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From Bradford Cross <bradford.n.cr...@gmail.com>
Subject Re: timestamp uses
Date Fri, 03 Apr 2009 15:49:00 GMT
I have another thread in progress re using HBase as a financial time series
database.

http://mail-archives.apache.org/mod_mbox/hadoop-hbase-user/200904.mbox/%3Cea7d6a710904011948l2a79bf18hfbc7a6102676b5f3@mail.gmail.com%3E



On Fri, Apr 3, 2009 at 8:38 AM, Jim Kellerman (POWERSET) <
Jim.Kellerman@microsoft.com> wrote:

> 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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