@Override
  public Set<WriteEntity> getAllOutputs() {
    return outputs;
  }
Verifies the file path existence. If the path is a directory, then it is
verified to not be a glob pattern. If the path is a file, then it is
verified to be a valid file name.
ql/src/java/org/apache/hadoop/hive/ql/parse/LoadSemanticAnalyzer.java