Peter A. Boncz

Centrum Wiskunde & Informatica | CWI · Research Group for Database Architectures

In this research project, we investigate an alternative to the standard cloud-centralized data architecture. Specifically, we aim to leave part of the application data under the control of the individual data owners in decentralized personal data stores. Our primary goal is to increase data minimization, i. e., enabling more sensitive personal data...

Ensuring the success of big graph processing for the next decade and beyond.

Graphs are by nature unifying abstractions that can leverage interconnectedness to represent, explore, predict, and explain real- and digital-world phenomena. Although real users and consumers of graph instances and graph workloads understand these abstractions, future problems will require new abstractions and systems. What needs to happen in the...

The Linked Data Benchmark Council's Social Network Benchmark (LDBC SNB) is an effort intended to test various functionalities of systems used for graph-like data management. For this, LDBC SNB uses the recognizable scenario of operating a social network, characterized by its graph-shaped data. LDBC SNB consists of two workloads that focus on differ...

Finding a good join order is crucial for query performance. In this paper, we introduce the Join Order Benchmark that works on real-life data riddled with correlations and introduces 113 complex join queries. We experimentally revisit the main components in the classic query optimizer architecture using a complex, real-world data set and realistic...

We describe a new deep learning approach to cardinality estimation. MSCN is a multi-set convolutional network, tailored to representing relational query plans, that employs set semantics to capture query features and true cardinalities. MSCN builds on sampling-based estimation, addressing its weaknesses when no sampled tuples qualify a predicate, a...

Increasing single instruction multiple data (SIMD) capabilities in modern hardware allows for compiling efficient data-parallel query pipelines. This means GPU-alike challenges arise: control flow divergence causes underutilization of vector-processing units. In this paper, we present efficient algorithms for the AVX-512 architecture to address thi...

In this short paper, we provide an early look at the LDBC Social Network Benchmark's Business Intelligence (BI) workload which tests graph data management systems on a graph business analytics workload. Its queries involve complex aggregations and navigations (joins) that touch large data volumes, which is typical in BI workloads, yet they depend h...

We report on a community effort between industry and academia to shape the future of graph query languages. We argue that existing graph database management systems should consider supporting a query language with two key characteristics. First, it should be composable, meaning, that graphs are the input and the output of queries. Second, the graph...

Geospatial joins are a core building block of connected mobility applications. An especially challenging problem are joins between streaming points and static polygons. Since points are not known beforehand, they cannot be indexed. Nevertheless, points need to be mapped to polygons with low latencies to enable real-time feedback. We present an adap...

To extend the coverage of Knowledge Bases (KBs), it is useful to integrate factual information from public tabular data. Ideally, the extracted information should not only be correct, but also novel. So far, the evaluation of state-of-the-art techniques for this task has focused primarily on the correctness of the extractions, but the novelty is le...

We report on a community effort between industry and academia to shape the future of graph query languages. We argue that existing graph database management systems should consider supporting a query language with two key characteristics. First, it should be composable, meaning, that graphs are the input and the output of queries. Second, the graph...

Comma Separated Value (CSV) files are commonly used to represent data. CSV is a very simple format, yet we show that it gives rise to a surprisingly large amount of ambiguities in its parsing and interpretation. We summarize the state-of-the-art in CSV parsers, which typically make a linear series of parsing and interpretation decisions, such that...

This paper partially explores the design space for efficient query processors on future hardware that is rich in SIMD capabilities. It departs from two well-known approaches: (1) interpreted block-at-a-time execution (a.k.a. "vector-ization") and (2) "data-centric" JIT compilation, as in the HyPer system. We argue that in between these two design p...

Reachability and shortest paths are among two of the most common queries realized on graphs. While graph frameworks and property graph databases provide an extensive and convenient built-in support for these operations, it is still both clunky and inefficient to perform on standard SQL DBMSs. In this paper, we present an extension to the standard S...

This short paper present a collection of GPU lightweight decompression algorithms implementations within a FOSS library, Giddy - the first to be published to offer such functionality. As the use of compression is important in ameliorating PCIe data transfer bottlenecks, we believe this library and its constituent implementations can serve as useful...

We build on our earlier finding that more than 95 % of the triples in actual RDF triple graphs have a remarkably tabular structure, whose schema does not necessarily follow from explicit metadata such as ontologies, but for which an RDF store can automatically derive by looking at the data using so-called “emergent schema” detection techniques. In...

