I think there might be some confusion about what the value VERSIONS=X for. HBase allows one to store multiple version at a specific row/column. They are distinguished by their timestamp, and provided in descending order - largest timestamp first. Normally one does not specifically set a timestamp, which then defaults to 'now' in millisecond accuracy as provided by System.currentTimeMillis().
The per-column family setting "VERSIONS" indicates how many versions (including the newest one) hbase should (a) retain (during compactions) and (b) return at maximum (since delayed compactions can allow more than X version temporarily). This is per row & column. One can always have unlimited rows and columns, but in the 'time dimention' at each point, the number of versions allowed is restricted by this setting. Does that answer your questions? On Fri, May 22, 2009 at 1:00 AM, Edward J. Yoon <[email protected]>wrote: > Hey, > > The different rows are in other table version. I think the 'versions' > is the table property, not row property. > > On Fri, May 22, 2009 at 4:33 PM, Ryan Rawson <[email protected]> wrote: > > Hey, > > > > those 2 entries have different rows ids, with different timestamps (same > > column, same value). > > > > btw, setting timestamps in a non-monotonically increasing order may cause > > performance and certain correctness issues on 0.20. Best to avoid it for > > production code if you can. > > > > On Fri, May 22, 2009 at 12:27 AM, Edward J. Yoon <[email protected] > >wrote: > > > >> OK, It's my typos, not my point. Result is same even if 'versions' is > >> 1. Anyway, Do you think 'version mixed' table should be appeared? > >> > >> hbase(main):025:0> describe 't1' > >> {NAME => 't1', IS_ROOT => 'false', IS_META => 'false', FAMILIES => > >> [{NAME => 'f1', BLOOMFILTER => 'false', COM > >> PRESSION => 'NONE', VERSIONS => '1', LENGTH => '2147483647', TTL => > >> '-1', IN_MEMORY => 'false', BLOCKCACHE => > >> 'false'}], INDEXES => []} > >> 1 row(s) in 0.0230 seconds > >> hbase(main):028:0> scan 't1' > >> ROW COLUMN+CELL > >> r1 column=f1:, timestamp=1, value=value > >> r2 column=f1:, timestamp=3, value=value > >> 2 row(s) in 0.0240 seconds > >> > >> On Fri, May 22, 2009 at 3:41 PM, Ryan Rawson <[email protected]> > wrote: > >> > Hey, > >> > > >> > I generally don't think of hbase entries like spreadsheets with > 'nulls' > >> in > >> > the empty locations. Its really more like an adjacency list, where > the > >> data > >> > is only there when it's there. > >> > > >> > But I was referring to your create, the key is 'VERSIONS' not > 'VERSION'. > >> > create 'table', {NAME=>'family', VERSIONS=>1} > >> > > >> > > >> > > >> > On Thu, May 21, 2009 at 11:35 PM, Edward J. Yoon < > [email protected] > >> >wrote: > >> > > >> >> Let's assume, there are two 2 * 2 sparse tables as below. > >> >> > >> >> t1 > >> >> ---- > >> >> null 2 > >> >> -1 null > >> >> > >> >> t2 > >> >> ---- > >> >> -3 null > >> >> null null > >> >> > >> >> I'll put these tables to table 'x'. And, The table 'x' will handle > >> >> only one version. Then, 't2' should be appeared, not 't1' + 't2' > >> >> table. > >> >> > >> >> Currently, Hbase shows the 't1' + 't2' table as below. > >> >> ---- > >> >> -3(t2) 2(t1) > >> >> -1(t1) null (what is this?) > >> >> > >> >> Should I update the all 't1' entries? > >> >> > >> >> On Fri, May 22, 2009 at 3:11 PM, Ryan Rawson <[email protected]> > >> wrote: > >> >> > The key is 'VERSIONS'. Give it another shot. > >> >> > > >> >> > -ryan > >> >> > > >> >> > On Thu, May 21, 2009 at 11:07 PM, Edward J. Yoon < > >> [email protected] > >> >> >wrote: > >> >> > > >> >> >> hbase(main):001:0> create 't1', {NAME=> 'f1', VERSION => 1} > >> >> >> hbase(main):002:0> put 't1', 'r1', 'f1' ,'value', 1 > >> >> >> hbase(main):007:0> put 't1', 'r2', 'f1:' ,'value', 2 > >> >> >> > >> >> >> I made a table 't1' as above. And, When scan this, > >> >> >> > >> >> >> hbase(main):008:0> scan 't1' > >> >> >> ROW COLUMN+CELL > >> >> >> r1 column=f1:, timestamp=1, value=value > >> >> >> r2 column=f1:, timestamp=2, value=value > >> >> >> 2 row(s) in 0.0330 seconds > >> >> >> > >> >> >> I expected only one row 'r2' (sparse table for time t2) but there > are > >> >> >> two tables on time dimension. I think it's a logical bug. The 't1' > >> >> >> should maintain only one version of time dimension table. > >> >> >> > >> >> >> What do you think? > >> >> >> -- > >> >> >> Best Regards, Edward J. Yoon @ NHN, corp. > >> >> >> [email protected] > >> >> >> http://blog.udanax.org > >> >> >> > >> >> > > >> >> > >> >> > >> >> > >> >> -- > >> >> Best Regards, Edward J. Yoon @ NHN, corp. > >> >> [email protected] > >> >> http://blog.udanax.org > >> >> > >> > > >> > >> > >> > >> -- > >> Best Regards, Edward J. Yoon @ NHN, corp. > >> [email protected] > >> http://blog.udanax.org > >> > > > > > > -- > Best Regards, Edward J. Yoon @ NHN, corp. > [email protected] > http://blog.udanax.org >
