Nested SQL Index

Our app suddenly went slow in one of the envs. The only change I made was to change the SQL. Before the release, SQL was something like this

Select EmployeeId 
From Employee 
Where Dept='CS' 
  and record_state='ACTIVE' 
  and EmployeeTypeId ='1' 

      

        
        
        
      

    

After SQL release

Select EmployeeId 
From Employee Where Dept='CS' 
 and record_state='ACTIVE' 
 and EmployeeTypeId IN ('1','2')

      

        
        
        
      

    

The index of this table is: employee_state_id_index (Dept, record_state, EmployeeTypeId) The index has not been changed. Is this index not helping new SQL? does the new SQL scan the entire table? I have no idea how indexes on a partition work. Appreciate your help and comments

Explain request plan

| Id  | Operation         | Name                     | Rows  | Bytes | Cost (%CPU)|

|   0 | DELETE STATEMENT  |                          |     1 |    57 |     4   (0)|
|   1 |  DELETE           | Employee                 |       |       |            |
|*  2 |   INDEX RANGE SCAN| employee_state_id_index  |     1 |    57 |     4   (0)|
--------------------------------------------------------------------------------

Predicate Information (identified by operation id):


PLAN_TABLE_OUTPUT


   2 - access("C"."Dept"='CS' AND
              "C"."RECORD_STATE"='ACTIVE')
       filter("C"."EmployeeTypeId"='1' OR
              "C"."EmployeeTypeId"='2')