What is the diff in 2 explain plans: diff_plan_cursor

0) Generate the diff plan report
We have sql_id gu7rvn4s4rb0m, and 2 child cursors 0 and 2
variable v clob
set serveroutput on
set autoprint on
set lines 150
exec :v := dbms_xplan.diff_plan_cursor('gu7rvn4s4rb0m', 0, 2);
http://stads59.us.oracle.com:8080/orarep/plandiff/all?task_id=119&format=html&method=qbreg

PL/SQL procedure successfully completed.


V
--------------------------------------------------------------------------------
TASK_119

Display the report, 2 options:
1) Display the report via XML DB
--open http port if needed, if you are on test/dev environment
exec dbms_xdb.SETHTTPPORT(8080);
--replacing url by local hostname
http://<db host name>:8080/orarep/plandiff/all?task_id=119&format=html&method=qbreg

2) Display in sqlplus
--report in text format, or replace format=html or format=xml
set define off;
set long 999999999
set pagesize 3000
select dbms_report.get_report(
        '/orarep/plandiff/all?task_id=119&format=text&method=qbreg')
from dual;

DBMS_REPORT.GET_REPORT('/ORAREP/PLANDIFF/ALL?TASK_ID=119&FORMAT=TEXT&METHOD=QBRE
--------------------------------------------------------------------------------
General Information
-------------------------------------------------------------------------------

 Task Information:                      Workload Information:
 -------------------------------------  -------------------------------------
  Task Name    : TASK_119
  Task Owner   : SYS
  Description  : diff_plan_cursor

Report Details: SQL Plan Comparison Query Block Diff
------------------------------------------------
| Query Block | SQL Plan 1 | SQL Plan 2 | Diff |
------------------------------------------------

Join Order Diff
-----------------------------------------
| Query Block | SQL Plan 1 | SQL Plan 2 |
-----------------------------------------

Join Method Diff
---------------------------------------------------------
| Query Block | Table to Join | SQL Plan 1 | SQL Plan 2 |
---------------------------------------------------------
| SEL$1       | "T2"@"SEL$1"  | HASH       | MERGE      |
---------------------------------------------------------

 Plan Id          : 325
 Plan Hash Value  : 2795996736

----------------------------------------
| Id  | Operation            | Name    |
----------------------------------------
|   0 | SELECT STATEMENT     |         |
| * 1 |   HASH JOIN          |         |
|   2 |    TABLE ACCESS FULL | TEST100 |
|   3 |    TABLE ACCESS FULL | TEST100 |
----------------------------------------

Predicate Information (identified by operation id):
------------------------------------------
* 1 - access("T1"."ID"="T2"."ID")

 Plan Id          : 326
 Plan Hash Value  : 216926072

-----------------------------------------
| Id  | Operation           | Name      |
-----------------------------------------
|   0 | SELECT STATEMENT    |           |
|   1 |   MERGE JOIN        |           |
|   2 |    INDEX FULL SCAN  | TEST100_I |
| * 3 |    SORT JOIN        |           |
|   4 |     INDEX FULL SCAN | TEST100_I |
-----------------------------------------

Predicate Information (identified by operation id):
------------------------------------------
* 3 - access("T1"."ID"="T2"."ID")
* 3 - filter("T1"."ID"="T2"."ID")

-----------------------------------------------------------------
| Diff | Transformation | SQL Plan 1 | SQL Plan 2 | Query block |
-----------------------------------------------------------------
| *    | . PARSER       | Yes        | Yes        | . SEL$1     |
-----------------------------------------------------------------