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https://issues.apache.org/jira/browse/HBASE-14070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15196699#comment-15196699
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stack commented on HBASE-14070:
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bq. The tracker just drops the older sequence id. It doesn't drop both.
I should have been more clear. These are two legit edits that just happen to
arrive at the same time. Let them be Puts that we'd want to aggregate at read
time for example.
bq. So putting sequence id through everything would be a pretty big behavioral
change as there's no other way to replace a cell at a timestamp.
Delete and then Put at the explicit coordinate only now that sequenceid is
respected, you can actually overwrite the delete.
> Hybrid Logical Clocks for HBase
> -------------------------------
>
> Key: HBASE-14070
> URL: https://issues.apache.org/jira/browse/HBASE-14070
> Project: HBase
> Issue Type: New Feature
> Reporter: Enis Soztutar
> Assignee: Enis Soztutar
> Attachments: HybridLogicalClocksforHBaseandPhoenix.docx,
> HybridLogicalClocksforHBaseandPhoenix.pdf
>
>
> HBase and Phoenix uses systems physical clock (PT) to give timestamps to
> events (read and writes). This works mostly when the system clock is strictly
> monotonically increasing and there is no cross-dependency between servers
> clocks. However we know that leap seconds, general clock skew and clock drift
> are in fact real.
> This jira proposes using Hybrid Logical Clocks (HLC) as an implementation of
> hybrid physical clock + a logical clock. HLC is best of both worlds where it
> keeps causality relationship similar to logical clocks, but still is
> compatible with NTP based physical system clock. HLC can be represented in
> 64bits.
> A design document is attached and also can be found here:
> https://docs.google.com/document/d/1LL2GAodiYi0waBz5ODGL4LDT4e_bXy8P9h6kWC05Bhw/edit#
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