Merge branch 'master' into sprockets

Conflicts:
	railties/lib/rails/application/configuration.rb

4 files changed, 50 insertions, 17 deletions

diff --git a/activerecord/lib/active_record/relation/batches.rb b/activerecord/lib/active_record/relation/batches.rb
index bf5a60f458..d52b84179f 100644
--- a/activerecord/lib/active_record/relation/batches.rb
+++ b/activerecord/lib/active_record/relation/batches.rb
@@ -83,7 +83,7 @@ module ActiveRecord
     private
 
     def batch_order
-      "#{table_name}.#{primary_key} ASC"
+      "#{quoted_table_name}.#{quoted_primary_key} ASC"
     end
   end
 end
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index c1842b1a96..869eebfa34 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -196,24 +196,22 @@ module ActiveRecord
     end
 
     def execute_simple_calculation(operation, column_name, distinct) #:nodoc:
-      column = aggregate_column(column_name)
-
       # Postgresql doesn't like ORDER BY when there are no GROUP BY
       relation = except(:order)
-      select_value = operation_over_aggregate_column(column, operation, distinct)
 
-      relation.select_values = [select_value]
+      if operation == "count" && (relation.limit_value || relation.offset_value)
+        # Shortcut when limit is zero.
+        return 0 if relation.limit_value == 0
 
-      query_builder = relation.arel
+        query_builder = build_count_subquery(relation, column_name, distinct)
+      else
+        column = aggregate_column(column_name)
 
-      if operation == "count"
-        limit  = relation.limit_value
-        offset = relation.offset_value
+        select_value = operation_over_aggregate_column(column, operation, distinct)
 
-        unless limit && offset
-          query_builder.limit  = nil
-          query_builder.offset = nil
-        end
+        relation.select_values = [select_value]
+
+        query_builder = relation.arel
       end
 
       type_cast_calculated_value(@klass.connection.select_value(query_builder.to_sql), column_for(column_name), operation)
@@ -312,5 +310,18 @@ module ActiveRecord
         select if select !~ /(,|\*)/
       end
     end
+
+    def build_count_subquery(relation, column_name, distinct)
+      column_alias = Arel.sql('count_column')
+      subquery_alias = Arel.sql('subquery_for_count')
+
+      aliased_column = aggregate_column(column_name == :all ? 1 : column_name).as(column_alias)
+      relation.select_values = [aliased_column]
+      subquery = relation.arel.as(subquery_alias)
+
+      sm = Arel::SelectManager.new relation.engine
+      select_value = operation_over_aggregate_column(column_alias, 'count', distinct)
+      sm.project(select_value).from(subquery)
+    end
   end
 end
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 426000fde1..8fa315bdf3 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -123,6 +123,12 @@ module ActiveRecord
       end
     end
 
+    # Same as +first+ but raises <tt>ActiveRecord::RecordNotFound</tt> if no record
+    # is found. Note that <tt>first!</tt> accepts no arguments.
+    def first!
+      first or raise RecordNotFound
+    end
+
     # A convenience wrapper for <tt>find(:last, *args)</tt>. You can pass in all the
     # same arguments to this method as you can to <tt>find(:last)</tt>.
     def last(*args)
@@ -137,6 +143,12 @@ module ActiveRecord
       end
     end
 
+    # Same as +last+ but raises <tt>ActiveRecord::RecordNotFound</tt> if no record
+    # is found. Note that <tt>last!</tt> accepts no arguments.
+    def last!
+      last or raise RecordNotFound
+    end
+
     # A convenience wrapper for <tt>find(:all, *args)</tt>. You can pass in all the
     # same arguments to this method as you can to <tt>find(:all)</tt>.
     def all(*args)
@@ -171,7 +183,9 @@ module ActiveRecord
     def exists?(id = nil)
       id = id.id if ActiveRecord::Base === id
 
-      relation = select("1").limit(1)
+      join_dependency = construct_join_dependency_for_association_find
+      relation = construct_relation_for_association_find(join_dependency)
+      relation = relation.except(:select).select("1").limit(1)
 
       case id
       when Array, Hash
@@ -180,14 +194,13 @@ module ActiveRecord
         relation = relation.where(table[primary_key].eq(id)) if id
       end
 
-      relation.first ? true : false
+      connection.select_value(relation.to_sql) ? true : false
     end
 
     protected
 
     def find_with_associations
-      including = (@eager_load_values + @includes_values).uniq
-      join_dependency = ActiveRecord::Associations::JoinDependency.new(@klass, including, [])
+      join_dependency = construct_join_dependency_for_association_find
       relation = construct_relation_for_association_find(join_dependency)
       rows = connection.select_all(relation.to_sql, 'SQL', relation.bind_values)
       join_dependency.instantiate(rows)
@@ -195,6 +208,11 @@ module ActiveRecord
       []
     end
 
+    def construct_join_dependency_for_association_find
+      including = (@eager_load_values + @includes_values).uniq
+      ActiveRecord::Associations::JoinDependency.new(@klass, including, [])
+    end
+
     def construct_relation_for_association_calculations
       including = (@eager_load_values + @includes_values).uniq
       join_dependency = ActiveRecord::Associations::JoinDependency.new(@klass, including, arel.froms.first)
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index 9470e7c6c5..02b7056989 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -62,6 +62,10 @@ module ActiveRecord
       relation
     end
 
+    def reorder(*args)
+      except(:order).order(args)
+    end
+
     def joins(*args)
       return self if args.compact.blank?