Sybase 12.4.2 manual Overview of indexes, Adaptive Server IQ index types, Indexing, 135

C H A P T E R 4 Adaptive Server IQ Indexes

About this chapter	This chapter describes the Adaptive Server IQ index types. It explains
	how you create an index, and provides information to help you decide
	what index types are best suited for the way you use the data in your
	database. It also includes performance and resource issues related to
	indexing.

Overview of indexes

Indexes are used to improve data retrieval performance. Traditional indexes use a B-tree index strategy to point to the data records. That strategy is valuable only if many unique data values are used to filter down to a very small set of records, as with columns of order numbers or customer names, as you would encounter in a transaction processing system.

Adaptive Server IQ indexes actually represent and store the data so that the data can be used for processing queries. This strategy is designed for the data warehousing environment, in which queries typically examine enormous numbers of records, often with relatively few unique values, and in which aggregate results are commonly required.

Adaptive Server IQ index types

When you load data into a table, Adaptive Server IQ stores data by column rather than by row, for each column in the table. The column orientation gives IQ indexes important advantages over traditional row-based indexing. Column storage structures your data according to the attributes you are interested in tracking. In a data warehousing environment, usually you want to look at specific attributes of thousands or millions of rows of data, rather than complete, single rows of data that typically are the focus in transaction processing. Column storage optimizes your ability to perform selections or calculations on the attributes you care about.

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