Correcting execution of distributed queries

A low overhead delay method for deciding when to correct a strategy is presented. Sampling is used to estimate the size relations and alternative heuristic strategies prepared in a background mode are used to decide when to correct. Correction is made only if lower overall delay is achieved, including correction time. Evaluation using a model of a distributed database indicates that the heuristic strategies are near optimal. Moreover, it suggests that it is usually correct to abort creation of an intermediate relation which is much larger than predicted.<
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