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From "Lars Hofhansl (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4583) Integrate RWCC with Append and Increment operations
Date Sat, 05 Nov 2011 04:48:52 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13144580#comment-13144580
] 

Lars Hofhansl commented on HBASE-4583:
--------------------------------------

I don't think that HBASE-2856 will address the issues I raised above (which is caused by deleting
KVs from the memstore).

Updating the WAL first, then applying the changes to the memstore, and making them visible
immediately, all while holding the rowlock is a relatively little change. It'll make Increment/Append/ICV
behave correctly in the face of failing WAL sync's, but will also significantly slow them
down (in terms of throughput, but not latency).

I will factor some common bits out (similar to my initial patch), so that if we want to tackle
this in the future (for example by maintaining the lowest current readpoint in use, or something),
there'll be just one place to change it.

If one want performance, one would set writeToWal to false; but maybe these three ops should
get another flag to allow for delayed log flush (which would be the current behavior).

Lastly, we can just document that the Append and Increment operations are convenience methods
for grouping many updates into a single roundtrip (not to achieve consistency between CFs).

                
> Integrate RWCC with Append and Increment operations
> ---------------------------------------------------
>
>                 Key: HBASE-4583
>                 URL: https://issues.apache.org/jira/browse/HBASE-4583
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.94.0
>
>         Attachments: 4583-v2.txt, 4583-v3.txt, 4583-v4.txt, 4583.txt
>
>
> Currently Increment and Append operations do not work with RWCC and hence a client could
see the results of multiple such operation mixed in the same Get/Scan.
> The semantics might be a bit more interesting here as upsert adds and removes to and
from the memstore.

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