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https://issues.apache.org/jira/browse/CASSANDRA-7056?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14043771#comment-14043771
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Peter Bailis edited comment on CASSANDRA-7056 at 6/25/14 5:16 PM:
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> RAMP has a requirement that anything being read/written that way is always
> written in the same groupings. If you update B,C and then update A,B. You
> can't read B,C anymore successfully, as the times on B and C will never match.
This isn't entirely correct. Let's say I do an atomic batch B1 that writes B =
1 and C = 1 with timestamp 1, then you do an atomic batch B2 that writes A = 2
and B = 2 at timestamp 2. Under RAMP, subsequent batch reads from B and C will
return B = 2, C = 1. The timestamps on B and C will indeed--as you point
out--never match, but simply returning matching timestamps is *not* not the
goal: the goal is that if you read any write in a given batch, you will read
the rest of the writes in the batch (to the items you requested in the batch
read)
was (Author: pbailis):
> RAMP has a requirement that anything being read/written that way is always
> written in the same groupings. If you update B,C and then update A,B. You
> can't read B,C anymore successfully, as the times on B and C will never match.
This isn't entirely correct. Let's say I do an atomic batch B1 that writes B =
1 and C = 1 with timestamp 1, then you do an atomic batch B2 that writes A = 2
and B = 2 at timestamp 2. Under RAMP, subsequent batch reads from B and C will
return B = 2, C = 1. The timestamps on B and C will indeed---as you point
out---never match, but simply returning matching timestamps is *not* not the
goal: the goal is that if you read any write in a given batch, you will read
the rest of the writes in the batch (to the items you requested in the batch
read)
> Add RAMP transactions
> ---------------------
>
> Key: CASSANDRA-7056
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7056
> Project: Cassandra
> Issue Type: Wish
> Components: Core
> Reporter: Tupshin Harper
> Priority: Minor
>
> We should take a look at
> [RAMP|http://www.bailis.org/blog/scalable-atomic-visibility-with-ramp-transactions/]
> transactions, and figure out if they can be used to provide more efficient
> LWT (or LWT-like) operations.
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