git notes after BFG?

I wrote the following bash script to transfer my notes from old objects. The solution is slow in single thread, not sure if it is safe to run several git notes commands in parallel.

while read string; do
    hashesArray=($string)
    git notes copy ${hashesArray[0]} ${hashesArray[1]}
    git notes remove --ignore-missing ${hashesArray[0]}
done <object-id-map.old-new.txt