Do Developers Refactor Data Access Code? An Empirical Study

TL;DR

This study empirically investigates refactoring practices in data access code within data-intensive systems, revealing prevalent refactoring types, their evolution over time, and their focus on code quality rather than SQL queries.

Contribution

It provides the first comprehensive empirical analysis of data access refactorings, highlighting their characteristics, evolution, and targeted functionalities in data-intensive systems.

Findings

Data access refactorings are common and vary in type.

Refactoring prevalence and types change as systems evolve.

Most refactorings target data fetching and insertion code.

Abstract

Developers often refactor code to improve the maintainability and comprehension of the software. There are many studies on refactoring activities in traditional software systems. However, refactoring in data-intensive systems is not well explored. Understanding the refactoring practices of developers is important to develop efficient tool support.We conducted a longitudinal study of refactoring activities in data access classes using 12 data-intensive subject systems. We investigated the prevalence and evolution of refactorings and the association of refactorings with data access smells. We also conducted a manual analysis of over 378 samples of data access refactoring instances to identify the functionalities of the code that are targeted by such refactorings. Our results show that (1) data access refactorings are prevalent and different in type. \textit{Rename variable} is the most prevalent data access refactoring. (2) The prevalence and type of refactorings vary as systems evolve in time. (3) Most data access refactorings target codes that implement data fetching and insertion. (4) Data access refactorings do not generally touch SQL queries. Overall, the results show that data access refactorings focus on improving the code quality but not the underlying data access operations. Hence, more work is needed from the research community on providing awareness and support to practitioners on the benefits of addressing data access smells with refactorings.