Ahana Pradhan

Ahana Pradhan, Srinivas Karthik, Imtiyazuddin Shaik et al.

Growing privacy regulations and internal governance mandates are driving demand for fine-grained, context-sensitive access control in data management systems. Among competing approaches, content-based access control -- where access decisions depend on the data values referenced by a query -- is becoming particularly prominent, and is supported directly in modern database engines. While simple content-based predicates often incur negligible overhead, increasingly rich policies can interact in subtle ways with query optimization, leading to significant and poorly understood performance variability. This paper investigates this gap by introducing a structural framework and expressive policy grammar for modelling content-based compliance policies and analysing their impact on query planning and execution in database systems. Building on this framework, we augment an analytical benchmark with structured policy workloads, enabling controlled evaluation of enforcement mechanisms and optimization strategies under combined query - policy workloads. Our experimental results show that policy structure has a decisive impact on optimizer behaviour and end-to-end performance, underscoring the need for policy-aware database and optimizer design.

Ahana Pradhan, Jayant Haritsa

Query reverse engineering (QRE) aims to synthesize a SQL query to connect a given database and result instance. A recent variation of QRE is where an additional input, an opaque executable containing a ground-truth query, is provided, and the goal is to non-invasively extract this specific query through only input-output examples. This variant, called Hidden Query Extraction (HQE), has a spectrum of industrial use-cases including query recovery, database security, and vendor migration. The reverse engineering (RE) tools developed for HQE, which are based on database mutation and generation techniques, can only extract flat queries with key-based equi joins and conjunctive arithmetic filter predicates, making them limited wrt both query structure and query operators. In this paper, we present Xpose, a HQE solution that elevates the extraction scope to realistic complex queries, such as those found in the TPCH benchmark. A two-pronged approach is taken: (1) The existing RE scope is substantially extended to incorporate union connectors, algebraic filter predicates, and disjunctions for both values and predicates. (2) The predictive power of LLMs is leveraged to convert business descriptions of the opaque application into extraction guidance, representing ``forward engineering" (FE). The FE module recognizes common constructs, such as nesting of sub-queries, outer joins, and scalar functions. In essence, FE establishes the broad query contours, while RE fleshes out the fine-grained details. We have evaluated Xpose on (a) E-TPCH, a query suite comprising the complete TPCH benchmark extended with queries featuring unions, diverse join types, and sub-queries; and (b) the real-world STACK benchmark. The experimental results demonstrate that its bi-directional engineering approach accurately extracts these complex queries, representing a significant step forward with regard to HQE coverage.

Ahana Pradhan, Rushikesh K. Joshi

In the context of dynamic evolution of workflow processes, the change region identifies the part of the old process from which migration to the new process is guaranteed to be inconsistent. However, this approach may lead to overestimated regions, incorrectly identifying migratable instances as non-migratable. This overestimation causes delays due to postponement of immediate migration. The paper analyzes this overestimation problem on a class of Petri nets models. Structural properties leading to conditions for minimal change regions and overestimations are developed resulting into classification of change regions into two types of change regions called Structural Change Regions and Perfect Structural Change Regions. Necessary and sufficient conditions for perfect regions are identified. The paper also discusses ways for computing the same in terms of structural properties of the old and the new processes.