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From Apache Wiki <wikidi...@apache.org>
Subject [Cassandra Wiki] Trivial Update of "Counters" by SylvainLebresne
Date Mon, 27 Jun 2011 17:09:49 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Cassandra Wiki" for change notification.

The "Counters" page has been changed by SylvainLebresne:
http://wiki.apache.org/cassandra/Counters?action=diff&rev1=12&rev2=13

  == Technical limitations ==
  
    * If a write fails unexpectedly (timeout or loss of connection to the coordinator node)
the client will not know if the operation has been performed. A retry can result in an over
count [[https://issues.apache.org/jira/browse/CASSANDRA-2495|CASSANDRA-2495]].
-   * Counter removal is intrinsically limited. For instance, if you issue very quickly the
sequence "increment, remove, increment" it is possible for the removal to be lost (if for
some reason the remove happens to be the last received messages). Hence, removal of counters
is provided for definitive removal, that is when the deleted counter is not increment afterwards.
Note that if you need to reset a counter, you can read its ''value'' and insert ''-value''.

+   * Counter removal is intrinsically limited. For instance, if you issue very quickly the
sequence "increment, remove, increment" it is possible for the removal to be lost (if for
some reason the remove happens to be the last received messages). Hence, removal of counters
is provided for definitive removal only, that is when the deleted counter is not increment
afterwards. Note that if you need to reset a counter, you can read its ''value'' and insert
''-value''. 
  
  == Further reading ==
- See [[https://issues.apache.org/jira/browse/CASSANDRA-1072|CASSANDRA-1072]] and especially
the [[https://issues.apache.org/jira/secure/attachment/12459754/Partitionedcountersdesigndoc.pdf|design
doc]] for further information about how this works internally.
+ See [[https://issues.apache.org/jira/browse/CASSANDRA-1072|CASSANDRA-1072]] and especially
the [[https://issues.apache.org/jira/secure/attachment/12459754/Partitionedcountersdesigndoc.pdf|design
doc]] for further information about how this works internally (but note that some of the limitation
fixed in these technical documents have been fixed since then, for instance all consistency
level '''are''' supported, for both reads and writes).
  

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