select table_schema,table_name,pg_size_pretty(pg_total_relation_size(table_schema||'."'||table_name||'"')) 
	from information_schema.tables
		where table_schema in(select scheme from schemas_list)
order by pg_total_relation_size(table_schema||'."'||table_name||'"') desc

             total       used       free     shared    buffers     cached
Mem:          8003       7825        177          0          5       1095
-/+ buffers/cache:       6724       1278
Swap:        51199      49425       1774

 for file in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done | sort -k 2 -n -r | less
postgres 49703700 kB
postgres 4147268 kB
postgres 258116 kB
postgres 248840 kB
postgres 201168 kB
postgres 181504 kB
postgres 161044 kB
postgres 152284 kB
postgres 138784 kB
postgres 97260 kB
postgres 68716 kB
...

explain
select table_schema,table_name,pg_size_pretty(pg_total_relation_size(table_schema||'."'||table_name||'"')) 
	from information_schema.tables
		where table_schema in(select scheme from schemas_list)
order by pg_total_relation_size(table_schema||'."'||table_name||'"') desc


Result  (cost=25820.68..26970.40 rows=20904 width=104)
  ->  Sort  (cost=25820.68..25872.94 rows=20904 width=200)
        Sort Key: (pg_total_relation_size(((((((nc.nspname)::information_schema.sql_identifier)::text || '."'::text) || ((c.relname)::information_schema.sql_identifier)::text) || '"'::text))::regclass)) DESC
        ->  Hash Left Join  (cost=11834.70..24320.66 rows=20904 width=200)
              Hash Cond: (c.reloftype = t.oid)
              ->  Hash Join  (cost=25.72..11753.92 rows=20904 width=132)
                    Hash Cond: (c.relnamespace = nc.oid)
                    ->  Seq Scan on pg_class c  (cost=0.00..11284.28 rows=62758 width=72)
                          Filter: ((relkind = ANY ('{r,v,f}'::"char"[])) AND (pg_has_role(relowner, 'USAGE'::text) OR has_table_privilege(oid, 'SELECT, INSERT, UPDATE, DELETE, TRUNCATE, REFERENCES, TRIGGER'::text) OR has_any_column_privilege(oid, 'SELECT, INSERT, UPDATE, REFERENCES'::text)))
                    ->  Hash  (cost=22.92..22.92 rows=224 width=68)
                          ->  Hash Semi Join  (cost=1.52..22.92 rows=224 width=68)
                                Hash Cond: (((nc.nspname)::information_schema.sql_identifier)::text = (schemas_list.scheme)::text)
                                ->  Seq Scan on pg_namespace nc  (cost=0.00..17.43 rows=449 width=68)
                                      Filter: (NOT pg_is_other_temp_schema(oid))
                                ->  Hash  (cost=1.23..1.23 rows=23 width=9)
                                      ->  Seq Scan on schemas_list  (cost=0.00..1.23 rows=23 width=9)
              ->  Hash  (cost=9560.51..9560.51 rows=179877 width=4)
                    ->  Hash Join  (cost=24.16..9560.51 rows=179877 width=4)
                          Hash Cond: (t.typnamespace = nt.oid)
                          ->  Seq Scan on pg_type t  (cost=0.00..7267.77 rows=179877 width=8)
                          ->  Hash  (cost=15.74..15.74 rows=674 width=4)
                                ->  Seq Scan on pg_namespace nt  (cost=0.00..15.74 rows=674 width=4)

explain
select n.nspname,c.relname,pg_size_pretty(pg_total_relation_size(n.nspname||'."'||c.relname||'"')) 
from pg_class c 
	join pg_namespace n on n.oid=c.relnamespace and nspname in(select scheme from schemas_list)
where c.relkind='r'
order by pg_total_relation_size(n.nspname||'."'||c.relname||'"') desc

Result  (cost=6652.28..6667.83 rows=311 width=168)
  Output: n.nspname, c.relname, pg_size_pretty((pg_total_relation_size((((((n.nspname)::text || '."'::text) || (c.relname)::text) || '"'::text))::regclass))), (pg_total_relation_size((((((n.nspname)::text || '."'::text) || (c.relname)::text) || '"'::text))::regclass))
  ->  Sort  (cost=6652.28..6653.05 rows=311 width=136)
        Output: n.nspname, c.relname, (pg_total_relation_size((((((n.nspname)::text || '."'::text) || (c.relname)::text) || '"'::text))::regclass))
        Sort Key: (pg_total_relation_size((((((n.nspname)::text || '."'::text) || (c.relname)::text) || '"'::text))::regclass)) DESC
        ->  Hash Join  (cost=19.68..6639.40 rows=311 width=136)
              Output: n.nspname, c.relname, pg_total_relation_size((((((n.nspname)::text || '."'::text) || (c.relname)::text) || '"'::text))::regclass)
              Hash Cond: (c.relnamespace = n.oid)
              ->  Seq Scan on pg_catalog.pg_class c  (cost=0.00..6576.94 rows=9128 width=68)
                    Output: c.relname, c.relnamespace, c.reltype, c.reloftype, c.relowner, c.relam, c.relfilenode, c.reltablespace, c.relpages, c.reltuples, c.relallvisible, c.reltoastrelid, c.relhasindex, c.relisshared, c.relpersistence, c.relkind, c.relnatts, c.relchecks, c.relhasoids, c.relhaspkey, c.relhasrules, c.relhastriggers, c.relhassubclass, c.relrowsecurity, c.relforcerowsecurity, c.relispopulated, c.relreplident, c.relfrozenxid, c.relminmxid, c.relacl, c.reloptions
                    Filter: (c.relkind = 'r'::"char")
              ->  Hash  (cost=19.39..19.39 rows=23 width=68)
                    Output: n.nspname, n.oid
                    ->  Hash Semi Join  (cost=1.52..19.39 rows=23 width=68)
                          Output: n.nspname, n.oid
                          Hash Cond: (n.nspname = (schemas_list.scheme)::name)
                          ->  Seq Scan on pg_catalog.pg_namespace n  (cost=0.00..15.74 rows=674 width=68)
                                Output: n.nspname, n.oid
                          ->  Hash  (cost=1.23..1.23 rows=23 width=9)
                                Output: schemas_list.scheme
                                ->  Seq Scan on schemas_list  (cost=0.00..1.23 rows=23 width=9)
                                      Output: schemas_list.scheme

select count(*) from pg_tables;
9166

select count(*) from pg_class where relkind='r';
9166

select n.nspname,c.relname,pg_size_pretty(pg_total_relation_size(n.nspname||'."'||c.relname||'"')) 
from pg_class c 
	join pg_namespace n on n.oid=c.relnamespace and nspname in(select scheme from schemas_list)
where c.relkind='r'
order by pg_total_relation_size(n.nspname||'."'||c.relname||'"') desc