Deferred Maintenance of Disk-Based Random Samples

Random sampling is a well-known technique for approximate processing of large datasets. We introduce a set of algorithms for incremental maintenance of large random samples on secondary storage. We show that the sample maintenance cost can be reduced by refreshing the sample in a deferred manner. We introduce a novel type of log file which follows the intuition that only a “sample” of the operations on the base data has to be considered to maintain a random sample in a statistically correct way. Additionally, we develop a deferred refresh algorithm which updates the sample by using fast sequential disk access only, and which does not require any main memory. We conducted an extensive set of experiments and found, that our algorithms reduce maintenance cost by several orders of magnitude

Optimized Generation and Maintenance of Materialized View using Adaptive Mechanism

Data Warehouse is storage of enormous amount of data gathered from multiple data sources, which is mainly used by managers for analysis purpose. Hence to make this data available in less amount of time is essential. Using Materialize view we can have result of query in less amount of time compared to access the same from base tables. To materialize all of the views is not possible since it requires storage space and maintenance cost. So it is required to select materialized view which minimizes response time of query and cost of maintenance. In this paper, effective approach is suggested for selection and maintenance of materialize view. DOI: 10.17762/ijritcc2321-8169.15050

Materialized View Replacement using Markovs Analysis

Materialized view is used in large data centric applications to expedite query processing. The efficiency of materialized view depends on degree of result found against the queries over the existing materialized views. Materialized views are constructed following different methodologies. Thus the efficacy of the materialized views depends on the methodology based on which these are formed. Construction of materialized views are often time consuming and moreover after a certain time the performance of the materialized views degrade when the nature of queries change. In this situation either new materialized views could be constructed from scratch or the existing views could be upgraded. Fresh construction of materialized views has higher time complexity hence the modification of the existing views is a better solution.Modification process of materialized view is classified under materialized view maintenance scheme. Materialized view maintenance is a continuous process and the system could be tuned to ensure a constant rate of performance. If a materialized view construction process is not supported by materialized view maintenance scheme that system would suffer from performance degradation. In this paper a new materialized view maintenance scheme is proposed using markovs analysis to ensure consistent performance. Markovs analysis is chosen here to predict steady state probability over initial probability

Data warehouse stream view update with multiple streaming.

The main objective of data warehousing is to store information representing an integration of base data from single or multiple data sources over an extended period of time. To provide fast access to the data, regardless of the availability of the data source, data warehouses often use materialized views. Materialized views are able to provide aggregation on some attributes to help Decision Support Systems. Updating materialized views in response to modifications in the base data is called materialized view maintenance. In some applications, for example, the stock market and banking systems, the source data is updated so frequently that we can consider them as a continuous stream of data. To keep the materialized view updated with respect to changes in the base tables in a traditional way will cause query response times to increase. This thesis proposes a new view maintenance algorithm for multiple streaming which improves semi-join methods and hash filter methods. Our proposed algorithm is able to update a view which joins two base tables where both of the base tables are in the form of data streams (always changing). By using a timestamp, building updategrams in parallel and by optimizing the joining cost between two data sources it can reduce the query response time or execution time significantly.Dept. of Computer Science. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .A336. Source: Masters Abstracts International, Volume: 44-03, page: 1391. Thesis (M.Sc.)--University of Windsor (Canada), 2005

Data warehouse stream view update with hash filter.

A data warehouse usually contains large amounts of information representing an integration of base data from one or more external data sources over a long period of time to provide fast-query response time. It stores materialized views which provide aggregation (SUM, MIX, MIN, COUNT and AVG) on some measure attributes of interest for data warehouse users. The process of updating materialized views in response to the modification of the base data is called materialized view maintenance. Some data warehouse application domains, like stock markets, credit cards, automated banking and web log domains depend on data sources updated as continuous streams of data. In particular, electronic stock trading markets such as the NASDAQ, generate large volumes of data, in bursts that are up to 4,200 messages per second. This thesis proposes a new view maintenance algorithm (StreamVup), which improves on semi join methods by using hash filters. The new algorithm first, reduce the amount of bytes transported through the network for streams tuples, and secondly reduces the cost of join operations during view update by eliminating the recompution of view updates caused by newly arriving duplicate tuples. (Abstract shortened by UMI.)Dept. of Computer Science. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .I85. Source: Masters Abstracts International, Volume: 42-05, page: 1753. Adviser: C. I. Ezeife. Thesis (M.Sc.)--University of Windsor (Canada), 2003

Maintenance-cost view-selection in large data warehouse systems: algorithms, implementations and evaluations.

