share column cache among subclasses, only look up columns per AR::Base subclass once

4 files changed, 22 insertions, 15 deletions

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 42226f83ea..f66b84935c 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -662,20 +662,16 @@ module ActiveRecord #:nodoc:
 
       # Returns an array of column objects for the table associated with this class.
       def columns
-        unless defined?(@columns) && @columns
-          @columns = connection.columns(table_name, "#{name} Columns")
-          @columns.each { |column| column.primary = column.name == primary_key }
-        end
-        @columns
+        @@columns[table_name] ||= connection.columns(
+          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_cache[table_name] ||= Hash[columns.map { |column| [column.name, column] }]
-      end
-
-      def columns_hash=(value)
-        @@columns_cache[table_name] = value
+        @@columns_hash[table_name] ||= Hash[columns.map { |column| [column.name, column] }]
       end
 
       # Returns an array of column names as strings.
@@ -732,11 +728,16 @@ module ActiveRecord #:nodoc:
       def reset_column_information
         connection.clear_cache!
         undefine_attribute_methods
-        self.columns_hash = nil
-        @column_names = @columns = @content_columns = @dynamic_methods_hash = @inheritance_column = nil
+        reset_column_cache
+        @column_names = @content_columns = @dynamic_methods_hash = @inheritance_column = nil
         @arel_engine = @relation = @arel_table = nil
       end
 
+      def reset_column_cache # :nodoc:
+        @@columns.delete table_name
+        @@columns_hash.delete table_name
+      end
+
       def attribute_method?(attribute)
         super || (table_exists? && column_names.include?(attribute.to_s.sub(/=$/, '')))
       end
@@ -1381,7 +1382,8 @@ MSG
           quoted_value
         end
     end
-    @@columns_cache = {}
+    @@columns_hash = {}
+    @@columns      = {}
 
     public
       # New objects can be instantiated as either empty (pass no construction parameter) or pre-set with
diff --git a/activerecord/lib/active_record/session_store.rb b/activerecord/lib/active_record/session_store.rb
index 68d9f89edd..e3342f046f 100644
--- a/activerecord/lib/active_record/session_store.rb
+++ b/activerecord/lib/active_record/session_store.rb
@@ -59,12 +59,12 @@ module ActiveRecord
       end
 
       def drop_table!
-        self.columns_hash = nil
+        reset_column_cache
         connection.drop_table table_name
       end
 
       def create_table!
-        self.columns_hash = nil
+        reset_column_cache
         connection.create_table(table_name) do |t|
           t.string session_id_column, :limit => 255
           t.text data_column_name
diff --git a/activerecord/test/cases/session_store/session_test.rb b/activerecord/test/cases/session_store/session_test.rb
index f906bda8c3..cee5ddd003 100644
--- a/activerecord/test/cases/session_store/session_test.rb
+++ b/activerecord/test/cases/session_store/session_test.rb
@@ -60,6 +60,7 @@ module ActiveRecord
       end
 
       def test_loaded?
+        Session.create_table!
         s = Session.new
         assert !s.loaded?, 'session is not loaded'
       end
diff --git a/activerecord/test/models/contact.rb b/activerecord/test/models/contact.rb
index 975a885331..5bbe7ebb12 100644
--- a/activerecord/test/models/contact.rb
+++ b/activerecord/test/models/contact.rb
@@ -1,4 +1,8 @@
 class Contact < ActiveRecord::Base
+  def self.columns
+    @columns
+  end
+
   # mock out self.columns so no pesky db is needed for these tests
   def self.column(name, sql_type = nil, options = {})
     @columns ||= []