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From: Matteo Bertozzi <theo.bertozzi@gmail.com>
Date: Tue, 19 May 2015 20:14:47 -0700
Message-ID: 
 <CAFb6HiLj79wubH+0RfRXM6sx9Ai3RpaHH2wWEaVd5uhxt25D_w@mail.gmail.com>
Subject: Re: Scan vs Get
To: user@hbase.apache.org
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Take a look at table.rb _scan_internal()
LIMIT is not passed to the server, so you fetch more rows
https://github.com/apache/hbase/blob/master/hbase-shell/src/main/ruby/hbase/table.rb#L495

Matteo


On Tue, May 19, 2015 at 8:11 PM, Jean-Marc Spaggiari <
jean-marc@spaggiari.org> wrote:

> I tried to run scan/get/scan/get many times, and always the same pattern.
> You can remove the "LIMIT => 1" parameter and you will get the same
> performances.
>
> Scan and get without the QC returns in very similar time. 191ms for one,
> 194ms for the other one.
>
> 2015-05-19 23:02 GMT-04:00 Ted Yu <yuzhihong@gmail.com>:
>
> > J-M:
> > How many times did you try the pair of queries ?
> >
> > Since scan was run first, this would give the get query some advantage,
> > right ?
> >
> > Cheers
> >
> > On Tue, May 19, 2015 at 7:34 PM, Jean-Marc Spaggiari <
> > jean-marc@spaggiari.org> wrote:
> >
> > > Are not Scan and Gets supposed to be almost as fast?
> > >
> > > I have a pretty small table with 65K lines, few columns (hundred?)
> trying
> > > to go a get and a scan.
> > >
> > > hbase(main):009:0> scan 'sensors', { COLUMNS =>
> > > ['v:f92acb5b-079a-42bc-913a-657f270a3dc1'], STARTROW => '000a', LIMIT
> =>
> > 1
> > > }
> > > ROW
> > > COLUMN+CELL
> > >
> > >  000a
> > > column=v:f92acb5b-079a-42bc-913a-657f270a3dc1, timestamp=1432088038576,
> > >
> >
> value=\x08000aHf92acb5b-079a-42bc-913a-657f270a3dc1\x0EFAILURE\x0CNE-858\x
> > >
> > >
> > >
> >
> 140-0000-000\x02\x96\x01SXOAXTPSIUFPPNUCIEVQGCIZHCEJBKGWINHKIHFRHWHNATAHAHQBFRAYLOAMQEGKLNZIFM
> > > 000a
> > > 1 row(s) in 12.6720 seconds
> > >
> > > hbase(main):010:0> get 'sensors', '000a', {COLUMN =>
> > > 'v:f92acb5b-079a-42bc-913a-657f270a3dc1'}
> > > COLUMN
> > > CELL
> > >
> > >  v:f92acb5b-079a-42bc-913a-657f270a3dc1
> > timestamp=1432088038576,
> > >
> > >
> >
> value=\x08000aHf92acb5b-079a-42bc-913a-657f270a3dc1\x0EFAILURE\x0CNE-858\x140-0000-000\x02\x96\x01SXOAXTPSIUFPPNUCIEVQGCI
> > >
> > > ZHCEJBKGWINHKIHFRHWHNATAHAHQBFRAYLOAMQEGKLNZIFM
> > > 000a
> > >
> > > 1 row(s) in 0.0280 seconds
> > >
> > >
> > > They both return the same result. However, the get returns in 28ms
> while
> > > the scan returns in 12672ms.
> > >
> > > How come can the scan be that slow? Is it normal? If I remove the QC
> from
> > > the scan, then it takes only 250ms to return all the columns. I think
> > > something is not correct.
> > >
> > > I'm running on 1.0.0-cdh5.4.0 so I guess it's the same for 1.0.x...
> > >
> > > JM
> > >
> >
>

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