fix(models): only update resources when tags are created (#9569)

api/CHANGELOG.md

@@ -14,7 +14,8 @@ All notable changes to the **Prowler API** are documented in this file.
 - Increased execution delay for the first scheduled scan tasks to 5 seconds[(#9558)](https://github.com/prowler-cloud/prowler/pull/9558)
 
 ### Fixed
-- Make `scan_id` a required filter in the compliance overview endpoint [(#9560)](https://github.com/prowler-cloud/prowler/pull/9560)
+- Made `scan_id` a required filter in the compliance overview endpoint [(#9560)](https://github.com/prowler-cloud/prowler/pull/9560)
+- Reduced unnecessary UPDATE resources operations by only saving when tag mappings change, lowering write load during scans [(#9569)](https://github.com/prowler-cloud/prowler/pull/9569)
 
 ---
 

api/src/backend/api/models.py

@@ -716,14 +716,19 @@ class Resource(RowLevelSecurityProtectedModel):
             self.clear_tags()
             return
 
-        # Add new relationships with the tenant_id field
+        # Add new relationships with the tenant_id field; avoid touching the
+        # Resource row unless a mapping is actually created to prevent noisy
+        # updates during scans.
+        mapping_created = False
         for tag in tags:
-            ResourceTagMapping.objects.update_or_create(
+            _, created = ResourceTagMapping.objects.update_or_create(
                 tag=tag, resource=self, tenant_id=self.tenant_id
             )
+            mapping_created = mapping_created or created
 
-        # Save the instance
-        self.save()
+        if mapping_created:
+            # Only bump updated_at when the tag set truly changed
+            self.save(update_fields=["updated_at"])
 
     class Meta(RowLevelSecurityProtectedModel.Meta):
         db_table = "resources"