GAMMA - A High Performance Dataflow Database Machine

In this paper, we present the design, implementation techniques, and initial performance evaluation of Gamma. Gamma is a new relational database machine that exploits dataflow query processing techniques. Gamma is a fully operational prototype consisting of 20 VAX 11/750 computers. The design of Gamma is based on what we learned from building our earlier multiprocessor database machine prototype (DIRECT) and several years of subsequent research on the problems raised by the DIRECT prototype. In addition to demonstrating that parallelism can really be made to work in a database machine context, the Gamma prototype shows how parallelism can be controlled with minimal control overhead through a combination of the use of algorithms based on hashing and the pipelining of data between processes. Except for 2 messages to initiate each operator of a query tree and 1 message when the operator terminates, the execution of a query is entirely self-scheduling.