Fix #7365: Optimize calculation of prefix utilization

Author: shuichiro-makigaki

netbox/ipam/models/ip.py

@@ -487,11 +487,9 @@ def get_utilization(self):
             utilization = int(float(child_prefixes.size) / self.prefix.size * 100)
         else:
             # Compile an IPSet to avoid counting duplicate IPs
-            child_ips = netaddr.IPSet()
-            for iprange in self.get_child_ranges():
-                child_ips.add(iprange.range)
-            for ip in self.get_child_ips():
-                child_ips.add(ip.address.ip)
+            child_ips = netaddr.IPSet(
+                [_.range for _ in self.get_child_ranges()] + [_.address.ip for _ in self.get_child_ips()]
+            )
 
             prefix_size = self.prefix.size
             if self.prefix.version == 4 and self.prefix.prefixlen < 31 and not self.is_pool: