Data Warehousing Modernization: Big Data Technology Implementation

Considering the challenges posed by Big Data, the cost to scale traditional data warehouses is high and the performances would be inadequate to meet the growing needs of the volume, variety and velocity of data. The Hadoop ecosystem answers both of the shortcomings. Hadoop has the ability to store and analyze large data sets in parallel on a distributed environment but cannot replace the existing data warehouses and RDBMS systems due to its own limitations explained in this paper. In this paper, I identify the reasons why many enterprises fail and struggle to adapt to Big Data technologies. A brief outline of two different technologies to handle Big Data will be presented in this paper: Using IBM’s Pure Data system for analytics (Netezza) usually used in reporting, and Hadoop with Hive which is used in analytics. Also, this paper covers the Enterprise architecture consisting of Hadoop that successful companies are adapting to analyze, filter, process, and store the data running along a massively parallel processing data warehouse. Despite, having the technology to support and process Big Data, industries are still struggling to meet their goals due to the lack of skilled personnel to study and analyze the data, in short data scientists and data statisticians

Evaluating partitioning and bucketing strategies for Hive-based Big Data Warehousing systems

Hive has long been one of the industry-leading systems for Data Warehousing in Big Data contexts, mainly organizing data into databases, tables, partitions and buckets, stored on top of an unstructured distributed file system like HDFS. Some studies were conducted for understanding the ways of optimizing the performance of several storage systems for Big Data Warehousing. However, few of them explore the impact of data organization strategies on query performance, when using Hive as the storage technology for implementing Big Data Warehousing systems. Therefore, this paper evaluates the impact of data partitioning and bucketing in Hive-based systems, testing different data organization strategies and verifying the efficiency of those strategies in query performance. The obtained results demonstrate the advantages of implementing Big Data Warehouses based on denormalized models and the potential benefit of using adequate partitioning strategies. Defining the partitions aligned with the attributes that are frequently used in the conditions/filters of the queries can significantly increase the efficiency of the system in terms of response time. In the more intensive workload benchmarked in this paper, overall decreases of about 40% in processing time were verified. The same is not verified with the use of bucketing strategies, which shows potential benefits in very specific scenarios, suggesting a more restricted use of this functionality, namely in the context of bucketing two tables by the join attribute of these tables.This work is supported by COMPETE: POCI-01-0145- FEDER-007043 and FCT—Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013, and by European Structural and Investment Funds in the FEDER com-ponent, through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project no. 002814; Funding Reference: POCI-01-0247-FEDER-002814]

The Family of MapReduce and Large Scale Data Processing Systems

In the last two decades, the continuous increase of computational power has produced an overwhelming flow of data which has called for a paradigm shift in the computing architecture and large scale data processing mechanisms. MapReduce is a simple and powerful programming model that enables easy development of scalable parallel applications to process vast amounts of data on large clusters of commodity machines. It isolates the application from the details of running a distributed program such as issues on data distribution, scheduling and fault tolerance. However, the original implementation of the MapReduce framework had some limitations that have been tackled by many research efforts in several followup works after its introduction. This article provides a comprehensive survey for a family of approaches and mechanisms of large scale data processing mechanisms that have been implemented based on the original idea of the MapReduce framework and are currently gaining a lot of momentum in both research and industrial communities. We also cover a set of introduced systems that have been implemented to provide declarative programming interfaces on top of the MapReduce framework. In addition, we review several large scale data processing systems that resemble some of the ideas of the MapReduce framework for different purposes and application scenarios. Finally, we discuss some of the future research directions for implementing the next generation of MapReduce-like solutions.Comment: arXiv admin note: text overlap with arXiv:1105.4252 by other author

Only Aggressive Elephants are Fast Elephants

Yellow elephants are slow. A major reason is that they consume their inputs entirely before responding to an elephant rider's orders. Some clever riders have trained their yellow elephants to only consume parts of the inputs before responding. However, the teaching time to make an elephant do that is high. So high that the teaching lessons often do not pay off. We take a different approach. We make elephants aggressive; only this will make them very fast. We propose HAIL (Hadoop Aggressive Indexing Library), an enhancement of HDFS and Hadoop MapReduce that dramatically improves runtimes of several classes of MapReduce jobs. HAIL changes the upload pipeline of HDFS in order to create different clustered indexes on each data block replica. An interesting feature of HAIL is that we typically create a win-win situation: we improve both data upload to HDFS and the runtime of the actual Hadoop MapReduce job. In terms of data upload, HAIL improves over HDFS by up to 60% with the default replication factor of three. In terms of query execution, we demonstrate that HAIL runs up to 68x faster than Hadoop. In our experiments, we use six clusters including physical and EC2 clusters of up to 100 nodes. A series of scalability experiments also demonstrates the superiority of HAIL.Comment: VLDB201

SAP HANA distributed in-memory database system: Transaction, session, and metadata management

One of the core principles of the SAP HANA database system is the comprehensive support of distributed query facility. Supporting scale-out scenarios was one of the major design principles of the system from the very beginning. Within this paper, we first give an overview of the overall functionality with respect to data allocation, metadata caching and query routing. We then dive into some level of detail for specific topics and explain features and methods not common in traditional disk-based database systems. In summary, the paper provides a comprehensive overview of distributed query processing in SAP HANA database to achieve scalability to handle large databases and heterogeneous types of workloads

Storage Format Selection and Optimization for Materialized Intermediate Results in Data-Intensive Flows

