Move preloading commits titles into TreeSummary

That will save us from N + 1 requests on rendering

app/controllers/projects/refs_controller.rb

@@ -45,7 +45,8 @@ class Projects::RefsController < Projects::ApplicationController
 
   def logs_tree
     tree_summary = ::Gitlab::TreeSummary.new(
-      @commit, @project, path: @path, offset: params[:offset], limit: 25)
+      @commit, @project, current_user,
+      path: @path, offset: params[:offset], limit: 25)
 
     respond_to do |format|
       format.html { render_404 }
@@ -60,10 +61,8 @@ class Projects::RefsController < Projects::ApplicationController
       # Deprecated due to https://gitlab.com/gitlab-org/gitlab/-/issues/36863
       # Will be removed soon https://gitlab.com/gitlab-org/gitlab/-/merge_requests/29895
       format.js do
-        @logs, commits = tree_summary.summarize
+        @logs, _ = tree_summary.summarize
         @more_log_url = more_url(tree_summary.next_offset) if tree_summary.more?
-
-        prerender_commit_full_titles!(commits)
       end
     end
   end
@@ -74,14 +73,6 @@ class Projects::RefsController < Projects::ApplicationController
     logs_file_project_ref_path(@project, @ref, @path, offset: offset)
   end
 
-  def prerender_commit_full_titles!(commits)
-    # Preload commit authors as they are used in rendering
-    commits.each(&:lazy_author)
-
-    renderer = Banzai::ObjectRenderer.new(user: current_user, default_project: @project)
-    renderer.render(commits, :full_title)
-  end
-
   def validate_ref_id
     return not_found! if params[:id].present? && params[:id] !~ Gitlab::PathRegex.git_reference_regex
   end

ee/spec/lib/gitlab/tree_summary_spec.rb

@@ -5,10 +5,11 @@ require 'spec_helper'
 describe Gitlab::TreeSummary do
   let_it_be(:project) { create(:project, :custom_repo, files: { 'a.txt' => '' }) }
   let_it_be(:path_lock) { create(:path_lock, project: project, path: 'a.txt') }
+  let_it_be(:user) { create(:user) }
 
   let(:commit) { project.repository.head_commit }
 
-  subject { described_class.new(commit, project).summarize.first }
+  subject { described_class.new(commit, project, user).summarize.first }
 
   describe '#summarize (entries)' do
     it 'includes path locks in entries' do

lib/gitlab/tree_summary.rb

@@ -8,14 +8,15 @@ module Gitlab
     CACHE_EXPIRE_IN = 1.hour
     MAX_OFFSET = 2**31
 
-    attr_reader :commit, :project, :path, :offset, :limit
+    attr_reader :commit, :project, :path, :offset, :limit, :user
 
     attr_reader :resolved_commits
     private :resolved_commits
 
-    def initialize(commit, project, params = {})
+    def initialize(commit, project, user, params = {})
       @commit = commit
       @project = project
+      @user = user
 
       @path = params.fetch(:path, nil).presence
       @offset = [params.fetch(:offset, 0).to_i, MAX_OFFSET].min
@@ -97,6 +98,7 @@ module Gitlab
         end
 
       commits_hsh = repository.list_last_commits_for_tree(commit.id, ensured_path, offset: offset, limit: limit)
+      prerender_commit_full_titles!(commits_hsh.values)
 
       entries.each do |entry|
         path_key = entry_path(entry)
@@ -105,7 +107,7 @@ module Gitlab
         if commit
           entry[:commit] = commit
           entry[:commit_path] = commit_path(commit)
-          entry[:commit_title_html] = markdown_field(commit, :title)
+          entry[:commit_title_html] = markdown_field(commit, :full_title)
         end
       end
     end
@@ -133,6 +135,14 @@ module Gitlab
     def tree
       strong_memoize(:tree) { repository.tree(commit.id, path) }
     end
+
+    def prerender_commit_full_titles!(commits)
+      # Preload commit authors as they are used in rendering
+      commits.each(&:lazy_author)
+
+      renderer = Banzai::ObjectRenderer.new(user: user, default_project: project)
+      renderer.render(commits, :full_title)
+    end
   end
 end
 

spec/lib/gitlab/tree_summary_spec.rb

@@ -8,12 +8,13 @@ describe Gitlab::TreeSummary do
   let(:project) { create(:project, :empty_repo) }
   let(:repo) { project.repository }
   let(:commit) { repo.head_commit }
+  let_it_be(:user) { create(:user) }
 
   let(:path) { nil }
   let(:offset) { nil }
   let(:limit) { nil }
 
-  subject(:summary) { described_class.new(commit, project, path: path, offset: offset, limit: limit) }
+  subject(:summary) { described_class.new(commit, project, user, path: path, offset: offset, limit: limit) }
 
   describe '#initialize' do
     it 'defaults offset to 0' do
@@ -141,6 +142,16 @@ describe Gitlab::TreeSummary do
         expect(entry).to include(:commit)
       end
     end
+
+    context 'rendering commits' do
+      it 'does not perform N + 1 request' do
+        summary
+
+        queries = ActiveRecord::QueryRecorder.new { summary.summarize }
+
+        expect(queries.count).to be <= 3
+      end
+    end
   end
 
   describe '#more?' do