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Oracle Data Warehouse Tuning for 10g
book

Oracle Data Warehouse Tuning for 10g

by Gavin JT Powell
April 2011
Intermediate to advanced content levelIntermediate to advanced
504 pages
16h 49m
English
Digital Press
Content preview from Oracle Data Warehouse Tuning for 10g
3.1
The Basics of Indexing 59
Chapter 3
Note:
In a data warehouse where fact tables become very large, bitmap
indexes created on foreign key indexed dimensional values can equate to
thousands of values. However, the ratio of fact to dimensional table rows
still makes a bitmap index a viable option. Thus, low cardinality is a relative
term. In other words, creating a bitmap index on a male or female valued
column in a table containing two rows is completely pointless!
Figure 3.4
A compressed
composite column
BTree index.
Figure 3.5
A bitmap index.
60
3.1
The Basics of Indexing
Bitmap Performance
In general, a bitmap index occupies less physical space ...
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Publisher Resources

ISBN: 9781555583354