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1) Package Initilization Performance Research

1@@@@ Cache a whole list of values (memory table)

You had batter exist a primary key for your test table, index by primary key

, moreover, you had batter choose the integer as the primary key.

such as the contents of a static, reference code lookup table.

Note:

The version of memory table is stoped in the loaded time

@@@Example: Prepare a emplu1 for handling exception in emplu2

And versus emplu2 which use memory table.

SYS@ocm> !cat tmp.sql

CREATE OR REPLACE PACKAGE emplu1

IS

FUNCTION onerow

( emp_id_in IN hr.employees.employee_id%TYPE )

RETURN hr.employees%ROWTYPE;

END;

/

CREATE OR REPLACE PACKAGE BODY emplu1

IS

FUNCTION onerow

( emp_id_in IN hr.employees.employee_id%TYPE )

RETURN hr.employees%ROWTYPE

IS

CURSOR onerow_cur IS

SELECT *

FROM hr.employees

WHERE employee_id = emp_id_in;

onerow_rec hr.employees%ROWTYPE;

BEGIN

OPEN onerow_cur;

FETCH onerow_cur INTO onerow_rec;

CLOSE onerow_cur;

RETURN onerow_rec;

END;

END;

/

SYS@ocm> @tmp.sql

Package created.

Package body created.

@@@Example: Cache table hr.employees to an associate array

calling data from the associate array.

SYS@ocm> !cat tmpx.sql

CREATE OR REPLACE PACKAGE emplu2

IS

FUNCTION onerow

( emp_id_in IN hr.employees.employee_id%TYPE )

RETURN hr.employees%ROWTYPE;

END;

/

CREATE OR REPLACE PACKAGE BODY emplu2

IS

----associate array " array(employee_id) := hr.employees%ROWTYPE "

TYPE tab_aat IS TABLE OF hr.employees%ROWTYPE

INDEX BY BINARY_INTEGER;

tab_aa tab_aat;

FUNCTION onerow

( emp_id_in IN hr.employees.employee_id%TYPE )

RETURN hr.employees%ROWTYPE

IS

BEGIN

RETURN tab_aa(emp_id_in);

EXCEPTION

WHEN NO_DATA_FOUND THEN

RETURN emplu1.onerow(emp_id_in);

END;

BEGIN

FOR rec IN (SELECT * FROM hr.employees)

LOOP

tab_aa(rec.employee_id) := rec;

END LOOP;

END;

/

SYS@ocm> @tmpx.sql

Package created.

Package body created.

@@@Create a anonymous block to test.

SYS@ocm> !cat test.sql

DECLARE

PROCEDURE test_memory_tab

( counter IN INTEGER

, emp_id_in IN hr.employees.employee_id%TYPE )

IS

emprec hr.employees%ROWTYPE;

BEGIN

sf_timer.set_factor(counter);

sf_timer.start_timer;

FOR i IN 1 .. counter

LOOP

emprec := emplu1.onerow(emp_id_in);

END LOOP;

sf_timer.show_elapsed_time('database table');

sf_timer.set_factor(counter);

sf_timer.start_timer;

FOR i IN 1 .. counter

LOOP

emprec := emplu2.onerow(emp_id_in);

END LOOP;

sf_timer.show_elapsed_time('memory table');

END;

BEGIN

test_memory_tab(10000000, 100);

END;

/

SYS@ocm> @test.sql

database table - Elapsed CPU : 197.48 seconds. Factored: .00002 seconds.

memory table - Elapsed CPU : 5.72 seconds. Factored: 0 seconds.

PL/SQL procedure successfully completed.

Summary:

Exactly quicker.

emplu1 grain data from cursor, even though it could cached in Share Pool,

so-called soft prase, still slow

emplu2 grain data from PGA, it is faster.

2@@@@ Cache a single value, such as the name of the current user

the global variable g_user hold the value of STANDARD.USER.

If you calling the function repetitively, It would be return from

cache, so more speed then run STANDARD.USER function each time.

Use the constant is fastest.

SYS@ocm> !cat tmp.sql

CREATE OR REPLACE PACKAGE thisuser

IS

cname CONSTANT VARCHAR2(30) := USER;

FUNCTION name RETURN VARCHAR2;

END;

/

CREATE OR REPLACE PACKAGE BODY thisuser

IS

g_user VARCHAR2(30) := USER;

FUNCTION name RETURN VARCHAR2 IS

BEGIN

RETURN g_user;

END;

END;

/

SYS@ocm> @tmp.sql

Package created.

Package body created.

@@@Package Constant is fastest, but danger, It is public

SYS@ocm> !cat test_thisuser.sql

CREATE OR REPLACE PROCEDURE test_thisuser

( count_in IN PLS_INTEGER )

IS

l_name all_users.username%TYPE;

BEGIN

----1. Use package function testuser.name

sf_timer.start_timer;

FOR i IN 1 .. count_in

LOOP

l_name := thisuser.name;

END LOOP;

sf_timer.show_elapsed_time('Packaged Function');

----2. Use the Package Constant

sf_timer.start_timer;

FOR i IN 1 .. count_in

LOOP

l_name := thisuser.cname;

END LOOP;

sf_timer.show_elapsed_time('Packaged Contant ');

----3. Use the built-in function STANDARD.USER

sf_timer.start_timer;

FOR i IN 1 .. count_in

LOOP

l_name := USER;

END LOOP;

sf_timer.show_elapsed_time('USER Function');

END test_thisuser;

/

BEGIN

test_thisuser(10000000);

END;

/

SYS@ocm> @test_thisuser.sql

Procedure created.

Packaged Function - Elapsed CPU : 2.03 seconds.

Packaged Contant - Elapsed CPU : .47 seconds.

USER Function - Elapsed CPU : 78.04 seconds.

PL/SQL procedure successfully completed.

Summary:

Package function is use the private variable or constant, it is more save

, after all it would be modifed by user when constant in package header.

At last, package function which use private variable is best, even though it

is not fastest.
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