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HBase, mail # user - HBase table - distinct values


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RE: HBase table - distinct values
Ramkrishna.S.Vasudevan 2012-10-11, 04:52
Are you planning to use region splits? Can the rowkey have the deptno?

Having dept no in another table, may be having a reverse mapping of deptno
to empno may be helpful too if such queries are frequent.

Regards
Ram
> -----Original Message-----
> From: Anoop Sam John [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, October 11, 2012 9:32 AM
> To: [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED]
> Subject: RE: HBase table - distinct values
>
> Hi Ravi
>          If dept_no is a CF:qualifier, to know all the dept numbers
> (distinct or not) you need a full table scan. As Doug said if it is a
> frequent online query don't think MR is a good choice..  If the data in
> your emp table is huge a full table scan also wont be that good I
> feel....  Can you guys think about storing dept number in another
> table?  If you people need query like select <empdetails> from emp
> where dept_no=?  (this query also)  you can think about creating
> secondary index implementation and indexing dept_no... You can use
> index table for above query as well as the 1st one you asked about.  :)
>
> -Anoop-
> ________________________________________
> From: [EMAIL PROTECTED] [[EMAIL PROTECTED]]
> Sent: Wednesday, October 10, 2012 7:51 PM
> To: [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]
> Subject: RE: HBase table - distinct values
>
> Hi,
>   Hbase table name  :- emp
>   Column family :- cf
>     Under the column family cf  we will be having the field name
> deptno
>
>
> Regards
> Raviprasad. T
> Mobile :-  91- 9894769541
>
>
> -----Anoop Sam John <[EMAIL PROTECTED]> wrote: -----
> To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>, "hbase-
> [EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> From: Anoop Sam John <[EMAIL PROTECTED]>
> Date: 10/10/2012 06:18PM
> Subject: RE: HBase table - distinct values
>
> Hi
> Your schema? 'deptno'  is a cf:qualifier?
>
> -Anoop-
> ________________________________________
> From: [EMAIL PROTECTED] [[EMAIL PROTECTED]]
> Sent: Wednesday, October 10, 2012 4:29 PM
> To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
> Subject: HBase table - distinct values
>
> Hi all,
>   Is it possible to select distinct value from Hbase table.
>
> Example :-
>    what is the equivalant code for the below Oracle code  in Hbase  ?
>
>   Select count (distinct deptno) from emp ;
>
> Regards
> Raviprasad. T
>
>
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