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Posted to commits@cassandra.apache.org by "C. Scott Andreas (JIRA)" <ji...@apache.org> on 2018/11/18 18:28:01 UTC
[jira] [Updated] (CASSANDRA-6506) counters++ split counter context
shards into separate cells
[ https://issues.apache.org/jira/browse/CASSANDRA-6506?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
C. Scott Andreas updated CASSANDRA-6506:
----------------------------------------
Component/s: Core
> counters++ split counter context shards into separate cells
> -----------------------------------------------------------
>
> Key: CASSANDRA-6506
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6506
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Aleksey Yeschenko
> Priority: Major
> Labels: counters
> Fix For: 4.x
>
>
> This change is related to, but somewhat orthogonal to CASSANDRA-6504.
> Currently all the shard tuples for a given counter cell are packed, in sorted order, in one binary blob. Thus reconciling N counter cells requires allocating a new byte buffer capable of holding the union of the two context's shards N-1 times.
> For writes, in post CASSANDRA-6504 world, it also means reading more data than we have to (the complete context, when all we need is the local node's global shard).
> Splitting the context into separate cells, one cell per shard, will help to improve this. We did a similar thing with super columns for CASSANDRA-3237. Incidentally, doing this split is now possible thanks to CASSANDRA-3237.
> Doing this would also simplify counter reconciliation logic. Getting rid of old contexts altogether can be done trivially with upgradesstables.
> In fact, we should be able to put the logical clock into the cell's timestamp, and use regular Cell-s and regular Cell reconcile() logic for the shards, especially once we get rid of the local/remote shards some time in the future (until then we still have to differentiate between global/remote/local shards and their priority rules).
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