The Hybrid Technique for Reference Materialization in Object Query Processing

  • Authors:
  • Quan Wang;David Maier;Leonard D. Shapiro

  • Affiliations:
  • -;-;-

  • Venue:
  • IDEAS '00 Proceedings of the 2000 International Symposium on Database Engineering & Applications
  • Year:
  • 2000

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Abstract

Resolving object references, or reference materialization, is a fundamental operation in object query evaluation. Existing reference materialization techniques fall into two categories: pointer-based and value-based. We identify several drawbacks of existing techniques and propose a hybrid technique that combines the advantages of each category. This technique relaxes the limitations of value-based techniques, while preserving much of their performance advantage over pointer-based techniques; it performs well in those cases where no existing algorithm is applicable or efficient. The hybrid technique shows even stronger performance advantages when moving from single-valued to collection-valued attributes. We present algebraic transformations to enable the hybrid technique in a rule-based query optimizer. Initial experimental results using a commercial object-oriented database show that the hybrid approach achieves significant speedup over current algorithms in many cases. The initial motivation for our work was the optimization and evaluation of object-oriented query languages, particularly OQL. However, the key features we have concentrated on, namely references and collection-valued attributes, are present in object-relational products and the SQL:1999 proposal.