class FunctionRegistryHolder implements AutoCloseable {

  public List<DrillFuncHolder> getHoldersByFunctionName(String functionName, AtomicInteger version) {
    try (@SuppressWarnings("unused") Closeable lock = readLock.open()) {
      if (version != null) {
        version.set(this.version);
      }
      Map<String, DrillFuncHolder> holders = functions.get(functionName);
      return holders == null ? new ArrayList<>() : new ArrayList<>(holders.values());
    }
  }

  public  FunctionRegistryHolder();

}