Add db:schema:cache:dump and db:schema:cache:clear tasks.

activerecord/lib/active_record/connection_adapters/schema_cache.rb

@@ -21,6 +21,15 @@ def table_exists?(name)
         @tables[name] = connection.table_exists?(name)
       end
 
+      # Add internal cache for table with +table_name+.
+      def add(table_name)
+        if table_exists?(table_name)
+          @primary_keys[table_name]
+          @columns[table_name]
+          @columns_hash[table_name]
+        end
+      end
+
       # Clears out internal caches
       def clear!
         @columns.clear

activerecord/lib/active_record/railties/databases.rake

@@ -372,6 +372,25 @@ db_namespace = namespace :db do
     task :load_if_ruby => 'db:create' do
       db_namespace["schema:load"].invoke if ActiveRecord::Base.schema_format == :ruby
     end
+
+    namespace :cache do
+      desc 'Create a db/schema_cache.dump file.'
+      task :dump => :environment do
+        con = ActiveRecord::Base.connection
+        filename = File.join(Rails.application.config.paths["db"].first, "schema_cache.dump")
+
+        con.schema_cache.clear!
+        con.tables.each { |table| con.schema_cache.add(table) }
+        open(filename, 'wb') { |f| f.write(Marshal.dump(con.schema_cache)) }
+      end
+
+      desc 'Clear a db/schema_cache.dump file.'
+      task :clear => :environment do
+        filename = File.join(Rails.application.config.paths["db"].first, "schema_cache.dump")
+        FileUtils.rm(filename) if File.exists?(filename)
+      end
+    end
+
   end
 
   namespace :structure do

railties/test/application/rake_test.rb

@@ -138,5 +138,24 @@ def test_rake_dump_structure_should_respect_db_structure_env_variable
       end
       assert File.exists?(File.join(app_path, 'db', 'my_structure.sql'))
     end
+
+    def test_rake_dump_schema_cache
+      Dir.chdir(app_path) do
+        `rails generate model post title:string`
+        `rails generate model product name:string`
+        `bundle exec rake db:migrate`
+        `bundle exec rake db:schema:cache:dump`
+      end
+      assert File.exists?(File.join(app_path, 'db', 'schema_cache.dump'))
+    end
+
+    def test_rake_clear_schema_cache
+      Dir.chdir(app_path) do
+        `bundle exec rake db:schema:cache:dump`
+        `bundle exec rake db:schema:cache:clear`
+      end
+      assert !File.exists?(File.join(app_path, 'db', 'schema_cache.dump'))
+    end
+
   end
 end