Implement query optimization

ram/roster/admin.py

@@ -158,6 +158,19 @@ class RollingStockAdmin(SortableAdminBase, admin.ModelAdmin):
     )
     save_as = True
 
+    def get_queryset(self, request):
+        """Optimize queryset with select_related and prefetch_related."""
+        qs = super().get_queryset(request)
+        return qs.select_related(
+            'rolling_class',
+            'rolling_class__company',
+            'rolling_class__type',
+            'manufacturer',
+            'scale',
+            'decoder',
+            'shop',
+        ).prefetch_related('tags', 'image')
+
     @admin.display(description="Country")
     def country_flag(self, obj):
         return format_html(

ram/roster/models.py

@@ -11,7 +11,7 @@ from tinymce import models as tinymce
 
 from ram.models import BaseModel, Image, PropertyInstance
 from ram.utils import DeduplicatedStorage, slugify
-from ram.managers import PublicManager
+from ram.managers import PublicManager, RollingStockManager
 from metadata.models import (
     Scale,
     Manufacturer,
@@ -248,7 +248,7 @@ class RollingStockJournal(models.Model):
     class Meta:
         ordering = ["date", "rolling_stock"]
 
-    objects = PublicManager()
+    objects = RollingStockManager()
 
 
 # @receiver(models.signals.post_delete, sender=Cab)