docs: private void clearSwapDir() throws IOException {
          if (! m_blockPathMap.isEmpty()) {
              throw new IllegalStateException("Attempt to clear swap directory when "
                      + "there are still managed blocks; use releaseAllBlocks() instead");
          }
  
          try (DirectoryStream<Path> dirStream = Files.newDirectoryStream(m_largeQuerySwapPath)) {
              Iterator<Path> it = dirStream.iterator();
              while (it.hasNext()) {
                  Path path = it.next();
                  VoltFile.recursivelyDelete(path.toFile());
              }
          }
      }