
114 Automated Physical Database Design and Tuning
B storage, we simply use T
tr
as the penalty associated with each
transformation tr.
6.2.3 Variations and Optimizations
We next briefly describe some minor optimizations and variations to the top-
down approach introduced in this section.
Shortcut evaluation: When evaluating the cost of a configuration C,we
might reach a point in which the SELECT cost of a subset of queries in
C is larger than the total cost of the current best configuration C
best
.In
this case, we know that neither C nor any configuration that is further
relaxed from C would be more efficient than C
best
. Therefore, we can stop
evaluating C (thus ...