Preload tests reports with Lookahead

- Preload tests report to avoid N+1 queries
for lastTestReportState and
lastTestReportManuallyCreated fields

ee/app/graphql/ee/types/project_type.rb

@@ -57,6 +57,7 @@ module EE
 
         field :requirements, ::Types::RequirementsManagement::RequirementType.connection_type, null: true,
               description: 'Find requirements',
+              extras: [:lookahead],
               resolver: ::Resolvers::RequirementsManagement::RequirementsResolver
 
         field :requirement_states_count, ::Types::RequirementsManagement::RequirementStatesCountType, null: true,

ee/app/graphql/resolvers/requirements_management/requirements_resolver.rb

@@ -3,6 +3,8 @@
 module Resolvers
   module RequirementsManagement
     class RequirementsResolver < BaseResolver
+      include LooksAhead
+
       argument :iid, GraphQL::ID_TYPE,
                required: false,
                description: 'IID of the requirement, e.g., "1"'
@@ -29,7 +31,7 @@ module Resolvers
 
       type Types::RequirementsManagement::RequirementType, null: true
 
-      def resolve(**args)
+      def resolve_with_lookahead(**args)
         # The project could have been loaded in batch by `BatchLoader`.
         # At this point we need the `id` of the project to query for issues, so
         # make sure it's loaded and not `nil` before continuing.
@@ -39,6 +41,19 @@ module Resolvers
         args[:project_id] = project.id
         args[:iids] ||= [args[:iid]].compact
 
+        apply_lookahead(find_requirements(args))
+      end
+
+      private
+
+      def preloads
+        {
+          last_test_report_state: [:test_reports],
+          last_test_report_manually_created: [:test_reports]
+        }
+      end
+
+      def find_requirements(args)
         ::RequirementsManagement::RequirementsFinder.new(context[:current_user], args).execute
       end
     end

ee/app/graphql/types/requirements_management/requirement_type.rb

@@ -27,14 +27,13 @@ module Types
       field :state, RequirementsManagement::RequirementStateEnum, null: false,
             description: 'State of the requirement'
 
-      field :last_test_report_state, RequirementsManagement::TestReportStateEnum, null: true, complexity: 5,
+      field :last_test_report_state, RequirementsManagement::TestReportStateEnum, null: true,
             description: 'Latest requirement test report state'
 
       field :last_test_report_manually_created,
             GraphQL::BOOLEAN_TYPE,
             method: :last_test_report_manually_created?,
             null: true,
-            complexity: 5,
             description: 'Indicates if latest test report was created by user'
 
       field :project, ProjectType, null: false,

ee/changelogs/unreleased/262096-use-lookahead-to-preload-queries-for-requirementtype.yml

+---
+title: Use Lookahead to preload tests reports when querying Requirements with GraphQL
+merge_request: 45195
+author:
+type: performance

ee/spec/requests/api/graphql/project/requirements_management/requirements_spec.rb

@@ -63,6 +63,30 @@ RSpec.describe 'getting a requirement list for a project' do
       end
     end
 
+    context 'query performance with test reports' do
+      let_it_be(:test_report) { create(:test_report, requirement: requirement, state: "passed") }
+      let(:fields) do
+        <<~QUERY
+        edges {
+          node {
+            lastTestReportState
+            lastTestReportManuallyCreated
+          }
+        }
+        QUERY
+      end
+
+      it 'avoids N+1 queries' do
+        control = ActiveRecord::QueryRecorder.new { post_graphql(query, current_user: current_user) }
+
+        create_list(:requirement, 3, project: project) do |requirement|
+          create(:test_report, requirement: requirement, state: "passed")
+        end
+
+        expect { post_graphql(query, current_user: current_user) }.not_to exceed_query_limit(control)
+      end
+    end
+
     describe 'filtering' do
       let_it_be(:filter_project) { create(:project, :public) }
       let_it_be(:other_project) { create(:project, :public) }