public boolean isRuntimeConstant() {
    boolean result = FunctionRegistry.isRuntimeConstant(genericUDF);
    for (ExprNodeEvaluator child : children) {
      if(result = result || child.isRuntimeConstant()) {
        return result;
      }
    }
    return result;
  }
Class to allow deferred evaluation for GenericUDF.
ql/src/java/org/apache/hadoop/hive/ql/exec/ExprNodeGenericFuncEvaluator.java