Hi, Weiping Consistency and isolation level are two different things. Strong data consistency means that you always get consistent reads after write (if you can order these events in a distributed system - read and write). Isolation level(s) are meaningful only in context of transactions : they determines how transaction integrity is visible to other users and systems.
>>serializable snapshot isolation at table level is possible No. If you want you can do this on the application layer - have separate table to keep read/write locks (table-wise). -Vlad On Tue, May 26, 2015 at 3:04 PM, Weiping Qu <[email protected]> wrote: > Dear HBase Community, > > As far as I know, HBase supports strong consistency at row level, strictly > to say, at region level I think, since one MVCC instance is used in each > HRegion instance to schedule writes and reads. > Read committed is the default transaction isolation level. > I am wondering whether serializable snapshot isolation at table level is > possible like Postgresql or other MVCC-based databases. > However, as a scan might span across multiple regions in HBase, it is > likely that the scan results would have phantom reads on certain regions. > So my questions is that, why strong consistency at region level instead of > table level? > Is that really not needed? or due to scalability or high availability? or > not easy to implement? > > Regards, > Weiping >
