Efficient implementation of loops in bottom-up evaluation of logic queries

Juhani Kuittinen, Otto Nurmi, Seppo Sippu, Eljas Soisalon-Soininen

Forskningsoutput: Kapitel i bok/rapport/konferenshandlingKonferensbidragVetenskapligPeer review

Sammanfattning

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.
Originalspråkengelska
Titel på gästpublikationProceedings of the 6th International Conference on Very Large Data Bases : August 13-16, 1990, Brisbane, Australia
RedaktörerDennis McLeod, Ron Sacks-Davis, Hans-Jörg Schek
Antal sidor8
UtgivningsortPalo Alto, CA
FörlagMorgan Kaufmann Publishers
Utgivningsdatum1990
Sidor372-379
ISBN (tryckt)1-55860-149-X
StatusPublicerad - 1990
MoE-publikationstypA4 Artikel i en konferenspublikation
EvenemangInternational Conference on Very Large Data Bases - Brisbane, Queensland, Australien
Varaktighet: 13 aug 199016 aug 1990
Konferensnummer: 16 (VLDB)

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  • 113 Data- och informationsvetenskap

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