how various cost estimation techniques can be combined with various heuristic rules during query optimization by the DBMS
Answers
Cost-based optimization technique is expensive, even with dynamic programming.
Heuristic optimization transforms the query-tree by using a set of rules that typically improves execution performance in DBMS.
Cost Estimation Techniques can be Combined with Various Heuristic Rules
Explanation:
The major intention of question optimization is to pick out the maximum green manner of imposing the relational algebra operations at the bottom feasible price.
Therefore, the question optimizer needs to now no longer rely entirely on heuristics rules, but, it needs to additionally estimate the price of executing the specific techniques and discover the method with the minimal price estimate.
The technique of optimizing the question with the aid of using deciding on a method the ones effects in minimal price is referred to as price-primarily based totally question optimization.
The price-primarily based totally question optimization makes use of formulae that estimate the charges for some of alternatives and selects the only with lowest price and maximum green to execute.