Pre-Size List in AvroInputFormat Avro File Lookup

    if (job.getBoolean(IGNORE_FILES_WITHOUT_EXTENSION_KEY, IGNORE_INPUTS_WITHOUT_EXTENSION_DEFAULT)) {
      List<FileStatus> result = new ArrayList<>();
      for (FileStatus file : super.listStatus(job))
        if (file.getPath().getName().endsWith(AvroOutputFormat.EXT))
          result.add(file);
      return result.toArray(new FileStatus[0]);
    } else {
      return super.listStatus(job);
    }

When a user runs an Avro MR job against a directory, it silently filters out files without an avro file extension. Fair enough. However, anecdotally, this is the primary use scenario, so this code probably does not filter out many files.

I suggest that this ArrayList be pre-sized. If there are a lot of files, and all of them have the avro file extension (base case), this ArrayList will had to be expanded multiple times (time and GC). If there is a large list and it gets filtered down a lot, a few hundred bytes are wasted.