TY - GEN A1 - Mintel, Mario A1 - Ramsauer, Ralf A1 - Lohmann, Daniel A1 - Scherzinger, Stefanie A1 - Mauerer, Wolfgang T1 - Fork à la carte für In-Memory-Datenbanken T2 - Frühjahrstreffen der Fachgruppen Betriebssysteme, Hamburg, 17. März 2022 Y1 - 2022 UR - https://www.lfdr.de/Publications/2022/FGBS_Spring22_Mintel.pdf ER - TY - JOUR A1 - Schönberger, Manuel A1 - Scherzinger, Stefanie A1 - Mauerer, Wolfgang T1 - Ready to Leap (by Co-Design)? Join Order Optimisation on Quantum Hardware JF - Proceedings of the ACM on Management of Data, PACMMOD N2 - The prospect of achieving computational speedups by exploiting quantum phenomena makes the use of quantum processing units (QPUs) attractive for many algorithmic database problems. Query optimisation, which concerns problems that typically need to explore large search spaces, seems like an ideal match for the known quantum algorithms. We present the first quantum implementation of join ordering, which is one of the most investigated and fundamental query optimisation problems, based on a reformulation to quadratic binary unconstrained optimisation problems. We empirically characterise our method on two state-of-the-art approaches (gate-based quantum computing and quantum annealing), and identify speed-ups compared to the best know classical join ordering approaches for input sizes that can be processed with current quantum annealers. However, we also confirm that limits of early-stage technology are quickly reached. Current QPUs are classified as noisy, intermediate scale quantum computers (NISQ), and are restricted by a variety of limitations that reduce their capabilities as compared to ideal future quantum computers, which prevents us from scaling up problem dimensions and reaching practical utility. To overcome these challenges, our formulation accounts for specific QPU properties and limitations, and allows us to trade between achievable solution quality and possible problem size. In contrast to all prior work on quantum computing for query optimisation and database-related challenges, we go beyond currently available QPUs, and explicitly target the scalability limitations: Using insights gained from numerical simulations and our experimental analysis, we identify key criteria for co-designing QPUs to improve their usefulness for join ordering, and show how even relatively minor physical architectural improvements can result in substantial enhancements. Finally, we outline a path towards practical utility of custom-designed QPUs. KW - Hardware KW - Quantum cmputation KW - Informations systems KW - Join algorithms Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-56634 N1 - Corresponding author: Manuel Schönberger VL - 1 IS - 1 SP - 1 EP - 27 PB - ACM CY - New York, NY, ER - TY - JOUR A1 - Thor, Andreas A1 - Scherzinger, Stefanie A1 - Specht, Günther T1 - Editorial JF - Datenbank-Spektrum Y1 - 2014 U6 - https://doi.org/10.1007/s13222-014-0162-1 VL - 14 IS - 2 SP - 81 EP - 84 PB - Springer ER - TY - CHAP A1 - Störl, Uta A1 - Müller, Daniel A1 - Tekleab, Alexander A1 - Tolale, Stephane A1 - Stenzel, Julian A1 - Klettke, Meike A1 - Scherzinger, Stefanie A1 - Storl, Uta A1 - Muller, Daniel T1 - Curating Variational Data in Application Development T2 - 2018 IEEE 34th International Conference on Data Engineering, 16-19 April 2018, Paris, France N2 - Building applications for processing data lakes is a software engineering challenge. We present Darwin, a middleware for applications that operate on variational data. This concerns data with heterogeneous structure, usually stored within a schema-flexible NoSQL database. Darwin assists application developers in essential data and schema curation tasks: Upon request, Darwin extracts a schema description, discovers the history of schema versions, and proposes mappings between these versions. Users of Darwin may interactively choose which mappings are most realistic. Darwin is further capable of rewriting queries at runtime, to ensure that queries also comply with legacy data. Alternatively, Darwin can migrate legacy data to reduce the structural heterogeneity. Using Darwin, developers may thus evolve their data in sync with their code. In our hands-on demo, we curate synthetic as well as real-life datasets. KW - data migration KW - Data mining KW - Evolution (biology) KW - history KW - NoSQL databases KW - query rewriting KW - schema evolution KW - schema management KW - Software KW - Task analysis KW - variational data Y1 - 2018 U6 - https://doi.org/10.1109/ICDE.2018.00187 SP - 1605 EP - 1608 PB - IEEE ER - TY - CHAP A1 - Mauerer, Wolfgang A1 - Scherzinger, Stefanie ED - Ailamaki, Anastasia T1 - Nullius in Verba: Reproducibility for Database Systems Research, Revisited T2 - 2021 IEEE 37th International Conference on Data Engineering (ICDE 2021): 19-22 April 2021, Chania, Greece N2 - Over the last decade, reproducibility of experimental results has been a prime focus in database systems research, and many high-profile conferences award results that can be independently verified. Since