Only perform iqdb update if md5 changed

app/jobs/update_external_cache_job.rb

@@ -4,6 +4,7 @@ class UpdateExternalCacheJob < ApplicationJob
   queue_as :cache
 
   def perform(image)
+    return unless image.cache_expired? || image.cached_data.blank?
     image.update_cache!
   end
 end

app/models/external_api_image.rb

@@ -85,6 +85,15 @@ class ExternalAPIImage < ApplicationRecord
       end
     end
 
+    def image_changed?
+      case site
+      when "e621", "femboyfans"
+        cached_data.try(:dig, "file", "md5") != cached_data_before_last_save.try(:dig, "file", "md5")
+      else
+        data_error("format image_changed?")
+      end
+    end
+
     def is_deleted?
       case site
       when "e621", "femboyfans"
@@ -151,7 +160,7 @@ class ExternalAPIImage < ApplicationRecord
       update(cached_data: data, cache_last_updated_at: Time.now)
       if is_deleted?
         api_image.remove_iqdb
-      else
+      elsif image_changed?
         api_image.update_iqdb
       end
       api_image.update(is_viewable: !is_deleted?)