Hello,

> Of course using RDBMS directly will give the best results.
> Especially for large data volumes. 
> But to have this feature in application layer  is convenient. 
>
Fritz Henglein has done some recent, interesting work in this area.
His WGP paper (http://www.diku.dk/hjemmesider/ansatte/henglein/papers/henglein2010d.pdf) is a good place to start if you're interested.

-Jeff

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