err = errNoSuchPolicy
				return
			}
		}
		newPolicySet = existingPolicySet.Union(policiesToUpdate)
	} else {
		// policies to detach => inputPolicies ∩ existing (intersection)
		policiesToUpdate = policiesToUpdate.Intersection(existingPolicySet)
		newPolicySet = existingPolicySet.Difference(policiesToUpdate)
	}
	// We return an error if the requested policy update will have no effect.

		for _, bucket := range buckets {
			bucketsSet.Add(bucket.Name)
			r, ok := dnsBuckets[bucket.Name]
			if !ok {
				bucketsToBeUpdated.Add(bucket.Name)
				continue
			}
			if !globalDomainIPs.Intersection(set.CreateStringSet(getHostsSlice(r)...)).IsEmpty() {
				if globalDomainIPs.Difference(set.CreateStringSet(getHostsSlice(r)...)).IsEmpty() && !domainMissing {
					// No difference in terms of domainIPs and nothing