17.10 - LT/ST-J1 Indexed Joins - Advanced SQL Engine - Teradata Database

Teradata Vantageā„¢ - SQL Request and Transaction Processing

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
User Guide
Publication ID
B035-1142-171K
Language
English (United States)

In the LT/ST-J1 class index join, some combination of the join columns of the small tables comprises an index of the large table.

Reasonable Indexed Joins, LT/ST-J1a

This subclass consists of those LT/ST-J1 joins in which the cardinality of the Cartesian product of the small tables is small relative to the cardinality of the large table.

The magnitude of this cardinality difference cannot be defined rigorously; it depends on factors such as the following:

  • Types of indexes defined
  • Conditions used by the old join plan
  • Conditions used by the new join plan
  • Size of the columns retrieved from the small tables

Unreasonable Indexed Joins, LT/ST-J1b

This subclass consists of all LT/ST-J1 joins that are not of subclass LT/ST-J1a (Reasonable Indexed Joins).