...in order to pull out the first value of every row to get a column.
Not sure I'm understanding you correctly, but if you only need the first column of every row, why not store only the first column (that would at least reduce memory usage somewhat).
The getline() method returns a reference to an array holding the columns. In other words, $row-> would be the first column.
If, OTOH, you actually do need access to all columns of all rows simultaneously, I'm afraid there's not much you can do except to upgrade memory (or write out the data into another (DB) file format that allows direct random access to individual fields).