VLDB 2026 Research / reviewers in the wild / expert
Rihan Hai 0001
dblp:163/0801-1
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27ranked-venue papers in the field
11as first author
21since 2021 · last 2025
0000-0002-3720-6585ORCID · verified
Domains — venue-derived; a paper can count in several
Database Systems & Data Management · 20 (9 first)Information Retrieval & Web Search · 4Business Process & Enterprise Data · 2 (2 first)Knowledge Engineering, Semantic Web & Information Systems · 1
| Year | Publication | Venue | Position |
|---|---|---|---|
| 2025 | Database is All You Need: Serving LLMs with Relational Queries
Vaishnav Srinidhi, Rihan Hai 0001 |
EDBT | 4 |
| 2025 | Accelerating machine learning queries with linear algebra query processingabstractAbstract The rapid growth of large-scale machine learning (ML) models has led numerous commercial companies to utilize ML models for generating predictive results to help business decision-making. As two primary components in traditional predictive pipelines, data processing, and model predictions often operate in separate execution environments, leading to redundant engineering and computations. Additionally, the diverging mathematical foundations of data processing and machine learning hinder cross-optimizations by combining these two components, thereby overlooking potential opportunities to expedite predictive pipelines. In this paper, we propose an operator fusion method based on GPU-accelerated linear algebraic evaluation of relational queries. Our method leverages linear algebra computation properties to merge operators in machine learning predictions and data processing, significantly accelerating predictive pipelines by up to 317x. We perform a complexity analysis to deliver quantitative insights into the advantages of operator fusion, considering various data and model dimensions. Furthermore, we extensively evaluate linear algebra query processing and operator fusion utilizing the widely-used Star Schema and TPC-DI benchmarks. Through comprehensive evaluations, we demonstrate the effectiveness and potential of our approach in improving the efficiency of data processing and machine learning workloads on modern hardware. Asterios Katsifodimos, Rihan Hai 0001 |
Distributed Parallel Databases | 3 |
| 2025 | WaveStitch: Flexible and Fast Conditional Time Series Generation With Diffusion ModelsabstractGenerating temporal data under conditions is crucial for forecasting, imputation, and generative tasks. Such data often has metadata and partially observed signals that jointly influence the generated values. However, existing methods face three key limitations: (1) they condition on either the metadata or observed values, but rarely both together; (2) they adopt either training-time approaches that fail to generalise to unseen scenarios, or inference-time approaches that ignore metadata; and (3) they suffer from trade-offs between generation speed and temporal coherence across time windows, choosing either slow but coherent autoregressive methods or fast but incoherent parallel ones. We propose WaveStitch, a novel diffusion-based method to overcome these hurdles through: (1) dual-sourced conditioning on both metadata and partially observed signals; (2) a hybrid training-inference architecture, incorporating metadata during training and observations at inference via gradient-based guidance; and (3) a novel pipeline-style paradigm that generates time windows in parallel while preserving coherence through an inference-time conditional loss and a stitching mechanism. Across diverse datasets, WaveStitch demonstrates adaptability to arbitrary patterns of observed signals, achieving 1.81x lower mean-squared-error compared to the state-of-the-art, and generates data up to 166.48x faster than autoregressive methods while maintaining coherence. Our code is available at: https://github.com/adis98/WaveStitch. Aditya Shankar, Lydia Y. Chen, Arie van Deursen, Rihan Hai 0001 |
Proc. ACM Manag. Data | 4 |
| 2025 | TranSQL + : Serving Large Language Models with SQL on Low-Resource HardwareabstractDeploying Large Language Models (LLMs) on resource-constrained devices remains challenging due to limited memory, lack of GPUs, and the complexity of existing runtimes. In this paper, we introduce TranSQL + , a template-based code generator that translates LLM computation graphs into pure SQL queries for execution in relational databases. Without relying on external libraries, TranSQL + , leverages mature database features-such as vectorized execution and out-of-core processing-for efficient inference. We further propose a row-to-column (ROW2COL) optimization that improves join efficiency in matrix operations. Evaluated on Llama3-8B and DeepSeekMoE models, TranSQL + achieves up to 20× lower prefill latency and 4× higher decoding speed compared to DeepSpeed Inference and Llama.cpp in low-memory and CPU-only configurations. Our results highlight relational databases as a practical environment for LLMs on low-resource hardware. Qiming Guo, Wenlu Wang, Rihan Hai 0001 |
