Query optimization for parallel execution
Šumit Ganguly, Waqar Hasan, Ravi Krishnamurthy · 1992
The decreasing cost of computing makes it economically viable to reduce the response time of decision support queries by using parallel execution to exploit inexpen-sive resources. This goal poses the following query op-timization problem: Mzntmzze response ttme subject to constraints on throughput, which we motivate as the dual of the traditional DBMS problem, We address this novel problem in the context of Select-Project-Join queries by extending the execution space, cost model and search al-gorithm that are widely used in commercial DBItlSs. We incorporate the sources and deterrents of parallelism in the traditional execution space. We show that a cost model can predict response time while accounting for the new aspects due to parallelism, We observe that the response time optimization metric violates a fundamen-tal assumption in the dynamic programming algorithm that is the linchpin in the optimizers of most commer-cial DBMSS. We extend dynamic programming and show how optimization metrics which correctly predict response time may be designed. 1