From 40ef5c4f149d359b3c6aeff0763f9a973bf41ddb Mon Sep 17 00:00:00 2001
From: Guo Xiang Tan <tgx_world@hotmail.com>
Date: Tue, 20 Jun 2017 13:02:39 +0900
Subject: [PATCH] PERF: Reduce memory allocation by
 `Emoji.unicode_replacements`.

Calling `Emoji.tonable_emojis` fetches from the cache but creates
a giant array each time it is called.

```
MemoryProfiler.report { Emoji.unicode_replacements }.pretty_print
```

Before:

```
Total allocated: 16560770 bytes (246364 objects)
Total retained:  784793 bytes (10624 objects)

allocated memory by gem
-----------------------------------
  10224581  activesupport-4.2.8
   3504241  hiredis-0.6.1
   1449466  discourse/app
    679314  2.4.1/lib
    419592  discourse/lib
    226720  redis-3.3.3
     56680  activerecord-4.2.8
       176  thread_safe-0.3.6
```

After:

```
Total allocated: 2127703 bytes (30556 objects)
Total retained:  798099 bytes (10735 objects)

allocated memory by gem
-----------------------------------
   1270762  discourse/app
    690149  2.4.1/lib
    106977  bootsnap-1.0.0
     48764  activesupport-4.2.8
      5266  logster-1.2.7
      2473  hiredis-0.6.1
      2056  redis-3.3.3
       840  discourse/lib
       240  activerecord-4.2.8
       176  thread_safe-0.3.6
```
---
 app/models/emoji.rb | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/app/models/emoji.rb b/app/models/emoji.rb
index b450597a4f6..b634a8f3535 100644
--- a/app/models/emoji.rb
+++ b/app/models/emoji.rb
@@ -118,6 +118,7 @@ class Emoji
     return @unicode_replacements if @unicode_replacements
 
     @unicode_replacements = {}
+    is_tonable_emojis = Emoji.tonable_emojis
 
     db['emojis'].each do |e|
       next if e['name'] == 'tm'
@@ -126,7 +127,7 @@ class Emoji
       next unless code
 
       @unicode_replacements[code] = e['name']
-      if Emoji.tonable_emojis.include?(e['name'])
+      if is_tonable_emojis.include?(e['name'])
         FITZPATRICK_SCALE.each_with_index do |scale, index|
           toned_code = (code.codepoints.insert(1, scale.to_i(16))).pack("U*")
           @unicode_replacements[toned_code] = "#{e['name']}:t#{index+2}"
@@ -156,6 +157,7 @@ class Emoji
   def self.lookup_unicode(name)
     @reverse_map ||= begin
       map = {}
+      is_tonable_emojis = Emoji.tonable_emojis
 
       db['emojis'].each do |e|
         next if e['name'] == 'tm'
@@ -164,7 +166,7 @@ class Emoji
         next unless code
 
         map[e['name']] = code
-        if Emoji.tonable_emojis.include?(e['name'])
+        if is_tonable_emojis.include?(e['name'])
           FITZPATRICK_SCALE.each_with_index do |scale, index|
             toned_code = (code.codepoints.insert(1, scale.to_i(16))).pack("U*")
             map["#{e['name']}:t#{index+2}"] = toned_code