Ok... it's really strange to me that Cassandra doesn't support data versioning cause all of other key-value databases support it (at least those who I know).
I have one remaining question: -in the case that I have more than 1 SSTable in the disk for the same column but with different data versions, is it possible to make a query to get the old version instead of the newest one? Regards, Felipe Mathias Schmidt (Computer Science UFRGS, RS, Brazil) 2012/5/16 Dave Brosius <dbros...@mebigfatguy.com>: > You're in for a world of hurt going down that rabbit hole. If you truely > want version data then you should think about changing your keying to > perhaps be a composite key where key is of form > > NaturalKey/VersionId > > Or if you want the versioning at the column level, use composite columns > with ColumnName/VersionId format > > > > > On 05/16/2012 10:16 AM, Felipe Schmidt wrote: >> >> That was very helpfull, thank you very much! >> >> I still have some questions: >> -it is possible to make Cassandra keep old value data after flushing? >> The same question for the memTable, before flushing. Seems to me that >> when I update some tuple, the old data will be overwrited in memTable, >> even before flushing. >> -it is possible to scan values from the memtable, maybe using the >> so-called Thrift API? Using the client-api I can just see the newest >> data version, I can't see what's really happening with the memTable. >> >> I ask that cause what I'll try to do is a Change Data Capture to >> Cassandra and the answers will define what kind of aproaches I'm able >> to use. >> >> Thanks in advance. >> >> Regards, >> Felipe Mathias Schmidt >> (Computer Science UFRGS, RS, Brazil) >> >> >> 2012/5/14 aaron morton<aa...@thelastpickle.com>: >>> >>> Cassandra does not provide access to multiple versions of the same >>> column. >>> It is essentially implementation detail. >>> >>> All mutations are written to the commit log in a binary format, see the >>> o.a.c.db.RowMutation.getSerializedBuffer() (If you want to tail it for >>> analysis you may want to change commitlog_sync in cassandra.yaml) >>> >>> Here is post about looking at multiple versions columns in an >>> sstable http://thelastpickle.com/2011/05/15/Deletes-and-Tombstones/ >>> >>> Remember that not all "versions" of a column are written to disk >>> (see http://thelastpickle.com/2011/04/28/Forces-of-Write-and-Read/). >>> Also >>> compaction will compress multiple versions of the same column from >>> multiple >>> files into a single version in a single file . >>> >>> Hope that helps. >>> >>> >>> ----------------- >>> Aaron Morton >>> Freelance Developer >>> @aaronmorton >>> http://www.thelastpickle.com >>> >>> On 14/05/2012, at 9:50 PM, Felipe Schmidt wrote: >>> >>> Yes, I need this information just for academic purposes. >>> >>> So, to read old data values, I tried to open the Commitlog using tail >>> -f and also the log files viewer of Ubuntu, but I can not see many >>> informations inside of the log! >>> Is there any other way to open this log? I didn't find any Cassandra >>> API for this purpose. >>> >>> Thanks averybody in advance. >>> >>> Regards, >>> Felipe Mathias Schmidt >>> (Computer Science UFRGS, RS, Brazil) >>> >>> >>> >>> >>> 2012/5/14 zhangcheng2<zhangche...@software.ict.ac.cn>: >>> >>> After compaciton, the old version data will gone! >>> >>> >>> ________________________________ >>> >>> zhangcheng2 >>> >>> >>> From: Felipe Schmidt >>> >>> Date: 2012-05-14 05:33 >>> >>> To: user >>> >>> Subject: Retrieving old data version for a given row >>> >>> I'm trying to retrieve old data version for some row but it seems not >>> >>> be possible. I'm a beginner with Cassandra and the unique aproach I >>> >>> know is looking to the SSTable in the storage folder, but if I insert >>> >>> some column and right after insert another value to the same row, >>> >>> after flushing, I only get the last value. >>> >>> Is there any way to get the old data version? Obviously, before >>> compaction. >>> >>> >>> Regards, >>> >>> Felipe Mathias Schmidt >>> >>> (Computer Science UFRGS, RS, Brazil) >>> >>> >>> >
