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From lars hofhansl <lhofha...@yahoo.com>
Subject Re: No. of families
Date Thu, 29 Dec 2011 06:18:31 GMT
Less is not necessarily better. HBase can ignore stores (column families) during a scan or
get if thatno columns in that family were requested.

So what you want to do is group columns that are typically queried together in a single column
family, and put
columns that are not typically queried together in separate families.


-- Lars


----- Original Message -----
From: Rohit Kelkar <rohitkelkar@gmail.com>
To: user@hbase.apache.org
Cc: 
Sent: Wednesday, December 28, 2011 9:01 PM
Subject: Re: No. of families

When we say less column families, how much is less? Is this guided by
a ratio of the number of rows stored in the Htable to number of column
families. Or number of tables to number of column families. If I
understand correctly, the content of each column family is stored in a
separate file. So does it have anything to do with the disk space
allocated to hadoop?

- Rohit Kelkar

On Wed, Dec 28, 2011 at 10:14 PM, Mohammad Tariq <dontariq@gmail.com> wrote:
> Hi Doug,
>
>  Thanks a lot for the reply.Ya, I had asked a similar
> question.Actually I am stuck with some schema design issue.I am sorry,
> the intention was not to ask the same thing repeatedly.I'll try to
> figure it out with the help of guidelines provided.Many thanks.
>
> Regards,
>     Mohammad Tariq
>
>
>
> On Wed, Dec 28, 2011 at 7:24 PM, Doug Meil
> <doug.meil@explorysmedical.com> wrote:
>>
>> Hi there-
>>
>> re:  "number of CF's"
>>
>> Yes.  Fewer is better.
>>
>> http://hbase.apache.org/book.html#schema
>>
>> re:  "sub column families"
>>
>>
>> There aren't "sub column families" - it's just columns (within a CF).
>>
>> http://hbase.apache.org/book.html#datamodel
>>
>>
>> If I am not mistaken you asked a similar question to the dist-list a few
>> weeks ago. The answers haven't changed.
>>
>>
>>
>>
>>
>>
>> On 12/28/11 2:53 AM, "Mohammad Tariq" <dontariq@gmail.com> wrote:
>>
>>>Hello all,
>>>
>>>    Having less no. of column families is advisable. It is feasible to
>>>have 2 or 3 sub column families within a single column family???I
>>>want to store xml data in Hbase and I have sub tags that may go down
>>>to 2 or 3 levels.
>>>
>>>Regards,
>>>    Mohammad Tariq
>>>
>>
>>


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