IQ Indexes

Before creating IQ indexes, you should consider the implications of various types of indexes on the database server memory and disk space.

The set of indexes you define for any given column can have dramatic impact on the speed of query processing. There are four main criteria for choosing indexes:

Number of unique values
Types of queries
Disk space usage
Data types

It is best to consider all criteria in combination, rather than individually. To decide on indexes, look closely at the data in each column.

Try to anticipate the number of unique and total values, the query results users will want from it, and whether the data will be used in ad hoc joins or join indexes.

For more information about choosing index types, see chapter Adaptive Server IQ Indexes in the Adaptive Server IQ Administration and Performance Guide.

Rebuilding IQ Indexes
As you develop a PDM or modify an existing one, you may change data types, alter the percentage of distinct values or change the number of values in tables. You must then rebuild the IQ indexes to reflect these changes.
Index Types
When you rebuild indexes, PowerDesigner determines the index type based on information contained from the table statistics. It uses the number field, which indicates the estimated number of records per table, and the percentage of distinct values to compute the number of unique values. If the user has not specified a number of rows for the table, PD assumes that the table will include at least 1 row of data.

Parent topic: Sybase IQ