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From yun peng <pengyunm...@gmail.com>
Subject Re: When does HBase set modification timestamp of a HFile?
Date Sun, 21 Oct 2012 01:42:49 GMT
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)?

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

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