feature suggestion: --preserve-blocking-factor

[Cook, Malcolm]

When using the --spreadstdin option, it may be desirable to ensure that the 
blocks "keep together" certain blocks of data.

For example the input may be sorted on column 3, and it may be the case that 
all lines having the same value for column 3 must be processed together.

Providing an option that allows for block breaks to be respect grouped records 
such as this would 

Perhaps a --preserve-blocking-factor option, which would be another stream/file 
that defined the blocking factor.

Allowing something like:

        cat someHugeTabFile parallel  --preserve-blocking-factor <(cut -f 3 
someHugeTabFile) someProg

or perhaps

        cat someHugeTabFile parallel  --preserve-blocking-factor '| cut -f 3' 
someProg



Malcolm Cook