Merge branch 'sh-optimize-label-finder' into 'master'

Reduce overhead of LabelFinder by avoiding #presence call

Some users experienced 502 timeouts when viewing group labels.
Labels#open_issues_count and Label#open_merge_requests_count were
taking a long time to load because they were loading every ActiveRecord
of the user-accessible projects into memory. This change modifies so
that only the IDs are loaded into memory.

Closes #23684

See merge request !7094
Signed-off-by: Rémy Coutable <remy@rymai.me>

CHANGELOG.md

@@ -19,6 +19,7 @@ Please view this file on the master branch, on stable branches it's out of date.
   - Fix reply-by-email not working due to queue name mismatch. !7068
   - Fix 404 for group pages when GitLab setup uses relative url. !7071
   - Fix `User#to_reference`. !7088
+  - Reduce overhead of `LabelFinder` by avoiding `#presence` call. !7094
   - Fix unauthorized users dragging on issue boards. !7096
 
 ## 8.13.0 (2016-10-22)

app/finders/labels_finder.rb

@@ -50,7 +50,7 @@ class LabelsFinder < UnionFinder
   end
 
   def projects_ids
-    params[:project_ids].presence
+    params[:project_ids]
   end
 
   def title