Skip to Main Content
Oracle in a Nutshell
book

Oracle in a Nutshell

by Rick Greenwald, David C. Kreines
December 2002
Intermediate to advanced content levelIntermediate to advanced
928 pages
85h 29m
English
O'Reilly Media, Inc.
Content preview from Oracle in a Nutshell

Statistics

The cost of any particular portion of an execution plan depends on the composition of the target data structures. The cost-based optimizer uses statistics about the data (e.g., information about the size and uniqueness of data in tables and indexes) to create optimal execution plans.

The types of statistics used by the cost-based optimizer are shown in Table 17-2.

Table 17-2. Statistics used by cost-based analyzer

Entity

Type of statistic

Table

Number of rows

Number of blocks

Number of unused blocks

Average available free space per block

Number of chained rows

Average row length

Remote average row length

Column

Number of distinct values per column (cardinality)

Remote cardinality

Second lowest column value

Second highest column value

Column density factor

Number of NULLs for the column

Data distribution factor

Index

Depth of index B*-tree structure

Number of leaf blocks

Number of distinct values

Average number of leaf blocks per key

Average number of data blocks per key

Clustering factor

System

I/O performance and utilization (new in Oracle9i)

CPU performance and utilization (new in Oracle9i)

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Start your free trial

You might also like

Oracle Internals

Oracle Internals

Donald K. Burleson
Oracle PL/SQL

Oracle PL/SQL

Lewis Cunningham
Oracle Essentials: Oracle9i, Oracle8i and Oracle8, Second Edition

Oracle Essentials: Oracle9i, Oracle8i and Oracle8, Second Edition

Rick Greenwald, Robert Stackowiak, Jonathan Stern

Publisher Resources

ISBN: 0596003366Errata Page