Handling non-deterministic data availability in parallel query execution

The situation of non-deterministic data availability, where it is not known a priori which of two or more processes will respond first, cannot be handled with standard techniques. The consequence is sub-optimal processing because of inefficient resource allocation and unnecessary delays. We develop an effective solution to the problem by extending the demand-driven evaluation paradigm to the end of using operators with more than just one output stream. We show how inter-process communication and non-deterministic data availability in parallel query processing reduce to cases that can be executed efficiently with the new evaluation paradigm