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From "Jim Kellerman (POWERSET)" <Jim.Keller...@microsoft.com>
Subject RE: timestamp uses
Date Fri, 03 Apr 2009 15:38:14 GMT
There are a number of Jiras open to address this issue.
See HBASE-33, HBASE-52 and HBASE-1182

---
Jim Kellerman, Powerset (Live Search, Microsoft Corporation)

> -----Original Message-----
> From: Genady [mailto:genadyg@exelate.com]
> Sent: Friday, April 03, 2009 2:56 AM
> To: hbase-user@hadoop.apache.org
> Subject: RE: timestamp uses
> 
> Jonathan,
> 
> Please correct me If I wrong, but one of the features that HBase obviously
> missing is possibility to select records based on timestamp range(week,
> month, etc.), as far as understand, it's possible to make select with
> specified timestamps, but in a most cases you want to select ranges. To
> solve it there is always option to put time/date as row key, but in most
> designs you can't do it.
> 
> Thanks,
> Gennady
> 
> 
> -----Original Message-----
> From: Jonathan Gray [mailto:jlist@streamy.com]
> Sent: Wednesday, April 01, 2009 7:55 PM
> To: hbase-user@hadoop.apache.org
> Subject: RE: timestamp uses
> 
> Wes,
> 
> The timestamp is used for versioning.
> 
> There have been arguments recently around 0.20 changes regarding whether
> the
> user should be allowed to manually set this stamp or it is always
> generated
> server-side according to NOW.
> 
> Currently the decision has been made to allow the user to manually set the
> stamp on insertion, to any stamp at or before now (but not in the future).
> This is so we can ensure when doing a flush that no entries in the
> storefile
> will have a stamp that is later than the flush stamp.
> 
> In the canonical use case for HBase, web crawling, timestamps are used to
> version and date each crawl.  You could then set HBase to keep the 10 most
> recent versions and older ones would be deleted on major compactions.
> 
> At the other extreme, you could set the timestamp then each individual
> column in a family could be a time-ordered list of whatever you want.  In
> practice, however, I've found that it makes more sense to encode stamps in
> your row keys or column names.
> 
> Hope that helps.
> 
> JG
> 
> > -----Original Message-----
> > From: Wes Chow [mailto:wes.chow@s7labs.com]
> > Sent: Wednesday, April 01, 2009 5:56 AM
> > To: hbase-user@hadoop.apache.org
> > Subject: timestamp uses
> >
> >
> > So far, few if any of the schema designs I've come across have really
> > talked about using the timestamp field and HBase's automatic deletion
> > of
> > old cells in a smart way.
> >
> > What is the timestamp typically used for? Snapshotting? Implementing
> > more complicated transactions than HBase natively supports?
> >
> >
> > Wes
> 
> 


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