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https://issues.apache.org/jira/browse/CASSANDRA-6870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13943192#comment-13943192
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Edward Capriolo commented on CASSANDRA-6870:
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{quote}
I'm not sure I understand the point. Are you arguing that we should support
read-before-write outside of paxos? In which case, as I said I'm not sure and I
think this deserve it's own conversation.
{quote}
It would be this code path without the paxos overhead. The user might have
1) optimistic concurrency.
2) an algorithm in which QUORUM satisfies the transformation without a need for
locking.
An example of #2 might be. I have a wide row of counts per minute for the last
hour. I know the last hour is over and I wish to consolidate this into a single
column. So read row at quorum-> write new cell at quorum. This action is
idempotent and would not require isolation or paxos.
> Transform operation
> -------------------
>
> Key: CASSANDRA-6870
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6870
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Edward Capriolo
> Assignee: Edward Capriolo
> Priority: Minor
>
> Compare and swap uses paxos to only update a value only if some criteria is
> met. If I understand correctly we should be able to use this feature to
> provide a wider variety of server side operations.
> For example inside a paxos transaction performing a slice and then using a
> function to manipulate the slice. You could accomplish features like append
> and increment this way without user needing to know the current value.
> I took a stab at doing this. I **think** I did it correctly. Comments welcome.
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