SQL query to view size of partitions that are compressed

Hi,

I would like to view the size of all my partiions that are using compression and how big they are in total. Im running this:

select count(*) , sum(s.bytes)/1024/1024/1024  GB from dba_segments s, DBA_TAB_PARTITIONS t where s.segment_name = t.table_name and t.compression = 'ENABLED' and s.owner='DW';

But the query has run for over 3h.

Is there a better way to check this?

Regards

S