Modern organizations produce and collect large volumes of data, that need to be processed repeatedly and quickly for gaining business insights. For such processing, typically, Data-intensive Flows (DIFs) are deployed on distributed processing frameworks. The DIFs of different users have many computation overlaps (i.e., parts of the processing are duplicated), thus wasting computational resources and increasing the overall cost. The output of these computation overlaps (known as intermediate results) can be materialized for reuse, which helps in reducing the cost and saves computational resources if properly done. Furthermore, the way such outputs are materialized must be considered, as different storage layouts (i.e., horizontal, vertical, and hybrid) can be used to reduce the I/O cost. In this PhD work, we first propose a novel approach for automatically materializing the intermediate results of DIFs through a multi-objective optimization method, which can tackle multiple and conflicting quality metrics. Next, we study the behavior of different operators of DIFs that are the first to process the loaded materialized results. Based on this study, we devise a rule-based approach, that decides the storage layout for materialized results based on the subsequent operation types. Despite improving the cost in general, the heuristic rules do not consider the amount of data read while making the choice, which could lead to a wrong decision. Thus, we design a cost model that is capable of finding the right storage layout for every scenario. The cost model uses data and workload characteristics to estimate the I/O cost of a materialized intermediate results with different storage layouts and chooses the one which has minimum cost. The results show that storage layouts help to reduce the loading time of materialized results and overall, they improve the performance of DIFs. The thesis also focuses on the optimization of the configurable parameters of hybrid layouts. We propose ATUN-HL (Auto TUNing Hybrid Layouts), which based on the same cost model and given the workload and characteristics of data, finds the optimal values for configurable parameters in hybrid layouts (i.e., Parquet). Finally, the thesis also studies the impact of parallelism in DIFs and hybrid layouts. Our proposed cost model helps to devise an approach for fine-tuning the parallelism by deciding the number of tasks and machines to process the data. Thus, the cost model proposed in this thesis, enables in choosing the best possible storage layout for materialized intermediate results, tuning the configurable parameters of hybrid layouts, and estimating the number of tasks and machines for the execution of DIFs.Moderne Unternehmen produzieren und sammeln große Datenmengen, die wiederholt und schnell verarbeitet werden müssen, um geschäftliche Erkenntnisse zu gewinnen. Für die Verarbeitung dieser Daten werden typischerweise Datenintensive Prozesse (DIFs) auf verteilten Systemen wie z.B. MapReduce bereitgestellt. Dabei ist festzustellen, dass die DIFs verschiedener Nutzer sich in großen Teilen überschneiden, wodurch viel Arbeit mehrfach geleistet, Ressourcen verschwendet und damit die Gesamtkosten erhöht werden. Um diesen Effekt entgegenzuwirken, können die Zwischenergebnisse der DIFs für spätere Wiederverwendungen materialisiert werden. Hierbei müssen vor allem die unterschiedlichen Speicherlayouts (horizontal, vertikal und hybrid) berücksichtigt werden. In dieser Doktorarbeit wird ein neuartiger Ansatz zur automatischen Materialisierung der Zwischenergebnisse von DIFs durch eine mehrkriterielle Optimierungsmethode vorgeschlagen, der in der Lage ist widersprüchliche Qualitätsmetriken zu behandeln. Des Weiteren wird untersucht die Wechselwirkung zwischen verschiedenen peratortypen und unterschiedlichen Speicherlayouts untersucht. Basierend auf dieser Untersuchung wird ein regelbasierter Ansatz vorgeschlagen, der das Speicherlayout für materialisierte Ergebnisse, basierend auf den nachfolgenden Operationstypen, festlegt. Obwohl sich die Gesamtkosten für die Ausführung der DIFs im Allgemeinen verbessern, ist der heuristische Ansatz nicht in der Lage die gelesene Datenmenge bei der Auswahl des Speicherlayouts zu berücksichtigen. Dies kann in einigen Fällen zu falschen Entscheidung führen. Aus diesem Grund wird ein Kostenmodell entwickelt, mit dem für jedes Szenario das richtige Speicherlayout gefunden werden kann. Das Kostenmodell schätzt anhand von Daten und Auslastungsmerkmalen die E/A-Kosten eines materialisierten Zwischenergebnisses mit unterschiedlichen Speicherlayouts und wählt das kostenminimale aus. Die Ergebnisse zeigen, dass Speicherlayouts die Ladezeit materialisierter Ergebnisse verkürzen und insgesamt die Leistung von DIFs verbessern. Die Arbeit befasst sich auch mit der Optimierung der konfigurierbaren Parameter von hybriden Layouts. Konkret wird der sogenannte ATUN-HL Ansatz (Auto TUNing Hybrid Layouts) entwickelt, der auf der Grundlage des gleichen Kostenmodells und unter Berücksichtigung der Auslastung und der Merkmale der Daten die optimalen Werte für konfigurierbare Parameter in Parquet, d.h. eine Implementierung von hybrider Layouts. Schließlich werden in dieser Arbeit auch die Auswirkungen von Parallelität in DIFs und hybriden Layouts untersucht. Dazu wird ein Ansatz entwickelt, der in der Lage ist die Anzahl der Aufgaben und dafür notwendigen Maschinen automatisch zu bestimmen. Zusammengefasst lässt sich festhalten, dass das in dieser Arbeit vorgeschlagene Kostenmodell es ermöglicht, das bestmögliche Speicherlayout für materialisierte Zwischenergebnisse zu ermitteln, die konfigurierbaren Parameter hybrider Layouts festzulegen und die Anzahl der Aufgaben und Maschinen für die Ausführung von DIFs zu schätzen