15.00 - Collecting Statistics on a Secondary Index - Teradata Database

Teradata Database SQL Data Definition Language Detailed Topics

Product
Teradata Database
Release Number
15.00
Content Type
Programming Reference
Publication ID
B035-1184-015K
Language
English (United States)

Collecting Statistics on a Secondary Index

You should collect statistics on your secondary indexes to enable the Optimizer to make the best use of them.

Note: You cannot collect statistics on a UDT column. This includes UDT columns that are components of an index. The Optimizer uses dynamic AMP sampling information for equality predicates on UDT columns and default selectivity for other predicates on UDT indexes for costing. The dynamic AMP sampling provides limited statistics information about the index. For example, it cannot detect nulls or skew. If a UDT index access path does not show any improved performance, you should consider dropping the index to avoid the overhead involved in its storage and maintenance.