  			"Your current database is located at [%v].\nThe "+
  			"additional database is located at %v", selectedDbPath,
  			duplicateDbPaths)
  	}
  }
docs: // warnMultipleDBs shows a warning if multiple block database types are detected.
  // This is not a situation most users want.  It is handy for development however
  // to support multiple side-by-side databases.