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From "Jonathan Hsieh (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10247) Client promises about timestamps
Date Fri, 27 Dec 2013 18:05:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13857602#comment-13857602
] 

Jonathan Hsieh commented on HBASE-10247:
----------------------------------------

I started looking into this -- the part I'm less familiar with the implementation about is
how to discern the distributed log replays and replication replays (which legitimately will
write timestamps) from fresh writes. 

I'd think the different replay writes would be tagged or marked so that we can make a simple
distinction in one place.

Ideally this would be a table scoped parameter, that can work with alter table, something
like MOD_TS_OK or INTRINSIC_TS_ONLY

> Client promises about timestamps
> --------------------------------
>
>                 Key: HBASE-10247
>                 URL: https://issues.apache.org/jira/browse/HBASE-10247
>             Project: HBase
>          Issue Type: Brainstorming
>            Reporter: Lars Hofhansl
>            Priority: Minor
>
> This is to start a discussion about timestamp promises declared per table of CF.
> For example if a client promises only monotonically increasing timestamps (or no custom
set timestamps) and VERSIONS=1, we can aggressively and easily remove old versions of the
same row/fam/col from the memstore before we flush, just by supplying a comparator that ignores
the timestamp (i.e. two KV just differing by TS would be considered equal).
> That would increase the performance of counters significantly.



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