3.5.IQ索引介绍.pdf

中国农业银行 Sybase数据库技术培训 ——IQ 索引介绍 王兵 wangb@global-tec.net 北京寰信通科技有限公司 Beijing Global Technology Co. Ltd. 2007年9月27 日 Global Technology Page 1 Types of Indexes Used by Typical RDBMSs Many databases use a balanced-tree (B- tree) index Global Technology Page 2 IQ’s Bitmap Indexes Bitmaps represent the given value as a particular bit mask (for example: 0, 1) Efficiently indexes data regardless of cardinality Easier to maintain (no need to drop and build indexes) Global Technology Page 3 IQ Index Characteristics Fast to load, fast to query Compact Requires less disk space than traditional B-tree indexes More data can be kept in memory Column-wise storage structures Key to fast query resolution IQ Index type selection is based on data type, cardinality, and how a column is used in queries Each index (access method) is stored and manipulated differently Can incrementally add, update or delete rows with rebuilding Global Technology Page 4 IQ Indexes in Queries Unlike other relational databases IQ will use all indexes on all columns used in query operations involving Count() and Count Distinct, Datepart functions Table Joins Where Clause search arguments Group By clauses To support a robust ad-hoc query environment you will want to create many indexes on your tables Global Technology Page 5 Review: Nine Index Types Global Technology