optimize for large files

app/controllers/submissions_controller.rb

@@ -6,12 +6,24 @@ class SubmissionsController < ApplicationController
 
   load_and_authorize_resource :submission, only: %i[show destroy]
 
+  PRELOAD_ALL_PAGES_AMOUNT = 200
+
   def show
     ActiveRecord::Associations::Preloader.new(
       records: [@submission],
-      associations: [:template, { template_schema_documents: [:blob, { preview_images_attachments: :blob }] }]
+      associations: [:template, { template_schema_documents: :blob }]
     ).call
 
+    total_pages =
+      @submission.template_schema_documents.sum { |e| e.metadata.dig('pdf', 'number_of_pages').to_i }
+
+    if total_pages < PRELOAD_ALL_PAGES_AMOUNT
+      ActiveRecord::Associations::Preloader.new(
+        records: @submission.template_schema_documents,
+        associations: [:blob, { preview_images_attachments: :blob }]
+      ).call
+    end
+
     render :show, layout: 'plain'
   end