private static boolean[] findPresentStreamsByColumn(
      List<OrcProto.Stream> streamList, List<OrcProto.Type> types) {
    boolean[] hasNull = new boolean[types.size()];
    for(OrcProto.Stream stream: streamList) {
      if (stream.hasKind() && (stream.getKind() == OrcProto.Stream.Kind.PRESENT)) {
        hasNull[stream.getColumn()] = true;
      }
    }
    return hasNull;
  }
Given a list of Streams find out which of them have a present stream.
(Present stream means that there are Null values)
@param streamList a list of streams
@param types stream types
@return a boolean array indexed by streamIds (true when a stream has Nulls)
ql/src/java/org/apache/hadoop/hive/ql/io/orc/encoded/EncodedReaderImpl.java