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The complexity of processing tree queries in distributed databases
Chihping Wang;
Parallel and Distributed Processing, 1990. Proceedings of the Second IEEE Symposium on
9-13 Dec. 1990
Page(s):604
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611
Abstract:
Semi-joins have been introduced to reduce the cost of processing distributed queries. The determine the optimal semi-join processing strategy, one must consider both the reduction effect and the transmission overhead. Researchers have studied the problem of finding the optimal semi-join strategies for processing tree queries. Although a number algorithms have been proposed, they either have a very high complexity or only solve special cases. It is conjectured that the tree query processing problem is inherently difficult. The author formally answers this question by proving it NP-hard
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