Dropping composite Primary Key does not drop the index

Today I have encountered a surprising fact:

Scenario is 10.2.0.1  Express Edition on Win32.

I have a table called job_history in the HR scheme which has a composit primary key : and there is an index for the primary key:

SQL> select index_name from user_indexes where table_name=’JOB_HISTORY’;

INDEX_NAME

Does the following info help to explain?

——————————
JHIST_EMP_ID_ST_DATE_PK
JHIST_JOB_IX
JHIST_EMPLOYEE_IX
JHIST_DEPARTMENT_IX

This is my constraint in the data dictionary:

SQL> select column_name , position
  2   from user_cons_columns
  3  where constraint_name=’JHIST_EMP_ID_ST_DATE_PK’;

COLUMN_NAME      POSITION
———————–    ———————————
EMPLOYEE_ID        1

START_DATE          2

 

Now I drop the primary key constraint

SQL> alter table job_history drop constraint
  2  JHIST_EMP_ID_ST_DATE_PK including indexes;

Table altered.

And here is the surprise:

SQL> select index_name from user_indexes where table_name=’JOB_HISTORY’;

INDEX_NAME
——————————
JHIST_EMP_ID_ST_DATE_PK
JHIST_JOB_IX
JHIST_EMPLOYEE_IX
JHIST_DEPARTMENT_IX

I do not see the point here. Why is the index still there?

Evern though I have explicitly written INCLUDING INDEXES.

BUG or Feature?!

Can anyone explain?