Preload job artifacts archive in pipeline details

This makes the PipelineDetailsEntity to by default
eager load the job_artifacts_archive.

In the case of PipelineSerializer, it does not rely on
PipelineDetailsEntity for preloading, because it does its
own preloading of pipeline relations. This is more performant
for cases where in there are multiple pipelines to preload.

app/models/ci/build.rb

@@ -114,6 +114,7 @@ module Ci
     end
 
     scope :eager_load_job_artifacts, -> { includes(:job_artifacts) }
+    scope :eager_load_job_artifacts_archive, -> { includes(:job_artifacts_archive) }
 
     scope :eager_load_everything, -> do
       includes(

app/serializers/pipeline_details_entity.rb

@@ -8,7 +8,12 @@ class PipelineDetailsEntity < PipelineEntity
   end
 
   expose :details do
-    expose :artifacts, using: BuildArtifactEntity
+    expose :artifacts do |pipeline, options|
+      rel = pipeline.artifacts
+      rel = rel.eager_load_job_artifacts_archive if options.fetch(:preload_job_artifacts_archive, true)
+
+      BuildArtifactEntity.represent(rel, options)
+    end
     expose :manual_actions, using: BuildActionEntity
     expose :scheduled_actions, using: BuildActionEntity
   end

app/serializers/pipeline_serializer.rb

@@ -7,6 +7,10 @@ class PipelineSerializer < BaseSerializer
   # rubocop: disable CodeReuse/ActiveRecord
   def represent(resource, opts = {})
     if resource.is_a?(ActiveRecord::Relation)
+      # We don't want PipelineDetailsEntity to preload the job_artifacts_archive
+      # because we do it with preloaded_relations in a more optimal way
+      # if the given resource is a collection of multiple pipelines.
+      opts[:preload_job_artifacts_archive] = false
       resource = resource.preload(preloaded_relations)
     end
 

changelogs/unreleased/eb-preload-artifacts-merge-request-widget.yml

+---
+title: Fix N+1 queries caused by loading job artifacts archive in pipeline details
+  entity
+merge_request: 25250
+author:
+type: fixed

spec/controllers/projects/pipelines_controller_spec.rb

@@ -171,7 +171,17 @@ describe Projects::PipelinesController do
 
     def create_build(pipeline, stage, stage_idx, name, user = nil)
       status = %w[created running pending success failed canceled].sample
-      create(:ci_build, pipeline: pipeline, stage: stage, stage_idx: stage_idx, name: name, status: status, user: user)
+      create(
+        :ci_build,
+        :artifacts,
+        artifacts_expire_at: 2.days.from_now,
+        pipeline: pipeline,
+        stage: stage,
+        stage_idx: stage_idx,
+        name: name,
+        status: status,
+        user: user
+      )
     end
   end
 

spec/serializers/pipeline_details_entity_spec.rb

@@ -173,5 +173,40 @@ describe PipelineDetailsEntity do
         expect(subject[:triggered].first[:project]).not_to be_nil
       end
     end
+
+    context 'when pipeline has expiring archive artifacts' do
+      let(:pipeline) { create(:ci_empty_pipeline) }
+      let!(:build_1) { create(:ci_build, :artifacts, pipeline: pipeline, artifacts_expire_at: 2.days.from_now, name: 'build_1') }
+      let!(:build_2) { create(:ci_build, :artifacts, pipeline: pipeline, artifacts_expire_at: 2.days.from_now, name: 'build_2') }
+      let!(:build_3) { create(:ci_build, :artifacts, pipeline: pipeline, artifacts_expire_at: 2.days.from_now, name: 'build_3') }
+
+      let(:names) { subject[:details][:artifacts].map { |a| a[:name] } }
+
+      context 'and preload_job_artifacts_archive is not defined in the options' do
+        it 'defaults to true and eager loads the job_artifacts_archive' do
+          recorder = ActiveRecord::QueryRecorder.new do
+            expect(names).to match_array(%w[build_1 build_2 build_3])
+          end
+
+          # This makes only one query to fetch all job artifacts
+          expect(recorder.count).to eq(42)
+        end
+      end
+
+      context 'and preload_job_artifacts_archive is set to false' do
+        let(:entity) do
+          described_class.represent(pipeline, request: request, preload_job_artifacts_archive: false)
+        end
+
+        it 'does not eager load the job_artifacts_archive' do
+          recorder = ActiveRecord::QueryRecorder.new do
+            expect(names).to match_array(%w[build_1 build_2 build_3])
+          end
+
+          # This makes one query for each job artifact
+          expect(recorder.count).to eq(44)
+        end
+      end
+    end
   end
 end