public void setDefinition(String def) {
    Support.Assert((definition == null), "Definition is already set");
    Support.Assert((def != null), "Definition can not be null");
    definition = def;
  }
(Re)evaluate in the context of the current iterations through the cross-product. If this
iterator is not dependent on the current iteration, then just return the previously evaluated
collection. Otherwise, re-evaluate. Returns null if the collection itself is null or UNDEFINED
geode-core/src/main/java/org/apache/geode/cache/query/internal/RuntimeIterator.java