【Oracle】SQL优化的重要工具--AUTOTRACE

【AUTOTRACE】SQL优化的重要工具--AUTOTRACE

提到SQL优化，不能不提AUTOTRACE的强大功能。使用起来非常便捷，不过在是使用之前，需要做一些配置的工作。简要的描述一下这个过程，供没有使用过的朋友参考。

1.使用sys用户执行plustrce脚本
sys@ora10g> @?/sqlplus/admin/plustrce
sys@ora10g> drop role plustrace;
drop role plustrace
*
ERROR at line 1:
ORA-01919: role 'PLUSTRACE' does not exist

sys@ora10g> create role plustrace;

Role created.

sys@ora10g> grant select on v_$sesstat to plustrace;

Grant succeeded.

sys@ora10g> grant select on v_$statname to plustrace;

Grant succeeded.

sys@ora10g> grant select on v_$mystat to plustrace;

Grant succeeded.

sys@ora10g> grant plustrace to dba with admin option;

Grant succeeded.

sys@ora10g> set echo off

2.将plustrace授权给public用户，以便保证所有用户都有权使用autotrace功能
sys@ora10g> grant plustrace to public;

Grant succeeded.

3.连接到具体的用户中，这里是sec用户
sys@ora10g> conn sec/sec
Connected.

4.使用“set autotrace”查看autotrace的命令提示
sec@ora10g> set autotrace
Usage: SET AUTOT[RACE] {OFF | ON | TRACE[ONLY]} [EXP[LAIN]] [STAT[ISTICS]]

5.这里演示一种设置方法
sec@ora10g> set autotrace traceonly
sec@ora10g> select * from cat;

20 rows selected.

Execution Plan
----------------------------------------------------------
Plan hash value: 3442307057

--------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 646 | 47804 | 33 (4)| 00:00:01 |
|* 1 | FILTER | | | | | |
|* 2 | TABLE ACCESS FULL | OBJ$ | 1324 | 97976 | 33 (4)| 00:00:01 |
|* 3 | TABLE ACCESS CLUSTER| TAB$ | 1 | 12 | 2 (0)| 00:00:01 |
|* 4 | INDEX UNIQUE SCAN | I_OBJ# | 1 | | 1 (0)| 00:00:01 |
--------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

1 - filter("O"."TYPE#"=4 OR "O"."TYPE#"=5 OR "O"."TYPE#"=6 OR
"O"."TYPE#"=2 AND NOT EXISTS (SELECT /*+ */ 0 FROM "SYS"."TAB$" "T"
WHERE "T"."OBJ#"=:B1 AND (BITAND("T"."PROPERTY",512)=512 OR
BITAND("T"."PROPERTY",8192)=8192)))
2 - filter("O"."OWNER#"=USERENV('SCHEMAID') AND "O"."LINKNAME" IS
NULL)
3 - filter(BITAND("T"."PROPERTY",512)=512 OR
BITAND("T"."PROPERTY",8192)=8192)
4 - access("T"."OBJ#"=:B1)

Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
207 consistent gets
0 physical reads
0 redo size
876 bytes sent via SQL*Net to client
492 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
20 rows processed

更多的有趣内容，请您慢慢挖掘。

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