Tandem has re-written its SQL compiler and its query execution engine into a new product that will be available on multiple operating systems. The new product uses a novel query execution engine and the authors highlight the unique aspects of the new engine. ServerWare SQL uses a data flow and scheduler driven task model to execute queries. Tasks communicate either via in-memory queues or via interprocess communication. Partitioned, pipelined, or independent operations are executed in parallel. By adding new task types the model can be easily extended. Parallelism in a distributed memory environment is implemented as a special "exchange" task type, as in the Volcano research prototype. Scheduling and load balancing are performed by separate scheduler tasks.
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