void addGroupOrRangeJunction(AbstractGroupOrRangeJunction gj) {
    if (groupJunctions == null) {
      groupJunctions = new ArrayList();
    }
    groupJunctions.add(gj);
  }
Add the GroupJunction for a Region as a part of CompositeGroupJunction , implying that their
exists atleast one equi join condition which involes the Region which the GroupJunction
represents

@param gj GroupJunction object which is a part of CompositeGroupJunction
geode-core/src/main/java/org/apache/geode/cache/query/internal/CompositeGroupJunction.java