> -Is there any other way to stract the contect of SSTable, writing a > java program for example instead of using sstable2json? Look at the code in sstale2json and copy it :)
> -I tried to get tombstons using the thrift API, but seems to be not > possible, is it right? When I try, the program throws an exception. No. Tombstones are not returned from API (See ColumnFamilyStore.getColumnFamily() ). You can see them if you use sstable2json. Cheers ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 30/05/2012, at 9:53 PM, Felipe Schmidt wrote: > I have further questions: > -Is there any other way to stract the contect of SSTable, writing a > java program for example instead of using sstable2json? > -I tried to get tombstons using the thrift API, but seems to be not > possible, is it right? When I try, the program throws an exception. > > thanks in advance > > Regards, > Felipe Mathias Schmidt > (Computer Science UFRGS, RS, Brazil) > > > > > 2012/5/24 aaron morton <aa...@thelastpickle.com>: >> 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). >> >> You can design it into your data model if you need it. >> >> >> 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? >> >> No. >> There is only ever 1 value for a column. >> The "older" copies of the column in the SSTables are artefacts of immutable >> on disk structures. >> If you want to see what's inside an SSTable use bin/sstable2json >> >> Cheers >> >> ----------------- >> Aaron Morton >> Freelance Developer >> @aaronmorton >> http://www.thelastpickle.com >> >> On 24/05/2012, at 9:42 PM, Felipe Schmidt wrote: >> >> 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) >> >> >> >> >> >>
