helps to keep focus on «hot» tables
top 10 tables by sum of io operatoins:

SELECT
st.schemaname||'.'||st.relname,
round (100*( 
		sum (coalesce(st.n_tup_ins,0)+coalesce(st.n_tup_upd,0)-coalesce(st.n_tup_hot_upd,0)+coalesce(st.n_tup_del,0)) 
) 
	/ 
(
		sum (coalesce(st.n_tup_ins,0)+coalesce(st.n_tup_upd,0)-coalesce(st.n_tup_hot_upd,0)+coalesce(st.n_tup_del,0)) over () 
),2) as pct_io_ops
 from pg_stat_user_tables st
JOIN pg_class c ON c.oid=st.relid 
LEFT JOIN pg_tablespace t ON t.oid=c.reltablespace
WHERE
coalesce(n_tup_ins,0)+coalesce(n_tup_upd,0)-coalesce(n_tup_hot_upd,0)+coalesce(n_tup_del,0)>100
group by st.schemaname||'.'||st.relname,st.n_tup_ins,st.n_tup_upd,st.n_tup_hot_upd,st.n_tup_del
order by pct_io_ops desc 
limit 10;

top 10 tables by index scans:

   SELECT 
        pg_stat_all_tables.schemaname||'.'||relid::regclass AS table, 
        round (100* (sum(pg_stat_user_indexes.idx_scan))
                      / (sum(pg_stat_user_indexes.idx_scan) over () )
                       ,2) pct_indx_scans
    FROM 
        pg_stat_user_indexes 
        JOIN pg_index USING (indexrelid)
        join pg_stat_all_tables using (relid)
        group by pg_stat_all_tables.schemaname||'.'||relid::regclass,pg_stat_user_indexes.idx_scan
        order by 2 desc 
        limit 10;