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From Piotr Praczyk <piotr.prac...@gmail.com>
Subject Re: Row filters
Date Mon, 15 Jun 2009 09:03:38 GMT
Thanks. I meant something a little different although. By fragment I meant
all the rows in the table lying ( in the lexicographiocal order) between the
row X and Y.
The getScanner calls of HTable allow me to specify such rows. Although I
wanted to have a sequence of such ragments : X_1 Y_1 ... X_n Y_n
after ending the range X_i Y_i  I would like the scanner to jump to X_{i+1}
Y_{i+1}. for example lets assume we have a table with rows

aa
ab
ac
ad
ae
ba
bb
bc
bd
be

n=2
X_1 = aa
Y_1 = ac
X_2 = bc
Y_2 = bd

I would like the scanner to return following rows: aa, ab, ac, bc, bd
[without using fileters to avoid linear searching].
It seems to be not very difficult to implement it myself, but probably there
must be some built-in mechanism since this usage looks like a common one.


cheers
Piotr

2009/6/15 Ryan Rawson <ryanobjc@gmail.com>

> And let me follow up a bit...
>
> The best configuration for a m-r job is to have the # of map tasks = # of
> regions in the table.  While a scanner can iterate between regions, once
> the
> table size gets really big, it's best in my experience, more reliable as
> well, to have a 1:1 correspondence between map tasks and regions.
>
> -ryan
>
> On Mon, Jun 15, 2009 at 1:55 AM, Ryan Rawson <ryanobjc@gmail.com> wrote:
>
> > Hey,
> >
> > The client-side scanner code already will move it to the next region when
> > it hits the end of a region.
> >
> > -ryan
> >
> >
> >
> > On Mon, Jun 15, 2009 at 1:52 AM, Piotr Praczyk <piotr.praczyk@gmail.com
> >wrote:
> >
> >> 2009/6/12 stack <stack@duboce.net>
> >>
> >> > On Fri, Jun 12, 2009 at 8:41 AM, Erik Holstad <erikholstad@gmail.com>
> >> > wrote:
> >> >
> >> > > ...
> >> > > not really sure how this
> >> > > was done in 0.19 and earlier.
> >> >
> >> >
> >> > There's a stoprow filter in 0.19.x and earlier.  There is also a
> >> getScanner
> >> > override that takes a start and stop row in 0.19.x (under the wraps it
> >> uses
> >> > stop row filter -- check the client source).
> >> > St>Ack
> >> >
> >>
> >> Thanks :-) It was very helpful.
> >> Do you know if there is any standard Scanner allowing to iterate over
> more
> >> than one table fragments ? [when one chunk finishes, jumping to the
> >> beginning of another] Or rather should I implement it myself ?
> >>
> >>
> >> Piotr
> >>
> >
> >
>

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