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 - TY - JOUR A1 - Klettke, Meike A1 - Störl, Uta A1 - Scherzinger, Stefanie T1 - Herausforderungen bei der Anwendungsentwicklung mit schema-flexiblen NoSQL-Datenbanken JF - HMD Praxis der Wirtschaftsinformatik N2 - NoSQL-Datenbanksysteme sind in den letzten Jahren sehr populär geworden, gute Gründe sprechen für ihren Einsatz: Eine attraktive Eigenschaft vieler Systeme ist ihre Schema-Flexibilität, die insbesondere in der agilen Anwendungsentwicklung Vorteile bietet. Durch horizontale Skalierbarkeit ermöglichen NoSQL-Datenbanksysteme eine effiziente Verarbeitung großer Datenmengen. Einige Systeme, die für die Datenhaltung interaktiver Anwendungen konzipiert sind, können zudem hochfrequente Nutzeranfragen bedienen. Diesen Vorteilen stehen eine Reihe von Nachteilen gegenüber, aus denen sich neue Herausforderungen für die Anwendungsentwicklung ergeben: Fehlende Standards bei den Anfragesprachen erschweren die Entwicklung datenbanksystemunabhängiger Anwendungen. Schema-Flexibilität im Datenbankmanagementsystem führt dazu, dass die Verantwortung für das Schema-Management in die Anwendung verlagert wird. Im vorliegenden Beitrag werden wesentliche Herausforderungen identifiziert und Lösungsansätze aus Forschung und Praxis vorgestellt. Dabei liegt der Fokus auf schema-flexiblen NoSQL-Datenbanksystemen, mit einem aggregat-orientierten Datenmodell, d. h. Key-Value Datenbanksysteme, dokumentenorientierten Datenbanksystemen und Column-Family Datenbanksystemen. NoSQL data stores have become very popular over the last years, as good reasons are justifying their application: One attractive feature of many systems is their schema flexibility, which may be preferable in agile software development projects. Due to their horizontal scalability, NoSQL data stores make it possible to efficiently process large amounts of data. Some systems, designed as data backends for interactive applications, can also manage highly frequent user requests. Apart from these advantages, there are also downsides to NoSQL data stores that create new challenges for software development: Missing standards in query languages make it difficult to build data store independent applications. Schema flexibility in the data store shifts the responsibility for schema management into the application. This article identifies substantial challenges as well as solution statements from research and practice. The focus of our survey is on schema-flexible NoSQL data management systems with an aggregate-oriented data model, i. e., key-value data management systems, as well as document and column family data management systems. KW - Abfragesprache KW - Applikationsentwicklung KW - Datenbank KW - Datenbanksystem KW - Datenmodell KW - Datensystem KW - horizontale Skalierbarkeit KW - Kolonnendaten KW - Managementsystem KW - Software-Entwicklung Y1 - 2016 U6 - https://doi.org/10.1365/s40702-016-0234-9 VL - 53 IS - 4 SP - 428 EP - 442 PB - Springer ER - TY - CHAP A1 - Klettke, Meike A1 - Störl, Uta A1 - Shenavai, Manuel A1 - Scherzinger, Stefanie A1 - Storl, Uta T1 - NoSQL schema evolution and big data migration at scale T2 - 2016 IEEE International Conference on Big Data (Big Data), 5-8 Dec. 2016, Washington, DC N2 - This paper explores scalable implementation strategies for carrying out lazy schema evolution in NoSQL data stores. For decades, schema evolution has been an evergreen in database research. Yet new challenges arise in the context of cloud-hosted data backends: With all database reads and writes charged by the provider, migrating the entire data instance eagerly into a new schema can be prohibitively expensive. Thus, lazy migration may be more cost-efficient, as legacy entities are only migrated in case they are actually accessed by the application. Related work has shown that the overhead of migrating data lazily is affordable when a single evolutionary change is carried out, such as adding a new property. In this paper, we focus on long-term schema evolution, where chains of pending schema evolution operations may have to be applied. Chains occur when legacy entities written several application releases back are finally accessed by the application. We discuss strategies for dealing with chains of evolution operations, in particular, the composition into a single, equivalent composite migration that performs the required version jump. Our experiments with MongoDB focus on scalable implementation strategies. Our lineup further compares the number of write operations, and thus, the operational costs of different data migration strategies. KW - Big data KW - Context KW - Data Migration Strategies KW - Data models KW - Databases KW - Incremental Migration KW - Lazy Composite Migration KW - Lazy Migration KW - NoSQL databases KW - Predictive Migration KW - Production KW - Runtime KW - schema evolution KW - Software Y1 - 2016 U6 - https://doi.org/10.1109/BigData.2016.7840924 SP - 2764 EP - 2774 PB - IEEE ER - TY - CHAP A1 - Möller, Mark Lukas A1 - Berton, Nicolas A1 - Klettke, Meike A1 - Scherzinger, Stefanie A1 - Störl, Uta T1 - jHound: Large-Scale Profiling of Open JSON Data T2 - Datenbanksysteme für Business, Technologie und Web (BTW 2019), 18. Fachtagung des GI-Fachbereichs "Datenbanken und Informationssysteme" (DBIS) : 4.