Re: Size functions inconsistent results

On Fri, Feb 25, 2022 at 12:10 PM Japin Li <japinli(at)hotmail(dot)com> wrote:
>
>
> I think, you forget the index size of toast table.
>
> with relations as (
> select schemaname, relname, relid
> from pg_stat_user_tables
> where relname = 'test_size'
> ),
> sizes as (
> select
> schemaname,
> r.relname,
>
> pg_total_relation_size(relid) AS total_bytes,
>
> pg_relation_size(relid, 'main') +
> pg_relation_size(relid, 'init') +
> pg_relation_size(relid, 'fsm') +
> pg_relation_size(relid, 'vm') AS heap_bytes,
> pg_indexes_size(relid) AS index_bytes,
> pg_table_size(reltoastrelid) + pg_indexes_size(reltoastrelid) AS
toast_bytes
> from relations r
> join pg_class on pg_class.oid = r.relid
> )
> select
> total_bytes, heap_bytes, index_bytes, toast_bytes,
> (total_bytes = (heap_bytes+index_bytes+toast_bytes)) as "Equal?",
> (total_bytes - (heap_bytes+index_bytes+toast_bytes)) as "Diff"
> from sizes;
>

Ahh perfect... thanks... make sense because pg_table_size don't compute the
indexes size, now it worked:

fabrizio=# with relations as (
select schemaname, relname, relid
from pg_stat_user_tables
where relname = 'test_size'
),
sizes as (
select
schemaname,
r.relname,

pg_total_relation_size(relid) AS total_bytes,

pg_relation_size(relid, 'main') +
pg_relation_size(relid, 'init') +
pg_relation_size(relid, 'fsm') +
pg_relation_size(relid, 'vm') AS heap_bytes,
pg_indexes_size(relid) AS index_bytes,
pg_table_size(reltoastrelid) + pg_indexes_size(reltoastrelid) AS
toast_bytes
from relations r
join pg_class on pg_class.oid = r.relid
)
select
total_bytes, heap_bytes, index_bytes, toast_bytes,
(total_bytes = (heap_bytes+index_bytes+toast_bytes)) as "Equal?",
(total_bytes - (heap_bytes+index_bytes+toast_bytes)) as "Diff"
from sizes;
total_bytes | heap_bytes | index_bytes | toast_bytes | Equal? | Diff
-------------+------------+-------------+-------------+--------+------
14622720 | 65536 | 40960 | 14516224 | t | 0
(1 row)

Regards,

--
Fabrízio de Royes Mello