From 52b9af10a12c4356b314b581bd49356cdb98de26 Mon Sep 17 00:00:00 2001
From: Guo Xiang Tan <tgx_world@hotmail.com>
Date: Mon, 19 Mar 2018 11:31:14 +0800
Subject: [PATCH] PERF: PG queries for the `UserEmail#email` column was not
 using the index.

---
 app/controllers/finish_installation_controller.rb | 2 +-
 app/models/user.rb                                | 4 +++-
 lib/admin_user_index_query.rb                     | 2 +-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/app/controllers/finish_installation_controller.rb b/app/controllers/finish_installation_controller.rb
index 848aa127f81..4640677ebca 100644
--- a/app/controllers/finish_installation_controller.rb
+++ b/app/controllers/finish_installation_controller.rb
@@ -15,7 +15,7 @@ class FinishInstallationController < ApplicationController
       email = params[:email].strip
       raise Discourse::InvalidParameters.new unless @allowed_emails.include?(email)
 
-      return redirect_confirm(email) if UserEmail.exists?(email: email)
+      return redirect_confirm(email) if UserEmail.where("lower(email) = ?", email).exists?
 
       @user.email = email
       @user.username = params[:username]
diff --git a/app/models/user.rb b/app/models/user.rb
index 0ac14d77a19..818053f66d7 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -134,7 +134,9 @@ class User < ActiveRecord::Base
   # set to true to optimize creation and save for imports
   attr_accessor :import_mode
 
-  scope :with_email, ->(email) { joins(:user_emails).where(user_emails: { email: email }) }
+  scope :with_email, ->(email) do
+    joins(:user_emails).where("lower(user_emails.email) = ?", email)
+  end
 
   scope :human_users, -> { where('users.id > 0') }
 
diff --git a/lib/admin_user_index_query.rb b/lib/admin_user_index_query.rb
index fd3da2a23af..ed2a0b5f55f 100644
--- a/lib/admin_user_index_query.rb
+++ b/lib/admin_user_index_query.rb
@@ -104,7 +104,7 @@ class AdminUserIndexQuery
   def filter_by_user_with_bypass(filter)
     if filter =~ /.+@.+/
       # probably an email so try the bypass
-      user_id = UserEmail.where(email: filter.downcase).pluck(:user_id).first
+      user_id = UserEmail.where("lower(email) = ?", filter.downcase).pluck(:user_id).first
       if user_id
         return @query.where('users.id = ?', user_id)
       end