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Add Aggregate Tables
Aggregate tables are among the most important methods that can be used to improve query performance. Ralph Kimball asserts in his books on Data Warehousing that they are the single most effective method a designer or administrator has to improve query performance.
The reason why aggregate tables are so powerful is clear; once aggregate tables have been created and identified as data sources, the Siebel Analytics server can rewrite queries to reference the smaller, more compact aggregate tables instead of larger detail tables. Any server can read thousands of rows much faster than it can read, join, group, order, and process millions of rows.
Typically, aggregate tables greatly improve performance when the table compresses detail data by a factor of ten or more. By reducing the demand on resources, aggregate tables also effectively increase the capacity of a computer system.
Figure 3 illustrates a situation where a Monthly aggregate table would improve the performance of queries that summarize data to a monthly level. Siebel Analytics can also use the Monthly table to rewrite queries that summarize data at quarterly and yearly levels. Thus, there is no need to create, load, and manage the two additional higher-level aggregate tables.
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Siebel Analytics Performance Tuning Guide Published: 18 April 2003 |
