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From Mohit Anchlia <mohitanch...@gmail.com>
Subject Re: Understanding scan behaviour
Date Sat, 30 Mar 2013 15:25:03 GMT
Thanks, that's a good point about last byte being max :)

When I query 1234555..1234556 do I also get row for 1234556 if one exist?

On Sat, Mar 30, 2013 at 6:55 AM, Asaf Mesika <asaf.mesika@gmail.com> wrote:

> Yes.
> Watch out for last byte being max
>
>
> On Fri, Mar 29, 2013 at 7:31 PM, Mohit Anchlia <mohitanchlia@gmail.com
> >wrote:
>
> > Thanks everyone, it's really helpful. I'll change my prefix filter to end
> > row. Is it necessary to increment the last byte? So if I have hash of
> > 1234555 my end key should be 1234556?
> >
> >
> > On Thu, Mar 28, 2013 at 11:20 PM, ramkrishna vasudevan <
> > ramkrishna.s.vasudevan@gmail.com> wrote:
> >
> > > Mohith,
> > >
> > > It is always better to go with start row and end row if you are knowing
> > > what are they.
> > > Just add one byte more to the actual end row (inclusive row) and form
> the
> > > end key.  This will narrow down the search.
> > >
> > > Remeber the byte comparison is the way that HBase scans.
> > > Regards
> > > Ram
> > >
> > > On Fri, Mar 29, 2013 at 11:18 AM, Li, Min <mili@microstrategy.com>
> > wrote:
> > >
> > > > Hi, Mohit,
> > > >
> > > > Try using ENDROW. STARTROW&ENDROW is much faster than PrefixFilter.
> > > >
> > > > "+" ascii code is 43
> > > > "," ascii code is 44
> > > >
> > > > scan 'SESSIONID_TIMELINE', {LIMIT => 1,STARTROW => '++++',
> > > ENDROW=>'+++,'}
> > > >
> > > > Min
> > > >
> > > > -----Original Message-----
> > > > From: Mohit Anchlia [mailto:mohitanchlia@gmail.com]
> > > > Sent: Friday, March 29, 2013 1:18 AM
> > > > To: user@hbase.apache.org
> > > > Subject: Re: Understanding scan behaviour
> > > >
> > > > 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 <yuzhihong@gmail.com> 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 <
> > mohitanchlia@gmail.com
> > > > > >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 <
> > > > > > jean-marc@spaggiari.org> 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 <mohitanchlia@gmail.com>:
> > > > > > > > My understanding is that the row key would start with
+++++
> for
> > > > > > instance.
> > > > > > > >
> > > > > > > > On Thu, Mar 28, 2013 at 7:53 AM, Jean-Marc Spaggiari
<
> > > > > > > > jean-marc@spaggiari.org> wrote:
> > > > > > > >
> > > > > > > >> Hi Mohit,
> > > > > > > >>
> > > > > > > >> I see nothing wrong with the results below. What
would I
> have
> > > > > > expected?
> > > > > > > >>
> > > > > > > >> JM
> > > > > > > >>
> > > > > > > >> 2013/3/28 Mohit Anchlia <mohitanchlia@gmail.com>:
> > > > > > > >>  > 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 <
> > > > > > > >> > ramkrishna.s.vasudevan@gmail.com> wrote:
> > > > > > > >> >
> > > > > > > >> >> Same question, same time :)
> > > > > > > >> >>
> > > > > > > >> >> Regards
> > > > > > > >> >> Ram
> > > > > > > >> >>
> > > > > > > >> >> On Thu, Mar 28, 2013 at 9:53 AM, ramkrishna
vasudevan <
> > > > > > > >> >> ramkrishna.s.vasudevan@gmail.com>
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
> > > > > > > >> row
> > > > > > > >> >> > that does not exist?
> > > > > > > >> >> >
> > > > > > > >> >> > Or you mean it is doing a full table
scan?
> > > > > > > >> >> >
> > > > > > > >> >> > Which version of HBase and what
type of filters are you
> > > > using?
> > > > > > > >> >> > Regards
> > > > > > > >> >> > Ram
> > > > > > > >> >> >
> > > > > > > >> >> >
> > > > > > > >> >> > On Thu, Mar 28, 2013 at 9:45 AM,
Mohit Anchlia <
> > > > > > > >> mohitanchlia@gmail.com
> > > > > > > >> >> >wrote:
> > > > > > > >> >> >
> > > > > > > >> >> >> I have key in the form of "hashedid
+ timestamp" but
> > when
> > > I
> > > > > run
> > > > > > > scan
> > > > > > > >> I
> > > > > > > >> >> get
> > > > > > > >> >> >> rows for almost every value.
For instance if I run
> scan
> > > for
> > > > > > > 'azzzaaa'
> > > > > > > >> >> that
> > > > > > > >> >> >> doesn't even exist even then
I get the results.
> > > > > > > >> >> >>
> > > > > > > >> >> >> Could someone help me understand
what might be going
> on
> > > > here?
> > > > > > > >> >> >>
> > > > > > > >> >> >
> > > > > > > >> >> >
> > > > > > > >> >>
> > > > > > > >>
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

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