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Multiple Query Optimization in Mediator Systems
| Content Provider | Semantic Scholar |
|---|---|
| Author | Özcan, Fatma Subrahmanian, V. S. |
| Copyright Year | 2007 |
| Abstract | With the increase in mediated applications, there are now mediated application servers that support concurrent client accesses. Multiple query optimization (MQO) is essential for efficient processing of concurrent read only queries. The MQO problem in mediated environments differs from that of ordinary relational MQO systems in two ways: first, in mediated environments, the MQO system must be capable of interacting with the “local” query optimizers of the various sources being accessed. Second, in mediated environments, the notionof what constitutes a “common” subexpression varies dramatically from one source to another, and the MQO system must be capable of working with these diverse notions of “common” subexpression. In this paper, we extend classical relational DBMS MQO techniques to the case of mediated applications. Our architecture has a compile-time and a runtime component. In the compile-time component, the developer describes common subexpressions via a set of structures called invariants. By computing all implied invariants at compile time, we eliminate the need for runtime implication checking. We propose and experimentally evaluate a generic algorithm and various heuristics for this. We develop run-time common expression identification algorithms which use the above invariants, and then develop two generic MQO algorithms that are tightly coupled to the common subexpression algorithm. We conduct experiments to study the compile-time performance and run-time savings generated using our algorithms. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.cs.umd.edu/~fatma/publications/mqo.ps.gz |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
