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

Switch to Threaded View
HBase >> mail # user >> schema design: rows vs wide columns

Copy link to this message
Re: schema design: rows vs wide columns

For the record, the refGuide mentions potential issues of CF lumpiness
that you mentioned:


6.2.1. Cardinality of ColumnFamilies

Where multiple ColumnFamilies exist in a single table, be aware of the
cardinality (i.e., number of rows).
      If ColumnFamilyA has 1 million rows and ColumnFamilyB has 1 billion
rows, ColumnFamilyA's data will likely be spread
      across many, many regions (and RegionServers).  This makes mass
scans for ColumnFamilyA less efficient.
Š. anything that needs to be updated/added for this?

On 4/8/13 12:39 AM, "lars hofhansl" <[EMAIL PROTECTED]> wrote:

>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 <[EMAIL PROTECTED]>
>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
>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 <[EMAIL PROTECTED] <javascript:;>>
>> wrote:
>> > On Sun, Apr 7, 2013 at 11:58 AM, Ted <[EMAIL PROTECTED]
>> wrote:
>> >
>> > > With regard to number of column families, 3 is the recommended
>> > >
>> >
>> > 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)