One-to-many data transformations through data mappers

  • Authors:

  • Paulo Carreira;Helena Galhardas;Antónia Lopes;João Pereira

  • Affiliations:

  • INESC-ID and Technical University of Lisbon, Avenida Prof. Cavaco Silva, Tagus Park, 2780-990, Porto-Salvo, Portugal and Faculty of Sciences, University of Lisbon, C6 - Piso 3, 1749-016 Lisboa, Po ...;INESC-ID and Technical University of Lisbon, Avenida Prof. Cavaco Silva, Tagus Park, 2780-990, Porto-Salvo, Portugal;Faculty of Sciences, University of Lisbon, C6 - Piso 3, 1749-016 Lisboa, Portugal;INESC-ID and Technical University of Lisbon, Avenida Prof. Cavaco Silva, Tagus Park, 2780-990, Porto-Salvo, Portugal

  • Venue:
  • Data & Knowledge Engineering
  • Year:
  • 2007

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Abstract

The optimization capabilities of RDBMSs make them attractive for executing data transformations. However, despite the fact that many useful data transformations can be expressed as relational queries, an important class of data transformations that produce several output tuples for a single input tuple cannot be expressed in that way. To overcome this limitation, we propose to extend Relational Algebra with a new operator named data mapper. In this paper, we formalize the data mapper operator and investigate some of its properties. We then propose a set of algebraic rewriting rules that enable the logical optimization of expressions with mappers and prove their correctness. Finally, we experimentally study the proposed optimizations and identify the key factors that influence the optimization gains.