Toad explain plan

Question

Hi,
I understand that reading output of an explain starts from the mostly indented lines.
Anyhow in TOAD (I am using version 9.7) toad Adds a number before each line in the explain plan tree. This number looks random to me because I cannot link it to the execution plan as per indentation.
Can anybody tell me what this number before each line is ?
Thanks
AK

Answer 1

askanaan wrote:
I understand that reading output of an explain starts from the mostly indented lines.
...Though this may "sometimes" be so, it is certainly not a general rule. It all depends on the (parent) operations that preceed/follow that "mostly indented line".
Here's a simple counter-example using the emp/dept tables.
  1  explain plan for
  2  select d.deptno
  3        ,d.dname
  4        ,(select count(*)
  5          from emp e
  6          where e.deptno=d.deptno) as count_emp
  7* from dept d
SQL> /
Explained.
SQL> @vp
More...
PLAN_TABLE_OUTPUT
Plan hash value: 4111639169
| Id  | Operation          | Name | Rows  | Bytes |
|   0 | SELECT STATEMENT   |      |     1 |    22 |
|   1 |  SORT AGGREGATE    |      |     1 |    13 |
|*  2 |   TABLE ACCESS FULL| EMP  |     1 |    13 |
|   3 |  TABLE ACCESS FULL | DEPT |     1 |    22 |
Predicate Information (identified by operation id):
   2 - filter("E"."DEPTNO"=:B1)This plan starts at line 3. Not 2, which is the "mostly indented line".
Here's another one:
  1  explain plan for
  2  select d.*
  3  from emp e
  4      ,(select d1.deptno
  5        from dept d1
  6        where d1.loc in (select d2.loc
  7                         from dept d2
  8                         group by d2.loc
  9                         having count(*) > 1)) d
10* where e.deptno = d.deptno
SQL> /
Explained.
SQL> @vp
More...
PLAN_TABLE_OUTPUT
Plan hash value: 1621130288
| Id  | Operation                     | Name          |
|   0 | SELECT STATEMENT              |               |
|   1 |  NESTED LOOPS SEMI            |               |
|   2 |   NESTED LOOPS                |               |
|   3 |    TABLE ACCESS FULL          | EMP           |
|   4 |    TABLE ACCESS BY INDEX ROWID| DEPT          |
|*  5 |     INDEX UNIQUE SCAN         | SYS_C00204096 |
|*  6 |   VIEW                        | VW_NSO_1      |
|*  7 |    FILTER                     |               |
|   8 |     SORT GROUP BY             |               |
|   9 |      TABLE ACCESS FULL        | DEPT          |
Predicate Information (identified by operation id):
   5 - access("E"."DEPTNO"="D1"."DEPTNO")
   6 - filter("D1"."LOC"="$nso_col_1")
   7 - filter(COUNT(*)>1)If you think this one starts at line 9, you're wrong again. It starts at line 3.
You need to understand all the "operations" that can appear in an execution plan.
Only then can you deduce where the execution of such plan really starts.
Toon