1 files changed, 18 insertions, 12 deletions

diff --git a/lib/gitlab/diff/file_collection/merge_request_diff.rb b/lib/gitlab/diff/file_collection/merge_request_diff.rb
index fcda1fe2233..c358ae428cf 100644
--- a/lib/gitlab/diff/file_collection/merge_request_diff.rb
+++ b/lib/gitlab/diff/file_collection/merge_request_diff.rb
@@ -13,22 +13,32 @@ module Gitlab
         end
 
         def diff_files
-          super.tap { |_| store_highlight_cache }
+          # Make sure to _not_ send any method call to Gitlab::Diff::File
+          # _before_ all of them were collected (`super`). Premature method calls will
+          # trigger N+1 RPCs to Gitaly through BatchLoader records (Blob.lazy).
+          #
+          diff_files = super
+
+          diff_files.each { |diff_file| cache_highlight!(diff_file) if cacheable?(diff_file) }
+          store_highlight_cache
+
+          diff_files
         end
 
         def real_size
           @merge_request_diff.real_size
         end
 
-        private
+        def clear_cache!
+          Rails.cache.delete(cache_key)
+        end
 
-        # Extracted method to highlight in the same iteration to the diff_collection.
-        def decorate_diff!(diff)
-          diff_file = super
-          cache_highlight!(diff_file) if cacheable?(diff_file)
-          diff_file
+        def cache_key
+          [@merge_request_diff, 'highlighted-diff-files', diff_options]
         end
 
+        private
+
         def highlight_diff_file_from_cache!(diff_file, cache_diff_lines)
           diff_file.highlighted_diff_lines = cache_diff_lines.map do |line|
             Gitlab::Diff::Line.init_from_hash(line)
@@ -62,16 +72,12 @@ module Gitlab
         end
 
         def store_highlight_cache
-          Rails.cache.write(cache_key, highlight_cache) if @highlight_cache_was_empty
+          Rails.cache.write(cache_key, highlight_cache, expires_in: 1.week) if @highlight_cache_was_empty
         end
 
         def cacheable?(diff_file)
           @merge_request_diff.present? && diff_file.text? && diff_file.diffable?
         end
-
-        def cache_key
-          [@merge_request_diff, 'highlighted-diff-files', diff_options]
-        end
       end
     end
   end