From 8c511c0b3ce02df75e8c089cb6cfd4e0a958a0cf Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Tue, 19 Oct 2010 20:53:53 -0700
Subject: swap out some n^2 for some n

---
 .../lib/active_record/relation/spawn_methods.rb      | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

(limited to 'activerecord/lib/active_record')

diff --git a/activerecord/lib/active_record/relation/spawn_methods.rb b/activerecord/lib/active_record/relation/spawn_methods.rb
index e644670019..b8b0898cc8 100644
--- a/activerecord/lib/active_record/relation/spawn_methods.rb
+++ b/activerecord/lib/active_record/relation/spawn_methods.rb
@@ -26,15 +26,21 @@ module ActiveRecord
 
       merged_relation = merged_relation.joins(r.joins_values)
 
-      merged_wheres = @where_values.dup
+      merged_wheres = @where_values.dup + r.where_values
 
-      r.where_values.each do |w|
-        if w.respond_to?(:operator) && w.operator == :==
-          merged_wheres = merged_wheres.reject {|p| p.respond_to?(:operator) && p.operator == :== && p.operand1.name == w.operand1.name }
-        end
+      equality_wheres = merged_wheres.find_all { |w|
+        w.respond_to?(:operator) && w.operator == :==
+      }
 
-        merged_wheres << w
-      end
+      equality_wheres_by_operand = equality_wheres.group_by { |eq|
+        eq.left.name
+      }
+
+      duplicates = equality_wheres_by_operand.map { |name, list|
+        list[0...-1]
+      }.flatten
+
+      merged_wheres -= duplicates
 
       merged_relation.where_values = merged_wheres
 
-- 
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