Optimize the query on Environment Detail page

This commit adds the database index to optimize the
query on Environment Detail page.

Changelog: performance

app/models/deployment.rb

@@ -46,7 +46,7 @@ class Deployment < ApplicationRecord
   scope :for_project, -> (project_id) { where(project_id: project_id) }
   scope :for_projects, -> (projects) { where(project: projects) }
 
-  scope :visible, -> { where(status: %i[running success failed canceled blocked]) }
+  scope :visible, -> { where(status: VISIBLE_STATUSES) }
   scope :stoppable, -> { where.not(on_stop: nil).where.not(deployable_id: nil).success }
   scope :active, -> { where(status: %i[created running]) }
   scope :upcoming, -> { where(status: %i[blocked running]) }
@@ -58,6 +58,7 @@ class Deployment < ApplicationRecord
 
   scope :ordered, -> { order(finished_at: :desc) }
 
+  VISIBLE_STATUSES = %i[running success failed canceled blocked].freeze
   FINISHED_STATUSES = %i[success failed canceled].freeze
 
   state_machine :status, initial: :created do

db/post_migrate/20220323152202_add_index_on_visible_deployments.rb

+# frozen_string_literal: true
+
+class AddIndexOnVisibleDeployments < Gitlab::Database::Migration[1.0]
+  disable_ddl_transaction!
+
+  INDEX_NAME = 'index_deployments_for_visible_scope'
+
+  def up
+    add_concurrent_index :deployments,
+      [:environment_id, :finished_at],
+      order: { finished_at: :desc },
+      where: 'status IN (1, 2, 3, 4, 6)',
+      name: INDEX_NAME
+  end
+
+  def down
+    remove_concurrent_index_by_name :deployments, INDEX_NAME
+  end
+end

db/schema_migrations/20220323152202

+47b87d4ea5d081904d561e461a266fe20dfcc1f771126340cf14c84302d3383d
\ No newline at end of file

db/structure.sql

@@ -27408,6 +27408,8 @@ CREATE UNIQUE INDEX index_deployment_clusters_on_cluster_id_and_deployment_id ON
 
 CREATE INDEX index_deployment_merge_requests_on_merge_request_id ON deployment_merge_requests USING btree (merge_request_id);
 
+CREATE INDEX index_deployments_for_visible_scope ON deployments USING btree (environment_id, finished_at DESC) WHERE (status = ANY (ARRAY[1, 2, 3, 4, 6]));
+
 CREATE INDEX index_deployments_on_archived_project_id_iid ON deployments USING btree (archived, project_id, iid);
 
 CREATE INDEX index_deployments_on_cluster_id_and_status ON deployments USING btree (cluster_id, status);

spec/models/deployment_spec.rb

@@ -524,6 +524,16 @@ RSpec.describe Deployment do
 
         is_expected.to contain_exactly(deployment1, deployment2, deployment3, deployment4, deployment5)
       end
+
+      it 'has a corresponding database index' do
+        index = ApplicationRecord.connection.indexes('deployments').find do |i|
+          i.name == 'index_deployments_for_visible_scope'
+        end
+
+        scope_values = described_class::VISIBLE_STATUSES.map { |s| described_class.statuses[s] }.to_s
+
+        expect(index.where).to include(scope_values)
+      end
     end
 
     describe 'upcoming' do