database systems research involves complex software stacks that non-trivially interact with hardware, sharing experimental setups is anything but trivial: Building a working reproduction package goes far beyond providing a DOI to some repository hosting data, code, and setup instructions.This tutorial revisits reproducible engineering in the face of state-of-the-art technology, and best practices gained in other computer science research communities. In particular, in the hands-on part, we demonstrate how to package entire system software stacks for dissemination. To ascertain long-term reproducibility over decades (or ideally, forever), we discuss why relying on open source technologies massively employed in industry has essential advantages over approaches crafted specifically for research. Supplementary material shows how version control systems that allow for non-linearly rewriting recorded history can document the structured genesis behind experimental setups in a way that is substantially easier to understand, without involvement of the original authors, compared to detour-ridden, strictly historic evolution. KW - Control systems KW - Data engineering KW - Database systems KW - docker KW - git KW - Hardware KW - Industries KW - Reproducibility of results KW - reproducible science KW - reproduction, reproduction package KW - scientific attribution KW - scientific method KW - Tutorials Y1 - 2021 SN - 978-1-7281-9184-3 U6 - https://doi.org/10.1109/ICDE51399.2021.00270 SP - 2377 EP - 2380 PB - IEEE CY - Piscataway, NJ ER - TY - CHAP A1 - Klettke, Meike A1 - Awolin, Hannes A1 - Störl, Uta A1 - Müller, Daniel A1 - Scherzinger, Stefanie A1 - Storl, Uta A1 - Muller, Daniel T1 - Uncovering the evolution history of data lakes T2 - 2017 IEEE International Conference on Big Data (Big Data),,11-14 Dec. 2017, Boston, MA, USA N2 - Data accumulating in data lakes can become inaccessible in the long run when its semantics are not available. The heterogeneity of data formats and the sheer volumes of data collections prohibit cleaning and unifying the data manually. Thus, tools for automated data lake analysis are of great interest. In this paper, we target the particular problem of reconstructing the schema evolution history from data lakes. Knowing how the data is structured, and how this structure has evolved over time, enables programmatic access to the lake. By deriving a sequence of schema versions, rather than a single schema, we take into account structural changes over time. Moreover, we address the challenge of detecting inclusion dependencies. This is a prerequisite for mapping between succeeding schema versions, and in particular, detecting nontrivial changes such as a property having been moved or copied. We evaluate our approach for detecting inclusion dependencies using the MovieLens dataset, as well an adaption of a dataset containing botanical descriptions, to cover specific edge cases. KW - Data mining KW - evolution operations KW - Grippers KW - history KW - inclusion dependencies KW - integrity constraints KW - Lakes KW - NoSQL databases KW - Protocols KW - schema version extraction Y1 - 2017 U6 - https://doi.org/10.1109/BigData.2017.8258204 SP - 2462 EP - 2471 PB - IEEE ER - TY - CHAP A1 - Mauerer, Wolfgang A1 - Ramsauer, Ralf A1 - Lucas, Edson R. F. A1 - Scherzinger, Stefanie T1 - Silentium! Run-Analyse-Eradicate the Noise out of the DB/OS Stack T2 - Datenbanksysteme für Business, Technologie und Web (BTW 2021): 13.-17. September 2021, Dresden, Deutschland N2 - When multiple tenants compete for resources, database performance tends to suffer. Yet there are scenarios where guaranteed sub-millisecond latencies are crucial, such as in real-time data processing, IoT devices, or when operating in safety-critical environments. In this paper, we study how to make query latencies deterministic in the face of noise (whether caused by other tenants or unrelated operating system tasks). We perform controlled experiments with an in-memory database engine in a multi-tenant setting, where we successively eradicate noisy interference from within the system software stack, to the point where the engine runs close to bare-metal on the underlying hardware. We show that we can achieve query latencies comparable to the database engine running as the sole tenant, but without noticeably impacting the workload of competing tenants. We discuss these results in the context of ongoing efforts to build custom operating systems for database workloads, and point out that for certain use cases, the margin for improvement is rather narrow. In fact, for scenarios like ours, existing operating systems might just be good enough, provided that they are expertly configured. We then critically discuss these findings in the light of a broader family of database systems (e.g., including disk-based), and how to extend the approach of this paper accordingly. Low-latency databases; tail latency; real-time databases; bounded-time query processing; DB-OS co-engineering KW - bounded-time query processing KW - DB-OS co-engineering KW - Low-latency databases KW - real-time databases KW - tail latency Y1 - 2021 U6 - https://doi.org/10.18420/btw2021-21 SP - 397 EP - 421 PB - Gesellschaft für Informatik ER - TY - CHAP A1 - Scherzinger, Stefanie A1 - Störl, Uta A1 - Klettke, Meike ED - Cheney, James ED - Neumann, Thomas T1 - A Datalog-based protocol for lazy data migration in agile NoSQL Application development T2 - Proceedings of the 15th Symposium on Database Programming Languages : SPLASH '15: Conference on Systems, Programming, Languages, and Applications: Software for Humanity, Pittsburgh PA USA, 27.10.2015 - 27.10.2015 N2 - We address a practical challenge in agile web development against NoSQL data stores: Upon a new release of the web application, entities already persisted in production no longer match the application code. Rather than migrating all legacy entities eagerly (prior to the release) and at the cost of application downtime, lazy data migration is a popular alternative: When a legacy entity is loaded by the application, all pending structural changes are applied. Yet correctly migrating legacy data from several releases back, involving more than one entity at-a-time, is not trivial. In this paper, we propose a holistic Datalog ¬non-rec model model for reading, writing, and migrating data. In implementing our model, we may blend established Datalog evaluation algorithms, such as an incremental evaluation with certain rules evaluated bottom-up, and certain rules evaluated top-down with sideways information passing. Our systematic approach guarantees that from the viewpoint of the application, it remains transparent whether data is migrated eagerly or lazily. Y1 - 2015 SN - 9781450339025 U6 - https://doi.org/10.1145/2815072.2815078 SP - 41 EP - 44 PB - ACM CY - New York, NY, USA ER - TY - CHAP A1 - Haubold, Florian A1 - Schildgen, Johannes A1 - Scherzinger, Stefanie A1 - Deßloch, Stefan ED - Mitschang, Bernhard T1 - ControVol Flex: Flexible Schema Evolution for NoSQL Application Development T2 - Datenbanksysteme für Business, Technologie und Web (BTW 2017) : 17. Fachtagung des GI-Fachbereichs "Datenbanken und Informationssyteme" (DBIS) : 06.-10.03.2017 in Stuttgart Deutschland N2 - We demonstrate ControVol Flex, an Eclipse plugin for controlled schema evolution in Java applications backed by NoSQL document stores. The sweet spot of our tool are applications that are deployed continuously against the same production data store: Each new release may bring about schema changes that conflict with legacy data already stored in production. The type system internal to the predecessor tool ControVol is able to detect common schema conflicts, and enables developers to resolve them with the help of object-mapper annotations. Our new tool ControVol Flex lets developers choose their schema-migration strategy, whether all legacy data is to be migrated eagerly by means of NotaQL transformation scripts, or lazily, as declared by object-mapper annotations. Our tool is even capable of carrying out both strategies in combination, eagerly migrating data in the background, while lazily migrating data that is meanwhile accessed by the application. From the viewpoint of the application, it remains transparent how legacy data is migrated: Every read access yields an entity that matches the structure that the current application code expects. Our live demo shows how ControVol Flex gracefully solves a broad range of common schema-evolution tasks. KW - Schema evolution KW - NotaQL KW - NoSQL Y1 - 2017 PB - Gesellschaft für Informatik e.V. (GI) CY - Bonn ER - TY - CHAP A1 - Störl, Uta A1 - Tekleab, Alexander A1 - Klettke, Meike A1 - Scherzinger, Stefanie A1 - Storl, Uta T1 - In for a Surprise When Migrating NoSQL Data T2 - 2018 IEEE 34th International Conference on Data Engineering (ICDE), 16-19 April 2018, Paris, France N2 - Schema-flexible NoSQL data stores lend themselves nicely for storing versioned data, a product of schema evolution. In this lightning talk, we apply pending schema changes to records that have been persisted several schema versions back. We present first experiments with MongoDB and Cassandra, where we explore the trade-off between applying chains of pending changes stepwise (one after the other), and as composite operations. Contrary to intuition, composite migration is not necessarily faster. The culprit is the computational overhead for deriving the compositions. However, caching composition formulae achieves a speed up: For Cassandra, we can cut the runtime by nearly 80%. Surprisingly, the relative speedup seems to be system-dependent. Our take away message is that in applying pending schema changes in NoSQL data stores, we need to base our design decisions on experimental evidence rather than on intuition alone. KW - composite migration KW - Conferences KW - Data engineering KW - data migration KW - Indexes KW - Lightning KW - NoSQL databases KW - Runtime KW - schema evolution KW - Tools Y1 - 2018 U6 - https://doi.org/10.1109/ICDE.2018.00202 SP - 1662 PB - IEEE ER -