From e98a877d6c0a5798ac9011e9d1b5331ae66257bb Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Tue, 8 Oct 2013 15:13:12 -0700
Subject: transform the association input so we can avoid type checks later.

We should consider moving the input munging outside the class
instantiation
---
 .../active_record/associations/join_dependency.rb  | 48 ++++++++++++++--------
 1 file changed, 31 insertions(+), 17 deletions(-)

diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index 74cbb95137..1d9db51c34 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -6,6 +6,30 @@ module ActiveRecord
 
       attr_reader :join_parts, :reflections, :alias_tracker, :base_klass
 
+      def self.make_tree(associations)
+        hash = {}
+        walk_tree associations, hash
+        hash
+      end
+
+      def self.walk_tree(associations, hash)
+        case associations
+        when Symbol, String
+          hash[associations.to_sym] ||= {}
+        when Array
+          associations.each do |assoc|
+            walk_tree assoc, hash
+          end
+        when Hash
+          associations.each do |k,v|
+            cache = hash[k] ||= {}
+            walk_tree v, cache
+          end
+        else
+          raise ConfigurationError, associations.inspect
+        end
+      end
+
       # base is the base class on which operation is taking place.
       # associations is the list of associations which are joined using hash, symbol or array.
       # joins is the list of all string join commnads and arel nodes.
@@ -34,13 +58,14 @@ module ActiveRecord
         @reflections   = []
         @alias_tracker = AliasTracker.new(base.connection, joins)
         @alias_tracker.aliased_name_for(base.table_name) # Updates the count for base.table_name to 1
-        build(associations, join_parts.last, Arel::InnerJoin)
+        tree = self.class.make_tree associations
+        build tree, join_parts.last, Arel::InnerJoin
       end
 
       def graft(*associations)
         associations.each do |association|
-          join_associations.detect {|a| association == a} ||
-            build(association.reflection.name, find_parent_part(association.parent) || join_base, association.join_type)
+          join_associations.detect { |a| association == a } ||
+            find_or_build_scalar(association.reflection.name, find_parent_part(association.parent) || join_base, association.join_type)
         end
         self
       end
@@ -150,20 +175,9 @@ module ActiveRecord
       end
 
       def build(associations, parent, join_type)
-        case associations
-        when Symbol, String
-          find_or_build_scalar associations, parent, join_type
-        when Array
-          associations.each do |association|
-            build(association, parent, join_type)
-          end
-        when Hash
-          associations.each do |left, right|
-            join_association = find_or_build_scalar left, parent, join_type
-            build(right, join_association, join_type)
-          end
-        else
-          raise ConfigurationError, associations.inspect
+        associations.each do |left, right|
+          join_association = find_or_build_scalar left, parent, join_type
+          build right, join_association, join_type
         end
       end
 
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