protected function add_soft_filter()
	{
		if ($this->_col_name !== null)
		{
			// Capture any filtering that has already been added
			$current_where = $this->where;

			// If there is no filtering then we don't need to add any special organization
			if ( ! empty($current_where))
			{
				$this->where = array();

				// Make sure the existing filtering is wrapped safely
				$this->and_where_open();
				$this->where = array_merge($this->where, $current_where);
				$this->and_where_close();
			}

			// Finally add the soft delete filtering
			$this->where($this->_col_name, null);
		}
	}