Fix versioning such that every update is unique
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Key: HBASE-4527
URL: https://issues.apache.org/jira/browse/HBASE-4527
Project: HBase
Issue Type: Wish
Reporter: stack
I wanted to use checkAndPut but there is a case where the check will not fail
though the cell has been updated: if a cell is update with exactly the value it
had before, we'll not know its been changed. hbase-4507 did a checkAndPut
where you could pass a timestamp as part of the check so we'd check the cell
value AND that the timestamp was the same.
This would work in most regards but one; an update is done in the same
millisecond. This is generally impossible but in a distributed system where
clocks drift and a region can be moved to a server whose clock is retarded, it
is within the realm of possibilities that it could happen. So we should deal.
One thought is that the version is made for sure unique. We could make the
timestamp wider still so probability of the edits arriving within the same
microsecond -- or whatever it is that a double gives you -- would require us to
run through a couple of billion universe expand/contract cycles or we could
have a monotonically increasing sequence id per millisecond.
There could be some overlap between this issue and the persisting of rwcc to
the filesystem (though not currently as rwcc is implemented).
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