15.00 - Case Study 2: Highly Nonunique Primary Index Values - Teradata Database

Teradata Database Design

prodname
Teradata Database
vrm_release
15.00
category
User Guide
featnum
B035-1094-015K

Case Study 2: Highly Nonunique Primary Index Values

This study defines a NUPI on customer_status. Because there are only two distinct values for this attribute (Active and Inactive), all rows hash to two AMPs, leaving the other four AMPs in the system unaffected by the customer table.

Distributions that are skewed like this cause major performance problems because they fail to harness the powerful parallel processing capabilities that make Teradata unique among commercially available relational database management systems.

The illustration shows the customer table rows stored on only two AMPs.