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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

RESTRICT_REFERENCES Pragma

Prior to Oracle8i, it was necessary to assert the purity level of a packaged procedure or function when using it directly or indirectly in a SQL statement. Beginning with Oracle8i, the PL/SQL runtime engine determines a program’s purity level automatically if no assertion exists. The RESTRICT REFERENCES pragma is still supported for backwards compatibility but it has been deprecated in Oracle9i.

The RESTRICT_REFERENCES pragma asserts a purity level. The syntax for the RESTRICT_REFERENCES pragma is:

PRAGMA RESTRICT_REFERENCES (program_name | DEFAULT, purity_level);

The keyword DEFAULT applies to all methods of an object type or all programs in a package.

You can specify from one to five purity levels, in any order, in a comma-delimited list. The purity level describes to what extent the program or method is free of side effects. Side effects are listed in the Table 9-3 with the purity levels they address.

Table 9-3. Purity levels and side effects

Purity level

Description

Restriction

WNDS

Write No Database State

Executes no INSERT, UPDATE, or DELETE statements

RNDS

Read No Database State

Executes no SELECT statements

WNPS

Write No Package State

Does not modify any package variables

RNPS

Read No Package State

Does not read any package variables

TRUST

Does not enforce the restrictions declared but allows the compiler to trust they are true

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Publisher Resources

ISBN: 0596003366Errata Page