Extending Elle for Transaction Workloads with Duplicate Values
For database practitioners and researchers, this work addresses a practical limitation of a widely-used validator, enabling isolation validation for workloads with duplicate values.
The paper extends the Elle isolation validator to handle transaction workloads with duplicate values, which are common in practice and can expose isolation bugs. The extension introduces a fine-grained dependency model and demonstrates effectiveness in detecting bugs with promising performance.
Elle is one of the most widely adopted black-box isolation validators. It crucially relies on the unique-value assumption for sound and efficient isolation validation. Yet, transaction workloads with duplicate values are highly relevant in practice: they naturally arise in real database systems, and many isolation bugs manifest only in their presence. In this paper, we extend Elle to handle such workloads by introducing a fine-grained dependency model that enables reasoning about dependencies between individual operations. We establish the soundness and completeness of our approach and implement it in a prototype. We also demonstrate its effectiveness in detecting isolation bugs and its promising performance.