Chunhui replied to this question on review board. Basically the force option is to repair overlapping regions or table with hole in its regions.
Personally I think online merge should detect merging regions with hole in between them and not require force flag in that case because logically they're adjacent. Cheers On Mar 16, 2013, at 5:52 AM, Jean-Marc Spaggiari <[email protected]> wrote: > Hi Ted, > > I jut gave it a look. > > I have updated it on the RB. > > Overall, this is very good and I'm eager to see that integrated! I'm > waiting for this feature since the beginning ;) > > Regarding non adjacent regions merge? Will the system still be > consistent after that? Or will hbck report some regions overlaps? > > JM > > > 2013/3/16 Ted Yu <[email protected]>: >> Hi, >> On behalf of Chunhui, I am requesting review for HBASE-7403 Online Merge. >> >> This JIRA was created 3 months ago. >> Chunhui has responded to review comments very promptly, including a major >> rewrite around the time split transaction was rewritten. >> >> This feature has widely been requested. I feel the patch is mostly ready to >> go in. >> Here is brief recap of the steps. >> >> Process of merging two regions: >> >> a.client sends RPC (dispatch merging regions) to master >> b.master moves the regions together (on the regionserver where the more >> heavily loaded region resided) >> c.master sends RPC (merge regions) to this regionserver >> d.Regionserver executes the region merge transaction in the thread pool >> >> I think step b is a nice simplification for the problem. In previous >> versions of the patch, the two merging regions stay on respective servers >> which required more complex coordination through zookeeper. >> >> High level comment as well as detailed review are both welcome. >> >> Thanks
