首页 > 数据库 > Oracle > 使用SQL PROFILE 给出合理的执行计划
SQL> drop table t purge;
Table dropped.
SQL> create table t as select object_id,object_name from dba_objects;
Table created.
SQL> insert into t select * from t;
14140 rows created.
SQL> /
28280 rows created.
SQL> /
56560 rows created.
SQL> /
113120 rows created.
SQL> update t set object_name='T';
226240 rows updated.
SQL> UPDATE T SET OBJECT_NAME='T1' WHERE ROWNUM=1;
1 row updated.
SQL> COMMIT;
Commit complete.
SQL>declare
my_task_name varchar2(30);
mysqltext clob;
begin
mysqltext := 'select * from t where object_NAME=''T1''';
my_task_name := dbms_sqltune.create_tuning_task(sql_text => mysqltext,
user_name => 'SCOTT',
scope => 'COMPREHENSIVE',
task_name => 'sql_tuning_test');
end;
/
PL/SQL procedure successfully completed.
SQL> exec dbms_sqltune.execute_tuning_task('sql_tuning_test');
PL/SQL procedure successfully completed.
SQL> SET LONG 999999
SQL> SET LINESIZE 1000
SQL> set serveroutput on size 999999
SQL> select dbms_sqltune.report_tuning_task('sql_tuning_test') from dual;
GENERAL INFORMATION SECTION
-------------------------------------------------------------------------------
Tuning Task Name : sql_tuning_test
Tuning Task Owner : SCOTT
Workload Type : Single SQL Statement
Scope : COMPREHENSIVE
Time Limit(seconds): 1800
Completion Status : COMPLETED
Started at : 08/25/2015 15:09:49
Completed at : 08/25/2015 15:09:50
-------------------------------------------------------------------------------
Schema Name: SCOTT
SQL ID : 2qkpfwtzpdc0d
SQL Text : select * from t where object_NAME='T1'
-------------------------------------------------------------------------------
FINDINGS SECTION (2 findings)
-------------------------------------------------------------------------------
1- Statistics Finding
---------------------
尚未分析表 "SCOTT"."T"。
Recommendation
--------------
- 考虑收集此表的优化程序统计信息。
execute dbms_stats.gather_table_stats(ownname => 'SCOTT', tabname => 'T',
estimate_percent => DBMS_STATS.AUTO_SAMPLE_SIZE, method_opt =>
'FOR ALL COLUMNS SIZE AUTO');
Rationale
---------
为了选择好的执行计划, 优化程序需要此表的最新统计信息。
2- Index Finding (see explain plans section below)
--------------------------------------------------
通过创建一个或多个索引可以改进此语句的执行计划。
Recommendation (estimated benefit: 99.1%)
-----------------------------------------
- 考虑运行可以改进物理方案设计的访问指导或者创建推荐的索引。
create index SCOTT.IDX$$_07230001 on SCOTT.T("OBJECT_NAME","OBJECT_ID");
Rationale
---------
创建推荐的索引可以显著地改进此语句的执行计划。但是, 使用典型的 SQL 工作量运行 "访问指导"
可能比单个语句更可取。通过这种方法可以获得全面的索引建议案, 包括计算索引维护的开销和附加的空间消耗。
-------------------------------------------------------------------------------
EXPLAIN PLANS SECTION
-------------------------------------------------------------------------------
1- Original
-----------
Plan hash value: 1601196873
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 11 | 869 | 224 (1)| 00:00:03 |
|* 1 | TABLE ACCESS FULL| T | 11 | 869 | 224 (1)| 00:00:03 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("OBJECT_NAME"='T1')
2- Using New Indices
--------------------
Plan hash value: 3722711773
-----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 79 | 2 (0)| 00:00:01 |
|* 1 | INDEX RANGE SCAN| IDX$$_07230001 | 1 | 79 | 2 (0)| 00:00:01 |
-----------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("OBJECT_NAME"='T1')
-------------------------------------------------------------------------------
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