今天看了老熊關於sql_profile的講解，受益匪淺，自己在本機也做了一通,感覺好記性不如爛筆頭還是得多總結總測試才能真正理解。 準備的資料如下，建立兩個表，一個大，一個小，然後做表分析 SQL> create table t1 as select object_id,object_name from dba_objects where rownum<=50000; Table created. SQL> create table t2 as select * from dba_objects; Table created. SQL> create index t2_idx on t2(object_id); Index created. SQL> exec dbms_stats.gather_table_stats(user,'t1',cascade=>true,method_opt=>'for all columns size 1'); PL/SQL procedure successfully completed. SQL> exec dbms_stats.gather_table_stats(user,'t2',cascade=>true,method_opt=>'for all columns size 1'); PL/SQL procedure successfully completed.

檢視task的name SQL> print tuning_task; TUNING_TASK -------------------------------------------------------------------------------------------------------------------------------- TASK_12352 如果sql語句本身不復雜，涉及的表不大的話，執行是很快的。如下檢視報告。 SQL> set long 99999 SQL> col comments format a200 SQL> SELECT dbms_sqltune.report_tuning_task(:tuning_task)COMMENTS FROM dual; COMMENTS -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- GENERAL INFORMATION SECTION ------------------------------------------------------------------------------- Tuning Task Name : TASK_12352 Tuning Task Owner : N1 Workload Type : Single SQL Statement Scope : COMPREHENSIVE Time Limit(seconds): 1800 Completion Status : COMPLETED Started at : 07/10/2014 15:04:18 Completed at : 07/10/2014 15:04:20 Schema Name: N1 SQL ID : 4zbqykx89yc8v SQL Text : select t1.*,t2.owner from t1,t2 where t1.object_name like '%T1%' and t1.object_id=t2.object_id ------------------------------------------------------------------------------- FINDINGS SECTION (1 finding) ------------------------------------------------------------------------------- 1- SQL Profile Finding (see explain plans section below) A potentially better execution plan was found for this statement. Recommendation (estimated benefit: 92.9%) ----------------------------------------- - Consider accepting the recommended SQL profile. execute dbms_sqltune.accept_sql_profile(task_name => 'TASK_12352',task_owner => 'N1', replace => TRUE); Validation results ------------------ The SQL profile was tested by executing both its plan and the original plan and measuring their respective execution statistics. A plan may have been only partially executed if the other could be run to completion in less time. Original Plan With SQL Profile % Improved ------------- ---------------- ---------- Completion Status: COMPLETE COMPLETE Elapsed Time (s): .042304 .006329 85.03 % CPU Time (s): .042293 .006399 84.86 % User I/O Time (s): 0 0 Buffer Gets: 4475 317 92.91 % Physical Read Requests: 0 0 Physical Write Requests: 0 0 Physical Read Bytes: 0 0 Physical Write Bytes: 0 0 Rows Processed: 26 26 Fetches: 26 26 Executions: 1 1 Notes ----- 1. Statistics for the original plan were averaged over 10 executions. 2. Statistics for the SQL profile plan were averaged over 10 executions. ------------------------------------------------------------------------------- EXPLAIN PLANS SECTION ------------------------------------------------------------------------------- 1- Original With Adjusted Cost ------------------------------ Plan hash value: 1838229974 --------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 26 | 1196 | 796 (1)| 00:00:10 | |* 1 | HASH JOIN | | 26 | 1196 | 796 (1)| 00:00:10 | |* 2 | TABLE ACCESS FULL| T1 | 26 | 806 | 47 (3)| 00:00:01 | | 3 | TABLE ACCESS FULL| T2 | 269K| 3952K| 748 (1)| 00:00:09 | --------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - access("T1"."OBJECT_ID"="T2"."OBJECT_ID") 2 - filter("T1"."OBJECT_NAME" LIKE '%T1%' AND "T1"."OBJECT_NAME" IS NOT NULL) 2- Using SQL Profile -------------------- Plan hash