The widespread adoption of database middleware for supporting distributed transaction processing is prevalent in numerous applications, with heterogeneous data sources deployed across national and international boundaries. However, transaction processing performance significantly drops due to the high network latency between the middleware and data sources and the long lock contention span, where transactions may be blocked while waiting for the locks held by concurrent transactions. In this paper, we propose GeoTP, a latency-aware geo-distributed transaction processing approach in database middleware. GeoTP incorporates three key techniques to enhance performance in geo-distributed scenarios. First, we propose a decentralized prepare mechanism to reduce network round-trips for distributed transactions. Second, we design a latency-aware scheduler to minimize the lock contention span by strategically delaying the lock acquisition. Third, heuristic optimizations are proposed for the scheduler to reduce the lock contention span further. We implemented GeoTP on Apache Shardingsphere, a state-of-the-art middleware, and extended it into Apache ScalarDB. Experimental results on YCSB and TPC-C demonstrate that GeoTP achieves up to 17.7x performance improvement.

Cloud-native database systems with multi-primary shared-storage architecture have emerged due to their superior performance over primary-secondary architecture on write-intensive workload scenarios. However, these systems face performance degradation as the proportion of shared data increases, adversely affecting their Cost-Performance Ratio (CPR). In this paper, we identify frequent page ownership transfers between primaries as a key factor contributing to these performance bottlenecks. To address this challenge, we propose Chimera, a multi-primary database system that employs a two-phase transaction scheduling mechanism, combined with a delay-fetch ownership transfer strategy to effectively reduce the overhead of ownership transfers. Extensive experiments on SmallBank and TPC-C benchmarks demonstrate that Chimera outperforms existing schedule methods for multi-primary systems, achieving performance gains of 1.86× ~19.03× on throughput.

Achieving the serializable isolation level is costly. Recent studies have revealed that adjusting specific query patterns within the workload can still achieve serializability, even at lower isolation levels. Nevertheless, these studies typically overlook the trade-off between the performance advantages of lower isolation levels and the overhead required to maintain serializability, potentially leading to suboptimal isolation level choices that fail to maximize performance. In this paper, we present TxnSails, a middle-tier solution designed to achieve serializable scheduling with self-adaptive isolation level selection. First, TxnSails incorporates a unified concurrency control algorithm that achieves serializability at lower isolation levels with minimal overhead. Second, TxnSails employs a deep learning method to characterize the trade-off between the performance benefits and overhead associated with lower isolation levels, thus predicting the optimal isolation level. Finally, TxnSails implements a cross-isolation validation mechanism to ensure serializability during real-time isolation level transitions. Extensive experiments demonstrate that TxnSails outperforms existing solutions by up to 26.7× and PostgreSQL 's serializable isolation level by up to 4.8×.

Relational DBMS implementations are expected to adhere to SQL standards. However, there are currently no tools available that can automatically verify this conformance. The main reasons are twofold. First, the SQL standard specification, documented in natural language, tends to be ambiguous and is not directly executable. Second, it is difficult to generate test queries that thoroughly cover all aspects, e.g., keywords and parameters, defined in the SQL specification. In this work, we introduce the first method for semantic conformance testing of RDBMSs. Our contributions are threefold. Firstly, we formally define the denotational semantics of SQL and implement them in Prolog, creating an executable reference RDBMS for differential testing against existing RDBMSs. Secondly, we propose three coverage criteria based on these formal semantics, along with a coverage-guided query generation algorithm that effectively generates queries achieving high semantic coverage. Lastly, we apply our approach to six widely-used and thoroughly tested RDBMSs, e.g., MySQL, PostgreSQL and OceanBase, uncovering 19 bugs and 13 inconsistencies, all of which are confirmed by RDBMS developers.

With the rapid development of web and mobile applications, as well as their wide adoption in different domains, more and more personal data is provided, consciously or unconsciously, to different application providers. Privacy policy is an important medium for users to understand what personal information has been collected and used. As data privacy protection is becoming a critical social issue, there are laws and regulations being enacted in different countries and regions, and the most representative one is the EU General Data Protection Regulation (GDPR). It is thus important to detect compliance issues among regulations, e.g., GDPR, with privacy policies, and provide intuitive results for data subjects (i.e., users), data collection party (i.e., service providers) and the regulatory authorities. In this work, we target to solve the problem of compliance analysis between GDPR (Article 13) and privacy policies. We format the task into a combination of a sentence classification step and a rule-based analysis step. We manually curate a corpus of 36,610 labeled sentences from 304 privacy policies, and benchmark our corpus with several standard sentence classifiers. We also conduct a rule-based analysis to detect compliance issues and a user study to evaluate the usability of our approach. The web-based tool AutoCompliance is publicly accessible 1.