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.

3 files changed, 5 insertions, 5 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