Query optimization in the CROQUE project

  • Andreas Heuer
  • Joachim Kröger
Object-Oriented Databases 4
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1134)


This paper describes some concepts for the evaluation and optimization of ODMG-OQL queries. We present a logical object algebra for the internal representation of OQL queries. Different optimization techniques are sketched: factorization of common subexpressions, dependency-based optimization, and query rewriting. Afterwards, our physical algebra is presented and a complex example of the optimization process is given. We describe our implementation and the present investigations using search strategies to find the best execution plan. In contrast to previous studies on the evaluation of object-oriented queries, we use a logical and a physical algebra in the process of evaluation and optimization of OQL queries, thus achieving logical data independence. Other basic ideas of our work are the integration of different optimization techniques into one approach and the use of cost functions especially valid for the object-oriented database system ObjectStore.


Query Evaluation Execution Plan Query Optimization Object Database Logical Algebra 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. [AF95]
    K. Aberer and G. Fischer. Semantic Query Optimization for Methods in Object-Oriented Database Systems. In Proc. of the 11th ICDE, Taipei, Taiwan, 1995.Google Scholar
  2. [Asm95]
    R. Asmus. Concept and Implementation of an Optimized OQL Query Processor on Top of ObjectStore. Master's thesis, CS Dept., University of Rostock, 1995. In german.Google Scholar
  3. [BMG93]
    J.A. Blakeley, W.J. McKenna, and G. Graefe. Experiences Building the Open OODB Query Optimizer. In Proc. of the ACM SIGMOD Conf., Washington DC, USA, 1993.Google Scholar
  4. [Cat94]
    R.G.G. Cattell, editor. The Object Database Standard: ODMG-93. Morgan Kaufmann, San Mateo, CA, 1994.Google Scholar
  5. [CD92]
    S. Cluet and C. Delobel. A General Framework for the Optimization of Object-Oriented Queries. In Proc. of the ACM SIGMOD Conf., San Diego, CA, 1992.Google Scholar
  6. [CG94]
    R. L. Cole and G. Graefe. Optimization of Dynamic Query Evaluation Plans. In Proc. of the ACM SIGMOD 23,2, 1994.Google Scholar
  7. [CM94]
    S. Cluet and G. Moerkotte. Nested Queries in Object Bases. In Proc. of the 4th Int'l Workshop on DBPL — Object Models and Languages, NY, 1994. Springer, London.Google Scholar
  8. [FM95]
    L. Fegaras and D. Maier. Towards an Effective Calculus for Object Query Languages. In Proc. of the ACM SIGMOD Conf., San Jose, CA, 1995.Google Scholar
  9. [FMS93]
    L. Fegaras, D. Maier, and T. Sheard. Specifying Rule-based Query Optimizers in a Reflective Framework. In Proc. of the 3rd DOOD, New York, 1993. Springer.Google Scholar
  10. [GGR+96]
    D. Gluche, T. Grust, H. Riedel, M. H. Scholl, A. Asmus, A. Heuer, and J. Kröger. The CROQUE project: Object Queries Dressed for Success. 1996. In preparation.Google Scholar
  11. [GS96]
    Torsten Grust and Marc H. Scholl. Translating OQL into Monoid Comprehensions — Stuck with Nested Loops? Technical Report 3/1996, Dept. of Mathematics and CS, University of Konstanz, 1996.Google Scholar
  12. [HFW90]
    A. Heuer, J. Fuchs, and U. Wiebking. OSCAR: An Object-Oriented Database System with a Nested Relational Kernel. In Proc. of the 9th Int. Conf. on Entity-Relationship Approach, Lausanne. Elsevier, 1990.Google Scholar
  13. [HK96]
    A. Heuer and J. Kröger. Query Optimization in the CROQUE Project (extended version). Preprint CS-05-96, CS Dept., University of Rostock, 1996.Google Scholar
  14. [JG91]
    Z. Jiao and P. M. D. Gray. Optimisation of Methods in a Navigational Query Language. In LNCS 566, Proc. of the 2nd DOOD, 1991.Google Scholar
  15. [KM90]
    A. Kemper and G. Moerkotte. Access Support in Object Bases. In Proc. of the ACM SIGMOD Conf. on Management of Data, Atlantic City, NJ, 1990.Google Scholar
  16. [LMS+93]
    T. W. Leung, G. Mitchell, B. Subramanian, B. Vance, S. L. Vandenberg, and S. B. Zdonik. The AQUA Data Model and Algebra. In Proc. of the 4th Int'l Workshop on DBPL, New York, 1993. Springer.Google Scholar
  17. [LS93]
    C. Laasch and M. H. Scholl. A Functional Object Database Language. In Proc. of the 4th Int'l Workshop on DBPL, New York, 1993. Springer.Google Scholar
  18. [Obj95]
    Object Design Inc. ObjectStore C++ Performance Release 4, 1995.Google Scholar
  19. [OHMS92]
    J. Orenstein, S. Haradhvala, B. Margulies, and D. Sakahara. Query Processing in the ObjectStore Database System. In Proc. ACM SIGMOD Conf. on Management of Data, 1992.Google Scholar
  20. [PS94]
    A. Poulovassilis and C. Small. Investigation of Algebraic Query Optimisation for Database Programming Languages. In Proc. of the 20th VLDB Conf., Santiago, Chile, 1994.Google Scholar
  21. [RS93]
    C. Rich and M.H. Scholl. Query Optimization in an OODBMS. In Proc. of the GI-Conf. on Database Systems “in Büro, Technik und Wissenschaft (BTW)”. Springer, Informatik aktuell, 1993.Google Scholar
  22. [RS96]
    H. Riedel and M. H. Scholl. The CROQUE-Model: Formalization of the Data Model and Queries. 1996. In preparation.Google Scholar
  23. [SAB94]
    H. J. Steenhagen, P. M. G. Apers, and H. M. Blanken. Optimization of Nested Queries in a Complex Object Model. In Proc. of the EDBT, Cambridge, 1994.Google Scholar
  24. [Tri91]
    P. Trinder. Comprehensions, a Query Notation for DBPLs. In Proc. of the 3rd Int'l Workshop on DBPL, Nafplion, Greece, 1991.Google Scholar
  25. [TW89]
    P. Trinder and P. Wadler. Improving List Comprehension Database Queries. In Proc. of TENCON'89, Bombay, India, 1989.Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1996

Authors and Affiliations

  • Andreas Heuer
    • 1
  • Joachim Kröger
    • 1
  1. 1.CS Dept.University of RostockRostockGermany

Personalised recommendations