环境:

OS:Red Hat Linux As 5

DB:10.2.0.4

SQL Access Advisor是伴随着10G出现的一个优化工具,提供对表分区,物化视图,索引,物化视图日志优化建议.下边通过对单个SQL的执行,查看Oracle给出的建议.

1.建表并生成测试数据

SQL> connect scott/scott

Connected.

SQL> drop table tb_test;

SQL> create table tb_test(id number not null,name varchar2(30));

Table created.

SQL> create index idx_tb_test on tb_test(id);

Index created.

SQL> declare

begin

for i in 1 .. 100000 loop

insert into tb_test values (i, 'test');

commit;

end loop;

end;

2.分析表

connect / as sysdba

begin

dbms_stats.gather_table_stats(ownname => 'SCOTT', tabname => 'TB_TEST',cascade => true);

end;

3.使用dbms_advisor.quick_tune生成优化建议

connect / as sysdba

declare

l_task_name VARCHAR2(255);

l_sql_stmt  VARCHAR2(4000);

begin

l_sql_stmt  := 'select /*+ full(t) */ * from scott.tb_test t where t.id = :1';

l_task_name := 'MY_FULL_ACCESS_TEST';

DBMS_ADVISOR.QUICK_TUNE(DBMS_ADVISOR.SQLACCESS_ADVISOR,

l_task_name,

l_sql_stmt);

exception when others then dbms_output.put_line(sqlerrm);

end;

我们这里造一个走全表扫描的索引,很明显走索引才是正确的,这里的目的主要是看oracle会给出什么样的建议.

4.查看优化建议

SQL> set serveroutput on;

SQL> set long 999999999;

SQL> begin

show_recm('MY_FULL_ACCESS_TEST');

end;

=========================================

Task_name = MY_FULL_ACCESS_TEST

Action ID: 1

Command : RETAIN INDEX

Attr1 (name)      : "SCOTT"."IDX_TB_TEST_N1"

Attr2 (tablespace):

Attr3             : "SCOTT"."TB_TEST"

Attr4             : BTREE

Attr5             :

----------------------------------------

=========END RECOMMENDATIONS============

PL/SQL procedure successfully completed.

从以上输出可以看出oracle给出的建议是走索引.

show_recm过程如下:

CREATE OR REPLACE PROCEDURE show_recm (in_task_name IN VARCHAR2) IS

CURSOR curs IS

SELECT DISTINCT action_id, command, attr1, attr2, attr3, attr4

FROM dba_advisor_actions

WHERE task_name = in_task_name

ORDER BY action_id;

v_action        number;

v_command     VARCHAR2(32);

v_attr1       VARCHAR2(4000);

v_attr2       VARCHAR2(4000);

v_attr3       VARCHAR2(4000);

v_attr4       VARCHAR2(4000);

v_attr5       VARCHAR2(4000);

BEGIN

OPEN curs;

DBMS_OUTPUT.PUT_LINE('=========================================');

DBMS_OUTPUT.PUT_LINE('Task_name = ' || in_task_name);

LOOP

FETCH curs INTO

v_action, v_command, v_attr1, v_attr2, v_attr3, v_attr4 ;

EXIT when curs%NOTFOUND;

DBMS_OUTPUT.PUT_LINE('Action ID: ' || v_action);

DBMS_OUTPUT.PUT_LINE('Command : ' || v_command);

DBMS_OUTPUT.PUT_LINE('Attr1 (name)      : ' || SUBSTR(v_attr1,1,30));

DBMS_OUTPUT.PUT_LINE('Attr2 (tablespace): ' || SUBSTR(v_attr2,1,30));

DBMS_OUTPUT.PUT_LINE('Attr3             : ' || SUBSTR(v_attr3,1,30));

DBMS_OUTPUT.PUT_LINE('Attr4             : ' || v_attr4);

DBMS_OUTPUT.PUT_LINE('Attr5             : ' || v_attr5);

DBMS_OUTPUT.PUT_LINE('----------------------------------------');

END LOOP;

CLOSE curs;

DBMS_OUTPUT.PUT_LINE('=========END RECOMMENDATIONS============');

END show_recm;

-- The End --