I'm pretty sure you're barking up a long and complex tree. The first problem (for xsv) is that it doesn't control the csv data. So it doesn't know what changes

I'm pretty sure you're barking up a long and complex tree. The first problem (for xsv) is that it doesn't control the csv data. So it doesn't know what changes were made. It could have even become an invalid csv file. The second problem is that insertions in sorted sequences are hard and are one of the fundamental problems in a database implementation: http://en.wikipedia.org/wiki/B-tree#The_database_problem http://en.wikipedia.org/wiki/B-tree#The_database_problem