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From "Tyler Hobbs (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8051) Add SERIAL and LOCAL_SERIAL consistency levels to cqlsh
Date Wed, 22 Apr 2015 17:00:06 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8051?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14507414#comment-14507414
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Tyler Hobbs commented on CASSANDRA-8051:
----------------------------------------

The patch handles setting serial consistency levels for reads, but not for writes.  This section
of the python driver docs explains how {{consistency_level}} and {{serial_consistency_level}}
work in conjunction: http://datastax.github.io/python-driver/api/cassandra/query.html#cassandra.query.Statement.serial_consistency_level.
 To support setting the {{serial_consistency_level}} for writes, we probably need a new cqlsh
command: {{SERIAL CONSISTENCY}}.

> 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: 2.0.15
>
>         Attachments: 8051-2.0.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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