Design of Optimization in Object-Oriented Queries
M. C. Nikose, Sheetal S. Dhande, P. R. Meghe · 2012
Query optimization is the process of finding the best or rather a reasonably efficient execution plan, thus by minimizing the time of query evaluation & the cost of evaluation to the level accepted by user. When a query jointly addresses very large and small collections, the iteration caused by query operator is driven by large collection and in each cycle a subquery which depends on an element of small collection is evaluated. The result return by subquery for such each element is same. Moreover, such a subquery is unnecessarily evaluated many times. The underlying idea used here is to rewrites such a query so that the loop is performed on small collection and inside each its cycle a subquery addressing a large collection is evaluated.