From 06447ac637b254e9b9c1f27ad8decbe5a7615aa6 Mon Sep 17 00:00:00 2001
From: Jeremy Stretch <jstretch@netboxlabs.com>
Date: Wed, 26 Nov 2025 11:48:50 -0500
Subject: [PATCH] Optimize replication of port mappings from DeviceType

---
 netbox/dcim/models/devices.py    | 13 ++++-------
 netbox/dcim/tests/test_models.py |  2 ++
 netbox/dcim/utils.py             | 37 ++++++++++++++++++++++----------
 3 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/netbox/dcim/models/devices.py b/netbox/dcim/models/devices.py
index 2679b7296..423265751 100644
--- a/netbox/dcim/models/devices.py
+++ b/netbox/dcim/models/devices.py
@@ -1,8 +1,7 @@
 import decimal
-import yaml
-
 from functools import cached_property
 
+import yaml
 from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
 from django.contrib.contenttypes.models import ContentType
 from django.core.exceptions import ValidationError
@@ -25,17 +24,15 @@ from extras.querysets import ConfigContextModelQuerySet
 from netbox.choices import ColorChoices
 from netbox.config import ConfigItem
 from netbox.models import NestedGroupModel, OrganizationalModel, PrimaryModel
-from netbox.models.mixins import WeightMixin
 from netbox.models.features import ContactsMixin, ImageAttachmentsMixin
+from netbox.models.mixins import WeightMixin
 from utilities.fields import ColorField, CounterCacheField
 from utilities.prefetch import get_prefetchable_fields
 from utilities.tracking import TrackingModelMixin
-from . import PortTemplateMapping
 from .device_components import *
 from .mixins import RenderConfigMixin
 from .modules import Module
 
-
 __all__ = (
     'Device',
     'DeviceRole',
@@ -1004,6 +1001,8 @@ class Device(
             self._instantiate_components(self.device_type.interfacetemplates.all())
             self._instantiate_components(self.device_type.rearporttemplates.all())
             self._instantiate_components(self.device_type.frontporttemplates.all())
+            # Replicate any front/rear port mappings from the DeviceType
+            create_port_mappings(self, self.device_type)
             # Disable bulk_create to accommodate MPTT
             self._instantiate_components(self.device_type.modulebaytemplates.all(), bulk_create=False)
             self._instantiate_components(self.device_type.devicebaytemplates.all())
@@ -1011,10 +1010,6 @@ class Device(
             self._instantiate_components(self.device_type.inventoryitemtemplates.all(), bulk_create=False)
             # Interface bridges have to be set after interface instantiation
             update_interface_bridges(self, self.device_type.interfacetemplates.all())
-            # Replicate any front/rear port mappings from the DeviceType
-            create_port_mappings(self, PortTemplateMapping.objects.filter(
-                front_port__device_type=self.device_type
-            ))
 
         # Update Site and Rack assignment for any child Devices
         devices = Device.objects.filter(parent_bay__device=self)
diff --git a/netbox/dcim/tests/test_models.py b/netbox/dcim/tests/test_models.py
index cd5ff0936..1f332ed21 100644
--- a/netbox/dcim/tests/test_models.py
+++ b/netbox/dcim/tests/test_models.py
@@ -537,6 +537,8 @@ class DeviceTestCase(TestCase):
         )
         self.assertEqual(frontport.cf['cf1'], 'foo')
 
+        self.assertTrue(PortMapping.objects.filter(front_port=frontport, rear_port=rearport).exists())
+
         modulebay = ModuleBay.objects.get(
             device=device,
             name='Module Bay 1'
diff --git a/netbox/dcim/utils.py b/netbox/dcim/utils.py
index 625003843..f5b94829e 100644
--- a/netbox/dcim/utils.py
+++ b/netbox/dcim/utils.py
@@ -85,20 +85,35 @@ def update_interface_bridges(device, interface_templates, module=None):
             interface.save()
 
 
-def create_port_mappings(device, templates, module=None):
+def create_port_mappings(device, device_type, module=None):
     """
     Replicate all front/rear port mappings from a DeviceType to the given device.
     """
-    from dcim.models.device_components import FrontPort, PortMapping, RearPort
+    from dcim.models import FrontPort, PortMapping, PortTemplateMapping, RearPort
 
+    templates = PortTemplateMapping.objects.filter(
+        front_port__device_type=device_type
+    ).prefetch_related('front_port', 'rear_port')
+
+    # Cache front & rear ports for efficient lookups by name
+    front_ports = {
+        fp.name: fp for fp in FrontPort.objects.filter(device=device)
+    }
+    rear_ports = {
+        rp.name: rp for rp in RearPort.objects.filter(device=device)
+    }
+
+    # Replicate PortMappings
+    mappings = []
     for template in templates:
-        front_port = FrontPort.objects.get(device=device, name=template.front_port.resolve_name(module=module))
-        rear_port = RearPort.objects.get(device=device, name=template.rear_port.resolve_name(module=module))
-
-        assignment = PortMapping(
-            front_port=front_port,
-            front_port_position=template.front_port_position,
-            rear_port=rear_port,
-            rear_port_position=template.rear_port_position,
+        front_port = front_ports.get(template.front_port.resolve_name(module=module))
+        rear_port = rear_ports.get(template.rear_port.resolve_name(module=module))
+        mappings.append(
+            PortMapping(
+                front_port=front_port,
+                front_port_position=template.front_port_position,
+                rear_port=rear_port,
+                rear_port_position=template.rear_port_position,
+            )
         )
-        assignment.save()
+    PortMapping.objects.bulk_create(mappings)