current MySQL driver fails to fetch PK name when the PK has USING option

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -516,7 +516,7 @@ def show_variable(name)
       def pk_and_sequence_for(table)
         execute_and_free("SHOW CREATE TABLE #{quote_table_name(table)}", 'SCHEMA') do |result|
           create_table = each_hash(result).first[:"Create Table"]
-          if create_table.to_s =~ /PRIMARY KEY\s+\((.+)\)/
+          if create_table.to_s =~ /PRIMARY KEY\s+(?:USING\s+\w+\s+)?\((.+)\)/
             keys = $1.split(",").map { |key| key.delete('`"') }
             keys.length == 1 ? [keys.first, nil] : nil
           else

activerecord/test/cases/adapters/mysql/mysql_adapter_test.rb

@@ -56,6 +56,36 @@ def test_tables_quoting
         end
       end
 
+      def test_pk_and_sequence_for
+        pk, seq = @conn.pk_and_sequence_for('ex')
+        assert_equal 'id', pk
+        assert_equal @conn.default_sequence_name('ex', 'id'), seq
+      end
+
+      def test_pk_and_sequence_for_with_non_standard_primary_key
+        @conn.exec_query('drop table if exists ex_with_non_standard_pk')
+        @conn.exec_query(<<-eosql)
+          CREATE TABLE `ex_with_non_standard_pk` (
+            `code` INT(11) DEFAULT NULL auto_increment,
+             PRIMARY KEY  (`code`))
+        eosql
+        pk, seq = @conn.pk_and_sequence_for('ex_with_non_standard_pk')
+        assert_equal 'code', pk
+        assert_equal @conn.default_sequence_name('ex_with_non_standard_pk', 'code'), seq
+      end
+
+      def test_pk_and_sequence_for_with_custom_index_type_pk
+        @conn.exec_query('drop table if exists ex_with_custom_index_type_pk')
+        @conn.exec_query(<<-eosql)
+          CREATE TABLE `ex_with_custom_index_type_pk` (
+            `id` INT(11) DEFAULT NULL auto_increment,
+             PRIMARY KEY  USING BTREE (`id`))
+        eosql
+        pk, seq = @conn.pk_and_sequence_for('ex_with_custom_index_type_pk')
+        assert_equal 'id', pk
+        assert_equal @conn.default_sequence_name('ex_with_custom_index_type_pk', 'id'), seq
+      end
+
       private
       def insert(ctx, data)
         binds   = data.map { |name, value|