Proc. ACM Manag. Data | 4 |
| 2025 | Quantum Data Management in the NISQ EraabstractQuantum computing has emerged as a transformative force in the evolution of computing technology. Recent efforts have applied quantum techniques to classical database challenges, such as query optimization, data integration, index selection, and transaction management. In this paper, we shift focus to a critical yet underexplored area: data management for quantum computing. We are currently in the noisy intermediate-scale quantum (NISQ) era, where qubits, while promising, are fragile and still limited in scale. After differentiating quantum data from classical data, we outline current and future data management paradigms in the NISQ era and beyond. We address the data management challenges arising from the emerging demands of near-term quantum computing. Our goal is to chart a clear course for future quantum-oriented data management research, establishing it as a cornerstone for the advancement of quantum computing in the NISQ era. Rihan Hai 0001, Shih-Han Hung, Tim Coopmans, Tim Littau, Floris Geerts |
Proc. VLDB Endow. | 1 |
| 2024 | Human-in-the-Loop Feature Discovery for Tabular DataabstractIn recent years, researchers have developed several methods to automate discovering datasets and augmenting features for training Machine Learning (ML) models. Together with feature selection, these efforts have paved the way towards what is termed the feature discovery process. Data scientists and engineers use automated feature discovery over tabular datasets to add new features from different sources and enrich training data. By surveying data practitioners, we have observed that automated feature discovery approaches do not allow data scientists to use their domain knowledge during the feature discovery process. In addition, automated feature discovery methods can leak private features or introduce biased ones. Andra Ionescu, Zeger Mouw, Efthimia Aivaloglou, Rihan Hai 0001, Asterios Katsifodimos |
CIKM | 4 |
| 2024 | LLM-PQA: LLM-enhanced Prediction Query AnsweringabstractThe advent of Large Language Models (LLMs) provides an opportunity to change the way queries are processed, moving beyond the constraints of conventional SQL-based database systems. However, using an LLM to answer a prediction query is still challenging, since an external ML model has to be employed and inference has to be performed in order to provide an answer. This paper introduces LLM-PQA, a novel tool that addresses prediction queries formulated in natural language. LLM-PQA is the first to combine the capabilities of LLMs and retrieval-augmented mechanism for the needs of prediction queries by integrating data lakes and model zoos. This integration provides users with access to a vast spectrum of heterogeneous data and diverse ML models, facilitating dynamic prediction query answering. In addition, LLM-PQA can dynamically train models on demand, based on specific query requirements, ensuring reliable and relevant results even when no pre-trained model in a model zoo, available for the task. Asterios Katsifodimos, Rihan Hai 0001 |
CIKM | 4 |
| 2024 | Quantum Data Management: From Theory to OpportunitiesabstractQuantum computing has emerged as a transformative tool for future data management. Classical problems in database domains, including query optimization, data integration, and transaction management, have recently been addressed using quantum computing techniques. This tutorial aims to establish the theoretical foundation essential for enhancing methodologies and practical implementations in this line of research. Moreover, this tutorial takes a forward-looking approach by delving into recent strides in quantum internet technologies and the nonlocality theory. We aim to shed light on the uncharted territory of future data systems tailored for the quantum internet. Rihan Hai 0001, Shih-Han Hung, Sebastian Feld |
ICDE | 1 |
| 2024 | Data Lakes: A Survey of Functions and Systems (Extended abstract)abstractData lakes are becoming increasingly prevalent for big data management and data analytics. In contrast to traditional ‘schema-on-write’ approaches such as data warehouses, data lakes are repositories storing raw data in its original formats and providing a common access interface. Despite the strong interest raised from both academia and industry, there is a large body of ambiguity regarding the definition, functions and available technologies for data lakes. A complete, coherent picture of data lake challenges and solutions is still missing. This survey reviews the development, architectures, and systems of data lakes. We provide a comprehensive overview of research questions for designing and building data lakes. We classify the existing approaches and systems based on their provided functions for data lakes, which makes this survey a useful technical reference for designing, implementing and deploying data lakes. We hope that the thorough comparison of existing solutions and the discussion of open research challenges in this survey will motivate the future development of data lake research and practice. Rihan Hai 0001, Christos Koutras, Christoph Quix, Matthias Jarke |
