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Peter Bailis edited comment on CASSANDRA-7056 at 6/25/14 5:16 PM: ------------------------------------------------------------------ > 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. -- This message was sent by Atlassian JIRA (v6.2#6252)