[jira] [Commented] (CASSANDRA-8051) Add SERIAL and LOCAL_SERIAL consistency levels to cqlsh

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

    [ https://issues.apache.org/jira/browse/CASSANDRA-8051?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14526391#comment-14526391 ] 

Stefania commented on CASSANDRA-8051:
-------------------------------------

[~thobbs] review is complete, 8051-2.1-v3 and 8051-2.0 can be committed if you are OK with them.

> Add SERIAL and LOCAL_SERIAL consistency levels to cqlsh
> -------------------------------------------------------
>
>                 Key: CASSANDRA-8051
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8051
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Tools
>            Reporter: Nicolas Favre-Felix
>            Assignee: Carl Yeksigian
>            Priority: Minor
>              Labels: cqlsh
>             Fix For: 2.0.x
>
>         Attachments: 8051-2.0.txt, 8051-2.1-v2.txt, 8051-2.1-v3.txt, 8051-2.1.txt, log-statements-2.0.txt, log-statements-2.1.txt, python-driver-fix.txt
>
>
> cqlsh does not support setting the serial consistency level. The default CL.SERIAL does not let users safely execute LWT alongside an app that runs at LOCAL_SERIAL, and can prevent any LWT from running when a DC is down (e.g. with 2 DCs, RF=3 in each.)
> Implementing this well is a bit tricky. A user setting the serial CL will probably not want all of their statements to have a serial CL attached, but only the conditional updates. At the same time it would be useful to support serial reads. "WITH CONSISTENCY LEVEL" used to provide this flexibility.
> I believe that it is currently impossible to run a SELECT at SERIAL or LOCAL_SERIAL; the only workaround seems to be to run a conditional update with a predicate that always resolves to False, and to rely on the CAS response to read the data.



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