Merge branch '4794-add-eager-loading-to-issue-metrics' into 'master'

Remove N+1 query from Issue::Metrics#record!

See merge request gitlab-org/gitlab!60589

app/models/issue/metrics.rb

@@ -24,6 +24,10 @@ class Issue::Metrics < ApplicationRecord
   private
 
   def issue_assigned_to_list_label?
-    issue.labels.any? { |label| label.lists.present? }
+    # Avoid another DB lookup when issue.labels are empty by adding a guard clause here
+    # We can't use issue.labels.empty? because that will cause a `Label Exists?` DB lookup
+    return false if issue.labels.length == 0 # rubocop:disable Style/ZeroLengthPredicate
+
+    issue.labels.includes(:lists).any? { |label| label.lists.present? }
   end
 end

changelogs/unreleased/4794-add-eager-loading-to-issue-metrics.yml

+---
+title: Remove N+1 query from Issue::Metrics#record
+merge_request: 60589
+author:
+type: performance

spec/models/issue/metrics_spec.rb

@@ -80,5 +80,20 @@ RSpec.describe Issue::Metrics do
         expect(metrics.first_added_to_board_at).to be_like_time(time)
       end
     end
+
+    describe "#record!" do
+      it "does not cause an N+1 query" do
+        label = create(:label)
+        subject.update!(label_ids: [label.id])
+
+        control_count = ActiveRecord::QueryRecorder.new { Issue::Metrics.find_by(issue: subject).record! }.count
+
+        additional_labels = create_list(:label, 4)
+
+        subject.update!(label_ids: additional_labels.map(&:id))
+
+        expect { Issue::Metrics.find_by(issue: subject).record! }.not_to exceed_query_limit(control_count)
+      end
+    end
   end
 end