17.10 - NUSI Bit Mapping - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Fundamentals

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
Publication ID
B035-1141-171K
Language
English (United States)

Bit mapping is a technique used by the Optimizer to effectively link several weakly selective indexes in a way that creates a result that drastically reduces the number of base rows that must be accessed to retrieve the desired data. The process determines common rowIDs among multiple NUSI values by means of the logical intersection operation.

Bit mapping is significantly faster than the three-part process of copying, sorting, and comparing rowID lists. Additionally, the technique dramatically reduces the number of base table I/Os required to retrieve the requested rows.

Related Information

  • When Vantage performs NUSI bit mapping, see Teradata Vantage™ - Database Design, B035-1094.
  • How NUSI bit maps are computed, see Teradata Vantage™ - Database Design, B035-1094.
  • Using the EXPLAIN modifier to determine if bit mapping is being used for your indexes, see Teradata Vantage™ - Database Design, B035-1094 or Teradata Vantage™ - SQL Data Manipulation Language, B035-1146.