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Peter Bailis edited comment on CASSANDRA-7056 at 6/25/14 5:19 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)
not match, but simply returning matching timestamps is *not* the goal: the goal
is that if you read any write in a given batch, you will be able to read the
rest of the writes in the batch (i.e., if you also attempt to read any other
items that were written in the batch, you will see the corresponding writes).
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)
not match, but simply returning matching timestamps is *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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