Speed up loading and filtering deploy keys and their projects

This commit changes how we eager-load projects, routes, and namespaces
required by the deploy keys endpoint, getting a 10x improvement in my
local testing.

The endpoint still doesn't scale in-general, but going from ~13 seconds
to dump a 63K result to generating the same thing in ~1.6 seconds seems
like a good improvement to me.

7 files changed, 29 insertions, 41 deletions

diff --git a/app/models/deploy_key.rb b/app/models/deploy_key.rb
index fb50da39ca3..0bd90bd28e3 100644
--- a/app/models/deploy_key.rb
+++ b/app/models/deploy_key.rb
@@ -9,6 +9,7 @@ class DeployKey < Key
 
   scope :in_projects, ->(projects) { joins(:deploy_keys_projects).where('deploy_keys_projects.project_id in (?)', projects) }
   scope :are_public,  -> { where(public: true) }
+  scope :with_projects, -> { includes(deploy_keys_projects: { project: [:route, :namespace] }) }
 
   ignore_column :can_push
 
@@ -23,7 +24,7 @@ class DeployKey < Key
   end
 
   def almost_orphaned?
-    self.deploy_keys_projects.length == 1
+    self.deploy_keys_projects.count == 1
   end
 
   def destroyed_when_orphaned?
@@ -47,6 +48,6 @@ class DeployKey < Key
   end
 
   def projects_with_write_access
-    Project.preload(:route).where(id: deploy_keys_projects.with_write_access.select(:project_id))
+    Project.with_route.where(id: deploy_keys_projects.with_write_access.select(:project_id))
   end
 end
diff --git a/app/models/deploy_keys_project.rb b/app/models/deploy_keys_project.rb
index 15906ed8e06..40c66d5bc4c 100644
--- a/app/models/deploy_keys_project.rb
+++ b/app/models/deploy_keys_project.rb
@@ -1,9 +1,8 @@
 # frozen_string_literal: true
 
 class DeployKeysProject < ApplicationRecord
-  belongs_to :project
+  belongs_to :project, inverse_of: :deploy_keys_projects
   belongs_to :deploy_key, inverse_of: :deploy_keys_projects
-
   scope :without_project_deleted,  -> { joins(:project).where(projects: { pending_delete: false }) }
   scope :in_project, ->(project) { where(project: project) }
   scope :with_write_access, -> { where(can_push: true) }
diff --git a/app/models/project.rb b/app/models/project.rb
index 8f234fba04f..33f1077e982 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -214,7 +214,7 @@ class Project < ApplicationRecord
     as: :source, class_name: 'ProjectMember', dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
   has_many :members_and_requesters, as: :source, class_name: 'ProjectMember'
 
-  has_many :deploy_keys_projects
+  has_many :deploy_keys_projects, inverse_of: :project
   has_many :deploy_keys, through: :deploy_keys_projects
   has_many :users_star_projects
   has_many :starrers, through: :users_star_projects, source: :user
diff --git a/app/presenters/projects/settings/deploy_keys_presenter.rb b/app/presenters/projects/settings/deploy_keys_presenter.rb
index 85518c9a3a4..6f8c4e1f902 100644
--- a/app/presenters/projects/settings/deploy_keys_presenter.rb
+++ b/app/presenters/projects/settings/deploy_keys_presenter.rb
@@ -12,48 +12,38 @@ module Projects
         @key ||= DeployKey.new.tap { |dk| dk.deploy_keys_projects.build }
       end
 
-      # rubocop: disable CodeReuse/ActiveRecord
       def enabled_keys
-        @enabled_keys ||= project.deploy_keys.includes(:projects)
-      end
-      # rubocop: enable CodeReuse/ActiveRecord
-
-      def any_keys_enabled?
-        enabled_keys.any?
+        project.deploy_keys
       end
 
       def available_keys
-        @available_keys ||= current_user.accessible_deploy_keys - enabled_keys
+        current_user
+          .accessible_deploy_keys
+          .id_not_in(enabled_keys.select(:id))
+          .with_projects
       end
 
