Gather_plan_statistics hint result not visible

Question

on my Oracle 11.2.0.1, I tried to use that hint as in example:
set autotrace on explain
select /*+ gather_plan_statistics */ 'x' from dual;
Execution Plan
Plan hash value: 272002086
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |      |     1 |     2 |     2   (0)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| DUAL |     1 |     2 |     2   (0)| 00:00:01 |
--------------------------------------------------------------------------as you see, there's no additional columns (E-rows, A-rows), and I don't know why.
what could cause this?
regards

Answer 1

This is just yet another limitation to autotrace. Use dbms_xplan and format the data how you need it.
SQL> select /*+ gather_plan_statistics */ 'x' from dual;
x
SQL> SELECT * FROM table(dbms_xplan.display_cursor(format=>'allstats'));
PLAN_TABLE_OUTPUT
SQL_ID  gxug7sz6nhqc3, child number 0
select /*+ gather_plan_statistics */ 'x' from dual
Plan hash value: 1388734953
| Id  | Operation        | Name | Starts | E-Rows | A-Rows |   A-Time   |
|   0 | SELECT STATEMENT |      |      4 |        |      4 |00:00:00.01 |
|   1 |  FAST DUAL       |      |      4 |      1 |      4 |00:00:00.01 |
PLAN_TABLE_OUTPUT
13 rows selected.Read more about the parameters and usage here:
http://docs.oracle.com/cd/B19306_01/appdev.102/b14258/d_xplan.htm