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Permanent link (DOI): https://doi.org/10.7939/R3RR1PT4M

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Theses and Dissertations

Trading Consistency for Synchronization Cost Reduction in Real-time On-Line Analytical Processing (OLAP) Systems Open Access

Descriptions

Other title
Subject/Keyword
Real-time OLAP
Inconsistency
Synchronization Reduction
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Li, You
Supervisor and department
Amaral, Jose(Computing Science)
Examining committee member and department
Zaïane, Osmar(Computing Science)
Lu, Paul(Computing Science)
Department
Department of Computing Science
Specialization

Date accepted
2014-09-29T14:22:45Z
Graduation date
2014-11
Degree
Master of Science
Degree level
Master's
Abstract
A real-time OLAP system caches previous queries' results to accelerate the processing of future queries. On such a system, whenever an update happens, affected cached values must be invalidated, or re-calculated, to maintain their consistency. Several different invalidation policies are used in real-time OLAP system. For all these policies, during the invalidation, the system must perform synchronization to ensure the consistency of cached values. Such synchronization can lead to poor scalability and may, therefore, dramatically degrades the throughput of the OLAP system. A synchronization-free invalidation policy was introduced in previous work to improve scalability. Such a policy results in stale cached values that can lead to incorrect query answers. To reduce the level of inconsistency in the system, this policy relies on independent threads, called {\it fresheners}, to recompute stale values. This thesis evaluates this policy with a manufacturer data set. It introduces new metrics to measure the level of inconsistency in the system. Based on these metrics, it measures the throughput improvement and number of incorrect results generated with this policy. Invalidation incurs high overhead even when the system is not performing synchronization. An alternative is to skip invalidation and to rely solely on fresheners to update incorrect results. This thesis introduces such a policy. This policy requires a more sophisticated strategy to keep the number of stale cached values to an acceptable level. This thesis also develops a framework to monitor the current status of the OLAP system and adjusts the number of fresheners. The goal of this framework is to deliver a stable, and acceptable, probability of incorrect results, due to stale cached values, under various workload.
Language
English
DOI
doi:10.7939/R3RR1PT4M
Rights
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
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