1 files changed, 27 insertions, 0 deletions
diff --git a/app/models/preloaders/merge_request_diff_preloader.rb b/app/models/preloaders/merge_request_diff_preloader.rb
new file mode 100644
index 00000000000..ee9995c497d
--- /dev/null
+++ b/app/models/preloaders/merge_request_diff_preloader.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+module Preloaders
+  # This class preloads the `merge_request_diff` association for the given merge request models.
+  #
+  # Usage:
+  #   merge_requests = MergeRequest.where(...)
+  #   Preloaders::MergeRequestDiffPreloader.new(merge_requests).preload_all
+  #   merge_requests.first.merge_request_diff # won't fire any query
+  class MergeRequestDiffPreloader
+    def initialize(merge_requests)
+      @merge_requests = merge_requests
+    end
+
+    def preload_all
+      merge_request_diffs = MergeRequestDiff.latest_diff_for_merge_requests(@merge_requests)
+      cache = merge_request_diffs.index_by { |diff| diff.merge_request_id }
+
+      @merge_requests.each do |merge_request|
+        merge_request_diff = cache[merge_request.id]
+
+        merge_request.association(:merge_request_diff).target = merge_request_diff
+        merge_request.association(:merge_request_diff).loaded!
+      end
+    end
+  end
+end