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From "R. Verlangen" <ro...@us2.nl>
Subject Re: yet a couple more questions on composite columns
Date Sat, 04 Feb 2012 19:29:44 GMT
I also made something like this a while ago. I decided to go for the
2-rows-solution: by doing that you don't have the need for super columns.
Cassandra is really good at reading, so this should not be an issue.

Cheers!

2012/2/4 Yiming Sun <yiming.sun@gmail.com>

> Thanks Andrey and Chris.  It sounds like we don't necessarily have to use
> composite columns.  From what I understand about dynamic CF, each row may
> have completely different data from other rows;  but in our case, the data
> in each row is similar to other rows; my concern was more about the
> homogeneity of the data between columns.
>
> In our original supercolumn-based schema, one special supercolumn is
> called "metadata" which contains a number of subcolumns to hold metadata
> describing each collection (e.g. number of documents, etc.), then the rest
> of the supercolumns in the same row are all IDs of documents belong to the
> collection, and for each document supercolumn, the subcolumns contain the
> document content as well as metadata on individual document (e.g. checksum
> of each document).
>
> To move away from the supercolumn schema, I could either create two CFs,
> one to hold metadata, the other document content; or I could create just
> one CF mixing metadata and doc content in the same row, and using composite
> column names to identify if the particular column is metadata or a
> document.  I am just wondering if you have any inputs on the pros and cons
> of each schema.
>
> -- Y.
>
>
> On Fri, Feb 3, 2012 at 10:27 PM, Chris Gerken <chrisgerken@mindspring.com>wrote:
>
>>
>>
>>
>> On 4 February 2012 06:21, Yiming Sun <yiming.sun@gmail.com> wrote:
>>
>>> I cannot have one composite column name with 3 components while another
>>> with 4 components?
>>
>>  Just put 4 components and left last empty (if it is same type)?!
>>
>> Another question I have is how flexible composite columns actually are.
>>>  If my data model has a CF containing US zip codes with the following
>>> composite columns:
>>>
>>> {OH:Spring Field} : 45503
>>> {OH:Columbus} : 43085
>>> {FL:Spring Field} : 32401
>>> {FL:Key West}  : 33040
>>>
>>> I know I can ask cassandra to "give me the zip codes of all cities in
>>> OH".  But can I ask it to "give me the zip codes of all cities named Spring
>>> Field" using this model?  Thanks.
>>>
>> No. You set first composite component at first.
>>
>>
>> I'd use a dynamic CF:
>> row key = state abbreviation
>> column name = city name
>> column value = zip code (or a complex object, one of whose properties is
>> zip code)
>>
>> you can iterate over the columns in a single row to get a state's city
>> names and their zip code and you can do a get_range_slices on all keys for
>> the columns starting and ending on the city name to find out the zip codes
>> for a cities with the given name.
>>
>> I think
>>
>> - Chris
>>
>
>

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