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From: innowireless TaeYun Kim <taeyun.kim@innowireless.co.kr>
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Subject: RE: Question on the number of column families
Date: Wed, 6 Aug 2014 13:48:21 +0900
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Thank you.

The 'dummy' column will always hold the value '1' (or even an empty =
string), that only signifies that this row exists. (And the real value =
is in the other 'big' column family)
The value is irrelevant since with current schema the filtering will be =
done by rowkey components alone. No column value is needed. (I will =
begin reading the filtering section shortly - it is only 6 pages ahead. =
So sorry for my premature thoughts)


-----Original Message-----
From: Ted Yu [mailto:yuzhihong@gmail.com]=20
Sent: Wednesday, August 06, 2014 1:38 PM
To: user@hbase.apache.org
Subject: Re: Question on the number of column families

bq. add a 'dummy' column family and apply HBASE-5416 technique

Adding dummy column family is not the way to utilize essential column =
family support - what would this dummy column family hold ?

bq. since I have not read the filtering section of the book I'm reading =
yet

Once you finish reading, you can look at the unit test =
(TestJoinedScanners) from HBASE-5416. You would understand this feature =
better.

Cheers


On Tue, Aug 5, 2014 at 9:21 PM, innowireless TaeYun Kim < =
taeyun.kim@innowireless.co.kr> wrote:

> Thank you all.
>
> Facts learned:
>
> - Having 130 column families is too much. Don't do that.
> - While scanning, an entire row will be read for filtering, unless
> HBASE-5416 technique is applied which makes only relevant column=20
> family is loaded. (But it seems that still one can't load just a=20
> column needed while
> scanning)
> - Big row size is maybe not good.
>
> Currently it seems appropriate to follow the one-column solution that=20
> Alok Singh suggested, in part since currently there is no reasonable=20
> grouping of the fields.
>
> Here is my current thinking:
>
> - One column family, one column. Field name will be included in =
rowkey.
> - Eliminate filtering altogether (in most case) by properly ordering=20
> rowkey components.
> - If a filtering is absolutely needed, add a 'dummy' column family and =

> apply HBASE-5416 technique to minimize disk read, since the field=20
> value can be large(~5MB). (This dummy column thing may not be right,=20
> I'm not sure, since I have not read the filtering section of the book=20
> I'm reading yet)
>
> Hope that I am not missing or misunderstanding something...
> (I'm a total newbie. I've started to read a HBase book since last=20
> week...)
>
>
>
>
>
>