@Override public boolean preVisit(final Operator visitable) { int degree = GenericTestPlan.this.getDegreeOfParallelism(); if (visitable instanceof GenericDataSource<?>) degree = 1; else if (degree > 1 && visitable instanceof FileDataSink) try { final Path path = new Path(((FileDataSink) visitable).getFilePath()); final FileSystem fs = path.getFileSystem(); final FileStatus f = fs.getFileStatus(path); if (!f.isDir()) { fs.delete(path, false); fs.mkdirs(path); } } catch (final IOException e) { e.printStackTrace(); } if (visitable.getDegreeOfParallelism() == -1) visitable.setDegreeOfParallelism(degree); return true; } });