[jira] [Resolved] (HBASE-4527) Fix versioning such that every update is unique

["Andrew Purtell (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-4527?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Purtell resolved HBASE-4527.
-----------------------------------
    Resolution: Incomplete

> Fix versioning such that every update is unique
> -----------------------------------------------
>
>                 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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