In this paper we introduce LDBC Graphalytics, a new industrial-grade benchmark for graph analysis platforms. It consists of six deterministic algorithms, standard datasets, synthetic dataset generators, and reference output, that enable the objective comparison of graph analysis platforms. Its test harness produces deep metrics that quantify multip...

This work aims at reducing the main-memory footprint in high performance hybrid OLTP & OLAP databases, while retaining high query performance and transactional throughput. For this purpose, an innovative compressed columnar storage format for cold data, called Data Blocks is introduced. Data Blocks further incorporate a new light-weight index struc...

Actian Vector in Hadoop (VectorH for short) is a new SQL-on-Hadoop system built on top of the fast Vectorwise analytical database system. VectorH achieves fault tolerance and storage scalability by relying on HDFS, and extends the state-of-the-art in SQL-on-Hadoop systems by instrumenting the HDFS replication policy to optimize read locality. Vecto...

Shortest-path computation is central to many graph queries. However, current graph-processing platforms tend to offer limited solutions, typically supporting only single-source and all-pairs shortest path algorithms, with poor filtering options. In this paper we address the shortest-path computation problem in two complementary directions. First, w...

Analytical workloads in data warehouses often include heavy joins where queries involve multiple fact tables in addition to the typical star-patterns, dimensional grouping and selections. In this paper we propose a new processing and storage framework called bitwise dimensional co-clustering (BDCC) that avoids replication and thus keeps updates fas...

Finding a good join order is crucial for query performance. In this paper, we introduce the Join Order Benchmark (JOB) and experimentally revisit the main components in the classic query optimizer architecture using a complex, real-world data set and realistic multi-join queries. We investigate the quality of industrial-strength cardinality estimat...

Graphs are increasingly used in industry, governance, and science. This has stimulated the appearance of many and diverse graph-processing platforms. Although platform diversity is beneficial, it also makes it very challenging to select the best platform for an application domain or one of its important applications, and to design new and tune exis...

The Linked Data Benchmark Council (LDBC) is now two years underway and has gathered strong industrial participation for its mission to establish benchmarks, and benchmarking practices for evaluating graph data management systems. The LDBC introduced a new choke-point driven methodology for developing benchmark workloads, which combines user input w...

We motivate and describe techniques that allow to detect an "emergent" relational schema from RDF data. We show that on a wide variety of datasets, the found structure explains well over 90% of the RDF triples. Further, we also describe technical solutions to the semantic challenge to give short names that humans find logical to these emergent tabl...

In this paper we consider the problem of generating parameters for benchmark queries so these have stable behavior despite being executed on datasets (real-world or synthetic) with skewed data distributions and value correlations. We show that uniform random sampling of the substitution parameters is not well suited for such benchmarks, since it re...

A system and method for buffer management in a database are provided in which a predictive buffer manager may be used. The predictive buffer manager and process may predict when each block in a buffer is going to be used and then manages the buffer based on the prediction.

One of the prime goals of the LOD2 project is improving the performance and scalability of RDF storage solutions so that the increasing amount of Linked Open Data (LOD) can be efficiently managed. Virtuoso has been chosen as the basic RDF store for the LOD2 project, and during the project it has been significantly improved by incorporating advanced...

With modern computer architecture evolving, two problems conspire against the state-of-the-art approaches in parallel query execution: (i) to take advantage of many-cores, all query work must be distributed evenly among (soon) hundreds of threads in order to achieve good speedup, yet (ii) dividing the work evenly is difficult even with accurate dat...

The Linked Data Benchmark Council (LDBC) is an EU project that aims to develop industry-strength benchmarks for graph and RDF data management systems. It includes the creation of a non-profit LDBC organization, where industry players and academia come together for managing the development of benchmarks as well as auditing and publishing official re...

In this paper we consider the problem of generating parameters for queries in RDF benchmarks. We show that uniform random sampling of the substitution parameters is not well suited for RDF benchmarks, since it results in unpredictable runtime behavior of queries. We formulate a formal problem of parameter generation to ensure stable and statistical...

The TPC-D benchmark was developed almost 20 years ago, and even though its current existence as TPC-H could be considered superseded by TPC-DS, one can still learn from it. We focus on the technical level, summarizing the challenges posed by the TPC-H workload as we now understand them, which we call “choke points”. We identify 28 different such ch...

The Linked Data Benchmark Council (LDBC) is an EU project that aims to develop industry-strength benchmarks for graph and RDF data management systems. LDBC introduces a so-called "choke-point" based benchmark development, through which experts identify key technical challenges, and introduce them in the benchmark workload, which we describe in some...

