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From Asaf Mesika <asaf.mes...@gmail.com>
Subject Re: How to implement this check put and then update something logic?
Date Sat, 11 May 2013 08:39:26 GMT
Maybe this problem is more in the graph domain? I know that there are projects aimed at representing
graphs at large scale better. I'm saying this since you have one ID referencing another ID
(using target ID).

On May 10, 2013, at 11:47 AM, "Liu, Raymond" <raymond.liu@intel.com> wrote:

> Thanks, seems there are no other better solution?
> Really need a "GetAndPut" atomic op here ...
>> You can do this by looping over a checkAndPut operation until it succeeds.
>> -Mike
>> On Thu, May 9, 2013 at 8:52 PM, Liu, Raymond <raymond.liu@intel.com>
>> wrote:
>>> Any suggestion?
>>>> Hi
>>>>      Say, I have four field for one record :id, status, targetid, and count.
>>>>      Status is on and off, target could reference other id, and
>>>> count will record the number of "on" status for all targetid from same id.
>>>>      The record could be add / delete, or updated to change the status.
>>>>      I could put count in another table, or put it in the same
>>>> table, it doesn't matter. As long as it can work.
>>>>      My question is how can I ensure its correctness of the "count"
>>>> field when run with multiple client update the table concurrently?
>>>>      The closet thing I can think of is checkAndPut, but I will need
>>>> two steps to find out the change of count, since checkAndPut etc can
>>>> only test a single value and with EQUAL comparator, thus I can only
>>>> check upon null firstly, then on or off. Thus when thing change
>>>> during this two step, I need to retry from first step until it succeed. This
>> could be bad when a lot of concurrent op is on going.
>>>>      And then, I need to update count by checkAndIncrement, though
>>>> if the above problem could be solved, the order of -1 +1 might not be
>>>> important for the final result, but in some intermediate time, it
>>>> might not reflect the real count of that time.
>>>>      I know this kind of transaction is not the target of HBASE, APP
>>>> should take care of it, then , what's the best practice on this? Any
>>>> quick simple solution for my problem? Client RowLock could solve this
>>>> issue, But it seems to me that it is not safe and is not recommended and
>> deprecated?
>>>>      Btw. Is that possible or practice to implement something like
>>>> PutAndGet which put in new row and return the old row back to client been
>> implemented?
>>>> That would help a lot for my case.
>>>> Best Regards,
>>>> Raymond Liu

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