Exactly, I have always been curious about the same thing - if we have live statistics on queries then what stops us from cloning data (to correctly capture stat

Exactly, I have always been curious about the same thing - if we have live statistics on queries then what stops us from cloning data (to correctly capture statics such as skew, etc.) and running these live queries with a bunch of knobs tuned automatically (which indexes, on which columns, etc.), and reporting the cost-throughput paretto optimum to the user? The configuration space is too large to explore randomly? And it's structure is too complex to produce automatic suggestions?