Scientific discovery has shifted from being an exercise of theory and computation, to become the exploration of an ocean of observational data. Scientists explore data originated from modern scientific instruments in order to discover interesting aspects of it and formulate their hypothesis. Such workloads press for new database functionality. We a...

Despite the fast growth and increasing popularity, the broad field of RDF and Graph database systems lacks an independent authority for developing benchmarks, and for neutrally assessing benchmark results through industry-strength auditing which would allow to quantify and compare the performance of existing and emerging systems. Inspired by the im...

Performance of query processing functions in a DBMS can be affected by many factors, including the hardware platform, data distributions, predicate parameters, compilation method, algorithmic variations and the interactions between these. Given that there are often different function implementations possible, there is a latent performance diversity...

Database systems typically execute queries in isolation. Sharing recurring intermediate and final results between successive query invocations is ignored or only exploited by caching final query results. The DBA is kept in the loop to make explicit sharing decisions by identifying and/or defining materialized views. Thus decisions are made only aft...

Schema design of analytical workloads provides opportunities to index, cluster, partition and/or materialize. With these opportunities also the complexity of finding the right setup rises. In this paper we present an automatic schema design approach for a table co-clustering scheme called Bitwise Dimensional Co-Clustering, aimed at schemas with a m...

We describe a system that incrementally translates SPARQL queries to Pig Latin and executes them on a Hadoop cluster. This system is designed to work efficiently on complex queries with many self-joins over huge datasets, avoiding job failures even in the case of joins with unexpected high-value skew. To be robust against cost estimation errors, ou...

Linked Stream Data, i.e., the RDF data model extended for representing stream data generated from sensors social network applications, is gaining popularity. This has motivated considerable work on developing corresponding data models associated with processing engines. However, current implemented engines have not been thoroughly evaluated to asse...

In this paper we present the Sandwich Operators, an elegant approach to exploit pre-sorting or pre-grouping from clustered storage schemes in operators such as Aggregation/Grouping, HashJoin, and Sort of a database management system. Thereby, each of these operator types is "sandwiched" by two new operators, namely PartitionSplit and PartitionResta...

Benchmarking graph-oriented database workloads and graph-oriented database systems is increasingly becoming relevant in analytical Big Data tasks, such as social network analysis. In graph data, structure is not mainly found inside the nodes, but especially in the way nodes happen to be connected, i.e. structural correlations. Because such structur...

In analytical applications, database systems often need to sustain workloads with multiple concurrent scans hitting the same table. The Cooperative Scans (CScans) framework, which introduces an Active Buffer Manager (ABM) component into the database architecture, has been the most effective and elaborate response to this problem, and was initially...

In 2008 a group of researchers behind the X100 database kernel created Vectorwise: a spin-off which together with the Actian corporation (previously Ingres) worked on bringing this technology to the market. Today, Vectorwise is a popular product and one of the examples of conversion of a research prototype into successful commercial software. We de...

Vector wise is a new entrant in the analytical database marketplace whose technology comes straight from innovations in the database research community in the past years. The product has since made waves due to its excellent performance in analytical customer workloads as well as benchmarks. We describe the history of Vector wise, as well as its ba...

Query optimization in RDF Stores is a challenging problem as SPARQL queries typically contain many more joins than equivalent relational plans, and hence lead to a large join order search space. In such cases, cost-based query optimization often is not possible. One practical reason for this is that statistics typically are missing in web scale set...

This paper tells the story of Vectorwise, a high-performance analytical database system, from multiple perspectives: its history from academic project to commercial product, the evolution of its technical architecture, customer reactions to the product and its future research and development roadmap. One take-away from this story is that the novelt...

Twenty-five Semantic Web and Database researchers met at the 2011 STI Semantic Summit in Riga, Latvia July 6-8, 2011[1] to discuss the opportunities and challenges posed by Big Data for the Semantic Web, Semantic Technologies, and Database communities. The unanimous conclusion was that the greatest shared challenge was not only engineering Big Data...

Actian Corporation recently entered into a cooperative relationship with VectorWise BV to integrate its Vector-Wise technology into the Ingres RDBMS server. The resulting commercial product has already achieved phenomenal performance results with the TPC-H industry standard benchmark, and has been well received in the analytical RDBMS market. This...

Compiling database queries into executable (sub-) programs provides substantial benefits comparing to traditional interpreted execution. Many of these benefits, such as reduced interpretation overhead, better instruction code locality, and providing opportunities to use SIMD instructions, have previously been provided by redesigning query processor...

