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From Vladimir Rodionov <vladrodio...@gmail.com>
Subject Re: conditional atomic operations
Date Tue, 26 Jan 2016 19:44:17 GMT
It is worth taking look at:


On Tue, Jan 26, 2016 at 11:26 AM, Yakubovich, Alexey <
Alexey.Yakubovich@searshc.com> wrote:

> I notices an unanswered question: “Check and Put method used with
> a long)”.  I would like to ask it in a slightly different form:
> Can you customize (within reasonable restrictions)) the
> condition for the atomic update?
> The HTable method
>         checkAndPut(byte[] row,
>   byte[] family,
>   byte[] qualifier,
> CompareFilter.CompareOp<
> https://archive.cloudera.com/cdh5/cdh/5/hbase/devapidocs/org/apache/hadoop/hbase/filter/CompareFilter.CompareOp.html>
> compareOp,
>   byte[] value,
> Put<
> https://archive.cloudera.com/cdh5/cdh/5/hbase/devapidocs/org/apache/hadoop/hbase/client/Put.html>
> put)
> Uses the CompareFilter.CompareOp enum. But what I would like is the
> complete customization of compareOp, with my own logic.
> And still, can you apply the existing checkAndPut with compareOp on a
> field that contains integer, or long, of my own class (in binary form)?
> (and naturally I need GREATER be in context of java.lang.Integer, not
> binary strings that represent integers).
> Or, if not, how to solve the following use case:
> Several spark executors updating the data structurer (in HBase table) that
> contains record as
> (pid:String, hits:int)
> I want the update only happens if the new value for the field hits is
> grater that the current value.
> Now suppose one of executors (E1) has a new value (V1) for the given pid.
> If it operates non-atomically  it could read current value V0, compare with
> new value and tries to update (if V1 > V0). But it could happen that
> current value was already been increased to V2 by another executor. The E1
> knows the prev. value and could use regular checkAndPut, so that update
> would not happen if current value was changed, but E1 still does’t know if
> new value (V1) is bigger than updated current value (V2), and and has no
> way but to attempt the same update again… (if V1 >V2).
> I hope I described the use case clearly, it seems very typical and
> elementary one. Can somebody please hint how to solve it?
> Thank you
> Alexey
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