Effect of a Split Interval on Simple Prefix B+-trees

This study examines the effect a split interval has on a simple pref ix B+-tree. A simple pref ix B+-tree is a cousin of the well-known B - tree indexing organization and a split interval is a proposed method to improve the performance of this organization. The purpose of this paper is to determine the usefulness of a split interval by empirically testing its effect on an experimental implementation of a simple pref ix B+-tree.Computing and Information Science

Study of Two Competing Index Mechanisms: Prefix B+-tree and Trie Structures

This thesis deals with two competing index mechanisms, namely, prefix B+-trees and trie structures, which are useful for handling varying size keys in document retrieval systems. Refinements and variants of these two indexing methods are studied. Tradeoffs of storage requirements and retrieval time or performance benefits and maintainance difficulties for various refining approaches are examined.Computing and Information Scienc

Prefix Recoding: a Front-end Compression Technique for Simple Prefix B-trees

This study examines the effect of receding common prefixes of shortest separators and thus extending the alphabet and compressing both the sequence set and the simple prefix B-tree index. The purpose of the study is to investigate the effect on a simple prefix B-tree of receding prefixes with a shorter symbol that maintains collating sequence order.Computing and Information Science

A Robust Scheme for Multilevel Extendible Hashing

Dynamic hashing, while surpassing other access methods for uniformly distributed data, usually performs badly for non-uniformly distributed data. We propose a robust scheme for multi-level extendible hashing allowing efficient processing of skewed data as well as uniformly distributed data. In order to test our access method we implemented it and compared it to several existing hashing schemes. The results of the experimental evaluation demonstrate the superiority of our approach in both index size and performance

The Ubiquitous B-tree: Volume II

Major developments relating to the B-tree from early 1979 through the fall of 1986 are presented. This updates the well-known article, The Ubiquitous B-Tree by Douglas Comer (Computing Surveys, June 1979). After a basic overview of B and B+ trees, recent research is cited as well as descriptions of nine B-tree variants developed since Comer\u27s article. The advantages and disadvantages of each variant over the basic B-tree are emphasized. Also included are a discussion of concurrency control issues in B-trees and a speculation on the future of B-trees

On Optimal Balance in B-Trees: What Does It Cost to Stay in Perfect Shape?

Any B-tree has height at least ceil[log_B(n)]. Static B-trees achieving this height are easy to build. In the dynamic case, however, standard B-tree rebalancing algorithms only maintain a height within a constant factor of this optimum. We investigate exactly how close to ceil[log_B(n)] the height of dynamic B-trees can be maintained as a function of the rebalancing cost. In this paper, we prove a lower bound on the cost of maintaining optimal height ceil[log_B(n)], which shows that this cost must increase from Omega(1/B) to Omega(n/B) rebalancing per update as n grows from one power of B to the next. We also provide an almost matching upper bound, demonstrating this lower bound to be essentially tight. We then give a variant upper bound which can maintain near-optimal height at low cost. As two special cases, we can maintain optimal height for all but a vanishing fraction of values of n using Theta(log_B(n)) amortized rebalancing cost per update and we can maintain a height of optimal plus one using O(1/B) amortized rebalancing cost per update. More generally, for any rebalancing budget, we can maintain (as n grows from one power of B to the next) optimal height essentially up to the point where the lower bound requires the budget to be exceeded, after which optimal height plus one is maintained. Finally, we prove that this balancing scheme gives B-trees with very good storage utilization

Similar pattern search for time-sectional oscillation in huge plasma waveform database

Recently there has been drastic data growth in many fusion plasma experiments. Some computer-aided assistance to find similar waveforms has become indispensable for accelerating data recognition and analysis. A similarity search for slowly varying waveforms, which applies “R-tree” index with Java implementation, was already reported [H. Nakanishi, T. Hochin, M. Kojima, LABCOM group, Search and retrieval method of similar plasma waveforms, Fusion Eng. Design 71 (1?4)(2004)189-193]. The next step is the search for time-sectional oscillation patterns. This requires neglecting the initial phase difference between many slices of waveforms. This new algorithm applies power spectrum density (PSD) values instead of FFT complex coefficients. To emphasize the difference between peak PSD frequency of each waveform, its Euclidean distance is multiplied by ωj/ωi (ωj>ωi). By applying “SR-tree” and fast numerical library implemented in C/C++, its computations have been accelerated. This enables the system to deal with much larger data sets. These modifications have successfully extended the application range toward them with verified accuracy

Relational-like file structure

The currently operational relational-like structure, as well as a primitive database management system is described. The proposed file structure integrates a B-tree variant, inverted files, and other structures to provide the underlying facility. The database management system supports multi-user, multi-database retrieval through relational views of both data and documents, as well as the interface to non-procedural languages. Emphasis regarding design decisions and tradeoffs were related to: 1) the Unix* operating system; 2) the access methods supported; 3) future development, such as document processing (information storage and retrieval), concurrency control and recovery