How to list index sizes

For non-partitioned global indexes in a specific schema:

select i.index_name, s.tablespace_name,round(sum(bytes)/1024/1024/1024) "GB"
from dba_indexes i join dba_segments s
on (i.index_name = s.segment_name)
where i.owner='SH'
and i.partitioned='NO'
group by i.index_name,s.tablespace_name
order by 3 desc;

INDEX_NAME	TABLESPACE_NAME	GB
AN_EEG_IDX	SH	2406
PK_EEG	SH	994
UIDX_REG_EEG	SH	502
IDX_REL_IDX	SH	156

For non-partitioned global indexes on a specific table:

select i.index_name, s.tablespace_name,round(sum(bytes)/1024/1024/1024) "GB"
from dba_indexes i join dba_segments s
on (i.index_name = s.segment_name)
where i.owner='SH'
and i.partitioned='NO'
and i.table_name = 'ACCOUNTING'
group by i.index_name,s.tablespace_name
order by 2 desc;

INDEX_NAME	TABLESPACE_NAME	GB
IDX_ACC1	SH	120
PK_ACC	SH	994

For partitioned indexes on a specific table:

select s.segment_name,round(sum(s.bytes)/1024/1024/1024,2) "GB" 
from dba_segments s
where segment_name IN (select unique index_name 
                        from dba_indexes 
                        where table_name='SALES' 
                        and PARTITIONED='YES'
                        and index_type <> 'LOB'
                        and owner='SH')
group by s.segment_name;

SEGMENT_NAME	GB
IDX_UK1	28
IDX_ACC_UK2	78,24

For all partitioned indexes in a specific schema:

select i.index_name,i.table_name,s.tablespace_name,round(sum(s.bytes)/1024/1024/1024) "GB"
from dba_indexes i join dba_segments s
on (i.index_name = s.segment_name)
where i.owner='SH'
and i.partitioned='YES'
and i.index_type <> 'LOB'
group by i.index_name,i.table_name,s.tablespace_name
order by 2 ;

INDEX_NAME	TABLE_NAME	TABLESPACE_NAME	GB
IDX_OP_AA	ENTITY	SH	260
IDX_OP_NA	ENTITY_HISTORY	SH	1082
IDX_VER_AA	EVENT	SH	28
IDX_VER_AA_HIST	EVENT	SH	78
IDX_WW_UK2	RELATION	SH	226
IDX_RELNO	RELATION_ENTITY	SH	350