Cluet S., Delobel C. "Towards a unification of rewrite based optimization techniques for object-oriented queries." In Proc. VII'eme journ'ees Bases de Donn'ees Advanc'ees, Lyon, France.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....have to invent new implementation techniques rather than building on existing ones. This simplicity may also have been one of the factors determining the relatively large practical success of the system. The query language supported is similar to those offered by other object oriented databases [CD91] but, like in deductive databases, more directly integrated with the rest of the data model; this has led to some useful ideas with many applications, such as the parameterization of query classes [SNJ93] The O Telos data model also naturally supports a two layered implementation technique for ....

Cluet S., Delobel C. "Towards a unification of rewrite based optimization techniques for object-oriented queries." In Proc. VII'eme journ'ees Bases de Donn'ees Advanc'ees, Lyon, France.

....and creation of such structures can lead to the regular use of path expressions to navigate through a structure. Current research on the optimization of path expressions involves the definition of indices for an expression [4, 22] and the use of Join operations to effect path navigation [5, 14, 16, 18]. Such research leads to new techniques for the optimization of query expressions. The exploration of complex structures also can lead to nested query expressions in which variables from outer expressions are referenced in nested expressions. For example, a query to find the garaging locations for ....

....provide an extensive set of rules for bulk data types. Current research on optimization in Orion [14] is directed toward the adaptation of relational techniques to the object oriented database. In particular they explore efficient alternatives to object navigation. Research on optimization in O 2 [5] combines this work with techniques that include the factorization of common subexpressions, cost based application of query rewrite rules, and the use of indexes and clustering to guide the query rewrite process and aid in determining access plans. These techniques are concerned, in particular, ....

S. Cluet and C. Delobel, "Towards a Unification of Rewrite Based Optimization Techniques for Object-Oriented Queries," tech. rep., Alta ir, B.P. 105, 78153, Rocquencourt France, May 1991.

....[121] while class based graphs are useful for manipulating path expressions [75, 91] A major shortcoming of these representations is the lack of support for subqueries. Class based approaches do not support subqueries at all, although Cluet and Delobel note that they are working on that problem [30]. Operator based approaches can support queries nested as input to another query but do not support query expressions in the terms of predicates. This results because these representations consider operations and data as the primary objects in the representation, and subjugate predicates involving ....

Sophie Cluet and Claude Delobel. Towards a Unification of Rewrite Based Optimization Techniques for Object-Oriented Queries. In Septi`emes Journ'ees Base de Donn'ees Avanc'ees, Lyons, France, Sep 1991. This paper is an early version of [31].

....connections, so that following a direct or a reverse connection requires about the same time. This was explicitly allowed in the benchmark specification. 5 Transformational Optimisations We first briefly list an overview of traditional works about optimisation [Ull82] Tri89] ZS89] CD91] assuming the reader familiar with those techniques. Then we focus on the adequacy of these techniques in the context of maps. 5.1 Overview The relational database technology identifies two kinds of query optimisation strategies: algebraic and implementation based. Algebraic optimisation ....

....over joins. In object oriented databases, similar techniques have been investigated: algebraic query rewriting [ZS89] BK90] method code optimisation, and the tree traversal technique used in the Orion system [BK89] Last, a formalism which unifies those different approaches is proposed in [CD91] 5.2 Algebraic Optimisations: Suitability for maps We consider most of the algebraic rewriting optimisations proposed in [Ull82] and see whether they are suitable in the context of maps. The main difficulties are introduced by the uniqueness of domain values in maps which disables some well ....

S. Cluet and C. Delobel. Toward a unification of rewrite based optimization techniques for object-oriented queries, 1991. To appear in PRC'BD3 September 1991.

....of objectoriented databases and their query optimizers. We propose the stack based approach to query languages as an adequate framework aiming at the same goals. 1 Introduction Object algebras are proposed as tools to formalise object oriented databases and their query languages (QLs) see [AbFi95, AlAr93, BaWi94, CDV88, Clue89, ClDe92, ClDe94, DGG94, GZC89, HFLP89, KeMa94, LMSVVZ93, Liu93, PoSm94, ShZd89a, ShZd89b, ShZd90, StOz90, SZLV93, SLVZ95, VaDe91], and many others. They are claimed to be well suited to solve query optimisation problems. In this paper we carry out a critical analysis of this research activity. There are two principal reasons motivating our work. First, we see in these algebras severe flaws, which cause doubts concerning ....

S. Cluet, C. Delobel. Towards a Unification of Rewrite-based Optimization Techniques for ObjectOriented Queries. (In) Query Processing for Advanced Database Systems. Morg an Kaufmann, 1994, pp. 245272

....the potential of object algebras, in the proposed forms, as formal and intellectual tools for the development of objectoriented databases and their query optimizers. 1 Introduction Object algebras are proposed as tools to formalise objectoriented databases and their query languages (QLs) see [AlAr93, BMG93, CDV88, Clue89, ClDe92, ClDe94, DGG94, GZC89, HFLP89, KeMa94, LMSVVZ93, PoSm94, ShZd89a, ShZd89b, ShZd90, StOz90, SZLV93, SLVZ95, VaDe91], and many others. They are claimed to be well suited for query optimization. In this paper we carry out a critical analysis of this research activity. There are two principal reasons motivating our work. First, we see in these algebras severe flaws, which cause doubts concerning their ....

S. Cluet, C. Delobel. Towards a Unification of Rewrite-based Optimization Techniques for ObjectOriented Queries. (In) Query Processing for Advanced Database Systems. Morgan Kaufmann, 1994, pp. 245-272.

....really physical level optimizations. There are many more opportunities for common subexpressions to appear in an object oriented query. Therefore recognition and elimination of these common subexpressions is an important optimization. Some work has been done at the source level by Cluet and Delobel[20], but they give no description of how their work impacts the plan generation stage. Lanzelotte, et al. 58, 59, 38, 60] are able to recognize common subexpressions by mapping queries onto the physical schema. Common subexpressions in path expressions appear in the class connection graph, a result ....

Sophie Cluet and Claude Delobel. Towards a unification of rewrite based optimization techniques for object-oriented queries. Got from GMS, February 1991.

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