almost fisted

activerecord/lib/active_record/base.rb

@@ -679,16 +679,12 @@ module ActiveRecord #:nodoc:
 
       # Returns an array of column objects for the table associated with this class.
       def columns
-        @@columns[table_name] ||= connection.columns(
+        connection_pool.columns[table_name]
-          table_name, "#{name} Columns"
-        ).tap { |columns|
-          columns.each { |column| column.primary = column.name == primary_key }
-        }
       end
 
       # Returns a hash of column objects for the table associated with this class.
       def columns_hash
-        @@columns_hash[table_name] ||= Hash[columns.map { |column| [column.name, column] }]
+        connection_pool.columns_hash[table_name]
       end
 
       # Returns an array of column names as strings.
@@ -745,21 +741,14 @@ module ActiveRecord #:nodoc:
       def reset_column_information
         connection.clear_cache!
         undefine_attribute_methods
-        reset_column_cache
+        connection_pool.clear_table_cache!(table_name) if table_exists?
+
         @column_names = @content_columns = @dynamic_methods_hash = @inheritance_column = nil
         @arel_engine = @relation = nil
       end
 
       def clear_cache! # :nodoc:
-        @@columns.clear
+        connection_pool.clear_cache!
-        @@columns_hash.clear
-        @@arel_tables.clear
-      end
-
-      def reset_column_cache # :nodoc:
-        @@columns.delete table_name
-        @@columns_hash.delete table_name
-        @@arel_tables.delete table_name
       end
 
       def attribute_method?(attribute)
@@ -858,7 +847,7 @@ module ActiveRecord #:nodoc:
       end
 
       def arel_table
-        @@arel_tables[table_name] ||= Arel::Table.new(table_name, arel_engine)
+        Arel::Table.new(table_name, arel_engine)
       end
 
       def arel_engine
@@ -1406,9 +1395,6 @@ MSG
           quoted_value
         end
     end
-    @@columns_hash = {}
-    @@columns      = {}
-    @@arel_tables  = {}
 
     public
       # New objects can be instantiated as either empty (pass no construction parameter) or pre-set with

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

@@ -125,6 +125,13 @@ module ActiveRecord
         @primary_keys.clear
       end
 
+      # Clear out internal caches for table with +table_name+
+      def clear_table_cache!(table_name)
+        @columns.delete table_name
+        @columns_hash.delete table_name
+        @primary_keys.delete table_name
+      end
+
       # Retrieve the connection associated with the current thread, or call
       # #checkout to obtain one if necessary.
       #

activerecord/lib/active_record/session_store.rb

@@ -59,12 +59,12 @@ module ActiveRecord
       end
 
       def drop_table!
-        reset_column_cache
+        connection_pool.clear_table_cache!(table_name)
         connection.drop_table table_name
       end
 
       def create_table!
-        reset_column_cache
+        connection_pool.clear_table_cache!(table_name)
         connection.create_table(table_name) do |t|
           t.string session_id_column, :limit => 255
           t.text data_column_name

activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb

@@ -757,10 +757,10 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     david = Developer.find(1)
     # clear cache possibly created by other tests
     david.projects.reset_column_information
-    assert_queries(0) { david.projects.columns; david.projects.columns }
+    assert_queries(1) { david.projects.columns; david.projects.columns }
     # and again to verify that reset_column_information clears the cache correctly
     david.projects.reset_column_information
-    assert_queries(0) { david.projects.columns; david.projects.columns }
+    assert_queries(1) { david.projects.columns; david.projects.columns }
   end
 
   def test_attributes_are_being_set_when_initialized_from_habm_association_with_where_clause