Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
HBase >> mail # user >> Parallel scan in HBase


Copy link to this message
-
Re: Parallel scan in HBase
Thank you guys,
@Mohammad : Yeah I should retreice all the rows and compare each of them to
a specific value.
As I understand that Hbase by default doesn't support parallel scan,but I
can implement it by my own through Coprocessors & knowing the start/end row
key on each region, am I correct ?

Farrokh

On Fri, Feb 1, 2013 at 8:37 PM, James Taylor <[EMAIL PROTECTED]> wrote:

> If you run a SQL query that does aggregation (i.e. uses a built-in
> aggregation function like COUNT or does a GROUP BY), Phoenix will
> orchestrate the running of a set of queries in parallel, segmented along
> your row key (driven by the start/stop key plus region boundaries). We take
> advantage of a nifty feature that Lars added where you can pass in your own
> ExecutorService to an HTable, so you could do something similar.
>
> Regards,
>
>     James
>
>
> On 02/01/2013 08:40 AM, Mohammad Tariq wrote:
>
>> Do you need to scan each n every row within that range?Or you need
>> specific
>> rows based on some filter?
>>
>> Warm Regards,
>> Tariq
>> https://mtariq.jux.com/
>> cloudfront.blogspot.com
>>
>>
>> On Fri, Feb 1, 2013 at 9:16 PM, lars hofhansl <[EMAIL PROTECTED]> wrote:
>>
>>  The scan contract in HBase is that all rows are returned in order, so all
>>> regions have to be traversed in order as well.
>>> It would be nice to add some facility to HBase to performs the scanning
>>> in
>>> parallel.
>>>
>>>
>>>
>>> ______________________________**__
>>>   From: Farrokh Shahriari <[EMAIL PROTECTED]**>
>>> To: [EMAIL PROTECTED]
>>> Sent: Friday, February 1, 2013 5:52 AM
>>> Subject: Parallel scan in HBase
>>>
>>> Hi there
>>> I have two question about scan in Hbase :
>>> 1) Does scan operation with specific filter run in parallel on different
>>> regionservers ?
>>> 2) I wanna know whether this code runs at client side for searching the
>>> retrieved results or not ?
>>>
>>>           for (Result result : scanner1) {
>>>                           for (KeyValue kv : result.raw()) {
>>>                           //
>>>                           // some coeds
>>>                           //
>>>                       }
>>>                 }
>>>
>>>
>>> Farrokh Shahriari
>>>
>>>
>>
>