fix another N+1 query for label priorities34510-board-issues-sql-speedup

added a QueryRecorder for IssuesController#index.json

3 files changed, 19 insertions, 3 deletions

diff --git a/app/controllers/boards/issues_controller.rb b/app/controllers/boards/issues_controller.rb
index 1c33f9a69d8..0d74078645a 100644
--- a/app/controllers/boards/issues_controller.rb
+++ b/app/controllers/boards/issues_controller.rb
@@ -12,10 +12,10 @@ module Boards
       issues = issues.page(params[:page]).per(params[:per] || 20)
       make_sure_position_is_set(issues)
       issues = issues.preload(:project,
-                              :labels,
                               :milestone,
                               :assignees,
-                              :notes => [:award_emoji, :author]
+                              labels: [:priorities],
+                              notes: [:award_emoji, :author]
                              )
 
       render json: {
diff --git a/app/models/label.rb b/app/models/label.rb
index 958141a7358..899028a01a0 100644
--- a/app/models/label.rb
+++ b/app/models/label.rb
@@ -127,7 +127,12 @@ class Label < ActiveRecord::Base
   end
 
   def priority(project)
-    priorities.find_by(project: project).try(:priority)
+    priority = if priorities.loaded?
+                 priorities.first { |p| p.project == project }
+               else
+                 priorities.find_by(project: project)
+               end
+    priority.try(:priority)
   end
 
   def template?
diff --git a/spec/controllers/boards/issues_controller_spec.rb b/spec/controllers/boards/issues_controller_spec.rb
index dfa06c78d46..5163099cd98 100644
--- a/spec/controllers/boards/issues_controller_spec.rb
+++ b/spec/controllers/boards/issues_controller_spec.rb
@@ -45,6 +45,17 @@ describe Boards::IssuesController do
           expect(parsed_response.length).to eq 2
           expect(development.issues.map(&:relative_position)).not_to include(nil)
         end
+
+        it 'avoids N+1 database queries' do
+          create(:labeled_issue, project: project, labels: [development])
+          control_count = ActiveRecord::QueryRecorder.new { list_issues(user: user, board: board, list: list2) }.count
+
+          # 25 issues is bigger than the page size
+          # the relative position will ignore the `#make_sure_position_set` queries
+          create_list(:labeled_issue, 25, project: project, labels: [development], assignees: [johndoe], relative_position: 1)
+
+          expect { list_issues(user: user, board: board, list: list2) }.not_to exceed_query_limit(control_count)
+        end
       end
 
       context 'with invalid list id' do