select t.schemaname, 
   COALESCE(cast(pg_partition_root((t.schemaname || '.' || t.relname)) as varchar(120)),
          cast(t.relname  as varchar(120))) as tablename,
    sum(n_live_tup) as rowcount
from pg_stat_user_tables t
group by
    t.schemaname,
    COALESCE(cast(pg_partition_root((t.schemaname || '.' || t.relname)) as varchar(120)),
          cast(t.relname  as varchar(120)));