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From lars hofhansl <la...@apache.org>
Subject Re: schema design: rows vs wide columns
Date Mon, 08 Apr 2013 04:39:00 GMT
I think the main problem is that all CFs have to be flushed if one gets large enough to require
a flush.
(Does anyone remember why exactly that is? And do we still need that now that the memstoreTS
is stored in the HFiles?)

So things are fine as long as all CFs have roughly the same size. But if you have one that
gets a lot of data and many others that are smaller, we'd end up with a lot of unnecessary
and small store files from the smaller CFs.

Anything else known that is bad about many column families?

-- Lars

 From: Andrew Purtell <apurtell@apache.org>
To: "user@hbase.apache.org" <user@hbase.apache.org> 
Sent: Sunday, April 7, 2013 3:52 PM
Subject: Re: schema design: rows vs wide columns
Is there a pointer to evidence/experiment backed analysis of this question?
I'm sure there is some basis for this text in the book but I recommend we
strike it. We could replace it with YCSB or LoadTestTool driven latency
graphs for different workloads maybe. Although that would also be a big
simplification of 'schema design' considerations, it would not be so
starkly lacking background.

On Sunday, April 7, 2013, Ted Yu wrote:

> From http://hbase.apache.org/book.html#number.of.cfs :
> HBase currently does not do well with anything above two or three column
> families so keep the number of column families in your schema low.
> Cheers
> On Sun, Apr 7, 2013 at 3:04 PM, Stack <stack@duboce.net <javascript:;>>
> wrote:
> > On Sun, Apr 7, 2013 at 11:58 AM, Ted <yuzhihong@gmail.com <javascript:;>>
> wrote:
> >
> > > With regard to number of column families, 3 is the recommended maximum.
> > >
> >
> > How did you come up w/ the number '3'?  Is it a 'hard' 3? Or does it
> > depend?  If the latter, on what does it depend?
> > Thanks,
> > St.Ack
> >

Best regards,

   - Andy

Problems worthy of attack prove their worth by hitting back. - Piet Hein
(via Tom White)
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