You will be implementing a data warehouse for one of your customers. In your design process, which index type is most likely to be used to improve the performance of some queries where the data is…

The correct answer is A. Bitmap indexes. Bitmap indexes are a highly compressed index type that tends to be used primarily for data Characteristic of Bitmap Indexes For columns with very few unique values (low cardinality) Columns that have low cardinality are good candidates (if the cardinality of a column is <= 0.1…

Introduction to Data Warehousing Concepts

Question

You will be implementing a data warehouse for one of your customers. In your design process, which index type is most likely to be used to improve the performance of some queries where the data is of low cardinality?

Options

ABitmap indexes
BB*-tree indexes
CReverse indexes
DInvisible indexes

How the community answered

(33 responses)

A
82% (27)
B
12% (4)
C
3% (1)
D
3% (1)

Explanation

Bitmap indexes are a highly compressed index type that tends to be used primarily for data Characteristic of Bitmap Indexes * For columns with very few unique values (low cardinality) * Columns that have low cardinality are good candidates (if the cardinality of a column is <= 0.1 % that the column is ideal candidate, consider also 0.2% - 1%) * Tables that have no or little insert/update are good candidates (static data in warehouse) * Stream of bits: each bit relates to a column value in a single row of table

Topics

#bitmap indexes#low cardinality#index selection#query performance

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