Fixes to have all test passing on PostgreSQL.

Calculations now use construct_calculation_arel, making construct_finder_arel less hackish.

Updated ARel to support PostgreSQL.

activerecord/lib/active_record/base.rb

@@ -688,9 +688,9 @@ module ActiveRecord #:nodoc:
       #   Person.exists?(['name LIKE ?', "%#{query}%"])
       #   Person.exists?
       def exists?(id_or_conditions = {})
-        construct_finder_arel({
+        connection.select_all(construct_finder_arel({
-          :conditions =>expand_id_conditions(id_or_conditions)
+          :conditions => expand_id_conditions(id_or_conditions)
-        }).project(arel_table[primary_key]).take(1).count > 0
+        }).project(arel_table[primary_key]).take(1).to_sql).size > 0
       end
 
       # Creates an object (or multiple objects) and saves it to the database, if validations pass.
@@ -1688,9 +1688,9 @@ module ActiveRecord #:nodoc:
           scope = scope(:find)
 
           # TODO add lock to Arel
-          arel_table(options[:from] || table_name).
+          arel_table(table_name).
-            join(options[:merged_joins] || construct_join(options[:joins], scope)).
+            join(construct_join(options[:joins], scope)).
-            where(options[:merged_conditions] || construct_conditions(options[:conditions], scope)).
+            where(construct_conditions(options[:conditions], scope)).
             project(options[:select] || (scope && scope[:select]) || default_select(options[:joins] || (scope && scope[:joins]))).
             group(construct_group(options[:group], options[:having], scope)).
             order(construct_order(options[:order], scope)).
@@ -1704,7 +1704,6 @@ module ActiveRecord #:nodoc:
         end
 
         def construct_join(joins, scope = :auto)
-          scope = scope(:find) if :auto == scope
           merged_joins = scope && scope[:joins] && joins ? merge_joins(scope[:joins], joins) : (joins || scope && scope[:joins])
           case merged_joins
           when Symbol, Hash, Array
@@ -1738,7 +1737,6 @@ module ActiveRecord #:nodoc:
 
         def construct_order(order, scope = :auto)
           sql = ''
-          scope = scope(:find) if :auto == scope
           scoped_order = scope[:order] if scope
           if order
             sql << order.to_s
@@ -1752,19 +1750,16 @@ module ActiveRecord #:nodoc:
         end
 
         def construct_limit(options, scope = :auto)
-          scope = scope(:find) if :auto == scope
           options[:limit] ||= scope[:limit] if scope
           options[:limit]
         end
 
         def construct_offset(options, scope = :auto)
-          scope = scope(:find) if :auto == scope
           options[:offset] ||= scope[:offset] if scope
           options[:offset]
         end
 
         def construct_conditions(conditions, scope = :auto)
-          scope = scope(:find) if :auto == scope
           conditions = [conditions]
           conditions << scope[:conditions] if scope
           conditions << type_condition if finder_needs_type_condition?

activerecord/lib/active_record/calculations.rb

@@ -153,9 +153,9 @@ module ActiveRecord
           conditions << construct_limited_ids_condition(conditions, options, join_dependency) if join_dependency && !using_limitable_reflections?(join_dependency.reflections) && ((scope && scope[:limit]) || options[:limit])
 
           if options[:group]
-            return execute_grouped_calculation(operation, column_name, options.merge(:merged_conditions => conditions, :merged_joins => joins, :distinct => distinct))
+            return execute_grouped_calculation(operation, column_name, options.merge(:conditions => conditions, :joins => joins, :distinct => distinct))
           else
-            return execute_simple_calculation(operation, column_name, options.merge(:merged_conditions => conditions, :merged_joins => joins, :distinct => distinct))
+            return execute_simple_calculation(operation, column_name, options.merge(:conditions => conditions, :joins => joins, :distinct => distinct))
           end
         end
         0
@@ -163,15 +163,16 @@ module ActiveRecord
 
       def execute_simple_calculation(operation, column_name, options) #:nodoc:
         table = options[:from] || table_name
+
         value = if operation == 'count'
           if column_name == :all && options[:select].blank?
             column_name = "*"
           elsif !options[:select].blank?
             column_name = options[:select]
           end
-          construct_finder_arel(options.merge(:select =>  Arel::Attribute.new(Arel(table), column_name).count(options[:distinct]))).select_value
+          construct_calculation_arel(options.merge(:select =>  Arel::Attribute.new(Arel(table), column_name).count(options[:distinct]))).select_value
         else
-          construct_finder_arel(options.merge(:select =>  Arel::Attribute.new(Arel(table), column_name).send(operation))).select_value
+          construct_calculation_arel(options.merge(:select =>  Arel::Attribute.new(Arel(table), column_name).send(operation))).select_value
         end
 
         type_cast_calculated_value(value, column_for(column_name), operation)
@@ -196,7 +197,7 @@ module ActiveRecord
           options[:select] = "#{arel_column.as(aggregate_alias).to_sql}, #{group_field} AS #{group_alias}"
         end
 
-        calculated_data = connection.select_all(construct_finder_sql(options))
+        calculated_data = connection.select_all(construct_calculation_arel(options).to_sql)
 
         if association
           key_ids     = calculated_data.collect { |row| row[group_alias] }
@@ -213,7 +214,22 @@ module ActiveRecord
         end
       end
 
-      protected
+     protected
+
+        def construct_calculation_arel(options)
+          scope = scope(:find)
+
+          arel_table(options[:from] || table_name).
+            join(options[:joins]).
+            where(options[:conditions]).
+            project(options[:select]).
+            group(construct_group(options[:group], options[:having], scope)).
+            order(options[:order].to_s).
+            take(construct_limit(options, scope)).
+            skip(construct_offset(options, scope)
+          )
+        end
+
         def construct_count_options_from_args(*args)
           options     = {}
           column_name = :all

arel

@@ -1 +1 @@
-Subproject commit f44853a5aa7f4481d99a3af4585f3a51272bc7f7
+Subproject commit de843c86518e4ac871d4bb5b0873bb6c184ac304