Querying Hazelcast hierarchical tree structures - mapreduce

Question

I'm trying to figure out how to query hierarchical tree structures in Hazelcast. Let's say I have an Organization class:
public class Organization {
private long id;
private long parentId;
}
and I have a User class:
public class NestupUser extends BaseEntity {
private long id;
private String firstName;
private String lastName;
private String email;
private String password;
private long organizationId;
}
Now, given an organizationId I want to find all users for that organization and all organizations which have that organization as a parent, have those organizations as a parent, etc.
I assume this would work as some sort of MapReduce, but is it possible to kick off more MapReduce tasks as part of one MapReduce?
Any help appreciated.

Answer 1

I ended up building a denormalized multimap so I could find all of the reachable organizations for a given org id. This is the code that sets up the structure on startup if it's not already set up by another node. This class also implements the entry listener interfaces to get callbacks when things change to keep the structure in sync (not shown, but not hard to do):
#PostConstruct
public void init() {
IMap<String, Organization> organizationMap = organizationService.getMap();
listenerRegistration = organizationMap.addLocalEntryListener(this);
MultiMap<String, String> orgStructureMap = getOrgStructureMap();
if (orgStructureMap.keySet().size() == 0) {
Collection<Organization> all = organizationService.getAll(null);
Set<String> visited = new HashSet<>();
for (Organization next : all) {
if (!visited.contains(next.getId())) {
while (next != null && next.getParentId() != null && !visited.contains(next.getParentId())) {
next = next.getParentOrganization();
}
recurseReferences(visited, next);
}
}
}
}
private void recurseReferences(Set<String> visited, Organization org) {
addAllReferences(org);
visited.add(org.getId());
Set<Organization> childOrganizations = org.getChildOrganizations();
for (Organization child : childOrganizations) {
recurseReferences(visited, child);
}
}
private void addAllReferences(Organization organization) {
MultiMap<String, String> orgStructureMap = getOrgStructureMap();
String parentId = organization.getParentId();
if (parentId != null) {
Set<Map.Entry<String, String>> entries = orgStructureMap.entrySet();
for (Map.Entry<String, String> next : entries) {
if (next.getValue().equals(parentId)) {
orgStructureMap.put(next.getKey(),organization.getId());
}
}
}
orgStructureMap.put(organization.getId(), organization.getId());
}
private void removeAllReferences(Organization organization) {
MultiMap<String, String> orgStructureMap = getOrgStructureMap();
Set<String> keys = orgStructureMap.keySet();
for (String key : keys) {
orgStructureMap.remove(key, organization.getId());
}
}