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HBase, mail # user - Understanding scan behaviour


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Re: Understanding scan behaviour
Mohit Anchlia 2013-03-28, 17:17
Could the prefix filter lead to full tablescan? In other words is
PrefixFilter applied after fetching the rows?

Another question I have is say I have row key abc and abd and I search for
row "abc", is it always guranteed to be the first key when returned from
scanned results? If so I can alway put a condition in the client app.

On Thu, Mar 28, 2013 at 9:15 AM, Ted Yu <[EMAIL PROTECTED]> wrote:

> Take a look at the following in
> hbase-server/src/main/ruby/shell/commands/scan.rb
> (trunk)
>
>   hbase> scan 't1', {FILTER => "(PrefixFilter ('row2') AND
>     (QualifierFilter (>=, 'binary:xyz'))) AND (TimestampsFilter ( 123,
> 456))"}
>
> Cheers
>
> On Thu, Mar 28, 2013 at 9:02 AM, Mohit Anchlia <[EMAIL PROTECTED]
> >wrote:
>
> > I see then I misunderstood the behaviour. My keys are id + timestamp so
> > that I can do a range type search. So what I really want is to return a
> row
> > where id matches the prefix. Is there a way to do this without having to
> > scan large amounts of data?
> >
> >
> >
> > On Thu, Mar 28, 2013 at 8:26 AM, Jean-Marc Spaggiari <
> > [EMAIL PROTECTED]> wrote:
> >
> > > Hi Mohit,
> > >
> > > "+" ascii code is 43
> > > "9" ascii code is 57.
> > >
> > > So "+9" is coming after "++". If you don't have any row with the exact
> > > key "+++++", HBase will look for the first one after this one. And in
> > > your case, it's +9hC\xFC\x82s\xABL3\xB3B\xC0\xF9\x87\x03\x7F\xFF\xF.
> > >
> > > JM
> > >
> > > 2013/3/28 Mohit Anchlia <[EMAIL PROTECTED]>:
> > > > My understanding is that the row key would start with +++++ for
> > instance.
> > > >
> > > > On Thu, Mar 28, 2013 at 7:53 AM, Jean-Marc Spaggiari <
> > > > [EMAIL PROTECTED]> wrote:
> > > >
> > > >> Hi Mohit,
> > > >>
> > > >> I see nothing wrong with the results below. What would I have
> > expected?
> > > >>
> > > >> JM
> > > >>
> > > >> 2013/3/28 Mohit Anchlia <[EMAIL PROTECTED]>:
> > > >>  > I am running 92.1 version and this is what happens.
> > > >> >
> > > >> >
> > > >> > hbase(main):003:0> scan 'SESSIONID_TIMELINE', {LIMIT => 1,
> STARTROW
> > =>
> > > >> > 'sdw0'}
> > > >> > ROW                                                  COLUMN+CELL
> > > >> >  s\xC1\xEAR\xDF\xEA&\x89\x91\xFF\x1A^\xB6d\xF0\xEC\x
> > > >> > column=SID_T_MTX:\x00\x00Rc, timestamp=1363056261106,
> > > >> > value=PAGE\x09\x091363056252990\x09\x09/
> > > >> >  7F\xFF\xFE\xC2\xA3\x84Z\x7F
> > > >> >
> > > >> > 1 row(s) in 0.0450 seconds
> > > >> > hbase(main):004:0> scan 'SESSIONID_TIMELINE', {LIMIT => 1,
> STARTROW
> > =>
> > > >> > '------'}
> > > >> > ROW                                                  COLUMN+CELL
> > > >> >  -\xA1\xAF>r\xBD\xE2L\x00\xCD*\xD7\xE8\xD6\x1Dk\x7F\
> > > >> > column=SID_T_MTX:\x00\x00hF, timestamp=1363384706714,
> > > >> > value=PAGE\x09239923973\x091363384698919\x09/
> > > >> >  xFF\xFE\xC2\x8F\xF0\xC1\xBF
> > > >> >   row(s) in 0.0500 seconds
> > > >> > hbase(main):005:0> scan 'SESSIONID_TIMELINE', {LIMIT => 1,
> STARTROW
> > =>
> > > >> > '++++'}
> > > >> > ROW                                                  COLUMN+CELL
> > > >> >  +9hC\xFC\x82s\xABL3\xB3B\xC0\xF9\x87\x03\x7F\xFF\xF
> > > >> > column=SID_T_MTX:\x00\x00<2, timestamp=1364404155426,
> > > >> > value=PAGE\x09\x091364404145275\x09 \x09/
> > > >> >  E\xC2S-\x08\x1F
> > > >> > 1 row(s) in 0.0640 seconds
> > > >> > hbase(main):006:0>
> > > >> >
> > > >> >
> > > >> > On Wed, Mar 27, 2013 at 9:23 PM, ramkrishna vasudevan <
> > > >> > [EMAIL PROTECTED]> wrote:
> > > >> >
> > > >> >> Same question, same time :)
> > > >> >>
> > > >> >> Regards
> > > >> >> Ram
> > > >> >>
> > > >> >> On Thu, Mar 28, 2013 at 9:53 AM, ramkrishna vasudevan <
> > > >> >> [EMAIL PROTECTED]> wrote:
> > > >> >>
> > > >> >> > Could you give us some more insights on this?
> > > >> >> > So you mean when you set the row key as 'azzzaaa', though this
> > row
> > > >> does
> > > >> >> > not exist, the scanner returns some other row?  Or it is giving
> > > you a
>