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https://issues.apache.org/jira/browse/CASSANDRA-5062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13591721#comment-13591721
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Sergio Bossa commented on CASSANDRA-5062:
-----------------------------------------
{quote}Sergio, the reason to go beyond pure Paxos by turning Learn into Commit
is twofold:
To allow a fresh start for a new round of CAS; otherwise, each new proposal is
stuck re-issuing the first accepted value
To move the data from the Paxos "maybe it's accepted but we don't know until we
get a majority" limbo into a normal sstable cell{quote}
Yes, I get why it's there, I'm just not sure it's actually needed (which may
well be due to my limited knowledge of hardcore C* internals, in particular
around HH, RR and AE).
By the way, I don't have enough time to do any more meaningful contributions to
this ticket, so I'm backing off: it is in good hands anyways :)
> 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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