-      # rubocop: disable CodeReuse/ActiveRecord
       def available_project_keys
-        @available_project_keys ||= current_user.project_deploy_keys.includes(:projects) - enabled_keys
-      end
-      # rubocop: enable CodeReuse/ActiveRecord
-
-      def key_available?(deploy_key)
-        available_keys.include?(deploy_key)
+        current_user
+          .project_deploy_keys
+          .id_not_in(enabled_keys.select(:id))
+          .with_projects
       end
 
-      # rubocop: disable CodeReuse/ActiveRecord
       def available_public_keys
-        return @available_public_keys if defined?(@available_public_keys)
-
-        @available_public_keys ||= DeployKey.are_public.includes(:projects) - enabled_keys
-
-        # Public keys that are already used by another accessible project are already
-        # in @available_project_keys.
-        @available_public_keys -= available_project_keys
+        DeployKey
+          .are_public
+          .id_not_in(enabled_keys.select(:id))
+          .id_not_in(available_project_keys.select(:id))
+          .with_projects
       end
-      # rubocop: enable CodeReuse/ActiveRecord
 
       def as_json
         serializer = DeployKeySerializer.new # rubocop: disable CodeReuse/Serializer
         opts = { user: current_user }
 
         {
-          enabled_keys: serializer.represent(enabled_keys, opts),
+          enabled_keys: serializer.represent(enabled_keys.with_projects, opts),
           available_project_keys: serializer.represent(available_project_keys, opts),
           public_keys: serializer.represent(available_public_keys, opts)
         }
diff --git a/app/serializers/deploy_key_entity.rb b/app/serializers/deploy_key_entity.rb
index 54bf030aba1..e47d6454780 100644
--- a/app/serializers/deploy_key_entity.rb
+++ b/app/serializers/deploy_key_entity.rb
@@ -10,9 +10,10 @@ class DeployKeyEntity < Grape::Entity
   expose :created_at
   expose :updated_at
   expose :deploy_keys_projects, using: DeployKeysProjectEntity do |deploy_key|
-    deploy_key.deploy_keys_projects
-              .without_project_deleted
-              .select { |deploy_key_project| Ability.allowed?(options[:user], :read_project, deploy_key_project.project) }
+    deploy_key.deploy_keys_projects.select do |deploy_key_project|
+      !deploy_key_project.project&.pending_delete? &&
+        Ability.allowed?(options[:user], :read_project, deploy_key_project.project)
+    end
   end
   expose :can_edit
 
diff --git a/changelogs/unreleased/43080-speed-up-deploy-keys.yml b/changelogs/unreleased/43080-speed-up-deploy-keys.yml
new file mode 100644
index 00000000000..73c9a9e5f82
--- /dev/null
+++ b/changelogs/unreleased/43080-speed-up-deploy-keys.yml
@@ -0,0 +1,5 @@
+---
+title: Speed up loading and filtering deploy keys and their projects
+merge_request: 31384
+author:
+type: performance
diff --git a/spec/presenters/projects/settings/deploy_keys_presenter_spec.rb b/spec/presenters/projects/settings/deploy_keys_presenter_spec.rb
index 001545bb5df..b4bf39f3cdb 100644
--- a/spec/presenters/projects/settings/deploy_keys_presenter_spec.rb
+++ b/spec/presenters/projects/settings/deploy_keys_presenter_spec.rb
@@ -29,10 +29,6 @@ describe Projects::Settings::DeployKeysPresenter do
     it 'returns the enabled_keys size' do
       expect(presenter.enabled_keys_size).to eq(1)
     end
-
-    it 'returns true if there is any enabled_keys' do
-      expect(presenter.any_keys_enabled?).to eq(true)
-    end
   end
 
   describe '#available_keys/#available_project_keys' do
@@ -54,9 +50,5 @@ describe Projects::Settings::DeployKeysPresenter do
     it 'returns the available_project_keys size' do
       expect(presenter.available_project_keys_size).to eq(1)
     end
-
-    it 'shows if there is an available key' do
-      expect(presenter.key_available?(deploy_key)).to eq(false)
-    end
   end
 end