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Date: Thu, 22 Nov 2012 10:10:11 +0800
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Subject: Re: delete rows without writing HLog may be appear in the future?
From: Bing Jiang <jiangbinglover@gmail.com>
To: user@hbase.apache.org, lars hofhansl <lhofhansl@yahoo.com>
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Thanks for all your suggestion and talk.
One idea occurs to me why not check or restore wal when compaction
executes. If it does, hbase can drop some unused hlog, I think that will be
effective to the issue.
please correct me if I am wrong.

---Bing

2012/11/22 lars hofhansl <lhofhansl@yahoo.com>

> I have it on my list of things to do to allow deferred WAL flush as a per
> operation option (right now it's a CF option).
> You really do not want to do anything with the WAL off. If you use
> deferred flush there is still a chance that this might happen (the RS cou=
ld
> die in the few seconds after a Delete before it is flushed to the WAL), b=
ut
> it should be a rare occurrance.
>
>
> -- Lars
>
>
>
> ________________________________
>  From: Bing Jiang <jiangbinglover@gmail.com>
> To: user@hbase.apache.org
> Sent: Wednesday, November 21, 2012 7:20 AM
> Subject: Re: delete rows without writing HLog may be appear in the future=
?
>
> we need to confirm that put must be safe,but deletes must be quick and
> low-latency.
> On Nov 21, 2012 11:10 PM, "Michael Segel" <michael_segel@hotmail.com>
> wrote:
>
> > Some time later?
> >
> > Time of course is relative, so I have to ask what occurred between the
> > write and the delete?
> > How much time? Did you have any compactions in between the write and th=
e
> > delete?
> >
> > Why are you not consistent in your use of the WAL ?
> >
> >
> > On Nov 21, 2012, at 6:37 AM, Bing Jiang <jiangbinglover@gmail.com>
> wrote:
> >
> > > hi=A3=ACall.
> > > I want to describe a phenomenon that happens to our hbase cluster.
> > > I use puts(List<Put>) to insert many records with writing hlog enable=
,
> > > and some time later I delete all of these records with writing hlog
> > disable.
> > > When one week later, i scan the table, I found some records I have
> delete
> > > reappear again.
> > > It is an interesting case. In my opinion, if we delete data without
> > enable
> > > writing hlog, when regionserver fails, the log will replay in another
> > > regionserver.
> > > Can anyone tell me if I persist on deleting records without enable
> > writing
> > > hlog, is there a way to prevent these records from reappearing again
> some
> > > time later?
> > >
> > > Cheers!
> > > --
> > > Bing Jiang
> > > weibo: http://weibo.com/jiangbinglover
> > > BLOG: http://blog.sina.com.cn/jiangbinglover
> > > BLOG: http://www.binospace.com
> > > National Research Center for Intelligent Computing Systems
> > > Institute of Computing technology
> > > Graduate University of Chinese Academy of Science
> >
> >
>


--=20
Bing Jiang
Tel=A3=BA(86)134-2619-1361
weibo: http://weibo.com/jiangbinglover
BLOG: http://blog.sina.com.cn/jiangbinglover
National Research Center for Intelligent Computing Systems
Institute of Computing technology
Graduate University of Chinese Academy of Science

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