private boolean disableMapJoinWithHint(List<ASTNode> hints) {
    if (hints == null || hints.size() == 0) {
      return false;
    }
    for (ASTNode hintNode : hints) {
      for (Node node : hintNode.getChildren()) {
        ASTNode hint = (ASTNode) node;
        if (hint.getChild(0).getType() != HintParser.TOK_MAPJOIN) {
          continue;
        }
        Tree args = hint.getChild(1);
        if (args.getChildCount() == 1) {
          String text = args.getChild(0).getText();
          if (text.equalsIgnoreCase("None")) {
            // Hint to disable mapjoin.
            return true;
          }
        }
      }
    }
    return false;
  }
disableMapJoinWithHint
@param hints
@return true if hint to disable hint is provided, else false
ql/src/java/org/apache/hadoop/hive/ql/parse/SemanticAnalyzer.java