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From Ted Zlatanov <...@lifelogs.com>
Subject Re: why have ColumnFamilies?
Date Wed, 03 Mar 2010 14:05:00 GMT
On Wed, 3 Mar 2010 14:43:14 +0100 Alexandre Conrad <alexandre.conrad@gmail.com> wrote:


AC> 2010/3/3 Ted Zlatanov <tzz@lifelogs.com>:
>> I don't understand the advantages of ColumnFamilies over a
>> SuperColumnFamily with just one supercolumn.  Why have the former if the
>> latter is functionally equivalent?

AC> As far as I understand, there's how I organize Cassandra entities:

AC> http://paste.pocoo.org/show/185126/

AC> Is this somehow correct?

This was your diagram (fixed-width font required):

> KeySpace                            
>    |                                
>    +-- Row                          
>         |                           
>         +-- ColumnFamily            
>                  |                  
>                  +-- Column         
>                  |                  
>                  +-- SuperColumn    
>                          |          
>                          +-- Column 

That's incorrect.  Here's a (shorter, correct) version:

KeySpace->Row->ColumnFamily->Column[name, value]

(a two-level map)

KeySpace->Row->SuperColumnFamily->SuperColumn[name]->Column[name, value]

(a three-level map)

My point was that conceptually, the three-level map can express the
two-level map.

Ted


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