Project R-16944

Consistent Transaction Processing under Mixed Isolation Levels (Research)

Transactions are a cornerstone of database systems, enabling application programmers to group a sequence of operations over database objects into one atomic unit. To avoid data anomalies, database systems enforce the isolation property requiring that the transaction as a whole is executed without interference from other concurrent transactions. A stringent notion for isolation is serializability specifying that every concurrent execution must be equivalent to one where transactions are executed in a serial order. As enforcing serializability can have a detrimental impact on performance, database systems usually offer lower isolation levels as a direct trade-off between correctness guarantees and improved throughput, placing the burden of reasoning about correctness involving concurrent transactions back on the application programmer. An emerging research line investigates in which settings specific lower isolation levels that ensure higher throughput do guarantee serializability. This is known as the robustness problem. The project investigates robustness under mixed allocations, allowing concurrent transactions to operate under different isolation levels, as well as robustness relative to application-specific consistency rules instead of serializability as a correctness criterion. These considered settings are highly relevant in practical applications, thereby paving the way for a radically different approach to ensure consistent executions in database systems.

01 November 2026 - 31 October 2029