Partition on CHAR Column is not working as expected.

Database

Partition on CHAR Column is not working as expected.

We have created PARTITION on CHAR column using CASE_N as like below. But it is not giving any performance in terms resource usage (CPU/Spool/ I/O). 

My question is when we filter data on parttion column the resource usage should come down compare to non-partition table (full table scan). but there is no change in resource usage.

PARTITION BY CASE_N(entity_type =  'biz-v1',entity_type =  'FLA', entity_type =  'FLV', entity_type =  'person-v1', NO CASE, UNKNOWN)

In some articles, they mentioned we need to create partition using HASHBUCKET(HASHROW(Column))+1. Is this true?.

Could you please suggest me correct definition for to create PARTITION on CHAR Column and let me know if I am missing anything here.

Thanks in advance for the help.