Improve filtering issues by label performance

app/controllers/concerns/issues_action.rb

@@ -5,8 +5,6 @@ module IssuesAction
   # rubocop:disable Gitlab/ModuleWithInstanceVariables
   def issues
     @finder_type = IssuesFinder
-    @label = finder.labels.first
-
     @issues = issuables_collection
               .non_archived
               .page(params[:page])

app/controllers/concerns/merge_requests_action.rb

@@ -5,7 +5,6 @@ module MergeRequestsAction
   # rubocop:disable Gitlab/ModuleWithInstanceVariables
   def merge_requests
     @finder_type = MergeRequestsFinder
-    @label = finder.labels.first
 
     @merge_requests = issuables_collection.page(params[:page])
 

app/finders/issuable_finder.rb

@@ -374,19 +374,14 @@ class IssuableFinder
   end
 
   def by_label(items)
-    if labels?
+    return items unless labels?
+
+    items =
       if filter_by_no_label?
-        items = items.without_label
+        items.without_label
       else
-        items = items.with_label(label_names, params[:sort])
-        items_projects = projects(items)
-
-        if items_projects
-          label_ids = LabelsFinder.new(current_user, project_ids: items_projects).execute(skip_authorization: true).select(:id)
-          items = items.where(labels: { id: label_ids })
-        end
+        items.with_label(label_names, params[:sort])
       end
-    end
 
     items
   end

changelogs/unreleased/issue_40500.yml

+---
+title: Fix timeout when filtering issues by label
+merge_request:
+author:
+type: performance

db/fixtures/development/22_labeled_issues_seed.rb

+# Creates a project with labeled issues for a user.
+# Run this single seed file using: rake db:seed_fu FILTER=labeled USER_ID=74.
+# If an USER_ID is not provided it will use the last created user.
+require './spec/support/sidekiq'
+
+class Gitlab::Seeder::LabeledIssues
+  include ::Gitlab::Utils
+
+  def initialize(user)
+    @user = user
+  end
+
+  def seed!
+    Sidekiq::Testing.inline! do
+      group = create_group
+      puts '.'
+
+      create_projects(group)
+      puts '.'
+
+      create_labels(group)
+      puts '.'
+
+      create_issues(group)
+      puts '.'
+    end
+
+    print '.'
+  end
+
+  private
+
+  def create_group
+    group_name = "group_of_#{@user.name}#{SecureRandom.hex(4)}"
+
+    group = Group.new(
+      name: group_name,
+      path: group_name,
+      description: FFaker::Lorem.sentence
+    )
+
+    group.save
+
+    group.add_owner(@user)
+
+    group
+  end
+
+  def create_projects(group)
+    5.times do
+      project_name = "project_#{SecureRandom.hex(6)}"
+      params = {
+        namespace_id: group.id,
+        name: project_name,
+        description: FFaker::Lorem.sentence,
+        visibility_level: Gitlab::VisibilityLevel.values.sample
+      }
+
+      Projects::CreateService.new(@user, params).execute
+    end
+  end
+
+  def create_labels(group)
+    group.projects.each do |project|
+      5.times do
+        label_title = FFaker::Vehicle.model
+        Labels::CreateService.new(title: label_title).execute(project: project)
+      end
+    end
+
+    10.times do
+      label_title = FFaker::Product.brand
+      Labels::CreateService.new(title: label_title).execute(group: group)
+    end
+  end
+
+  def create_issues(group)
+    # Get only group labels
+    group_labels =
+      LabelsFinder.new(@user, group_id: group.id).execute.where.not(group_id: nil)
+
+    group.projects.each do |project|
+      label_ids = project.labels.pluck(:id).sample(5)
+      label_ids.push(*group.labels.sample(4))
+
+      50.times do
+        issue_params = {
+          title: FFaker::Lorem.sentence(6),
+          description: FFaker::Lorem.sentence,
+          state: 'opened',
+          label_ids: label_ids
+
+        }
+
+        Issues::CreateService.new(project, @user, issue_params).execute if project.project_feature.present?
+      end
+    end
+  end
+end
+
+Gitlab::Seeder.quiet do
+  user_id = ENV['USER_ID']
+
+  user =
+    if user_id.present?
+      User.find(user_id)
+    else
+      User.last
+    end
+
+  Gitlab::Seeder::LabeledIssues.new(user).seed!
+end