Allocating Isolation Levels to Transactions in a Multiversion Setting

Brecht Vandevoort, Bas Ketsman, Frank Neven

Onderzoeksoutput: Conference paperResearch

Samenvatting

A serializable concurrency control mechanism ensures consistency for OLTP systems at the expense of a reduced transaction throughput. A DBMS therefore usually offers the possibility to allocate lower isolation levels for some transactions when it is safe to do so. However, such trading of consistency for efficiency does not come with any safety guarantees. In this paper, we study the mixed robustness problem which asks whether, for a given set of transactions and a given allocation of isolation levels, every possible interleaved execution of those transactions that is allowed under the provided allocation is always serializable. That is, whether the given allocation is indeed safe. While robustness has already been studied in the literature for the homogeneous setting where all transactions are allocated the same isolation level, the heterogeneous setting that we consider in this paper, despite its practical relevance, has largely been ignored. We focus on multiversion concurrency control and consider the isolation levels that are available in Postgres and Oracle: read committed (RC), snapshot isolation (SI) and serializable snapshot isolation (SSI). We show that the mixed robustness problem can be decided in polynomial time. In addition, we provide a polynomial time algorithm for computing the optimal robust allocation for a given set of transactions, prioritizing lower over higher isolation levels. The present results therefore establish the groundwork to automate isolation level allocation within existing databases supporting multiversion concurrency control.

Originele taal-2English
TitelPODS 2023 - Proceedings of the 42nd ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems
UitgeverijAssociation for Computing Machinery
Pagina's69-78
Aantal pagina's10
ISBN van elektronische versie9798400701276
DOI's
StatusPublished - 18 jun 2023
Evenement42nd ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems, PODS 2023 - Seattle, United States
Duur: 18 jun 202323 jun 2023

Publicatie series

NaamProceedings of the ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems

Conference

Conference42nd ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems, PODS 2023
Land/RegioUnited States
StadSeattle
Periode18/06/2323/06/23

Bibliografische nota

Publisher Copyright:
© 2023 ACM.

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