Though it is not required to run upgradesstables, but upgradesstables -a
will re-write the file to kick out tombstones, in sizeTieredcompaction, the
largest files may stay a long time to wait for the next compaction to
kick out tombstones.
So it really depends, to run it or not, usually upgrades
Andrey:
cassandra every cell has a timestamp, select writetime (..) can see
the timestamp,
cassandra merge cells when compaction, when read, sort by timestamp.
for you example, if you left pad the writetime to column value (writetime +
cell value), then sort, shall return what you see no
