Resolve N + 1 for JIRA pulls

When API request performed for multiple pulls
the number of SQL requests depends on the number of MRs

app/models/merge_request.rb

@@ -316,6 +316,7 @@ class MergeRequest < ApplicationRecord
   }
 
   scope :with_csv_entity_associations, -> { preload(:assignees, :approved_by_users, :author, :milestone, metrics: [:merged_by]) }
+  scope :with_jira_integration_associations, -> { preload(:metrics, :assignees, :author, :target_project, :source_project) }
 
   scope :by_target_branch_wildcard, ->(wildcard_branch_name) do
     where("target_branch LIKE ?", ApplicationRecord.sanitize_sql_like(wildcard_branch_name).tr('*', '%'))

changelogs/unreleased/id-n-1-for-jira-pulls.yml

+---
+title: Resolve N + 1 for JIRA pulls
+merge_request: 57482
+author:
+type: performance

lib/api/v3/github.rb

@@ -75,11 +75,14 @@ module API
         # rubocop: enable CodeReuse/ActiveRecord
 
         def authorized_merge_requests
-          MergeRequestsFinder.new(current_user, authorized_only: !current_user.admin?).execute
+          MergeRequestsFinder.new(current_user, authorized_only: !current_user.admin?)
+            .execute.with_jira_integration_associations
         end
 
         def authorized_merge_requests_for_project(project)
-          MergeRequestsFinder.new(current_user, authorized_only: !current_user.admin?, project_id: project.id).execute
+          MergeRequestsFinder
+            .new(current_user, authorized_only: !current_user.admin?, project_id: project.id)
+            .execute.with_jira_integration_associations
         end
 
         # rubocop: disable CodeReuse/ActiveRecord

spec/requests/api/v3/github_spec.rb

@@ -3,10 +3,10 @@
 require 'spec_helper'
 
 RSpec.describe API::V3::Github do
-  let(:user) { create(:user) }
-  let(:unauthorized_user) { create(:user) }
-  let(:admin) { create(:user, :admin) }
-  let(:project) { create(:project, :repository, creator: user) }
+  let_it_be(:user) { create(:user) }
+  let_it_be(:unauthorized_user) { create(:user) }
+  let_it_be(:admin) { create(:user, :admin) }
+  let_it_be(:project) { create(:project, :repository, creator: user) }
 
   before do
     project.add_maintainer(user)
@@ -210,14 +210,14 @@ RSpec.describe API::V3::Github do
   end
 
   describe 'repo pulls' do
-    let(:project2) { create(:project, :repository, creator: user) }
-    let(:assignee) { create(:user) }
-    let(:assignee2) { create(:user) }
-    let!(:merge_request) do
+    let_it_be(:project2) { create(:project, :repository, creator: user) }
+    let_it_be(:assignee) { create(:user) }
+    let_it_be(:assignee2) { create(:user) }
+    let_it_be(:merge_request) do
       create(:merge_request, source_project: project, target_project: project, author: user, assignees: [assignee])
     end
 
-    let!(:merge_request_2) do
+    let_it_be(:merge_request_2) do
       create(:merge_request, source_project: project2, target_project: project2, author: user, assignees: [assignee, assignee2])
     end
 
@@ -225,26 +225,54 @@ RSpec.describe API::V3::Github do
       project2.add_maintainer(user)
     end
 
+    def perform_request
+      jira_get v3_api(route, user)
+    end
+
     describe 'GET /-/jira/pulls' do
+      let(:route) { '/repos/-/jira/pulls' }
+
       it 'returns an array of merge requests with github format' do
-        jira_get v3_api('/repos/-/jira/pulls', user)
+        perform_request
 
         expect(response).to have_gitlab_http_status(:ok)
         expect(json_response).to be_an(Array)
         expect(json_response.size).to eq(2)
         expect(response).to match_response_schema('entities/github/pull_requests')
       end
+
+      it 'returns multiple merge requests without N + 1' do
+        perform_request
+
+        control_count = ActiveRecord::QueryRecorder.new { perform_request }.count
+
+        create(:merge_request, source_project: project, source_branch: 'fix')
+
+        expect { perform_request }.not_to exceed_query_limit(control_count)
+      end
     end
 
     describe 'GET /repos/:namespace/:project/pulls' do
+      let(:route) { "/repos/#{project.namespace.path}/#{project.path}/pulls" }
+
       it 'returns an array of merge requests for the proper project in github format' do
-        jira_get v3_api("/repos/#{project.namespace.path}/#{project.path}/pulls", user)
+        perform_request
 
         expect(response).to have_gitlab_http_status(:ok)
         expect(json_response).to be_an(Array)
         expect(json_response.size).to eq(1)
         expect(response).to match_response_schema('entities/github/pull_requests')
       end
+
+      it 'returns multiple merge requests without N + 1' do
+        perform_request
+
+        control_count = ActiveRecord::QueryRecorder.new { perform_request }.count
+
+        create(:merge_request, source_project: project, source_branch: 'fix')
+
+        expect { perform_request }.not_to exceed_query_limit(control_count)
+      end
     end
 
     describe 'GET /repos/:namespace/:project/pulls/:id' do