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From Takahiko Kawasaki <daru...@gmail.com>
Subject Re: Put w/ timestamp -> Deleteall -> Put w/ timestamp fails
Date Wed, 15 Aug 2012 05:53:28 GMT
Dear Harsh,

Thank you very much for your detailed explanation. I could understand
what had been going on during my put/scan/delete operations. I'll modify
my application and test programs taking the timestamp implementation
into consideration.

Best Regards,
Takahiko Kawasaki

2012/8/15 Harsh J <harsh@cloudera.com>

> When a Delete occurs, an insert is made with the timestamp being the
> current time (to indicate it is the latest version). Hence, when you
> insert a value after this with an _older_ timestamp, it is not taken
> in as the latest version, and is hence ignored when scanning. This is
> why you do not see the data.
>
> If you instead insert this after a compaction has fully run on this
> store file, then your value will indeed get shown after insert, cause
> at that moment there wouldn't exist such a row with a latest timestamp
> at all.
>
> hbase(main):060:0> flush 'test-table'
> 0 row(s) in 0.1020 seconds
>
> hbase(main):061:0> major_compact 'test-table'
> 0 row(s) in 0.0400 seconds
>
> hbase(main):062:0> put 'test-table', 'row4', 'test-family', 'value', 10
> 0 row(s) in 0.0230 seconds
>
> hbase(main):063:0> scan 'test-table'
> ROW                   COLUMN+CELL
>  row4                 column=test-family:, timestamp=10, value=value
> 1 row(s) in 0.0060 seconds
>
> I suppose this is why it is recommended not to mess with the
> timestamps manually, and instead just rely on versions.
>
> On Tue, Aug 14, 2012 at 8:24 PM, Takahiko Kawasaki <daru.tk@gmail.com>
> wrote:
> > Hello,
> >
> > I have a problem where 'put' with timestamp does not succeed.
> > I did the following at the HBase shell.
> >
> > (1) Do 'put' with timestamp.
> >       # 'scan' shows 1 row.
> >
> > (2) Delete the row by 'deleteall'.
> >       # 'scan' says "0 row(s)".
> >
> > (3) Do 'put' again by the same command line as (1).
> >       # 'scan' says "0 row(s)" ! Why?
> >
> > (4) Increment the timestamp value by 1 and try 'put' again.
> >       # 'scan' still says "0 row(s)"! Why?
> >
> > The command lines I actually typed are as follows and the attached
> > file is the output from the command lines.
> >
> > scan 'test-table'
> > put 'test-table', 'row3', 'test-family', 'value'
> > scan 'test-table'
> > deleteall 'test-table', 'row3'
> > scan 'test-table'
> > put 'test-table', 'row3', 'test-family', 'value'
> > scan 'test-table'
> > deleteall 'test-table', 'row3'
> > scan 'test-table'
> > put 'test-table', 'row4', 'test-family', 'value', 10
> > scan 'test-table'
> > deleteall 'test-table', 'row4'
> > scan 'test-table'
> > put 'test-table', 'row4', 'test-family', 'value', 10
> > scan 'test-table'
> > put 'test-table', 'row4', 'test-family', 'value', 10
> > scan 'test-table'
> > quit
> >
> > Is this behavior the HBase specification?
> >
> > My cluster is built using CDH4 and the HBase version is 0.92.1-cdh4.0.0.
> >
> > Could anyone give me any insight, please?
> >
> > Best Regards,
> > Takahiko Kawasaki
>
>
>
> --
> Harsh J
>

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