Taking the Shortcut: Actively Incorporating the Virtual Memory Index of the OS to Hardware-Accelerate Database Indexing

Index structures often materialize one or multiple levels of explicit indirections (aka pointers) to allow for a quick traversal to the data of interest. Unfortunately, dereferencing a pointer to go from one level to the other is costly since additionally to following the address, it involves two address translations from virtual memory to physical memory under the hood. In the worst case, such an address translation is resolved by an index access itself, namely by a lookup into the page table, a central hardware-accelerated index structure of the OS. However, if the page table is anyways constantly queried, it raises the question whether we can actively incorporate it into our database indexes and make it work for us. Precisely, instead of materializing indirections in form of pointers, we propose to express these indirections directly in the page table wherever possible. By introducing such shortcuts, we (a) effectively reduce the height of traversal during lookups and (b) exploit the hardware-acceleration of lookups in the page table. In this work, we analyze the strengths and considerations of this approach and showcase its effectiveness at the case of the real-world indexing scheme extendible hashing

Main Memory Adaptive Indexing for Multi-core Systems

Adaptive indexing is a concept that considers index creation in databases as a by-product of query processing; as opposed to traditional full index creation where the indexing effort is performed up front before answering any queries. Adaptive indexing has received a considerable amount of attention, and several algorithms have been proposed over the past few years; including a recent experimental study comparing a large number of existing methods. Until now, however, most adaptive indexing algorithms have been designed single-threaded, yet with multi-core systems already well established, the idea of designing parallel algorithms for adaptive indexing is very natural. In this regard only one parallel algorithm for adaptive indexing has recently appeared in the literature: The parallel version of standard cracking. In this paper we describe three alternative parallel algorithms for adaptive indexing, including a second variant of a parallel standard cracking algorithm. Additionally, we describe a hybrid parallel sorting algorithm, and a NUMA-aware method based on sorting. We then thoroughly compare all these algorithms experimentally; along a variant of a recently published parallel version of radix sort. Parallel sorting algorithms serve as a realistic baseline for multi-threaded adaptive indexing techniques. In total we experimentally compare seven parallel algorithms. Additionally, we extensively profile all considered algorithms. The initial set of experiments considered in this paper indicates that our parallel algorithms significantly improve over previously known ones. Our results suggest that, although adaptive indexing algorithms are a good design choice in single-threaded environments, the rules change considerably in the parallel case. That is, in future highly-parallel environments, sorting algorithms could be serious alternatives to adaptive indexing.Comment: 26 pages, 7 figure

The Easiest Way of Turning your Relational Database into a Blockchain -- and the Cost of Doing So

Blockchain systems essentially consist of two levels: The network level has the responsibility of distributing an ordered stream of transactions to all nodes of the network in exactly the same way, even in the presence of a certain amount of malicious parties (byzantine fault tolerance). On the node level, each node then receives this ordered stream of transactions and executes it within some sort of transaction processing system, typically to alter some kind of state. This clear separation into two levels as well as drastically different application requirements have led to the materialization of the network level in form of so-called blockchain frameworks. While providing all the "blockchain features", these frameworks leave the node level backend flexible or even left to be implemented depending on the specific needs of the application. In the following paper, we present how to integrate a highly versatile transaction processing system, namely a relational DBMS, into such a blockchain framework. As framework, we use the popular Tendermint Core, now part of the Ignite/Cosmos eco-system, which can run both public and permissioned networks and combine it with relational DBMSs as the backend. This results in a "relational blockchain", which is able to run deterministic SQL on a fully replicated relational database. Apart from presenting the integration and its pitfalls, we will carefully evaluate the performance implications of such combinations, in particular, the throughput and latency overhead caused by the blockchain layer on top of the DBMS. As a result, we give recommendations on how to run such a systems combination efficiently in practice

Welche ökonomischen Aspekte sollten in der Europäischen Verfassung berücksichtigt werden?

Im Dezember 2001 beschloss der Europäische Rat von Laeken, einen »Konvent zur Zukunft Europas« einzuberufen. Er erhielt den Auftrag, die Vereinfachung und Reorganisation der Verträge zu prüfen und eine Europäische Verfassung vorzubereiten. Die Verfassung soll die EU für das 21. Jahrhundert rüsten, insbesondere muss sie auch den Bedürfnissen der vielen neuen Mitglieder Rechnung tragen. Nach Ansicht von Prof. Dr. Bruno S. Frey, Institut für Empirische Wirtschaftsforschung der Universität Zürich, enthalten die bisher vorliegenden Verfassungsentwürfe kaum irgendwelche innovative Elemente. Nach wie vor stünden die Nationalstaaten im Zentrum. »Eine in die Zukunft orientierte Europäische Verfassung sollte ... genügend Flexibilität für die Entstehung neuer staatlicher Ordnungen aufweisen und nicht einfach die heute bestehenden Einheiten zementieren.« Prof. Dr. Charles B. Blankart, Humboldt Universität zu Berlin, und Prof. Dr. Dennis C. Mueller, Universität Wien, bezeichnen »die derzeitigen Entscheidungsstrukturen mit Rat und Parlament als konkurrierenden Organen« als unklar und widersprüchlich. Die zunächst notwendige Entscheidung in Richtung Staatenbund oder Bundesstaat sei bei der Zusammensetzung des Konvents aber kaum zu erwarten. Klaus Hänsch, MdEP, der Mitglied des Präsidiums des Konvents zur Zukunft Europas ist und die Arbeitsgruppe »Economic governance« leitet, betont dagegen, der Konvent habe den Auftrag, die Union demokratischer, transparenter und effizienter zu machen. Er ziele nicht darauf ab, die Politiken der Union neu zu definieren oder zu ändern.Verfassung, Europäische Wirtschafts- und Währungsunion, EU-Staaten

Molecular s-block metal hydrides : synthesis, structure and homogeneous catalysis

In this thesis, the synthesis and characterization of s-block metal hydrides, silicates and silanides and their reactivity as well as application as homogeneous catalysts is described

Die Umsetzung des Schutzauftrages zur Sicherung des Kindeswohlesgemäß § 8a SGB VIII im Jugendamt Chemnitz

Die Diplomarbeit befasst sich mit der praktischen Umsetzung des Schutzauftrages zur Sicherung des Kindeswohles gemäß § 8a SGB VIII des Jugendamtes in Chemnitz. Hierzu wurde eine empirische Untersuchung von 5 Fachteams des All-gemeinen Sozialen Dienstes als ein Sachgebiet des Jugendamtes durchgeführt. Mit Hilfe eines Fragebogens wird die Qualität des täglichen Handelns der Fach-kräfte des ASD des Jugendamtes Chemnitz in Bezug auf den § 8a SGB VIII ermittelt und der Fragestellung nachgegangen, ob ihre praktische Arbeit der rechtlichen Neuregelung gerecht werden kann. Die Ergebnisse der Befragung bezüglich der praktischen Umsetzung des § 8a SGB VIII im ASD des Jugendamtes Chemnitz wurden anhand der rechtlichen Neuregelung und der „Handlungsorientierung des Amtes für Jugend und Familie bei Kindesmisshandlung“ bewertet