Capturing the characteristics of real-world analytical workloads is challenging yet critical for advancing industry practices and academic research. Historically, obtaining accurate query and data characteristics has been difficult, largely because detailed workload information has often been confined to on-premises database systems. With the rise of cloud-native databases like Snowflake, it has become possible to analyze production query workloads at scale and in greater detail. Leveraging this capability, this study presents a comprehensive analysis of analytics workloads across diverse customers and industries. In particular, we investigate the query characteristics of 667 million queries issued by the most popular BI tools against Snowflake over a two-week period. Based on this dataset, this paper makes two primary contributions: first, we conduct a detailed examination of query properties, with particular attention to filters, joins, aggregations, and other previously underexplored aspects. Second, we uncover unique and practically relevant query patterns that are typically absent from standard database benchmarks.

Accurately predicting the cardinality of intermediate plan operations is an essential part of any modern relational query optimizer. The accuracy of said estimates has a strong and direct impact on the quality of the generated plans, and incorrect estimates can have a negative impact on query performance. One of the biggest challenges in this field is to predict the result size of join operations. Kernel Density Estimation (KDE) is a statistical method to estimate multivariate probability distributions from a data sample. Previously, we introduced a modern, self-tuning selectivity estimator for range scans based on KDE that out-performs state-of-the-art multidimensional histograms and is efficient to evaluate on graphics cards. In this paper, we extend these bandwidth-optimized KDE models to estimate the result size of single and multiple joins. In particular, we propose two approaches: (1) Building a KDE model from a sample drawn from the join result. (2) Efficiently combining the information from base table KDE models. We evaluated our KDE-based join estimators on a variety of synthetic and real-world datasets, demonstrating that they are superior to state-of-the art join estimators based on sketching or sampling.

Maintaining random data samples under database updates is a fundamental operation in modern database engines. While multiple algorithms exist for this problem, none is tailored to the special case of maintaining data samples on graphics cards. Due to the limited interconnect bandwidth to main memory, any GPU-resident algorithm must try to avoid data transfers across the PCI Express bus where possible ‐ a property that we call transfer-ecient. In this demonstration, we present an approximate, transfer-ecient sample maintenance algorithm that piggybacks on a GPUaccelerated selectivity estimator and utilizes query feedback to selectively identify and replace outdated points. We provide an implementation of the algorithm and interactively demonstrate its quality and its transfer performance in comparison to traditional maintenance algorithms.

Quickly and accurately estimating the selectivity of multidimensional predicates is a vital part of a modern relational query optimizer. The state-of-the art in this field are multidimensional histograms, which offer good estimation quality but are complex to construct and hard to maintain. Kernel Density Estimation (KDE) is an interesting alternative that does not suffer from these problems. However, existing KDE-based selectivity estimators can hardly compete with the estimation quality of state-of-the art methods.

Satisfying the performance needs of tomorrow typically im-plies using modern processor capabilities (such as single in-struction, multiple data) and co-processors (such as graphics processing units) to accelerate database operations. Algo-rithms are typically hand-tuned to the underlying (co-)pro-cessors. This solution is error-prone, introduces high imple-mentation and maintenance cost and one implementations is not portable to other (co-)processors. To this end, we argue for a combination of database research with modern software-engineering approaches. We emphasize our vision of generating optimized database algorithms tailored to used (co-)processors from a common code base. With this, we maximize performance while minimizing implementation and maintenance effort of hardware-tailored database operations. 1.

The increasingly heterogeneous modern hardware landscape is forcing database vendors to rethink basic design decisions: With more and more architectures to support, the traditional approach of building on hand-tuned operators might simply become too costand labor-intensive. With this problem in mind, we introduced the notion of a hardware-oblivious database engine, which avoids devicespecific optimizations and targets multiple different hardware architectures from a single code-base. We demonstrated the feasibility of this concept through Ocelot, a prototypical hardware-oblivious database that uses OpenCL to provide operators that can run on multiple architectures. In this demonstration, we show how we modified Ocelot to support self-learning algorithm adaptivity: The ability to automatically learn which algorithms are optimal for a given operation on a given hardware architecture. We present how to specify operators that can be executed by multiple algorithms, provide details about the underlying learning and decision routines, and demonstrate how our system picks the optimal algorithm when running on systems with multiple devices, such as CPUs and graphics cards.

The increasing heterogeneity in hardware systems gives developers many opportunities to add more functionality and computational power to the system. As a consequence, modern database systems will need to be able to adapt to a wide variety of heterogeneous architectures. While porting single operators to accelerator architectures is well-understood, a more generic approach is needed for the whole database system. In prior work, we presented a generic hardware-oblivious database system, where the operators can be executed on the main processor as well as on a large number of accelerator architectures. However, to achieve fully heterogeneous query processing, placement decisions are needed for the database operators. We enhance the presented system with heterogeneity-aware operator placement (HOP) to take a major step towards designing a database system that can efficiently exploit highly heterogeneous hardware environments. In this demonstration, we are focusing on the placement-integration aspect as well as presenting the resulting database system.

The past years saw the emergence of highly heterogeneous server architectures that feature multiple accelerators in addition to the main processor. Efficiently exploiting these systems for data processing is a challenging research problem that comprises many facets, including how to find an optimal operator placement strategy, how to estimate runtime costs across different hardware architectures, and how to manage the code and maintenance blowup caused by having to support multiple architectures. In prior work, we already discussed solutions to some of these problems: First, we showed that specifying operators in a hardware-oblivious way can prevent code blowup while still maintaining competitive performance when supporting multiple architectures. Second, we presented learning cost functions and several heuristics to efficiently place operators across all available devices. In this demonstration, we provide further insights into this line of work by presenting our combined system Ocelot/HyPE. Our system integrates a hardware-oblivious data processing engine with a learning query optimizer for placement decisions, resulting in a highly adaptive DBMS that is specifically tailored towards heterogeneous hardware environments.

The multi-core architectures of today's computer systems make parallelism a necessity for performance critical applications. Writing such applications in a generic, hardware-oblivious manner is a challenging problem: Current database systems thus rely on labor-intensive and error-prone manual tuning to exploit the full potential of modern parallel hardware architectures like multi-core CPUs and graphics cards. We propose an alternative design for a parallel database engine, based on a single set of hardware-oblivious operators, which are compiled down to the actual hardware at runtime. This design reduces the development overhead for parallel database engines, while achieving competitive performance to hand-tuned systems. We provide a proof-of-concept for this design by integrating operators written using the parallel programming framework OpenCL into the open-source database MonetDB. Following this approach, we achieve efficient, yet highly portable parallel code without the need for optimization by hand. We evaluated our implementation against MonetDB using TPC-H derived queries and observed a performance that rivals that of MonetDB's query execution on the CPU and surpasses it on the GPU. In addition, we show that the same set of operators runs nearly unchanged on a GPU, demonstrating the feasibility of our approach.

Large-scale data analysis applications require processing and analyzing of Terabytes or even Petabytes of data, particularly in the areas of web analysis or scientific data management. This trend has been discussed as "web-scale data management" in a panel at VLDB 2009. Formerly, parallel data processing was the domain of parallel database systems. Today, novel requirements like scaling out to thousands of machines, improved fault-tolerance, and schema free processing have made a case for new approaches.