From 0675210c959153ae826f3ceccb6b4fbcb2783daa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rafael=20Mendon=C3=A7a=20Fran=C3=A7a?=
 <rafaelmfranca@gmail.com>
Date: Tue, 8 Sep 2015 01:04:22 -0300
Subject: Memoized reflections accessor
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Its value never change since associations are defined at class load time
so there is no need to build the hash everytime the method is called.

Before this change:

    Calculating -------------------------------------
             reflections   804.000  i/100ms
    -------------------------------------------------
             reflections      8.213k (±26.2%) i/s -     36.180k

After this change:

    Calculating -------------------------------------
             reflections    24.548k i/100ms
    -------------------------------------------------
             reflections      1.591M (±25.7%) i/s -      7.364M

Benchmark script:

    require 'bundler/setup'

    require 'active_record'
    require 'benchmark/ips'

    ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
    ActiveRecord::Migration.verbose = false

    ActiveRecord::Schema.define do
      100.times do |i|
        create_table "users#{i}", force: true
      end

      create_table :cars, force: true do |t|
        100.times do |i|
          t.references "users#{i}"
        end
      end
    end

    class Car < ActiveRecord::Base
      100.times do |i|
        belongs_to "users#{i}".to_sym
      end
    end

    Benchmark.ips do |x|
      x.report('reflections') { Car.reflections }
    end
---
 activerecord/lib/active_record/reflection.rb | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

(limited to 'activerecord/lib')

diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index 5360db6a19..e7f56d09e3 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -32,6 +32,7 @@ module ActiveRecord
     end
 
     def self.add_reflection(ar, name, reflection)
+      ar.clear_reflections_cache
       ar._reflections = ar._reflections.merge(name.to_s => reflection)
     end
 
@@ -67,18 +68,22 @@ module ActiveRecord
       #
       # @api public
       def reflections
-        ref = {}
-        _reflections.each do |name, reflection|
-          parent_reflection = reflection.parent_reflection
+        @__reflections ||= begin
+          ref = {}
 
-          if parent_reflection
-            parent_name = parent_reflection.name
-            ref[parent_name.to_s] = parent_reflection
-          else
-            ref[name] = reflection
+          _reflections.each do |name, reflection|
+            parent_reflection = reflection.parent_reflection
+
+            if parent_reflection
+              parent_name = parent_reflection.name
+              ref[parent_name.to_s] = parent_reflection
+            else
+              ref[name] = reflection
+            end
           end
+
+          ref
         end
-        ref
       end
 
       # Returns an array of AssociationReflection objects for all the
@@ -118,6 +123,10 @@ module ActiveRecord
       def reflect_on_all_autosave_associations
         reflections.values.select { |reflection| reflection.options[:autosave] }
       end
+
+      def clear_reflections_cache #:nodoc:
+        @__reflection = nil
+      end
     end
 
     # Holds all the methods that are shared between MacroReflection, AssociationReflection
-- 
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