ICDE | 1 |
| 2024 | AutoFeat: Transitive Feature Discovery over Join PathsabstractCan we automatically discover machine learning (ML) features in a large data lake in order to increase the accuracy of a given ML model? Existing solutions either focus on simple star schemata, failing to discover features in more complex real-world schemata or consider only PK-FK relationships in clean, curated databases. However, real-world data lakes can contain long join paths of uncurated joinability relationships resulting from automated dataset discovery methods. This paper proposes a novel ranking-based feature discovery method called AutoFeat. Given a base table with a target label, AutoFeat explores multi-hop, transitive join paths to find relevant features in order to augment the base table with additional features, ultimately leading to increased accuracy of an ML model. AutoFeat is general: it evaluates the predictive power of features without the need to train an ML model, ranking join paths using the concepts of relevance and redundancy. Our experiments on real-world open data show that AutoFeat is efficient: it can find features of high predictive power on data lakes with an increased number of dataset joinability relationships 5x-44x faster than baseline approaches. In addition, AutoFeat is effective, improving accuracy by 16% on average compared to the baseline approaches, even in noisy, uncurated data lakes. Andra Ionescu, Kiril Vasilev, Florena Buse, Rihan Hai 0001, Asterios Katsifodimos |
ICDE | 4 |
| 2024 | Model Selection with Model Zoo via Graph LearningabstractPre-trained deep learning (DL) models are increasingly accessible in public repositories, i.e., model zoos. Given a new prediction task, finding the best model to fine-tune can be computationally intensive and costly, especially when the number of pre-trained models is large. Selecting the right pre-trained models is crucial, yet complicated by the diversity of models from various model families (like ResNet, Vit, Swin) and the hidden relationships between models and datasets. Existing methods, which utilize basic information from models and datasets to compute scores indicating model performance on target datasets, overlook the intrinsic relationships, limiting their effectiveness in model selection. In this study, we introduce TransferGraph, a novel framework that reformulates model selection as a graph learning problem. TransferGraph constructs a graph using extensive metadata extracted from models and datasets, while capturing their inherent relationships. Through comprehensive experiments across 16 real datasets, both images and texts, we demonstrate TransferGraph's effectiveness in capturing essential model-dataset relationships, yielding up to a 32% improvement in correlation between predicted performance and the actual fine-tuning results compared to the state-of-the-art methods. Hilco van der Wilk, Danning Zhan, Megha Khosla, Alessandro Bozzon, Rihan Hai 0001 |
ICDE | 6 |
| 2024 | S i 1 o F use: Cross-silo Synthetic Data Generation with Latent Tabular Diffusion ModelsabstractSynthetic tabular data is crucial for sharing and augmenting data across silos, especially for enterprises with proprietary data. However, existing synthesizers are designed for centrally stored data. Hence, they struggle with real-world scenarios where features are distributed across multiple silos, necessitating on-premise data storage. We introduce SiloFuse, a novel generative framework for high-quality synthesis from cross-silo tabular data. To ensure privacy, SiloFuse utilizes a distributed latent tabular diffusion architecture. Through autoencoders, latent representations are learned for each client's features, masking their actual values. We employ stacked dis-tributed training to improve communication efficiency, reducing the number of rounds to a single step. Under SiloFuse, we prove the impossibility of data reconstruction for vertically partitioned synthesis and quantify privacy risks through three attacks using our benchmark framework. Experimental results on nine datasets showcase SiloFuse's competence against centralized diffusion-based synthesizers. Notably, SiloFuse achieves 43.8 and 29.8 higher percentage points over GANs in resemblance and utility. Experiments on communication show stacked training's fixed cost compared to the growing costs of end-to-end training as the number of training iterations increases. Additionally, SiloFuse proves robust to feature permutations and varying numbers of clients. Aditya Shankar, Hans Brouwer, Rihan Hai 0001, Lydia Y. Chen |
