maria-developers team mailing list archive

[Arjen Lentz <arjen@xxxxxxxxxxxxx>]

Hi Monty, all

On 07/08/2010, at 11:27 PM, Michael Widenius wrote:
> We have plans to add dynamic columns into MariaDB soon.
> This will probably happen in 5.3, assuming there is some interest in
> this feature.
>
> With dynamic columns you can store 'any' number of columns in a blob.
> In effect, each row in the database may have it's own set of columns.
> One will be able to trivially access and update data in the dynamic
> columns and also add/drop columns inside the blob.
>
> Example usage:
>
> SELECT column_get(blob, 1, varchar(100)) from table_with_dynamic;
>
> UPDATE table_with_dynamic SET blob=column_add(blob, 2, "hello")  
> where id=1;
>
> UPDATE table_with_dynamic SET blob=column_del(blob,4) where id=5;
>
> Note that 'column_add()' will replace any old value with the given  
> column_id.
>
> Future ideas:
> - Allow indexing with name instead of numbers. When this is done we  
> can drop the
> type as part of column_get()
> - Allow indexing on dynamic fields.
>
> You can find a full specification of this feature here:
> http://askmonty.org/worklog/Server-BackLog/?tid=34


The idea is good, based on what Google's BigTable (see the Hypertable  
specs) introduced.
It provides a mild level of denormalisation, enabling better  
scalability.
And in the case of MariaDB, you keep the same familiar and convenient  
API. That's important.

I think the word "column" is very wrong in the above example. It's  
more like "subattributes".
See what the terminology in bigtable/hypertable was... Perhaps Mark  
has insights on this too.

I'm for it, it solves a real need that people are already trying to  
solve (with desperately bad design decisions ;-).

Regards,
Arjen.
--
Arjen Lentz, Exec.Director @ Open Query (http://openquery.com)
Exceptional Services for MySQL at a fixed budget.

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