More efficient thumbnail field

src/backend/InvenTree/InvenTree/serializers.py

@@ -944,6 +944,26 @@ class InvenTreeAttachmentSerializerField(serializers.FileField):
         return default_storage.url(str(value))
 
 
+class InvenTreeThumbnailField(serializers.CharField):
+    """Read-only field which renders the thumbnail URL for a model instance.
+
+    The instance must implement get_thumbnail_url() (e.g. InvenTreeImageMixin).
+
+    Note: This is more efficient than CharField(source='get_thumbnail_url'),
+    as DRF inspects the signature of a callable source for every serialized row.
+    """
+
+    def __init__(self, **kwargs):
+        """Initialize the field as read-only, sourced from the instance itself."""
+        kwargs['source'] = '*'
+        kwargs['read_only'] = True
+        super().__init__(**kwargs)
+
+    def to_representation(self, value):
+        """Return the thumbnail URL for the provided instance."""
+        return value.get_thumbnail_url()
+
+
 class InvenTreeImageSerializerField(serializers.ImageField):
     """Custom image serializer.
 

src/backend/InvenTree/company/serializers.py

@@ -23,6 +23,7 @@ from InvenTree.serializers import (
     InvenTreeModelSerializer,
     InvenTreeMoneySerializer,
     InvenTreeTaggitSerializer,
+    InvenTreeThumbnailField,
     OptionalField,
     apply_duplicate_copy_options,
 )
@@ -58,7 +59,7 @@ class CompanyBriefSerializer(InvenTreeModelSerializer):
 
     image = InvenTreeImageSerializerField(read_only=True)
 
-    thumbnail = serializers.CharField(source='get_thumbnail_url', read_only=True)
+    thumbnail = InvenTreeThumbnailField()
 
 
 @register_importer()

src/backend/InvenTree/part/serializers.py

@@ -323,7 +323,7 @@ class PartBriefSerializer(
     image = InvenTree.serializers.InvenTreeImageSerializerField(
         read_only=True, allow_null=True
     )
-    thumbnail = serializers.CharField(source='get_thumbnail_url', read_only=True)
+    thumbnail = InvenTree.serializers.InvenTreeThumbnailField()
 
     IPN = serializers.CharField(
         required=False,
@@ -840,7 +840,7 @@ class PartSerializer(
     image = InvenTree.serializers.InvenTreeImageSerializerField(
         required=False, allow_null=True
     )
-    thumbnail = serializers.CharField(source='get_thumbnail_url', read_only=True)
+    thumbnail = InvenTree.serializers.InvenTreeThumbnailField()
     starred = serializers.SerializerMethodField()
 
     # PrimaryKeyRelated fields (Note: enforcing field type here results in much faster queries, somehow...)