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How To Find Optimal Index Key COMPRESS Level For Indexes (Doc ID 601690.1)

Last updated on AUGUST 04, 2018

Applies to:

Oracle Database - Enterprise Edition - Version 9.2.0.1 and later
Information in this document applies to any platform.
***Checked for relevance on 04-JUN-2014***


Goal

In a test comparing resulting object size and the COMPRESS integer for index key compression, increasing the COMPRESS integer when creating/altering indexes does not always result in a smaller size.

Example:

How do you know what the value of N should be for this SQL?

SQL> CREATE INDEX test_index
ON test_table (keycol1, keycol2, keycol3, keycol4, keycol5, keycol6)
COMPRESS N;

The following data was obtained by substituting various values for COMPRESS:

SIZE(MB) OPTION
======== ===========
200      COMPRESS
152      COMPRESS  1
144      COMPRESS  2
120      COMPRESS  3 <-- this would appear to be optimal for this example
168      COMPRESS  4
200      COMPRESS  5

Solution

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