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From lohit <lohit.vijayar...@gmail.com>
Subject Re: When does HBase set modification timestamp of a HFile?
Date Sun, 21 Oct 2012 04:45:24 GMT
Looks like StoreFile.getModificationTime is returning you in seconds
precision.
I am not sure what other APIs could be used here, but if you know the
location of StoreFile try one of the FileSystem APIs
http://hadoop.apache.org/docs/current/api/org/apache/hadoop/fs/FileStatus.html#getModificationTime()


2012/10/20 yun peng <pengyunmomo@gmail.com>

> Hi lohit and Stack,
> You are right, it always ends with 000. My setup in the test is hbase
> 0.94.2 running on local vfs.  Is this tied with current hbase
> implementation or something to do with my particular setup (so I can
> re-configure to make it more precise)?
> Thanks,
> Yun
>
> On Sat, Oct 20, 2012 at 7:54 PM, lohit <lohit.vijayarenu@gmail.com> wrote:
> > Last 3 digits of the timestamp you got from fetching
> getModificationTime()
> > has all zeros 1350764448000
> > Do you get all zeros all the time? May be the time precision is not what
> > you are looking for here?
> >
> > 2012/10/20 yun peng <pengyunmomo@gmail.com>
> >
> >> Hi, All,
> >> I am trying to understand how and when hbase set the modification
> >> timestamp for hfiles. My original intention is to get a timestamp when
> >> a hfile is generated (when last write to a hfile in compaction).
> >> StoreFile.getModificationTime() looks a good candidate but after
> >> initial tests, it has some behaviour that confuses.
> >>
> >> My test case is like,
> >> @hbase shell
> >> put 'usertable', "key1", 'cf:c1', "v1"
> >> put 'usertable', "key1", 'cf:c1', "v2"
> >> get 'usertable', 'key1', {COLUMN => 'cf:c1', VERSIONS => 4}
> >> flush 'usertable'
> >> major_compact 'usertable'
> >>
> >> for the get operation, it echoes
> >> COLUMN             CELL
> >>  cf:c1             timestamp=1350764448150, value=v2
> >>  cf:c1             timestamp=1350764448114, value=v1
> >>
> >> but when I try to get modification timestamp of the hfile generated by
> >> major_compact, it is 1350764448000, which is smaller/earlier than that
> >> of the keyvalues (which are actually put first). I have run the same
> >> test this couple of times, and it is not always: sometime modification
> >> timestamp is eariler sometimes it's later than keyvalue's.
> >>
> >> Anyone knows how HBase set modification timestamp of hfile and that of
> >> a keyvalue pair? Or generally, how should I get a timestamp indicating
> >> when the last write to a hfile occurs?
> >>
> >> regards,
> >> Yun
> >>
> >
> >
> >
> > --
> > Have a Nice Day!
> > Lohit
>



-- 
Have a Nice Day!
Lohit

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