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HBase, mail # user - default region splitting on which value?


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Re: default region splitting on which value?
Ted Yu 2013-04-21, 01:34
Thanks for sharing the information below.

How do you plan to store time (when the bus gets to each stop) in the row ?
Or maybe it is not of importance to you ?

On Sat, Apr 20, 2013 at 2:24 PM, Pal Konyves <[EMAIL PROTECTED]> wrote:

> I am making a paper for school about HBase, so the data I chose is not a
> real usable example. I am familiar with GTFS that is a de facto standard
> for storing information about public transportation schedules: when vehicle
> arrives to a stop and where it goes toward.
>
> I chose to genrate the rows on the fly, where each row represents a
> sequence of 'bus' stops that make a route from the first stop until the
> last stop.
> e.g.: [first_stop_id,last_stop_id],string_sequence_of_stops
> where within the [...] is the rowkey.
>
> So long story short, I generate the data. I want to use the HBase java
> client api to store the rows with Put. I plan to randomize it by picking
> random first_stop_id-s, and use more threads.
>
> the rowkeys will still have a sequence, because the way I generate the rows
> will output about 100-1000 rows starting with the same first_stop_id within
> the rowkey. The total ammount of rows will be about billions, and would
> take up about 1TB.
>
>
> On Sat, Apr 20, 2013 at 10:54 PM, Ted Yu <[EMAIL PROTECTED]> wrote:
>
> > The answer to your first question is yes - midkey of the key range would
> > be chosen as split key.
> >
> > For #2, can you tell us how you plan to randomize the loading ?
> > Bulk load normally means preparing HFiles which would be loaded directly
> > into your table.
> >
> > Cheers
> >
> > On Apr 20, 2013, at 1:11 PM, Pal Konyves <[EMAIL PROTECTED]> wrote:
> >
> > > Hi Ted,
> > > Only one family, my data is very simple key-value, although I want to
> > make
> > > sequential scan, so making a hash of the key is not an option.
> > >
> > >
> > >
> > > On Sat, Apr 20, 2013 at 10:07 PM, Ted Yu <[EMAIL PROTECTED]> wrote:
> > >
> > >> How many column families do you have ?
> > >>
> > >> For #3, per-splitting table at the row keys corresponding to peaks
> makes
> > >> sense.
> > >>
> > >> On Apr 20, 2013, at 10:52 AM, Pal Konyves <[EMAIL PROTECTED]>
> > wrote:
> > >>
> > >>> Hi,
> > >>>
> > >>> I am just reading about region splitting. By default - as I
> understand
> > -
> > >>> Hbase handles splitting the regions. I just don't know how to imagine
> > on
> > >>> which key it splits the regions.
> > >>>
> > >>> 1) For example when I write MD5 hash of rowkeys, they are most
> probably
> > >>> evenly distributed from
> > >>> 000000... to FFFFF... right? When  Hbase starts with one region, all
> > the
> > >>> writes goes into that region, and when the HFile get's too big, it
> just
> > >>> gets for example the median value of the stored keys, and split the
> > >> region
> > >>> by this?
> > >>>
> > >>> 2) I want to bulk load tons of data with the HBase java client API
> put
> > >>> operations. I want it to perform well. My keys are numeric sequential
> > >>> values (which I know from this post, I cannot load into Hbase
> > >> sequentially,
> > >>> because the Hbase tables are going to be sad
> > >>
> >
> http://ikaisays.com/2011/01/25/app-engine-datastore-tip-monotonically-increasing-values-are-bad/
> > >>> )
> > >>> So I thought I would pre-split the table into regions, and load the
> > data
> > >>> randomized. This way I will get good distribution among region
> servers
> > in
> > >>> terms of network IO from the beginning. Is that a good idea?
> > >>>
> > >>> 3) If my rowkeys are not evenly distributed in the keyspace, but they
> > >> show
> > >>> some peaks or bursts. e.g. 000-999, but most of the keys gather
> around
> > >> 020
> > >>> and 060 values, is it a good idea to have the pre region splits at
> > those
> > >>> peaks?
> > >>>
> > >>> Thanks in advance,
> > >>> Pal
> > >>
> >
>