[HDFS-11931] FileSystem Simplify / Optimize listStatus Method

• Type: Improvement
• Status: Patch Available
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 2.7.3, 3.0.0-alpha3
• Component/s: fs
• Flags: Patch
• Assignee: Unassigned
• Reporter: David Mollitor
• Created: 05/Jun/17 15:52
• Updated: 05/Jun/17 18:59

Description

org.apache.hadoop.fs.FileSystem.listStatus(ArrayList<FileStatus>, Path, PathFilter)

  /*
   * Filter files/directories in the given path using the user-supplied path
   * filter. Results are added to the given array <code>results</code>.
   */
  private void listStatus(ArrayList<FileStatus> results, Path f,
      PathFilter filter) throws FileNotFoundException, IOException {
    FileStatus listing[] = listStatus(f);
    if (listing == null) {
      throw new IOException("Error accessing " + f);
    }

    for (int i = 0; i < listing.length; i++) {
      if (filter.accept(listing[i].getPath())) {
        results.add(listing[i]);
      }
    }
  }

org.apache.hadoop.fs.FileSystem.listStatus(Path, PathFilter)

  public FileStatus[] listStatus(Path f, PathFilter filter) 
                                   throws FileNotFoundException, IOException {
    ArrayList<FileStatus> results = new ArrayList<FileStatus>();
    listStatus(results, f, filter);
    return results.toArray(new FileStatus[results.size()]);
  }

We can be smarter about this:

1. Use enhanced for-loops
2. Optimize for the case where there are zero files in a directory, save on object instantiation
3. More encapsulated design

Issue Links

• duplicates: HADOOP-14477 FileSystem Simplify / Optimize listStatus Method