Merge branch 'user-by-login-performance' into 'master'

Improve User.by_login performance

This greatly speeds up the performance of `User.by_login`. I adopted some changes from @haynes in this patch, the credits go to him for coming up with those originally.

Fixes #2341

See merge request !1545

1 files changed, 8 insertions, 2 deletions

diff --git a/app/models/user.rb b/app/models/user.rb
index 889d2d3b867..17ccb3b8788 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -68,6 +68,7 @@ class User < ActiveRecord::Base
   include Referable
   include Sortable
   include TokenAuthenticatable
+  include CaseSensitivity
 
   default_value_for :admin, false
   default_value_for :can_create_group, gitlab_config.default_can_create_group
@@ -273,8 +274,13 @@ class User < ActiveRecord::Base
     end
 
     def by_login(login)
-      where('lower(username) = :value OR lower(email) = :value',
-            value: login.to_s.downcase).first
+      return nil unless login
+
+      if login.include?('@'.freeze)
+        unscoped.iwhere(email: login).take
+      else
+        unscoped.iwhere(username: login).take
+      end
     end
 
     def find_by_username!(username)