Shows which indexes are mostly used:

select 
	i.schemaname as schema_name, 
	i.relname as table_name, 
	i.indexrelname as index_name, 
	i.idx_blks_hit as number_of_hits
from pg_statio_all_indexes i
where schemaname not in ( 'pg_catalog', 'pg_toast')
order by number_of_hits desc