Query Optimization in Multidatabase Systems

摘要: Global query execution in a multidatabase system can be done parallelly, as all the local databases are independent. In this paper, cost model that considers parallel of subqueries for global is developed. order to obtain maximum parallelism execution, it required find plan represented form bushy tree and should balanced maximal possible extent with respect time. A new bottom up approach called Agglomerative Approach (AA) proposed construct trees By deterministic nature approach, generates optimal solutions. This minima problem will severe case graph queries, i.e., queries structure. Simulated annealing (SA) employed (near) solution. These approaches (AA SA) suitable handling on-line off-line respectively. Hybrid (HA), an integration AA SA, optimize which estimated time spent on optimization known priori. Results obtained SA both structured presented.