Complicated Oracle Grouping Composite CUBE Query - oracle

Question

I need to use the CUBE grouping function in order to get every possible combination so that this report can be used on APEX with parameters controlling how the report views. My full query is too complicated to show and will probably just confuse the situation. here I have the cutdown version
Select /*+ NO_PARALLEL */ ETP_ETPC_UID,
Decode (Grouping(ETP_ET_UID), 1, '-Grouped-', ETP_ET_UID),
/* Decode (Grouping(ETP_ET_UID), 1, '-Grouped-', ET_ABBR), */
Decode (Grouping(ETP_REFERENCE_1), 1, '-Grouped-', ETP_REFERENCE_1),
Decode (Grouping(ETP_REFERENCE_2), 1, '-Grouped-', ETP_REFERENCE_2),
Sum(ETP_COUNT)
From ETP_PROFILE,
ET_EVENT_TYPE
Where ETP_ET_UID = ET_UID
Group By
ETP_ETPC_UID,
Cube( /*(*/ETP_ET_UID/*, ET_ABBR)*/ , ETP_REFERENCE_1, ETP_REFERENCE_2)
The issue I am currently having is to do with the sections I have commented out. According to this Oracle Base article the composite column is meant to be treated as 1, so great, I can have the ET_ABBR in my query and just set ET_UID and ET_ABBR as a composite (un-comment my code and you will see).
When I do this, it seems to ridiculously increase the cost of the query (according to explain plan) and indeed it takes forever to run. If I remove my ET_ABBR column (how the code is right now with comments in place) it loads very quick and Explain plan cost is great.
Am I doing something wrong here, should I be using Grouping Sets or something like that? This is the first time I am messing with these special grouping commands, and they seem to be good, but very confusing.
EDIT:
Explain plan for Commented Query:
Plan hash value: 3169115854
------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 142K| 9M| 408 (3)| 00:00:05 | | |
| 1 | SORT GROUP BY | | 142K| 9M| 408 (3)| 00:00:05 | | |
| 2 | GENERATE CUBE | | 142K| 9M| 408 (3)| 00:00:05 | | |
| 3 | SORT GROUP BY | | 142K| 9M| 408 (3)| 00:00:05 | | |
| 4 | PARTITION RANGE ALL| | 142K| 9M| 401 (1)| 00:00:05 | 1 |1048575|
| 5 | PARTITION LIST ALL| | 142K| 9M| 401 (1)| 00:00:05 | 1 | 10 |
| 6 | TABLE ACCESS FULL| ETP_PROFILE | 142K| 9M| 401 (1)| 00:00:05 | 1 |1048575|
------------------------------------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement (level=2)
Explain Plan for un-commented code:
Plan hash value: 2063641247
--------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
--------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 54 | 6426 | 427 (4)| 00:00:06 | | |
| 1 | TEMP TABLE TRANSFORMATION | | | | | | | |
| 2 | MULTI-TABLE INSERT | | | | | | | |
| 3 | SORT GROUP BY ROLLUP | | 54 | 4536 | 412 (3)| 00:00:05 | | |
|* 4 | HASH JOIN | | 142K| 11M| 406 (1)| 00:00:05 | | |
| 5 | TABLE ACCESS FULL | ET_EVENT_TYPE | 55 | 605 | 4 (0)| 00:00:01 | | |
| 6 | PARTITION RANGE ALL | | 142K| 9M| 401 (1)| 00:00:05 | 1 |1048575|
| 7 | PARTITION LIST ALL | | 142K| 9M| 401 (1)| 00:00:05 | 1 | 10 |
| 8 | TABLE ACCESS FULL | ETP_PROFILE | 142K| 9M| 401 (1)| 00:00:05 | 1 |1048575|
| 9 | DIRECT LOAD INTO | SYS_TEMP_0FD9D6E6F_E9BC1839 | | | | | | |
| 10 | DIRECT LOAD INTO | SYS_TEMP_0FD9D6E70_E9BC1839 | | | | | | |
| 11 | LOAD AS SELECT | SYS_TEMP_0FD9D6E70_E9BC1839 | | | | | | |
| 12 | SORT GROUP BY ROLLUP | | 54 | 3402 | 3 (34)| 00:00:01 | | |
| 13 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6E6F_E9BC1839 | 54 | 3402 | 2 (0)| 00:00:01 | | |
| 14 | MULTI-TABLE INSERT | | | | | | | |
| 15 | SORT GROUP BY ROLLUP | | 54 | 3240 | 3 (34)| 00:00:01 | | |
| 16 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6E6F_E9BC1839 | 54 | 3240 | 2 (0)| 00:00:01 | | |
| 17 | DIRECT LOAD INTO | SYS_TEMP_0FD9D6E71_E9BC1839 | | | | | | |
| 18 | DIRECT LOAD INTO | SYS_TEMP_0FD9D6E70_E9BC1839 | | | | | | |
| 19 | LOAD AS SELECT | SYS_TEMP_0FD9D6E70_E9BC1839 | | | | | | |
| 20 | SORT GROUP BY ROLLUP | | 54 | 2322 | 3 (34)| 00:00:01 | | |
| 21 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6E71_E9BC1839 | 54 | 2322 | 2 (0)| 00:00:01 | | |
| 22 | VIEW | | 162 | 19278 | 6 (0)| 00:00:01 | | |
| 23 | VIEW | | 162 | 15066 | 6 (0)| 00:00:01 | | |
| 24 | UNION-ALL | | | | | | | |
| 25 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6E6F_E9BC1839 | 54 | 4536 | 2 (0)| 00:00:01 | | |
| 26 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6E70_E9BC1839 | 54 | 4536 | 2 (0)| 00:00:01 | | |
| 27 | TABLE ACCESS FULL | SYS_TEMP_0FD9D6E71_E9BC1839 | 54 | 3240 | 2 (0)| 00:00:01 | | |
--------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
4 - access("SYS_TBL_$2$"."ETP_ET_UID"="SYS_TBL_$1$"."ET_UID")
Note
-----
- dynamic sampling used for this statement (level=2)