Data Consistency in Transactional Storage Systems: A Centralised Semantics

Xiong, Shale; Cerone, Andrea; Raad, Azalea; Gardner, Philippa

doi:10.4230/lipics.ecoop.2020.21

Cited by 5 publications

(3 citation statements)

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“…Driven by black-box testing of SI, we base our GP-based characterization on Cerone and Gotsman's formal specification [10]. In particular, our new characterization: (i) targets the prevalent strong session variant of SI [10,18], where sessions have been adopted by many production databases, e.g., DGraph [19], Galera [12], and CockroachDB [13]; (ii) does not rely on implementation details such as concurrency control mechanisms as in [4], timestamps as in [1], and the operational semantics of the underlying database as in [45]; (iii) and naturally models uncertain dependencies inherent to black-box testing using generalized constraints (Section 3) and enables the acceleration of SMT solving by compacting constraints (Section 5.4).…”

Section: Related Workmentioning

confidence: 99%

“…First, despite previous attempts to characterize SI [1,4,45], its semantics is usually explained in terms of low-level implementation choices invisible to the database outsiders. Consequently, one must guess the dependencies (aka uncertain/unknown dependencies) between client-observable data, for example, which of two writes was first recorded in the database.…”

Section: Introductionmentioning

confidence: 99%

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Efficient Black-Box Checking of Snapshot Isolation in Databases

et al. 2023

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Snapshot isolation (SI) is a prevalent weak isolation level that avoids the performance penalty imposed by serializability and simultaneously prevents various undesired data anomalies. Nevertheless, SI anomalies have recently been found in production cloud databases that claim to provide the SI guarantee. Given the complex and often unavailable internals of such databases, a black-box SI checker is highly desirable. In this paper we present PolySI, a black-box checker that efficiently checks SI and provides understandable counterexamples upon detecting violations. PolySI builds on a characterization of SI using generalized polygraphs (GPs), for which we establish its soundness and completeness. PolySI employs an SMT solver and also accelerates SMT solving by utilizing a compact constraint encoding of GPs and domain-specific optimizations for pruning constraints. As our extensive assessment demonstrates, PolySI successfully reproduces all of 2477 known SI anomalies, detects novel SI violations in three production cloud databases, identifies their causes, outperforms the state-of-the-art black-box checkers under a wide range of workloads, and can scale up to large workloads.

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Section: Related Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Efficient Black-Box Checking of Snapshot Isolation in Databases

et al. 2023

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“…Distributed key/value stores have to contend with copies of keys being present in multiple nodes at a time. Several works verify consistency of operations performed on such data structures [Chordia et al 2013;Kaki et al 2018;Xiong et al 2020], including linearizability [Wang et al 2019]. In the distributed context, the main technical challenge arises from data replication and the ensuing weakly consistent semantics of concurrent operations.…”

Section: Related Workmentioning

confidence: 99%

Verifying Concurrent Multicopy Search Structures

Patel¹,

Krishna²,

Shasha³

et al. 2021

Preprint

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Multicopy search structures such as log-structured merge (LSM) trees are optimized for high insert/update/delete (collectively known as upsert) performance. In such data structures, an upsert on key 𝑘, which adds (𝑘, 𝑣) where 𝑣 can be a value or a tombstone, is added to the root node even if 𝑘 is already present in other nodes. Thus there may be multiple copies of 𝑘 in the search structure. A search on 𝑘 aims to return the value associated with the most recent upsert. We present a general framework for verifying linearizability of concurrent multicopy search structures that abstracts from the underlying representation of the data structure in memory, enabling proof-reuse across diverse implementations. Based on our framework, we propose template algorithms for a) LSM structures forming arbitrary directed acyclic graphs and b) differential file structures, and formally verify these templates in the concurrent separation logic Iris. We also instantiate the LSM template to obtain the first verified concurrent in-memory LSM tree implementation.

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Verifying concurrent multicopy search structures

Patel

Krishna

Shasha

et al. 2021

Proc. ACM Program. Lang.

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Multicopy search structures such as log-structured merge (LSM) trees are optimized for high insert/update/delete (collectively known as upsert) performance. In such data structures, an upsert on key k , which adds ( k , v ) where v can be a value or a tombstone, is added to the root node even if k is already present in other nodes. Thus there may be multiple copies of k in the search structure. A search on k aims to return the value associated with the most recent upsert. We present a general framework for verifying linearizability of concurrent multicopy search structures that abstracts from the underlying representation of the data structure in memory, enabling proof-reuse across diverse implementations. Based on our framework, we propose template algorithms for (a) LSM structures forming arbitrary directed acyclic graphs and (b) differential file structures, and formally verify these templates in the concurrent separation logic Iris. We also instantiate the LSM template to obtain the first verified concurrent in-memory LSM tree implementation.

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Data Consistency in Transactional Storage Systems: A Centralised Semantics

Cited by 5 publications

References 0 publications

Efficient Black-Box Checking of Snapshot Isolation in Databases

Efficient Black-Box Checking of Snapshot Isolation in Databases

Verifying Concurrent Multicopy Search Structures

Verifying concurrent multicopy search structures

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