An initial study on refactoring tactics

Software refactoring might be done in two different tactics. The first one is XP-style small-step refactoring, also called floss refactoring. The other tactic, called root canal refactoring, is to set aside an extended period specially for refactoring. Floss refactoring, as one of the corner stones of XP, is well acknowledged. In contrast, root canal refactoring is doubted, especially by XP advocators. Despite the doubts, however, no large scale empirical study on refactoring tactics has been reported. In contrast to the doubts, cases of root canal refactoring have been reported from industry, e.g., Microsoft. Researchers from academe have also proposed various approaches to facilitating root canal refactoring. To this end, this paper would investigate the following questions. (1)How often are the two different tactics employed, respectively? (2) Is there any correlation between refactoring tactics and categories of refactorings? In other words, are some kinds of refactorings more likely than others to be done as floss refactorings or root canal refactorings? To answer these questions, we analyze refactoring histories collected by Eclipse Usage Data Collector (UDC). The data are collected from 753,367 engineers worldwide. Analysis results suggest that about 11.5 percent of refactorings collected by UDC are root canal refactorings, whereas others (88.5 percent) are floss refactorings. We also find that some kinds of refactorings, e.g., Introduce Parameter, are more likely than others to be performed as root canal refactorings.