17.10 - Guidelines for Using Row Compression With Join Index Columns - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Definition Language Detailed Topics

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
Publication ID
B035-1184-171K
Language
English (United States)

A column set with a high number of distinct values cannot be row compressed because it rarely (and in the case of a primary key or unique index, never) repeats. Other column sets, notably foreign key and status code columns, are generally highly non-distinct: their values repeat frequently. Row compression capitalizes on the redundancy of frequently repeating column values by storing them once in the fixed part of the index row along with multiple repeated values in the repeated part of the index row. Typically, primary key table column values are specified as the repeating part and foreign key table columns are specified in the fixed part of the index definition.

See Teradata Vantage™ - Database Design, B035-1094 for more information about row compression for join indexes.