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From "Cristian Opris (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5062) Support CAS
Date Mon, 04 Mar 2013 15:23:14 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13592282#comment-13592282
] 

Cristian Opris commented on CASSANDRA-5062:
-------------------------------------------

FWIW, just to clarify my own examples, I can't speak for Jonathan: *version counter or most
recent commit is NOT the paxos proposal number*. The Paxos proposal number I've ommitted in
most of my examples except for the last more detailed one. Timeuuid is fine for proposal number.

Also with regard to logging/no logging. I believe you only need to keep a log if you plan
to replicate operations rather than state. 
Transfering state (as we discussed so far) does not require a log but makes it impractical
to replicate large values, so this is the main trade off, I don't believe it's got anything
to do with paxos.
                
> 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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