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From Ted Yu <yuzhih...@gmail.com>
Subject Re: How are version conflicts handled in HBase?
Date Fri, 05 Jun 2015 15:55:19 GMT
Dia:
Have you tried command in the following form in hbase shell ?

  hbase> t.get 'r1', {COLUMN => 'c1', TIMERANGE => [ts1, ts2], VERSIONS =>
4}

Cheers

On Fri, Jun 5, 2015 at 8:50 AM, Dia Kharrat <dkharrat@gmail.com> wrote:

> Ted: Yes, I've already read the HBase documentation, but didn't find
> anything that directly answered my question. My question was simply whether
> it's possible to get cells with the same timestamp with concurrent Puts to
> the same cell.
>
> Vlad: Thanks for the information. Yep, I've also noticed the behavior of
> the last-write-wins when testing directly in hbase shell and writing out
> two values to the same cell with an identical timestamp.
>
> So, I gather that an application writing to the same cell concurrently will
> result in potential data loss when the write is at the exact same
> millisecond, correct? For my use-case, I'm not necessarily looking for
> uniqueness for the timestamp, but want to ensure I can still access all
> versions of the cell, even ones with the same timestamp.
>
> Dia
>
> On Thu, Jun 4, 2015 at 7:05 PM, Vladimir Rodionov <vladrodionov@gmail.com>
> wrote:
>
> > >> Please read http://hbase.apache.org/book.html#_store
> >
> > How does this answer original question?
> >
> > -Vlad
> >
> > On Thu, Jun 4, 2015 at 6:30 PM, Ted Yu <yuzhihong@gmail.com> wrote:
> >
> > > Dia:
> > > Please read http://hbase.apache.org/book.html#_store
> > >
> > > Cheers
> > >
> > > On Thu, Jun 4, 2015 at 6:02 PM, Vladimir Rodionov <
> > vladrodionov@gmail.com>
> > > wrote:
> > >
> > > > Yes, last write wins (with higher sequenceId). MemStore will resolve
> > this
> > > > conflict and only the last
> > > > put will be added eventually, unless ... between these two puts
> > > MemStore's
> > > > snapshot is created.
> > > > I this case put #1 will be saved in  a snapshot and eventually will
> > make
> > > it
> > > > into a store file, but this is just my speculations.
> > > >
> > > > -Vlad
> > > >
> > > > On Thu, Jun 4, 2015 at 5:08 PM, Dia Kharrat <dkharrat@gmail.com>
> > wrote:
> > > >
> > > > > I'm trying to confirm the behavior of HBase when there are
> concurrent
> > > > > writes to the same cell that happen at the exact same millisecond
> and
> > > not
> > > > > providing a timestamp value to the Put operations (i.e. relying on
> > > > current
> > > > > time of region server). Is it possible that such concurrent writes
> > > result
> > > > > in a cell with an identical version value or does HBase have a
> > > mechanism
> > > > to
> > > > > protect against that?
> > > > >
> > > > > If that's the case, my understanding is that last write wins,
> > correct?
> > > > >
> > > > > Thanks,
> > > > > Dia
> > > > >
> > > >
> > >
> >
>

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