Choi Chi Hon.Thesis (M.Phil.)--Chinese University of Hong Kong, 2003.Includes bibliographical references (leaves 120-126).Abstracts in English and Chinese.Abstract --- p.iAbstract (Chinese) --- p.iiAcknowledgement --- p.iiiContents --- p.ivList of Figures --- p.viiiList of Tables --- p.xChapter 1 --- Introduction --- p.1Chapter 1.1 --- Maintenance Cost View Selection Problem --- p.2Chapter 1.2 --- Previous Research Works --- p.3Chapter 1.3 --- Major Contributions --- p.4Chapter 1.4 --- Thesis Organization --- p.6Chapter 2 --- Literature Review --- p.7Chapter 2.1 --- Data Warehouse and OLAP Systems --- p.8Chapter 2.1.1 --- What Is Data Warehouse? --- p.8Chapter 2.1.2 --- What Is OLAP? --- p.10Chapter 2.1.3 --- Difference Between Operational Database Systems and OLAP --- p.10Chapter 2.1.4 --- Data Warehouse Architecture --- p.12Chapter 2.1.5 --- Multidimensional Data Model --- p.13Chapter 2.1.6 --- Star Schema and Snowflake Schema --- p.15Chapter 2.1.7 --- Data Cube --- p.17Chapter 2.1.8 --- ROLAP and MOLAP --- p.19Chapter 2.1.9 --- Query Optimization --- p.20Chapter 2.2 --- Materialized View --- p.22Chapter 2.2.1 --- What Is A Materialized View --- p.23Chapter 2.2.2 --- The Role of Materialized View in OLAP --- p.23Chapter 2.2.3 --- The Challenges in Exploiting Materialized View --- p.24Chapter 2.2.4 --- What Is View Maintenance --- p.25Chapter 2.3 --- View Selection --- p.27Chapter 2.3.1 --- Selection Strategy --- p.27Chapter 2.4 --- Summary --- p.32Chapter 3 --- Problem Definition --- p.33Chapter 3.1 --- View Selection Under Constraint --- p.33Chapter 3.2 --- The Lattice Framework for Maintenance Cost View Selection Prob- lem --- p.35Chapter 3.3 --- The Difficulties of Maintenance Cost View Selection Problem --- p.39Chapter 3.4 --- Summary --- p.41Chapter 4 --- What Difference Heuristics Make --- p.43Chapter 4.1 --- Motivation --- p.44Chapter 4.2 --- Example --- p.46Chapter 4.3 --- Existing Algorithms --- p.49Chapter 4.3.1 --- A*-Heuristic --- p.51Chapter 4.3.2 --- Inverted-Tree Greedy --- p.52Chapter 4.3.3 --- Two-Phase Greedy --- p.54Chapter 4.3.4 --- Integrated Greedy --- p.57Chapter 4.4 --- A Performance Study --- p.60Chapter 4.5 --- Summary --- p.68Chapter 5 --- Materialized View Selection as Constrained Evolutionary Opti- mization --- p.71Chapter 5.1 --- Motivation --- p.72Chapter 5.2 --- Evolutionary Algorithms --- p.73Chapter 5.2.1 --- Constraint Handling: Penalty v.s. Stochastic Ranking --- p.74Chapter 5.2.2 --- The New Stochastic Ranking Evolutionary Algorithm --- p.78Chapter 5.3 --- Experimental Studies --- p.81Chapter 5.3.1 --- Experimental Setup --- p.82Chapter 5.3.2 --- Experimental Results --- p.82Chapter 5.4 --- Summary --- p.89Chapter 6 --- Dynamic Materialized View Management Based On Predicates --- p.90Chapter 6.1 --- Motivation --- p.91Chapter 6.2 --- Examples --- p.93Chapter 6.3 --- Related Work: Static Prepartitioning-Based Materialized View Management --- p.96Chapter 6.4 --- A New Dynamic Predicate-based Partitioning Approach --- p.99Chapter 6.4.1 --- System Overview --- p.102Chapter 6.4.2 --- Partition Advisor --- p.103Chapter 6.4.3 --- View Manager --- p.104Chapter 6.5 --- A Performance Study --- p.108Chapter 6.5.1 --- Performance Metrics --- p.110Chapter 6.5.2 --- Feasibility Studies --- p.110Chapter 6.5.3 --- Query Locality --- p.112Chapter 6.5.4 --- The Effectiveness of Disk Size --- p.115Chapter 6.5.5 --- Scalability --- p.115Chapter 6.6 --- Summary --- p.116Chapter 7 --- Conclusions and Future Work --- p.118Bibliography --- p.12

The {RDF}-3X Engine for Scalable Management of {RDF} Data

RDF is a data model for schema-free structured information that is gaining momentum in the context of Semantic-Web data, life sciences, and also Web 2.0 platforms. The ``pay-as-you-go'' nature of RDF and the flexible pattern-matching capabilities of its query language SPARQL entail efficiency and scalability challenges for complex queries including long join paths. This paper presents the RDF-3X engine, an implementation of SPARQL that achieves excellent performance by pursuing a RISC-style architecture with streamlined indexing and query processing. The physical design is identical for all RDF-3X databases regardless of their workloads, and completely eliminates the need for index tuning by exhaustive indexes for all permutations of subject-property-object triples and their binary and unary projections. These indexes are highly compressed, and the query processor can aggressively leverage fast merge joins with excellent performance of processor caches. The query optimizer is able to choose optimal join orders even for complex queries, with a cost model that includes statistical synopses for entire join paths. Although RDF-3X is optimized for queries, it also provides good support for efficient online updates by means of a staging architecture: direct updates to the main database indexes are deferred, and instead applied to compact differential indexes which are later merged into the main indexes in a batched manner. Experimental studies with several large-scale datasets with more than 50 million RDF triples and benchmark queries that include pattern matching, manyway star-joins, and long path-joins demonstrate that RDF-3X can outperform the previously best alternatives by one or two orders of magnitude