value: 1022743391 --------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 26 | 1196 | 49 (0)| 00:00:01 | | 1 | NESTED LOOPS | | | | | | | 2 | NESTED LOOPS | | 26 | 1196 | 49 (0)| 00:00:01 | |* 3 | TABLE ACCESS FULL | T1 | 26 | 806 | 47 (3)| 00:00:01 | |* 4 | INDEX RANGE SCAN | T2_IDX | 1 | | 1 (0)| 00:00:01 | | 5 | TABLE ACCESS BY INDEX ROWID| T2 | 1 | 15 | 1 (0)| 00:00:01 | --------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 3 - filter("T1"."OBJECT_NAME" LIKE '%T1%' AND "T1"."OBJECT_NAME" IS NOT NULL) 4 - access("T1"."OBJECT_ID"="T2"."OBJECT_ID") ------------------------------------------------------------------------------- 可以從報告看出，改進確實是很客觀的，提升了90%以上。 來簡單驗證一下，先得accept 一下。 SQL> execute dbms_sqltune.accept_sql_profile(task_name => 'TASK_12352',task_owner => 'N1', replace => TRUE); PL/SQL procedure successfully completed. 再來查詢一下，看看是否啟用了profile SQL> set autot trace exp stat SQL> select t1.*,t2.owner from t1,t2 where t1.object_name like '%T1%' and t1.object_id=t2.object_id / 26 rows selected. Execution Plan ---------------------------------------------------------- Plan hash value: 1022743391 --------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 26 | 1196 | 49 (0)| 00:00:01 | | 1 | NESTED LOOPS | | | | | | | 2 | NESTED LOOPS | | 26 | 1196 | 49 (0)| 00:00:01 | |* 3 | TABLE ACCESS FULL | T1 | 26 | 806 | 47 (3)| 00:00:01 | |* 4 | INDEX RANGE SCAN | T2_IDX | 1 | | 1 (0)| 00:00:01 | | 5 | TABLE ACCESS BY INDEX ROWID| T2 | 1 | 15 | 1 (0)| 00:00:01 | --------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 3 - filter("T1"."OBJECT_NAME" LIKE '%T1%' AND "T1"."OBJECT_NAME" IS NOT NULL) 4 - access("T1"."OBJECT_ID"="T2"."OBJECT_ID") Note ----- - SQL profile "SYS_SQLPROF_01471f52938e0000" used for this statement

Statistics ---------------------------------------------------------- 34 recursive calls 1 db block gets 338 consistent gets 3 physical reads 196 redo size 1669 bytes sent via SQL*Net to client 531 bytes received via SQL*Net from client 3 SQL*Net roundtrips to/from client 1 sorts (memory) 0 sorts (disk) 26 rows processed 再來看看如果改動了sql語句，多加了些空格，看看profile還能不能正常啟用。 SQL> select t1.*,t2.owner from t1,t2 where t1.object_name like '%T1%' and t1.object_id= t2.object_id 2 / 26 rows selected. Elapsed: 00:00:00.02 Execution Plan ---------------------------------------------------------- Plan hash value: 1022743391 --------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 26 | 1196 | 49 (0)| 00:00:01 | | 1 | NESTED LOOPS | | | | | | | 2 | NESTED LOOPS | | 26 | 1196 | 49 (0)| 00:00:01 | |* 3 | TABLE ACCESS FULL | T1 | 26 | 806 | 47 (3)| 00:00:01 | |* 4 | INDEX RANGE SCAN | T2_IDX | 1 | | 1 (0)| 00:00:01 | | 5 | TABLE ACCESS BY INDEX ROWID| T2 | 1 | 15 | 1 (0)| 00:00:01 | --------------------------------------------------------------------------------------- Predicate Information (identified by operation id): -------------------------------------------------- 3 - filter("T1"."OBJECT_NAME" LIKE '%T1%' AND "T1"."OBJECT_NAME" IS NOT NULL) 4 - access("T1"."OBJECT_ID"="T2"."OBJECT_ID") Note ----- - SQL profile "SYS_SQLPROF_01471f52938e0000" used for this statement Statistics ---------------------------------------------------------- 0 recursive calls 0 db block gets 323 consistent gets 0 physical reads 0 redo size 1669 bytes sent via SQL*Net to client 530 bytes received via SQL*Net from client 3 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 26 rows processed 可以看到，還是正常啟用了。另外，庫裡的cursor_sharing引數如下。 SQL> show parameter cursor NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ cursor_bind_capture_destination string memory+disk cursor_sharing string EXACT 所以在使用中，對於sql調優來說還是可以嘗試使用sql_profile的，確實提供了不少的知識集。