Bringing Back-in-Time Debugging Down to the Database

TL;DR

This paper introduces TARDISP, a back-in-time debugger for SAP HANA databases that enables developers to step queries backwards and inspect past database states efficiently, addressing a gap in database-level debugging tools.

Contribution

The paper presents a novel back-in-time debugging approach for databases, including a SQL extension and implementation for SAP HANA, enabling temporal query inspection with low overhead.

Findings

Effective backward stepping in SAP HANA demonstrated

Low performance and memory overhead achieved

Positive developer feedback from SAP project evaluation

Abstract

With back-in-time debuggers, developers can explore what happened before observable failures by following infection chains back to their root causes. While there are several such debuggers for object-oriented programming languages, we do not know of any back-in-time capabilities at the database-level. Thus, if failures are caused by SQL scripts or stored procedures, developers have difficulties in understanding their unexpected behavior. In this paper, we present an approach for bringing back-in-time debugging down to the SAP HANA in-memory database. Our TARDISP debugger allows developers to step queries backwards and inspecting the database at previous and arbitrary points in time. With the help of a SQL extension, we can express queries covering a period of execution time within a debugging session and handle large amounts of data with low overhead on performance and memory. The entire approach has been evaluated within a development project at SAP and shows promising results with respect to the gathered developer feedback.

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