Looking for more information on Relational Optimization setting

Hi folks,

Since upgrading to SPS6 I noticed a new option in my analytic views called 'Allow relational optimization'.  I'm trying to learn more about this but all I'm finding in the latest SPS6 documentation is a very brief example;

EXAMPLE

You can enable relational optimization for your analytic view such as, Optimize stacked SQL for example, convert

SELECT a, SUM(X) FROM ( SELECT * FROM AV) GROUP BY A

to

SELECT A, SUM(X) FROM AV GROUP BY A

This example is not making sense to me at least the way it's written.  Can somebody perhaps explain differently or a better example of how this setting works?

Thanks,

-Patrick