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Date: Mon, 8 Apr 2013 21:58:17 +0000 (UTC)
From: "Jonathan Ellis (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Message-ID: <JIRA.12623764.1355412285561.130519.1365458297761@arcas>
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Subject: [jira] [Commented] (CASSANDRA-5062) Support CAS
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    [ https://issues.apache.org/jira/browse/CASSANDRA-5062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13625891#comment-13625891 ] 

Jonathan Ellis commented on CASSANDRA-5062:
-------------------------------------------

bq. Also, I think we're lacking something around reads and around CL.SERIAL. I think we at least need to support CL.SERIAL reads, that would have to go through paxos (so they play inProgress values). But I would a relatively big fan to also allow a (non-SERIAL) CL in cas() that would be applied to the final commit of the cas write

Yes, I think I mentioned both of these as "stuff that is missing."  Would rather make them follow-on tickets.
                
> Support CAS
> -----------
>
>                 Key: CASSANDRA-5062
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5062
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: API, Core
>            Reporter: Jonathan Ellis
>             Fix For: 2.0
>
>         Attachments: half-baked commit 1.jpg, half-baked commit 2.jpg, half-baked commit 3.jpg
>
>
> "Strong" consistency is not enough to prevent race conditions.  The classic example is user account creation: we want to ensure usernames are unique, so we only want to signal account creation success if nobody else has created the account yet.  But naive read-then-write allows clients to race and both think they have a green light to create.

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