Afficher le plan d’exécution avec les stats de chaque étape

pachot — Tue, 11 Jun 2013 10:40:41 +0000

Pour poster un plan d’exécution dans les forums, il est important de montrer les statistiques d’exécution et pas seulement les estimations – car s’il on a un problème c’est peut-être justement que les estimations sont fausses.

Voici comment faire facilement sous sqlplus.

Les exemples complets sont ici: demo

1. On s’assure que SQLPlus ne lance pas d’autres requêtes

set serveroutput off autotrace off

et que le format est lisible

set pagesize 1000 linesize 200 trimspool on

2. On ajoute le hint GATHER_PLAN_STATISTICS et on exécute la requête:

select /*+ GATHER_PLAN_STATISTICS */ level,ename,dname,sal from emp join dept using(deptno) connect by empno= prior mgr start with empno=7499 order by 1 desc;

LEVEL	ENAME	DNAME	SAL
3	KING	ACCOUNTING	5000
2	BLAKE	SALES	2850
1	ALLEN	SALES	1600

3. On affiche les stats avec DBMS_XPLAN:

select * from table(dbms_xplan.display_cursor(null,null,'allstats last'));

   PLAN_TABLE_OUTPUT                                                                                                                
   SQL_ID 9uxp6bpf203yn, child number 0                                                                                             
   -------------------------------------                                                                                            
   select /*+ GATHER_PLAN_STATISTICS */ level,ename,dname,sal from emp                                                              
   join dept using(deptno) connect by empno= prior mgr start with                                                                   
   empno=7499 order by 1 desc                                                                                                       
                                                                                                                                    
   Plan hash value: 2206269999                                                                                                      
                                                                                                                                    
   -------------------------------------------------------------------------------------------------------------------------------- 
   | Id  | Operation                       | Name    | Starts | E-Rows | A-Rows |   A-Time   | Buffers |  OMem |  1Mem | Used-Mem | 
   -------------------------------------------------------------------------------------------------------------------------------- 
   |   0 | SELECT STATEMENT                |         |      1 |        |      3 |00:00:00.01 |      12 |       |       |          | 
   |   1 |  SORT ORDER BY                  |         |      1 |      2 |      3 |00:00:00.01 |      12 |  2048 |  2048 | 2048  (0)| 
   |*  2 |   CONNECT BY WITH FILTERING     |         |      1 |        |      3 |00:00:00.01 |      12 |  2048 |  2048 | 2048  (0)| 
   |   3 |    NESTED LOOPS                 |         |      1 |      1 |      1 |00:00:00.01 |       4 |       |       |          | 
   |   4 |     TABLE ACCESS BY INDEX ROWID | EMP     |      1 |      1 |      1 |00:00:00.01 |       2 |       |       |          | 
   |*  5 |      INDEX UNIQUE SCAN          | PK_EMP  |      1 |      1 |      1 |00:00:00.01 |       1 |       |       |          | 
   |   6 |     TABLE ACCESS BY INDEX ROWID | DEPT    |      1 |      1 |      1 |00:00:00.01 |       2 |       |       |          | 
   |*  7 |      INDEX UNIQUE SCAN          | PK_DEPT |      1 |      1 |      1 |00:00:00.01 |       1 |       |       |          | 
   |   8 |    NESTED LOOPS                 |         |      3 |      1 |      2 |00:00:00.01 |       8 |       |       |          | 
   |   9 |     NESTED LOOPS                |         |      3 |      1 |      2 |00:00:00.01 |       4 |       |       |          | 
   |  10 |      CONNECT BY PUMP            |         |      3 |        |      3 |00:00:00.01 |       0 |       |       |          | 
   |  11 |      TABLE ACCESS BY INDEX ROWID| EMP     |      3 |      1 |      2 |00:00:00.01 |       4 |       |       |          | 
   |* 12 |       INDEX UNIQUE SCAN         | PK_EMP  |      3 |      1 |      2 |00:00:00.01 |       2 |       |       |          | 
   |  13 |     TABLE ACCESS BY INDEX ROWID | DEPT    |      2 |      1 |      2 |00:00:00.01 |       4 |       |       |          | 
   |* 14 |      INDEX UNIQUE SCAN          | PK_DEPT |      2 |      1 |      2 |00:00:00.01 |       2 |       |       |          | 
   -------------------------------------------------------------------------------------------------------------------------------- 
                                                                                                                                    
   Predicate Information (identified by operation id):                                                                              
   ---------------------------------------------------                                                                              
                                                                                                                                    
   2 - access("EMPNO"=PRIOR NULL)                                                                                                   
   5 - access("EMP"."EMPNO"=7499)                                                                                                   
   7 - access("EMP"."DEPTNO"="DEPT"."DEPTNO")                                                                                       
   12 - access("EMP"."EMPNO"="connect$_by$_pump$_004"."prior mgr ")                                                                 
   14 - access("EMP"."DEPTNO"="DEPT"."DEPTNO")                                                                                      
                                                                                                                                    
   Note                                                                                                                             
   -----                                                                                                                            
   - dynamic statistics used: dynamic sampling (level=2)

Oracle - Concepts et Exemples » Plan d’exécution

Afficher le plan d’exécution avec les stats de chaque étape