From 6751b1032070a3b26e89a151cbe564a354eb580d Mon Sep 17 00:00:00 2001
From: lvl0nax <lvl0nax@gmail.com>
Date: Fri, 13 May 2016 16:43:01 +0300
Subject: Perfomance fix for Enumerable#index_by
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Calculating -------------------------------------
              before    34.731k i/100ms
               after    48.206k i/100ms
-------------------------------------------------
              before    508.451k (± 1.2%) i/s -      2.570M
               after    720.068k (± 0.9%) i/s -      3.615M
Comparison:
               after:   720067.6 i/s
              before:   508451.1 i/s - 1.42x slower
---
 activesupport/lib/active_support/core_ext/enumerable.rb | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'activesupport/lib')

diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index 9a893157ea..8ebe758078 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -34,7 +34,9 @@ module Enumerable
   #     => { "Chade- Fowlersburg-e" => <Person ...>, "David Heinemeier Hansson" => <Person ...>, ...}
   def index_by
     if block_given?
-      Hash[map { |elem| [yield(elem), elem] }]
+      result = {}
+      each { |elem| result[yield(elem)] = elem }
+      result
     else
       to_enum(:index_by) { size if respond_to?(:size) }
     end
-- 
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