1 files changed, 65 insertions, 0 deletions
diff --git a/spec/models/preloaders/environments/deployment_preloader_spec.rb b/spec/models/preloaders/environments/deployment_preloader_spec.rb
new file mode 100644
index 00000000000..c1812d45628
--- /dev/null
+++ b/spec/models/preloaders/environments/deployment_preloader_spec.rb
@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Preloaders::Environments::DeploymentPreloader do
+  let_it_be(:user) { create(:user) }
+  let_it_be(:project, reload: true) { create(:project, :repository) }
+
+  let_it_be(:pipeline) { create(:ci_pipeline, user: user, project: project, sha: project.commit.sha) }
+  let_it_be(:ci_build_a) { create(:ci_build, user: user, project: project, pipeline: pipeline) }
+  let_it_be(:ci_build_b) { create(:ci_build, user: user, project: project, pipeline: pipeline) }
+  let_it_be(:ci_build_c) { create(:ci_build, user: user, project: project, pipeline: pipeline) }
+
+  let_it_be(:environment_a) { create(:environment, project: project, state: :available) }
+  let_it_be(:environment_b) { create(:environment, project: project, state: :available) }
+
+  before do
+    create(:deployment, :success, project: project, environment: environment_a, deployable: ci_build_a)
+    create(:deployment, :success, project: project, environment: environment_a, deployable: ci_build_b)
+    create(:deployment, :success, project: project, environment: environment_b, deployable: ci_build_c)
+  end
+
+  def preload_association(association_name)
+    described_class.new(project.environments)
+      .execute_with_union(association_name, deployment_associations)
+  end
+
+  def deployment_associations
+    {
+      user: [],
+      deployable: {
+        pipeline: {
+          manual_actions: []
+        }
+      }
+    }
+  end
+
+  it 'does not trigger N+1 queries' do
+    control = ActiveRecord::QueryRecorder.new { preload_association(:last_deployment) }
+
+    ci_build_d = create(:ci_build, user: user, project: project, pipeline: pipeline)
+    create(:deployment, :success, project: project, environment: environment_b, deployable: ci_build_d)
+
+    expect { preload_association(:last_deployment) }.not_to exceed_query_limit(control)
+  end
+
+  it 'batch loads the dependent associations' do
+    preload_association(:last_deployment)
+
+    expect do
+      project.environments.first.last_deployment.deployable.pipeline.manual_actions
+    end.not_to exceed_query_limit(0)
+  end
+
+  # Example query scoped with IN clause for `last_deployment` association preload:
+  # SELECT DISTINCT ON (environment_id) deployments.* FROM "deployments" WHERE "deployments"."status" IN (1, 2, 3, 4, 6) AND "deployments"."environment_id" IN (35, 34, 33) ORDER BY environment_id, deployments.id DESC
+  it 'avoids scoping with IN clause during preload' do
+    control = ActiveRecord::QueryRecorder.new { preload_association(:last_deployment) }
+
+    default_preload_query = control.occurrences_by_line_method.first[1][:occurrences].any? { |i| i.include?('"deployments"."environment_id" IN') }
+
+    expect(default_preload_query).to be(false)
+  end
+end