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....@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 > >
