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From "Aleksey Yeschenko (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-6880) counters++ lock on cells, not partitions
Date Tue, 18 Mar 2014 13:03:43 GMT
Aleksey Yeschenko created CASSANDRA-6880:
--------------------------------------------

             Summary: counters++ lock on cells, not partitions
                 Key: CASSANDRA-6880
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6880
             Project: Cassandra
          Issue Type: Improvement
            Reporter: Aleksey Yeschenko
            Assignee: Aleksey Yeschenko
             Fix For: 2.1 beta2


I'm starting to think that we should switch to locking by cells, not by partitions, when updating
counters.

With the current 2.1 counters, if nothing changes, the new recommendation would become "use
smaller partitions, batch updates to the same partition", and that goes against what we usually
recommend:
1. Prefer wide partitions to narrow partitions
2. Don't batch counter updates (because you risk to exaggerate undercounting/overcounting
in case of a timeout)

Locking on cells would cause C* to have to grab more locks for batch counter updates, but
would give us generally more predictable performance (independent of partition wideness),
and won't force people to remodel their data model if they have often concurrently-updated
counters in the same few wide partitions.

(It's a small change, code-wise)



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