Intermediate solution set of delta iteration

Hi all, Are there any approaches here I could get intermediate solution sets from every delta iteration? I tried union but the compiler gave me the error: Exception in thread "main" org.apache.flink.api.common.InvalidProgramException: Error: The only operations allowed on the solution set are Joi

Using a POJO class wrapping an ArrayList

Hi all, Now I am building a POJO class for key selectors. Here is the class: public class Ids implements Comparable, Serializable{ private static final long serialVersionUID = 1L; private ArrayList ids = new ArrayList(); Ids() {}