This Article 
   
 Share 
   
 Bibliographic References 
   
 Add to: 
 
Digg
Furl
Spurl
Blink
Simpy
Google
Del.icio.us
Y!MyWeb
 
 Search 
   
An Optimal Algorithm for Processing Distributed Star Queries
October 1985 (vol. 11 no. 10)
pp. 1097-1107
A.L.P. Chen, System Development Corporation
The problem of optimal query processing in distributed database systems was shown to be NP-hard. However, for a special type of queries called star queries, we have developed a polynomial optimal algorithm. Semijoin tactics are applied for query processing. An execution graph is introduced to represent the semijoin programs associated with the distributed processing of the queries. We then identify optimality properties of semijoin programs for star queries, and use these properties to derive the optimal semijoin program. We have shown that the optimal semijoin program can be found from serial semijoin strategies, defined as serial semijoin programs which include each semijoin associated with the query exactly once. By making certain assumptions on the file sizes and the semijoin selectivities, we can obtain the optimal semijoin program from these strategies in polynomial time. Our assumption on selectivites is consistent in the sense that we consider the selectivity of a semijoin based on the current database state, i.e., we take into consideration the reduction effects of all prior semijoins.
Index Terms:
star queries, Distributed database systems, optimal algorithms, query optimization, relational data model, semijoin programs, semijoin selectivity
Citation:
A.L.P. Chen, V.O.K. Li, "An Optimal Algorithm for Processing Distributed Star Queries," IEEE Transactions on Software Engineering, vol. 11, no. 10, pp. 1097-1107, Oct. 1985, doi:10.1109/TSE.1985.231857
Usage of this product signifies your acceptance of the Terms of Use.