def get_path(self):
"""
Return the path as a list of prefetched objects.
"""
# Compile a list of IDs to prefetch for each type of model in the path
to_prefetch = defaultdict(list)
for node in self.path:
ct_id, object_id = decompile_path_node(node)
to_prefetch[ct_id].append(object_id)
# Prefetch path objects using one query per model type. Prefetch related devices where appropriate.
prefetched = {}
for ct_id, object_ids in to_prefetch.items():
model_class = ContentType.objects.get_for_id(ct_id).model_class()
queryset = model_class.objects.filter(pk__in=object_ids)
if hasattr(model_class, "device"):
queryset = queryset.prefetch_related("device")
prefetched[ct_id] = {obj.id: obj for obj in queryset}
# Replicate the path using the prefetched objects.
path = []
for node in self.path:
ct_id, object_id = decompile_path_node(node)
path.append(prefetched[ct_id][object_id])
return path
def get_total_length(self):
"""
Return the sum of the length of each cable in the path.
"""
cable_ids = [
# Starting from the first element, every third element in the path should be a Cable
decompile_path_node(self.path[i])[1]
for i in range(0, len(self.path), 3)
]
return Cable.objects.filter(id__in=cable_ids).aggregate(total=Sum("_abs_length"))["total"]