Index Structures Lecture 13: Choosing the Right Index Structure, Slides of Research Methodology

Download Index Structures Lecture 13: Choosing the Right Index Structure and more Slides Research Methodology in PDF only on Docsity! Objectives_template file:///C|/Documents%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/ist_data/lecture13/13_1.htm[6/14/2012 3:37:10 PM] Module 4: Index Structures Lecture 13: Index structure The Lecture Contains: Index structure Binary search tree (BST) B-tree B+-tree Order Objectives_template file:///C|/Documents%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/ist_data/lecture13/13_2.htm[6/14/2012 3:37:10 PM] Module 4: Index Structures Lecture 13: Index structure Index structure Five important questions when deciding on an index structure: Type of data Points or shapes or intervals Discrete or continuous Dimensionality and/or distance Queries on data Index data or index space where data resides Static or dynamic Memory (small) or disk-resident (large) Objectives_template file:///C|/Documents%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/ist_data/lecture13/13_5.htm[6/14/2012 3:37:10 PM] Module 4: Index Structures Lecture 13: Index structure Binary search tree (BST) Binary tree Unbalanced If a node has key , then every key in left subtree and every key in right subtree follows the properties: Searching, insertion, deletion takes time on average. Worst-case times are due to unbalanced property. AVL-trees, Red-black trees, etc. are balanced. Objectives_template file:///C|/Documents%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/ist_data/lecture13/13_6.htm[6/14/2012 3:37:11 PM] Module 4: Index Structures Lecture 13: Index structure B-tree A B-tree of order has the following properties: Leaf nodes are in same level (balanced) and contain no data Internal nodes (not the root) have between and 2 keys Root has at least 1 key An internal node with keys have children Child pointers in leaf nodes are null Branching factor = Objectives_template file:///C|/Documents%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/ist_data/lecture13/13_7.htm[6/14/2012 3:37:11 PM] Module 4: Index Structures Lecture 13: Index structure B+-tree Balanced All data are in the leaf nodes Leaf nodes have keys and data pointers Internal nodes contain keys and child pointers Keys dene range of values for children Often siblings are connected by pointers to avoid parent traversal