From 5fbd0ff460ec982cce570266f53176a8cf071326 Mon Sep 17 00:00:00 2001
From: Stan Hu <stanhu@gmail.com>
Date: Sun, 23 Jun 2019 14:34:49 -0700
Subject: Memoize non-existent custom appearances

This saves about 5 SQL calls per page if no custom appearance is
specified.
---
 app/helpers/appearances_helper.rb                       |  5 ++++-
 changelogs/unreleased/sh-strong-memoize-appearances.yml |  5 +++++
 spec/helpers/appearances_helper_spec.rb                 | 16 ++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 changelogs/unreleased/sh-strong-memoize-appearances.yml

diff --git a/app/helpers/appearances_helper.rb b/app/helpers/appearances_helper.rb
index c0db9910143..6b43d52c775 100644
--- a/app/helpers/appearances_helper.rb
+++ b/app/helpers/appearances_helper.rb
@@ -2,6 +2,7 @@
 
 module AppearancesHelper
   include MarkupHelper
+  include Gitlab::Utils::StrongMemoize
 
   def brand_title
     current_appearance&.title.presence || default_brand_title
@@ -25,7 +26,9 @@ module AppearancesHelper
   end
 
   def current_appearance
-    @appearance ||= Appearance.current
+    strong_memoize(:current_appearance) do
+      Appearance.current
+    end
   end
 
   def brand_header_logo
diff --git a/changelogs/unreleased/sh-strong-memoize-appearances.yml b/changelogs/unreleased/sh-strong-memoize-appearances.yml
new file mode 100644
index 00000000000..dc4fe1c4d8e
--- /dev/null
+++ b/changelogs/unreleased/sh-strong-memoize-appearances.yml
@@ -0,0 +1,5 @@
+---
+title: Memoize non-existent custom appearances
+merge_request: 29957
+author:
+type: performance
diff --git a/spec/helpers/appearances_helper_spec.rb b/spec/helpers/appearances_helper_spec.rb
index a3511e078ce..ed3e31b3c53 100644
--- a/spec/helpers/appearances_helper_spec.rb
+++ b/spec/helpers/appearances_helper_spec.rb
@@ -8,6 +8,22 @@ describe AppearancesHelper do
     allow(helper).to receive(:current_user).and_return(user)
   end
 
+  describe '.current_appearance' do
+    it 'memoizes empty appearance' do
+      expect(Appearance).to receive(:current).once
+
+      2.times { helper.current_appearance }
+    end
+
+    it 'memoizes custom appearance' do
+      create(:appearance)
+
+      expect(Appearance).to receive(:current).once.and_call_original
+
+      2.times { helper.current_appearance }
+    end
+  end
+
   describe '#header_message' do
     it 'returns nil when header message field is not set' do
       create(:appearance)
-- 
cgit v1.2.1