The code gets reprogrammed and some of the code is no longer needed with the passage of time and then you need to ensure any new development avoids referencing old APIs. Removing old code can be a problem as far as backwards compatibility is concerned. Oracle database 12.2 introduces the "DEPRECATE PRAGMA" to mark code as deprecated and display compiler warnings if deprecated code is referenced by any newly compiled code.
How To Use DEPRECATE PRAGMA
Compiler warnings must be enabled for us to see the results of the
DEPRECATE pragma.-- Enable just deprecated code warnings.
ALTER SESSION SET PLSQL_WARNINGS='ENABLE:(6019,6020,6021,6022)';
-- Enable all warnings.
ALTER SESSION SET PLSQL_WARNINGS='ENABLE:ALL';
The
DEPRECATE pragma has two variations. Without an additional literal the standard messages are displayed. Not surprisingly, when we compile the deprecated code we see a message.
CREATE OR REPLACE PROCEDURE my_proc AUTHID DEFINER AS
PRAGMA DEPRECATE(my_proc);
BEGIN
NULL;
END;
/
SP2-0804: Procedure created with compilation warnings
SQL> SHOW ERRORS
Errors for PROCEDURE MY_PROC:
-------- -----------------------------------------------------------------
LINE/COL ERROR
2/3 PLW-06019: entity MY_PROC is deprecated
SQL>
More importantly, if we write some code that references the deprecated procedure we will see a warning.
CREATE OR REPLACE PROCEDURE my_calling_proc AUTHID DEFINER AS
BEGIN
my_proc;
END;
/
SQL> SHOW ERRORS
SP2-0804: Procedure created with compilation warnings
-------- -----------------------------------------------------------------
Errors for PROCEDURE MY_CALLING_PROC:
LINE/COL ERROR
SQL>
3/3 PLW-06020: reference to a deprecated entity: MY_PROC declared in
unit MY_PROC[1,11]
We can use a literal string to alter the compiler warning message, which can be used to indicate the API we should have called rather than the deprecated API.
CREATE OR REPLACE PROCEDURE my_proc AUTHID DEFINER AS
PRAGMA DEPRECATE(my_proc, 'Use MY_PROC2 instead of MY_PROC.');
BEGIN
NULL;
END;
/
SP2-0804: Procedure created with compilation warnings
SQL> SHOW ERRORS
Errors for PROCEDURE MY_PROC:
-------- -----------------------------------------------------------------
LINE/COL ERROR
2/3 PLW-06019: entity MY_PROC is deprecated
CREATE OR REPLACE PROCEDURE my_calling_proc AUTHID DEFINER AS
SQL>
BEGIN
my_proc;
END;
/
-------- -----------------------------------------------------------------
Errors for PROCEDURE MY_CALLING_PROC:
LINE/COL ERROR
3/3 PLW-06020: reference to a deprecated entity: MY_PROC declared in
unit MY_PROC[1,11]. Use MY_PROC2 instead of MY_PROC.
SQL>
How To Deprecate Packages
A whole package can be deprecated as follows.
CREATE OR REPLACE PACKAGE my_package AUTHID DEFINER AS
PRAGMA DEPRECATE(my_package);
PROCEDURE my_procedure;
PROCEDURE my_procedure(p_in IN NUMBER);
FUNCTION my_function RETURN NUMBER;
SP2-0808: Package created with compilation warnings
END my_package;
/
SQL> SHOW ERRORS
-------- -----------------------------------------------------------------
Errors for PACKAGE MY_PACKAGE:
LINE/COL ERROR
SQL>
2/3 PLW-06019: entity MY_PACKAGE is deprecated
We can mark individual items in the package as deprecated, rather than the whole package.
CREATE OR REPLACE PACKAGE my_package AUTHID DEFINER AS
PROCEDURE my_procedure;
PRAGMA DEPRECATE(my_procedure);
PROCEDURE my_procedure(p_in IN NUMBER);
FUNCTION my_function RETURN NUMBER;
SP2-0808: Package created with compilation warnings
END my_package;
/
SQL> SHOW ERRORS
-------- -----------------------------------------------------------------
Errors for PACKAGE MY_PACKAGE:
LINE/COL ERROR
SQL>
3/3 PLW-06019: entity MY_PROCEDURE is deprecated
We can also mark package cursors, types, variables and exceptions as deprecated.
CREATE OR REPLACE PACKAGE my_package AUTHID DEFINER AS
CURSOR c_cursor IS
SELECT dummy FROM dual;
PRAGMA DEPRECATE(c_cursor);
TYPE t_rec IS RECORD (
id NUMBER,
description VARCHAR2(50)
);
PRAGMA DEPRECATE(t_rec);
g_var NUMBER := 1;
PRAGMA DEPRECATE(g_var);
ex_my_exception EXCEPTION;
PRAGMA DEPRECATE (ex_my_exception);
END my_package;
/
SP2-0808: Package created with compilation warnings
SQL> SHOW ERRORS
Errors for PACKAGE MY_PACKAGE:
-------- -----------------------------------------------------------------
LINE/COL ERROR
EXCEPTION_INIT
0/0 PLW-05021: exception EX_MY_EXCEPTION does not have a pragma
10/3 PLW-06019: entity T_REC is deprecated
4/3 PLW-06019: entity C_CURSOR is deprecated
12/9 PLW-06026: package specification exposes global variable
SQL>
13/3 PLW-06019: entity G_VAR is deprecated
16/3 PLW-06019: entity EX_MY_EXCEPTION is deprecated
How To Deprecate Object Types
We can deprecate object types and their member functions in a similar way to packages. The following example deprecates the whole object type.
CREATE OR REPLACE TYPE t_my_type AUTHID DEFINER AS OBJECT (
PRAGMA DEPRECATE(t_my_type),
id NUMBER,
description VARCHAR2(50),
MEMBER PROCEDURE my_procedure,
MEMBER FUNCTION my_function RETURN NUMBER
);
/
SP2-0816: Type created with compilation warnings
SQL> SHOW ERRORS
Errors for TYPE T_MY_TYPE:
-------- -----------------------------------------------------------------
LINE/COL ERROR
5/10 PLW-07203: parameter 'SELF' may benefit from use of the NOCOPY
2/3 PLW-06019: entity T_MY_TYPE is deprecated
SQL>
compiler hint
The following example deprecates individual properties and member functions.
CREATE OR REPLACE TYPE t_my_type AUTHID DEFINER AS OBJECT (
id NUMBER,
description VARCHAR2(50),
PRAGMA DEPRECATE(description),
MEMBER PROCEDURE my_procedure,
PRAGMA DEPRECATE(my_procedure),
MEMBER FUNCTION my_function RETURN NUMBER
);
/
SP2-0816: Type created with compilation warnings
SQL> SHOW ERRORS
Errors for TYPE T_MY_TYPE:
-------- -----------------------------------------------------------------
LINE/COL ERROR
5/10 PLW-07203: parameter 'SELF' may benefit from use of the NOCOPY
4/3 PLW-06019: entity DESCRIPTION is deprecated
6/3 PLW-06019: entity MY_PROCEDURE is deprecated
compiler hint
SQL>
This is how Deprecate Pragma works.