ICDE | 3 |
| 2024 | Cross-Source ML Model TrainingabstractMachine learning (ML) often operates on data fragmented across silos through two paradigms: distributed or centralized. This study illuminates the underexplored signifi-cance of data integration (DI) metadata in both methodologies. Our contribution is threefold. First, we formalize the complex relationships of data sources with DI metadata. Second, we propose an approach that transforms DI metadata into matrix representations, and streamlines data transformation and linear algebra operations over source datasets. Third, we present an optimization method, effectively deciding between factorization versus materialization. By leveraging logic-based pruning rules and an ML-based cost estimator, our approach outperforms state-of-the-art baselines and makes the trade-off of factorization and materialization with up to 90.5% accuracy. Rihan Hai 0001 |
ICDE | 2 |
| 2024 | Amalur: The Convergence of Data Integration and Machine LearningabstractMachine learning (ML) training data is often scattered across disparate collections of datasets, calleddata silos. This fragmentation poses a major challenge for data-intensive ML applications: integrating and transforming data residing in different sources demand a lot of manual work and computational resources. With data privacy constraints, data often cannot leave the premises of data silos; hence model training should proceed in a decentralized manner. In this work, we present a vision of bridging traditional data integration (DI) techniques with the requirements of modern machine learning systems. We explore the possibilities of utilizing metadata obtained from data integration processes for improving the effectiveness, efficiency, and privacy of ML models. Towards this direction, we analyze ML training and inference over data silos. Bringing data integration and machine learning together, we highlight new research opportunities from the aspects of systems, representations, factorized learning, and federated learning. Danning Zhan, Yan Kang 0001, Lydia Y. Chen, Alessandro Bozzon, Rihan Hai 0001 |
IEEE Trans. Knowl. Data Eng. | 7 |
| 2023 | Topio Marketplace: Search and Discovery of Geospatial Data
Andra Ionescu, Alexandra Alexandridou, Leonidas Ikonomou, Kyriakos Psarakis, Kostas Patroumpas, Georgios Chatzigeorgakidis, Dimitrios Skoutas 0001, Spiros Athanasiou, Rihan Hai 0001, Asterios Katsifodimos |
EDBT | 9 |
| 2023 | Amalur: Data Integration Meets Machine LearningabstractMachine learning (ML) training data is often scattered across disparate collections of datasets, called data silos. This fragmentation poses a major challenge for data-intensive ML applications: integrating and transforming data residing in different sources demand a lot of manual work and computational resources. With data privacy and security constraints, data often cannot leave the premises of data silos, hence model training should proceed in a decentralized manner. In this work, we present a vision of how to bridge the traditional data integration (DI) techniques with the requirements of modern machine learning. We explore the possibilities of utilizing metadata obtained from data integration processes for improving the effectiveness and efficiency of ML models. Towards this direction, we analyze two common use cases over data silos, feature augmentation and federated learning. Bringing data integration and machine learning together, we highlight new research opportunities from the aspects of systems, representations, factorized learning and federated learning. Rihan Hai 0001, Christos Koutras, Andra Ionescu, Jessie van Schijndel, Yan Kang 0001, Asterios Katsifodimos |
ICDE | 1 |
| 2023 | Macaroni: Crawling and Enriching Metadata from Public Model Zoos
Henk Kant, Rihan Hai 0001, Asterios Katsifodimos, Alessandro Bozzon |
ICWE | 3 |
| 2023 | Optimizing ML Inference Queries Under Constraints
Mariette Schönfeld, Marios Fragkoulis, Rihan Hai 0001, Alessandro Bozzon, Asterios Katsifodimos |
ICWE | 5 |
| 2023 | Accelerating Machine Learning Queries with Linear Algebra Query ProcessingabstractThe rapid growth of large-scale machine learning (ML) models has led numerous commercial companies to utilize ML models for generating predictive results to help business decision-making. As two primary components in traditional predictive pipelines, data processing, and model predictions often operate in separate execution environments, leading to redundant engineering and computations. Additionally, the diverging mathematical foundations of data processing and machine learning hinder cross-optimizations by combining these two components, thereby overlooking potential opportunities to expedite predictive pipelines. Asterios Katsifodimos, Rihan Hai 0001 |
SSDBM | 3 |
