Incremental Relational Lenses

TL;DR

This paper introduces incremental relational lenses that enable efficient, small-change propagation for view updates in databases, demonstrating significant performance improvements over non-incremental methods.

Contribution

It presents the first implementation and evaluation of incremental relational lenses, enhancing their practicality for expressive, language-level view updates.

Findings

Order of magnitude performance improvement over non-incremental approach

Effective small-change propagation for view updates

Supports expressive view updates without database updatable view support

Abstract

Lenses are a popular approach to bidirectional transformations, a generalisation of the view update problem in databases, in which we wish to make changes to source tables to effect a desired change on a view. However, perhaps surprisingly, lenses have seldom actually been used to implement updatable views in databases. Bohannon, Pierce and Vaughan proposed an approach to updatable views called relational lenses, but to the best of our knowledge this proposal has not been implemented or evaluated to date. We propose incremental relational lenses, that equip relational lenses with change-propagating semantics that map small changes to the view to (potentially) small changes to the source tables. We also present a language-integrated implementation of relational lenses and a detailed experimental evaluation, showing orders of magnitude improvement over the non-incremental approach. Our work shows that relational lenses can be used to support expressive and efficient view updates at the language level, without relying on updatable view support from the underlying database.