Add support schema cache dump and load.

activerecord/lib/active_record/connection_adapters/schema_cache.rb

@@ -6,21 +6,12 @@ class SchemaCache
 
       def initialize(conn)
         @connection = conn
-        @tables     = {}
 
-        @columns = Hash.new do |h, table_name|
-          h[table_name] = conn.columns(table_name)
-        end
-
-        @columns_hash = Hash.new do |h, table_name|
-          h[table_name] = Hash[columns[table_name].map { |col|
-            [col.name, col]
-          }]
-        end
-
-        @primary_keys = Hash.new do |h, table_name|
-          h[table_name] = table_exists?(table_name) ? conn.primary_key(table_name) : nil
-        end
+        @columns      = {}
+        @columns_hash = {}
+        @primary_keys = {}
+        @tables       = {}
+        prepare_default_proc
       end
 
       # A cached lookup for table existence.
@@ -45,6 +36,35 @@ def clear_table_cache!(table_name)
         @primary_keys.delete table_name
         @tables.delete table_name
       end
+
+      def marshal_dump
+        [:@columns, :@columns_hash, :@primary_keys, :@tables].map do |val|
+          self.instance_variable_get(val).inject({}) { |h, v| h[v[0]] = v[1]; h }
+        end
+      end
+
+      def marshal_load(array)
+        @columns, @columns_hash, @primary_keys, @tables = array
+        prepare_default_proc
+      end
+
+      private
+
+      def prepare_default_proc
+        @columns.default_proc = Proc.new do |h, table_name|
+          h[table_name] = connection.columns(table_name)
+        end
+
+        @columns_hash.default_proc = Proc.new do |h, table_name|
+          h[table_name] = Hash[columns[table_name].map { |col|
+            [col.name, col]
+          }]
+        end
+
+        @primary_keys.default_proc = Proc.new do |h, table_name|
+          h[table_name] = table_exists?(table_name) ? connection.primary_key(table_name) : nil
+        end
+      end
     end
   end
 end

activerecord/test/cases/connection_adapters/schema_cache_test.rb

@@ -39,6 +39,21 @@ def test_clearing
         assert_equal 0, @cache.tables.size
         assert_equal 0, @cache.primary_keys.size
       end
+
+      def test_dump_and_load
+        @cache.columns['posts']
+        @cache.columns_hash['posts']
+        @cache.tables['posts']
+        @cache.primary_keys['posts']
+
+        @cache = Marshal.load(Marshal.dump(@cache))
+
+        assert_equal 12, @cache.columns['posts'].size
+        assert_equal 12, @cache.columns_hash['posts'].size
+        assert @cache.tables['posts']
+        assert_equal 'id', @cache.primary_keys['posts']
+      end
+
     end
   end
 end