Efficient Implementation of Loops in Bottom-Up Evaluation of Logic Queries.

Juhani Kuittinen, Otto Nurmi, Seppo Sippu, Eljas Soisalon-Soininen: Efficient Implementation of Loops in Bottom-Up Evaluation of Logic Queries. VLDB 1990: 372-379

@inproceedings{DBLP:conf/vldb/KuittinenNSS90,
  author    = {Juhani Kuittinen and
               Otto Nurmi and
               Seppo Sippu and
               Eljas Soisalon-Soininen},
  editor    = {Dennis McLeod and
               Ron Sacks-Davis and
               Hans-J{\"o}rg Schek},
  title     = {Efficient Implementation of Loops in Bottom-Up Evaluation of
               Logic Queries},
  booktitle = {16th International Conference on Very Large Data Bases, August
               13-16, 1990, Brisbane, Queensland, Australia, Proceedings},
  publisher = {Morgan Kaufmann},
  year      = {1990},
  isbn      = {1-55860-149-X},
  pages     = {372-379},
  ee        = {db/conf/vldb/KuittinenNSS90.html},
  crossref  = {DBLP:conf/vldb/90},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}

Abstract

We consider the efficient implementation of the bottom-up evaluation method for recursive queries in logic databases. In the bottom-up evaluation algorithms the non-mutually-recursive rules are evaluated in certain order, whereas the evaluation order within a set of the mutually recursive rules is free. However, significant savings in join operations can be achieved by arranging the mutually recursive rules appropriately. We present an algorithm for splitting the evaluation loop for mutually recursive rules into subloops and for determining the order in which the rules shouldbe evaluated within a loop. The semi- naive evaluation algorithm is modified accordingly to gain advantagefrom the evaluation order and to work with the incremental relations ("deltas") appearing at different levels in the loop structure. The computation within a subloop is optimized by identifying loop- invariant factors in the rules to be evaluated. Using an experimental logic database system we demonstrate the usefulness of our algorithm in implementing data- log queries optimized by the "magic sets" and related term rewriting strategies.

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Dennis McLeod, Ron Sacks-Davis, Hans-Jörg Schek (Eds.): 16th International Conference on Very Large Data Bases, August 13-16, 1990, Brisbane, Queensland, Australia, Proceedings. Morgan Kaufmann 1990, ISBN 1-55860-149-X

References

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Contents
[15]: Jeffrey D. Ullman: Principles of Database and Knowledge-Base Systems, Volume II. Computer Science Press 1989, ISBN 0-7167-8162-X
Contents
[16]: Jeffrey D. Ullman: Bottom-Up Beats Top-Down for Datalog. PODS 1989: 140-149