-8. März 2019 in Rostock N2 - We present jHound, a tool for profiling large collections of JSON data, and apply it to thousands of data sets holding open government data. jHound reports key characteristics of JSON documents, such as their nesting depth. As we show, jHound can help detect structural outliers, and most importantly, badly encoded documents: jHound can pinpoint certain cases of documents that use string-typed values where other native JSON datatypes would have been a better match. Moreover, we can detect certain cases of maladaptively structured JSON documents, which obviously do not comply with good data modeling practices. By interactively exploring particular example documents, we hope to inspire discussions in the community about what makes a good JSON encoding. KW - Datenerhebung KW - Datenformat KW - Datenmodell KW - Eigenschaftskennwert KW - Hauptspeicher KW - Histogramm KW - Zeitüberwachung Y1 - 2018 UR - https://btw.informatik.uni-rostock.de/index.php/de/tagungsbaende/send/3-tagungsbaende/tagungsband.pdf SN - 978-3-88579-683-1 VL - 289 SP - 557 EP - 560 PB - GI - Gesellschaft für Informatik CY - Bonn ER - TY - CHAP A1 - Hillenbrand, Andrea A1 - Levchenko, Maksym A1 - Störl, Uta A1 - Scherzinger, Stefanie A1 - Klettke, Meike ED - Boncz, Peter ED - Manegold, Stefan ED - Ailamaki, Anastasia ED - Deshpande, Amol ED - Kraska, Tim T1 - MigCast : Putting a Price Tag on Data Model Evolution in NoSQL Data Stores T2 - Proceedings of the 2019 International Conference on Management of Data (SIGMOD/PODS '19) June 2019, Amsterdam, Netherlands N2 - We demonstrate MigCast, a tool-based advisor for exploring data migration strategies in the context of developing NoSQL-backed applications. Users of MigCast can consider their options for evolving their data model along with legacy data already persisted in the cloud-hosted production data-base. They can explore alternative actions as the financial costs are predicted respective to the cloud provider chosen. Thereby they are better equipped to assess potential consequences of imminent data migration decisions. To this end, MigCast maintains an internal cost model, taking into account characteristics of the data instance, expected work-load, data model changes, and cloud provider pricing models. Hence, MigCast enables software project stakeholders to remain in control of the operative costs and to make informed decisions evolving their applications. KW - Data Migration Strategies KW - latency KW - migration costs KW - NoSQL databases KW - Predictive Migration KW - schema evolution Y1 - 2019 SN - 9781450356435 U6 - https://doi.org/10.1145/3299869.3320223 SP - 1925 EP - 1928 PB - ACM CY - New York, NY, USA ER - TY - CHAP A1 - Störl, Uta A1 - Müller, Daniel A1 - Klettke, Meike A1 - Scherzinger, Stefanie ED - Mitschang, Bernhard T1 - Enabling Efficient Agile Software Development of NoSQL-backed Applications 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 - NoSQL databases are popular in agile software development, where a frequently changing database schema imposes challenges for the production database. In this demo, we present Darwin, a middleware for systematic, tool-based support specifically designed for NoSQL database systems. Darwin carries out schema evolution and data migration tasks. To the best of our knowledge, Darwin is the first tool of its kind that supports both eager and lazy NoSQL data migration. Y1 - 2017 SN - 978-3-88579-659-6 PB - Gesellschaft für Informatik e.V. (GI) CY - Bonn ER - TY - CHAP A1 - Scherzinger, Stefanie A1 - Sombach, Stephanie A1 - Wiech, Katharina A1 - Klettke, Meike A1 - Störl, Uta T1 - Datalution: a tool for continuous schema evolution in NoSQL-backed web applications T2 - QUDOS 2016: Proceedings of the 2nd International Workshop on Quality-Aware DevOps N2 - When an incremental release of a web application is deployed, the structure of data already persisted in the production database may no longer match what the application code expects. Traditionally, eager schema migration is called for, where all legacy data is migrated in one go. With the growing popularity of schema-flexible NoSQL data stores, lazy forms of data migration have emerged: Legacy entities are migrated on-the-fly, one at-a-time, when they are loaded by the application. In this demo, we present Datalution, a tool demonstrating the merits of lazy data migration. Datalution can apply chains of pending schema changes, due to its Datalog-based internal representation. The Datalution approach thus ensures that schema evolution, as part of continous deployment, is carried out correctly. Y1 - 2016 U6 - https://doi.org/10.1145/2945408.2945416 SP - 38 EP - 39 PB - ACM ER - TY - JOUR A1 - Klettke, Meike A1 - Scherzinger, Stefanie A1 - Störl, Uta T1 - Datenbanken ohne Schema? JF - Datenbank-Spektrum N2 - In der Entwicklung von interaktiven Web-Anwendungen sind NoSQL-Datenbanksysteme zunehmend beliebt, nicht zuletzt, weil sie flexible Datenmodelle erlauben. Das erleichtert insbesondere ein agiles Projektmanagement, das sich durch häufige Releases und entsprechend häufige Änderungen am Datenmodell auszeichnet. In diesem Artikel geben wir einen Überblick über die besonderen Herausforderungen der agilen Anwendungsentwicklung gegen schemalose NoSQL-Datenbanksysteme. Wir stellen Strategien für die Schema-Evolution aus der Praxis vor, und postulieren unsere Vision einer eigenen Schema-Management-Komponente für NoSQL-Datenbanksysteme, die für eine kontinuierliche und systematische Schema-Evolution ausgelegt ist. KW - NoSQL-Datenbanksysteme KW - Schema-Evolution KW - Schema-Informationen Y1 - 2014 U6 - https://doi.org/10.1007/s13222-014-0156-z VL - 14 IS - 2 SP - 119 EP - 129 PB - Springer ER - TY - JOUR A1 - Störl, Uta A1 - Klettke, Meike A1 - Scherzinger, Stefanie T1 - Kurz erklärt: Objekt-NoSQL-Mapping JF - Datenbank-Spektrum Y1 - 2016 U6 - https://doi.org/10.1007/s13222-016-0212-y VL - 16 IS - 1 SP - 83 EP - 87 PB - Springer ER -