oracle explain plan autotrace - ghdrako/doc_snipets GitHub Wiki

<Oracle_Home>/rdbms/admin/utlxplan.sql 

SQL> @?/rdbms/admin/utlxplan.sql

SQL> explain plan for
2 select *
3 from hr_employees
4 full join hr_departments
5 on emp_dep_id = dep_id;

SQL> @?/rdbms/admin/utlxpls.sql
PLAN_TABLE_OUTPUT
---------------------------
Plan hash value: 2757235693
-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |
Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 124 | 44392 |
6 (0)| 00:01 |
| 1 | VIEW | VW_FOJ_0 | 124 | 44392 |
6 (0)| 00:01 |
|* 2 | HASH JOIN FULL OU| | 124 | 11408 |
6 (0)| 00:01 |
| 3 | TABLE ACCESS FUL| HR_DEPARTMEN| 28 | 588 |
3 (0)| 00:01 |
| 4 | TABLE ACCESS FUL| HR_EMPLOYEES| 107 | 7597 |
3 (0)| 00:01 |
-----------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("EMP_DEP_ID"="DEP_ID")

Autotrace

SQL> connect sys as sysdba
SQL> @?/sqlplus/admin/plustrce.sql
SQL> grant plustrace to public;
SQL> connect demo_user/demo_pwd;

SQL> set autotrace traceonly
SQL> select *
2 from hr_employees
3 full join hr_departments
4 on emp_dep_id = dep_id;

To get the actual rowsorurce execution statistics (that's the data in the A-Row,A-Time -- and Buffers columns), you must either use the gather_pal_statistics hint in your query or you must set the statistics_level parameter to ALL (default TYPICAL). Notice serveroutput off - to ensure thet the execution pala is the last query execution plan

  • STARTS - the number of times particular step is executed
  • E-Rows - the number of rows that optimizer estimated by each step rowsource operation
  • A-Rows - the actual number of rows
  • A-Time - the actual elapsed duration for each plan operation. Note that parent steps include the durations of their child steps
  • Buffers - the actual count of access operations upon buffers in the buffer cache( logical I/O (LIO)). Note that parent steps include the buffer access count of their child steps
set serveroutput off 
select /*+ gather_plan_statistics */ * from ord where order_no = 256769 ; 
select * from table(dbms_xplan.display_cursor(null,null,'ALLSTATS LAST'));