From 0d6a51d74ec244392eeb2b1d47302403d0d86dce Mon Sep 17 00:00:00 2001
From: Tom Hughes <tom@compton.nu>
Date: Fri, 18 Nov 2011 10:21:37 +0000
Subject: [PATCH] Monkey patch CPK to fix problems with polymorphic has_many

---
 config/initializers/composite_primary_keys.rb | 80 +++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 config/initializers/composite_primary_keys.rb

diff --git a/config/initializers/composite_primary_keys.rb b/config/initializers/composite_primary_keys.rb
new file mode 100644
index 000000000..e928df39f
--- /dev/null
+++ b/config/initializers/composite_primary_keys.rb
@@ -0,0 +1,80 @@
+module ActiveRecord
+  module Associations
+    class AssociationScope
+      def add_constraints(scope)
+        tables = construct_tables
+
+        chain.each_with_index do |reflection, i|
+          table, foreign_table = tables.shift, tables.first
+
+          if reflection.source_macro == :has_and_belongs_to_many
+            join_table = tables.shift
+
+            # CPK
+            # scope = scope.joins(join(
+            #  join_table,
+            #  table[reflection.active_record_primary_key].
+            #    eq(join_table[reflection.association_foreign_key])
+            #))
+            predicate = cpk_join_predicate(table, reflection.association_primary_key,
+                                           join_table, reflection.association_foreign_key)
+            scope = scope.joins(join(join_table, predicate))
+
+            table, foreign_table = join_table, tables.first
+          end
+
+          if reflection.source_macro == :belongs_to
+            if reflection.options[:polymorphic]
+              key = reflection.association_primary_key(klass)
+            else
+              key = reflection.association_primary_key
+            end
+
+            foreign_key = reflection.foreign_key
+          else
+            key         = reflection.foreign_key
+            foreign_key = reflection.active_record_primary_key
+          end
+
+          conditions = self.conditions[i]
+
+          if reflection == chain.last
+            # CPK
+            # scope = scope.where(table[key].eq(owner[foreign_key]))
+            predicate = cpk_join_predicate(table, key, owner, foreign_key)
+            scope = scope.where(predicate)
+
+            if reflection.type
+              scope = scope.where(table[reflection.type].eq(owner.class.base_class.name))
+            end
+
+            conditions.each do |condition|
+              if options[:through] && condition.is_a?(Hash)
+                condition = { table.name => condition }
+              end
+
+              scope = scope.where(interpolate(condition))
+            end
+          else
+            # CPK
+            # constraint = table[key].eq(foreign_table[foreign_key])
+            constraint = cpk_join_predicate(table, key, foreign_table, foreign_key)
+
+            if reflection.type
+              type = chain[i + 1].klass.base_class.name
+              constraint = constraint.and(table[reflection.type].eq(type))
+            end
+
+            scope = scope.joins(join(foreign_table, constraint))
+
+            unless conditions.empty?
+              scope = scope.where(sanitize(conditions, table))
+            end
+          end
+        end
+
+        scope
+      end
+    end
+  end
+end
-- 
2.39.5