private static Object getLiteral(Configuration conf, ExprNodeDesc child, BoxType boxType) {
    if (child instanceof ExprNodeConstantDesc) {
      return boxLiteral((ExprNodeConstantDesc) child, boxType);
    } else if (child instanceof ExprNodeDynamicValueDesc) {
      LiteralDelegate value = ((ExprNodeDynamicValueDesc) child).getDynamicValue();
      value.setConf(conf);
      return value;
    }
    return null;
  }
Find the child that is the literal.
@param expr the parent node to check
@param boxType the type of the expression
@return the literal boxed if found or null
ql/src/java/org/apache/hadoop/hive/ql/io/sarg/ConvertAstToSearchArg.java