Data warehouses underlying virtual observatories stress the capabilities of database management systems in many ways. They are filled, on a daily basis, with large amounts of factual information derived from intensive data scrubbing and computational feature extraction pipelines. The predominant data processing techniques focus on parallel loads an...

We investigate techniques to automatically decompose any XQuery query-including updating queries specified by the XQuery Update Facility (XQUF)-into subqueries, that can be executed near their data sources, i.e., function-shipping. The main challenge addressed here is to ensure that the decomposed queries properly respect XML node identity and pres...

In this paper we investigate techniques that allow for on-line updates to columnar databases, leaving intact their high read-only performance. Rather than keeping differential structures organized by the table key values, the core proposition of this paper is that this can better be done by keeping track of the tuple position of the modifications....

We demonstrate ROX, a run-time optimizer of XQueries, that focuses on finding the best execution order of XPath steps and relational joins in an XQuery. The problem of join ordering has been extensively researched, but the proposed techniques are still unsatisfying. These either rely on a cost model which might result in inaccurate estimations, or...

The last few years have been exciting for data management system designers. The explosion in user and enterprise data coupled with the availability of newer, cheaper, and more capable hardware have lead system designers and researchers to rethink and, in some cases, reinvent the traditional DBMS architecture. In the space of data warehousing and an...

Traditional optimizers fail to pick good execution plans, when faced with increasingly complex queries and large data sets. This failure is even more acute in the context of XQuery, due to the structured nature of the XML language. To overcome the vulnerabilities of traditional optimizers, we have previously proposed ROX, a Run-time Optimizer for X...

We demonstrate ROX, a run-time optimizer of XQueries, that focuses on finding the best execution order of XPath steps and relational joins in an XQuery. The problem of join ordering has been extensively researched, but the proposed techniques are still unsatisfying. These either rely on a cost model which might result in inaccurate estimations, or...

This chapter surveys and discusses the evolution of a certain class of database architectures, more recently referred to as “vertical databases”. The topics discussed in this chapter include the evolution of storage structures from the 1970’s till now, data compression techniques, and query processing techniques for single- and multi-variable queri...

Exact substring matching queries on large data collections can be answered using q-gram indices, that store for each occurring q-byte pattern an (ordered) posting list with the positions of all occurrences. Such gram indices are known to provide fast query response time and to allow the index to be created quickly even on huge disk-based datasets....

Column-oriented database systems (column-stores) have attracted a lot of attention in the past few years. Column-stores, in a nutshell, store each database table column separately, with attribute values belonging to the same column stored contiguously, compressed, and densely packed, as opposed to traditional database systems that store entire reco...

The holy grail for database architecture research is to find a solution that is Scalable & Speedy, to run on anything from small ARM processors up to globally distributed compute clusters, Stable & Secure, to service a broad user community, Small & Simple, to be comprehensible to a small team of programmers, Self-managing, to let it run out-of-the-...

Column-oriented database systems (column-stores) have attracted a lot of attention in the past few years. Column-stores, in a nutshell, store each database table column separately, with attribute values belonging to the same column stored contiguously, compressed, and densely packed, as opposed to traditional database systems that store entire reco...

Optimization of complex XQueries combining many XPath steps and joins is currently hindered by the absence of good cardinality estimation and cost models for XQuery. Additionally, the state-of- the-art of even relational query optimization still struggles to cope with cost model estimation errors that increase with plan size, as well as with the ef...

Materialized views, a rdbms silver bullet, demonstrate its e-cacy in many applications, especially as a data warehousing/decison support system tool. The pivot of playing materialized views e-ciently is view selection. Though studied for over thirty years in rdbms, the selection is hard to make in the context of xml databases, where both the semi-s...

We describe a collection of indices for XML text, element, and attribute node values that (i) consume little storage, (ii) have low maintenance overhead, (iii) permit fast equi-lookup on string values, and (iv) support range-lookup on any XML typed value (e.g., double, dateTime). The equi-lookup string value index depends on an elaborate hash funct...

Abstract— We investigate techniques to automatically decom- pose any XQuery query into subqueries, that can be executed near their data sources; i.e., function-shipping. In this scenario, the subqueries being executed remotely may have XML node- valued parameters or results, that must be shipped in some way. The main challenge addressed here is to...

StreetTiVo is a project that aims at bringing research results into the living room; in particular, a mix of current results in the areas of Peer-to-Peer XML Database Management System (P2P XDBMS), advanced multimedia analysis techniques, and advanced information retrieval techniques. The project develops a plug-in application for the so-called Hom...