Fix N+1 for searching commits

app/controllers/concerns/renders_commits.rb

@@ -17,12 +17,13 @@ module RendersCommits
   def set_commits_for_rendering(commits, commits_count: nil)
     @total_commit_count = commits_count || commits.size
     limited, @hidden_commit_count = limited_commits(commits, @total_commit_count)
-    commits.each(&:lazy_author) # preload authors
     prepare_commits_for_rendering(limited)
   end
   # rubocop: enable Gitlab/ModuleWithInstanceVariables
 
   def prepare_commits_for_rendering(commits)
+    commits.each(&:lazy_author) # preload commits' authors
+
     Banzai::CommitRenderer.render(commits, @project, current_user) # rubocop:disable Gitlab/ModuleWithInstanceVariables
 
     commits

changelogs/unreleased/327006-fix-search-commits-n-plus-1.yml

+---
+title: Fix N+1 for searching commits
+merge_request: 58867
+author:
+type: performance

spec/controllers/concerns/renders_commits_spec.rb

@@ -57,4 +57,16 @@ RSpec.describe RendersCommits do
       end.not_to exceed_all_query_limit(control_count)
     end
   end
+
+  describe '.prepare_commits_for_rendering' do
+    it 'avoids N+1' do
+      control = ActiveRecord::QueryRecorder.new do
+        subject.prepare_commits_for_rendering(merge_request.commits.take(1))
+      end
+
+      expect do
+        subject.prepare_commits_for_rendering(merge_request.commits)
+      end.not_to exceed_all_query_limit(control.count)
+    end
+  end
 end