Parallel Query Processing
Multiprocessor query processing
Parallel query processing designates the transformation of high-level queries into execution plans that can be efficiently executed in parallel, on a multiprocessor computer. This is achieved by exploiting the way data is placed in parallel and the various execution techniques offered by the parallel database system. As in query processing, the transformation from the query into the execution plan to be executed must be both correct and yield efficient execution. Correctness is obtained by using well-defined mappings in some algebra, e.g., relational algebra, which provides a good abstraction of the execution system. Efficient execution is crucial for high-performance, e.g., good query response time or high query throughput. It is obtained by exploiting efficient parallel execution techniques and query optimization which selects the most efficient parallel execution plan among all equivalent plans.
The main forms of parallelism which...