Metadata Lookup for Distributed Query Optimization in P2P Environment

摘要

Due to the characteristics of P2P systems, SQL query processing in these systems is more difficult than traditional DBMS. In this context, query optimization is even more complex. In this paper, we propose two methods allowing optimizer to avoid the bad choices which could be taken because of the lack of informations or the obsolete statistics found on the node initializing the query. The basic idea is to take advantage of the location phase to obtain metadata needed for the optimization phase. The performance evaluation of the proposed methods shows that both methods can improve the execution of complex queries in terms of response time and volume of inter-site transmitted data.