CSV export performance optimizations

Avoids creating unnecessary arrays in Issuable#labels_hash
Uses cached issues count in CSV export modal

app/controllers/projects/issues_controller.rb

@@ -25,7 +25,6 @@ class Projects::IssuesController < Projects::ApplicationController
   def index
     @collection_type    = "Issue"
     @issues             = issues_collection
-    @issues_count       = @issues.count
 
     @issues             = @issues.page(params[:page])
     @issuable_meta_data = issuable_meta_data(@issues, @collection_type)

app/helpers/issuables_helper.rb

@@ -134,10 +134,7 @@ module IssuablesHelper
 
     state_title = titles[state] || state.to_s.humanize
 
-    count =
-      Rails.cache.fetch(issuables_state_counter_cache_key(issuable_type, state), expires_in: 2.minutes) do
-        issuables_count_for_state(issuable_type, state)
-      end
+    count = cached_issuables_count_for_state(issuable_type, state)
 
     html = content_tag(:span, state_title)
     html << " " << content_tag(:span, number_with_delimiter(count), class: 'badge')
@@ -145,6 +142,12 @@ module IssuablesHelper
     html.html_safe
   end
 
+  def cached_issuables_count_for_state(issuable_type, state)
+    Rails.cache.fetch(issuables_state_counter_cache_key(issuable_type, state), expires_in: 2.minutes) do
+      issuables_count_for_state(issuable_type, state)
+    end
+  end
+
   def cached_assigned_issuables_count(assignee, issuable_type, state)
     cache_key = hexdigest(['assigned_issuables_count', assignee.id, issuable_type, state].join('-'))
     Rails.cache.fetch(cache_key, expires_in: 2.minutes) do

app/models/concerns/issuable.rb

@@ -179,8 +179,9 @@ module Issuable
     end
 
     def labels_hash
-      eager_load(:labels).pluck(:id, 'labels.title').inject(Hash.new([])) do |memo, (issue_id, label)|
-        memo[issue_id] += [label]
+      eager_load(:labels).pluck(:id, 'labels.title').inject({}) do |memo, (issue_id, label)|
+        memo[issue_id] ||= []
+        memo[issue_id] << label
         memo
       end
     end

app/views/projects/issues/export_issues/_csv_download.html.haml

@@ -10,7 +10,7 @@
       .modal-header
         = icon('check', { class: 'export-checkmark' })
         %strong
-          #{@issues_count} issues selected
+          #{cached_issuables_count_for_state(:issues, params['state'])} issues selected
       .modal-body
         %div
           The CSV export will be created in the background. Once it is finished, it will be attached to an email sent to

spec/features/issues/csv_spec.rb

@@ -12,7 +12,7 @@ describe 'Issues csv', feature: true do
 
   def request_csv(params = {})
     visit namespace_project_issues_path(project.namespace, project, params)
-    click_on 'Download CSV'
+    click_on 'Export as CSV'
     click_on 'Export issues'
   end