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<p>The semijoin has been used as an effective operator in reducing data transmission and processing over a network that allows forward size reduction of relations and intermediate results generated during the processing of a distributed query. The authors propose a relational operator, two-way semijoin, which enhanced the semijoin with backward size reduction capability for more cost-effective query processing. A pipeline N-way join algorithm for joining the reduced relations residing on N sites is introduced. The main advantage of this algorithm is that it eliminates the need for transferring and storing intermediate results among the sites. A set of experiments showing that the proposed algorithm outperforms all known conventional join algorithms that generate intermediate results is included.</p>
2-way semijoin program; data transmission; network; forward size reduction; intermediate results; distributed query; relational operator; backward size reduction; query processing; pipeline N-way join algorithm; sites; database theory; distributed databases; parallel algorithms; pipeline processing; programming theory; relational databases
H. Kang, N. Roussopoulos, "A Pipeline N-Way Join Algorithm Based on the 2-Way Semijoin Program", IEEE Transactions on Knowledge & Data Engineering, vol. 3, no. , pp. 486-495, December 1991, doi:10.1109/69.109109
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