Merge branch 'sh-optimize-todos-api' into 'master'

Significantly reduce N+1 queries in /api/v4/todos endpoint

Closes #40378

See merge request gitlab-org/gitlab-ce!25711

3 files changed, 16 insertions, 1 deletions

diff --git a/app/models/issue.rb b/app/models/issue.rb
index 071ad50fddc..deab53d25e7 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -64,6 +64,7 @@ class Issue < ActiveRecord::Base
   scope :order_closest_future_date, -> { reorder('CASE WHEN issues.due_date >= CURRENT_DATE THEN 0 ELSE 1 END ASC, ABS(CURRENT_DATE - issues.due_date) ASC') }
 
   scope :preload_associations, -> { preload(:labels, project: :namespace) }
+  scope :with_api_entity_associations, -> { preload(:timelogs, :assignees, :author, :notes, :labels, project: [:route, { namespace: :route }] ) }
 
   scope :public_only, -> { where(confidential: false) }
   scope :confidential_only, -> { where(confidential: true) }
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index b67797f5404..acf80addc6a 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -184,6 +184,13 @@ class MergeRequest < ActiveRecord::Base
   scope :assigned, -> { where("assignee_id IS NOT NULL") }
   scope :unassigned, -> { where("assignee_id IS NULL") }
   scope :assigned_to, ->(u) { where(assignee_id: u.id)}
+  scope :with_api_entity_associations, -> {
+    preload(:author, :assignee, :notes, :labels, :milestone, :timelogs,
+            latest_merge_request_diff: [:merge_request_diff_commits],
+            metrics: [:latest_closed_by, :merged_by],
+            target_project: [:route, { namespace: :route }],
+            source_project: [:route, { namespace: :route }])
+  }
 
   participant :assignee
 
diff --git a/app/models/todo.rb b/app/models/todo.rb
index d9b86d941b6..2b0dee875a3 100644
--- a/app/models/todo.rb
+++ b/app/models/todo.rb
@@ -31,7 +31,13 @@ class Todo < ActiveRecord::Base
   belongs_to :note
   belongs_to :project
   belongs_to :group
-  belongs_to :target, polymorphic: true, touch: true # rubocop:disable Cop/PolymorphicAssociations
+  belongs_to :target, -> {
+    if self.klass.respond_to?(:with_api_entity_associations)
+      self.with_api_entity_associations
+    else
+      self
+    end
+  }, polymorphic: true, touch: true # rubocop:disable Cop/PolymorphicAssociations
   belongs_to :user
 
   delegate :name, :email, to: :author, prefix: true, allow_nil: true
@@ -52,6 +58,7 @@ class Todo < ActiveRecord::Base
   scope :for_type, -> (type) { where(target_type: type) }
   scope :for_target, -> (id) { where(target_id: id) }
   scope :for_commit, -> (id) { where(commit_id: id) }
+  scope :with_api_entity_associations, -> { preload(:target, :author, :note, group: :route, project: [:route, { namespace: :route }]) }
 
   state_machine :state, initial: :pending do
     event :done do