public function destroy($schema, $table=null)
    {
        $mapper = $this->_mapper($schema);
        $table = $table ? $this->_connection($schema)->table($table) : $mapper->table();

        $sequencePool = $this->_connection($schema)->sequencePool();
        $sequencePool->initialize();

        // delete any sequences
        foreach ($schema->properties() as $prop) {
            if (property_exists($prop->type, 'sequence')) {
                $sequencePool->delete($mapper->sequenceName($prop));
            }
        }

        // destory the table
        $table->dropIfExists();

        return $this;
    }