fixed-length records

Just a note, I believe the OP didn't say that the lines are fixed-length.

Note that a sequential walk through the file, "flipping a coin each time," is not the same, statistically. Any actual implementation would heavily favor the head of the file.

I believe this would help: http://blog.cloudera.com/blog/2013/04/hadoop-stratified-randosampling-algorithm/

In reply to Re^2: Building a new file by filtering a randomized old file on two fields by Anonymous Monk
in thread Building a new file by filtering a randomized old file on two fields by mbp

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