| 2023 | Data Lakes: A Survey of Functions and SystemsabstractData lakes are becoming increasingly prevalent for big data management and data analytics. In contrast to traditional ‘schema-on-write’ approaches such as data warehouses, data lakes are repositories storing raw data in its original formats and providing a common access interface. Despite the strong interest raised from both academia and industry, there is a large body of ambiguity regarding the definition, functions and available technologies for data lakes. A complete, coherent picture of data lake challenges and solutions is still missing. This survey reviews the development, architectures, and systems of data lakes. We provide a comprehensive overview of research questions for designing and building data lakes. We classify the existing approaches and systems based on their provided functions for data lakes, which makes this survey a useful technical reference for designing, implementing and deploying data lakes. We hope that the thorough comparison of existing solutions and the discussion of open research challenges in this survey will motivate the future development of data lake research and practice. Rihan Hai 0001, Christos Koutras, Christoph Quix, Matthias Jarke |
IEEE Trans. Knowl. Data Eng. | 1 |
| 2022 | Amalur: Next-generation Data Integration in Data Lakes
Rihan Hai 0001, Christos Koutras, Andra Ionescu, Asterios Katsifodimos |
CIDR | 1 |
| 2019 | Relaxed Functional Dependency Discovery in Heterogeneous Data Lakes
Rihan Hai 0001, Christoph Quix |
ER | 1 |
| 2019 | Rewriting of Plain SO Tgds into Nested TgdsabstractSchema mappings express the relationships between sources in data interoperability scenarios and can be expressed in various formalisms. Source-to-target tuple-generating dependencies (s-t tgds) can be easily used for data transformation or query rewriting tasks. Second-order tgds (SO tgds) are more expressive as they can also represent the composition and inversion of s-t tgds. Yet, the expressive power of SO tgds comes with the problem of undecidability for some reasoning tasks. Nested tgds and plain SO tgds are mapping languages that are between s-t tgds and SO tgds in terms of expressivity, and their properties have been studied in the recent years. Nested tgds are less expressive than plain SO tgds, but the logical equivalence problem for nested tgds is decidable. However, a detailed characterization of plain SO tgds that have an equivalent nested tgd is missing. In this paper, we present an algorithmic solution for translating plain SO tgds into nested tgds. The algorithm computes one or more nested tgds, if a given plain SO tgd is rewritable. Furthermore, we are able to give a detailed characterization of those plain SO tgds for which an equivalent nested tgd exists, based on the structural properties of the source predicates and Skolem functions in the plain SO tgd. In the evaluation, we show that our algorithm covers a larger subset of plain SO tgds than previous approaches and that a rewriting can be computed efficiently although the algorithm has the exponential complexity. Rihan Hai 0001, Christoph Quix |
Proc. VLDB Endow. | 1 |
| 2018 | Query Rewriting for Heterogeneous Data Lakes
Rihan Hai 0001, Christoph Quix |
ADBIS | 1 |
| 2018 | Nested Schema Mappings for Integrating JSON
Rihan Hai 0001, Christoph Quix, David Kensche |
ER | 1 |
| 2016 | Constance: An Intelligent Data Lake SystemabstractAs the challenge of our time, Big Data still has many research hassles, especially the variety of data. The high diversity of data sources often results in information silos, a collection of non-integrated data management systems with heterogeneous schemas, query languages, and APIs. Data Lake systems have been proposed as a solution to this problem, by providing a schema-less repository for raw data with a common access interface. However, just dumping all data into a data lake without any metadata management, would only lead to a 'data swamp'. To avoid this, we propose Constance, a Data Lake system with sophisticated metadata management over raw data extracted from heterogeneous data sources. Constance discovers, extracts, and summarizes the structural metadata from the data sources, and annotates data and metadata with semantic information to avoid ambiguities. With embedded query rewriting engines supporting structured data and semi-structured data, Constance provides users a unified interface for query processing and data exploration. During the demo, we will walk through each functional component of Constance. Constance will be applied to two real-life use cases in order to show attendees the importance and usefulness of our generic and extensible data lake system. Rihan Hai 0001, Sandra Geisler, Christoph Quix |
SIGMOD Conference | 1 |
| 2015 | An Ontology-based Collaboration Recommender System using PatentsabstractS.389-394 Sandra Geisler, Rihan Hai 0001, Christoph Quix |
KEOD | 2 |