func (e *SelectStatement) Eval(input, output Record) (Record, error) {
	ok, err := e.isPassingWhereClause(input)
	if err != nil || !ok {
		// Either error or row did not pass where clause
		return nil, err
	}

	if e.selectAST.Expression.All {
		// Return the input record for `SELECT * FROM
		// .. WHERE ..`

		// Update count of records output.
		e.outputCount++