It's no problem to use 23 # column indices and 10.000 lines?

No problem at all.  As there are no more than two lines of data kept in memory at any point in time, the number of lines is essentially irrelevant. And 23 columns isn't really a lot either... (BTW, note that you only have to give names (constants) to column indices that you actually need to access or modify, like 3,7,8,9 and 10,11,12).