Revert "ARel only requires the connection from the AR class. Simply return the...

Revert "ARel only requires the connection from the AR class. Simply return the AR class rather than jump through hoops and store ivars"

This reverts commit d65e3b48.

activerecord/lib/active_record/base.rb

@@ -747,7 +747,7 @@ def reset_column_information
         undefine_attribute_methods
         reset_column_cache
         @column_names = @content_columns = @dynamic_methods_hash = @inheritance_column = nil
-        @relation = nil
+        @arel_engine = @relation = nil
       end
 
       def reset_column_cache # :nodoc:
@@ -856,7 +856,13 @@ def arel_table
       end
 
       def arel_engine
-        self
+        @arel_engine ||= begin
+          if self == ActiveRecord::Base
+            ActiveRecord::Base
+          else
+            connection_handler.connection_pools[name] ? self : superclass.arel_engine
+          end
+        end
       end
 
       # Returns a scope for this class without taking into account the default_scope.

activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb

@@ -50,34 +50,34 @@ def connection
     # may be returned on an error.
     def self.establish_connection(spec = nil)
       case spec
-      when nil
-        raise AdapterNotSpecified unless defined?(Rails.env)
-        establish_connection(Rails.env)
-      when ConnectionSpecification
-        self.connection_handler.establish_connection(name, spec)
-      when Symbol, String
-        if configuration = configurations[spec.to_s]
-          establish_connection(configuration)
+        when nil
+          raise AdapterNotSpecified unless defined?(Rails.env)
+          establish_connection(Rails.env)
+        when ConnectionSpecification
+          self.connection_handler.establish_connection(name, spec)
+        when Symbol, String
+          if configuration = configurations[spec.to_s]
+            establish_connection(configuration)
+          else
+            raise AdapterNotSpecified, "#{spec} database is not configured"
+          end
         else
-          raise AdapterNotSpecified, "#{spec} database is not configured"
-        end
-      else
-        spec = spec.symbolize_keys
-        unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end
+          spec = spec.symbolize_keys
+          unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end
 
-        begin
-          require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
-        rescue LoadError => e
-          raise "Please install the #{spec[:adapter]} adapter: `gem install activerecord-#{spec[:adapter]}-adapter` (#{e})"
-        end
+          begin
+            require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
+          rescue LoadError => e
+            raise "Please install the #{spec[:adapter]} adapter: `gem install activerecord-#{spec[:adapter]}-adapter` (#{e})"
+          end
 
-        adapter_method = "#{spec[:adapter]}_connection"
-        unless respond_to?(adapter_method)
-          raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter"
-        end
+          adapter_method = "#{spec[:adapter]}_connection"
+          unless respond_to?(adapter_method)
+            raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter"
+          end
 
-        remove_connection
-        establish_connection(ConnectionSpecification.new(spec, adapter_method))
+          remove_connection
+          establish_connection(ConnectionSpecification.new(spec, adapter_method))
       end
     end
 

activerecord/test/cases/multiple_db_test.rb

@@ -84,8 +84,8 @@ def test_transactions_across_databases
     assert_equal "Ruby Developer", Entrant.find(1).name
   end
 
-  def test_connections
-    assert_not_equal Entrant.connection, Course.connection
-    assert_equal Entrant.connection, Bird.connection
+  def test_arel_table_engines
+    assert_not_equal Entrant.arel_engine, Course.arel_engine
+    assert_equal Entrant.arel_engine, Bird.arel_engine
   end
 end