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Posted to commits@cassandra.apache.org by "Yang Yang (JIRA)" <ji...@apache.org> on 2011/06/15 08:27:47 UTC
[jira] [Commented] (CASSANDRA-2774) one way to make counter delete
work better
[ https://issues.apache.org/jira/browse/CASSANDRA-2774?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13049649#comment-13049649 ]
Yang Yang commented on CASSANDRA-2774:
--------------------------------------
see original jira https://issues.apache.org/jira/browse/CASSANDRA-2101
> one way to make counter delete work better
> ------------------------------------------
>
> Key: CASSANDRA-2774
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2774
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Yang Yang
>
> current Counter does not work with delete, because different merging order of sstables would produces different result, for example:
> add 1
> delete
> add 2
> if the merging happens by 1-2, (1,2)--3 order, the result we see will be 2
> if merging is: 1--3, (1,3)--2, the result will be 3.
> the issue is that delete now can not separate out previous adds and adds later than the delete. supposedly a delete is to create a completely new incarnation of the counter, or a new "lifetime", or "epoch". the new approach utilizes the concept of "epoch number", so that each delete bumps up the epoch number. since each write is replicated (replicate on write is almost always enabled in practice, if this is a concern, we could further force ROW in case of delete ), so the epoch number is global to a replica set
> changes are attached, existing tests pass fine, some tests are modified since the semantic is changed a bit. some cql tests do not pass in the original 0.8.0 source, that's not the fault of this change.
> see details at http://mail-archives.apache.org/mod_mbox/cassandra-user/201106.mbox/%3CBANLkTikQcgLSNwtT-9HvqpSeoo7SF58SnA@mail.gmail.com%3E
> the goal of this is to make delete work ( at least with consistent behavior, yes in case of long network partition, the behavior is not ideal, but it's consistent with the definition of logical clock), so that we could have expiring Counters
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