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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14635) Support table level configuration of monotonic reads
Date Fri, 10 Aug 2018 06:40:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14635?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16575827#comment-16575827
] 

Benedict commented on CASSANDRA-14635:
--------------------------------------

Importantly, our present-day support for read monotonicity inherently breaks our guarantee
of write atomicity.  If you need write atomicity, you must have the capability to disable
read-repair entirely (and hence read monotonicity), so we really should provide this option.

> Support table level configuration of monotonic reads
> ----------------------------------------------------
>
>                 Key: CASSANDRA-14635
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14635
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Coordination
>            Reporter: Ariel Weisberg
>            Priority: Major
>
> In CASSANDRA-10726 it was discussed that allowing expert users to forgo monotonic reads
might be desirable. It is practical to control monotonicity of reads at a fine grained level
because it involves changing the behavior of read repair on a per read basis.
> Per CASSANDRA-14593 we already don't preserve update atomicity down to the column level.
You could read the key out of a row and read repair the key, pass the key to another process
which attempts to read the value, but finds the value is null because read repair only repairs
the data (including columns) that is part of the read. IMO it's a stretch to say that reads
are monotonic. It is technically correct, the best kind of correct, but far from as useful
as it should be.
> An initial implementation could make read repair asynchronous or forgo read repair entirely.
This would improve the throughput and latency of reads.



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