size of table + toasted tables + indexes != pg_total_relation_size

Hi,
I'm trying to investigate some storage issues at one of my customers
environments:

One of the databases occupies too much storage (almost1T) :
select t1.datname AS db_name,
pg_size_pretty(pg_database_size(t1.datname)) as db_size
from pg_database t1
order by pg_database_size(t1.datname) desc

output :
[image: image.png]

When I searched for the biggest objects in DB1 I saw that the total sum
isnt even close to 100G :
select a.relname as table_name,pg_relation_size(a.oid, 'main')/1024/1024 as
main_MB,
pg_relation_size(a.oid, 'fsm')/1024/1024 as fsm_MB,
pg_relation_size(a.oid, 'vm')/1024/1024 as vm_MB,
pg_relation_size(a.oid, 'init')/1024/1024 as init_MB,
pg_table_size(a.oid)/1024/1024 AS relation_size_mb,
pg_indexes_size(a.oid)/1024/1024 as indexes_MB,
pg_total_relation_size(a.oid)/1024/1024 as total_size_MB
from pg_class a where relkind in ('r','t') order by relation_size_mb
desc,total_size_MB desc limit 100;

[image: image.png]
pg_toast_17610 is the session`s toasted table
pg_toast_17315 is the attachment`s toasted table.

The local dba used to run vacuum full on a daily basis on those tables. As
a result of that, every time autovacuum tried to run on those tables it
stopped(saw it in the logs..).

Now, I thought that the pg_total_relation_size should include also all the
dead tuples and the toasted tables. Why then the total_size of the
sessions table doesnt include the pg_toast_17610 ?

In addition, I saw from pg_stat_activity that the session table has about
198 dead tuples and the toasted table has about 83833 dead tuples. It seems
that the autoanalyze has never run on the toasted table.

Any idea what is the root cause then for the huge database size ? why the
total size of the table doesnt include the toasted table ?

Thanks.

Aw 252 916