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From Lars H <lhofha...@yahoo.com>
Subject Re: No. of families
Date Fri, 30 Dec 2011 16:51:23 GMT
I think the code in ScanQueryMatcher would suggest a performance limit somewhere in the high
10k's of columns.
This is a completely unscientific guess just from looking at the code. 

Jesse Yates <jesse.k.yates@gmail.com> schrieb:

>Out of curiosity (havent rtfm on this yet) do we have any hard bounds/performance impact
on the max number of column families/qualifiers? Has that behavior changed with the dynamic
cf stuff that fairly recently got rolled in? 
>
>Further, any pointers on where to start digging into the code on this would be great!
>
>Thanks!
>
>- Jesse Yates
>
>Sent from my iPhone.
>
>On Dec 29, 2011, at 1:18 AM, lars hofhansl <lhofhansl@yahoo.com> wrote:
>
>> 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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