Re: Difference in the size of database size and relations - Mailing list pgsql-admin

From Jerry Sievers
Subject Re: Difference in the size of database size and relations
Date
Msg-id 86vbyw1sw0.fsf@jerry.enova.com
Whole thread Raw
In response to Difference in the size of database size and relations  (Luis <luisico@gmail.com>)
List pgsql-admin
Luis <luisico@gmail.com> writes:

> Hi,
>
> I have noticed a weird thing in different databases.
> When I run pg_database_size on some databases they report a pretty
> high value and if I take a look to all relations the sum of all of
> them is not even the half of the one reported by pg_database_size.
>
> Although I've seen this in different databases, this is a specific example.
>
>
> This are the sizes reported by this query:
>
> SELECT pg_size_pretty(pg_relation_size(C.oid)) AS "size"
>   FROM pg_class C
>   LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
>   WHERE nspname NOT IN ('pg_catalog', 'information_schema')
>   ORDER BY pg_relation_size(C.oid) DESC
>   LIMIT 20;
>

Try just comparing what pg_database_size() tells you vs a sum() over
relpages*8192 (assuming standard page size).  You may have to do some
casting to bigint depending how large your DB is.

>   size
> ---------
>  99 MB
>  45 MB
>  10 MB
>  8528 kB
>  5280 kB
>  4352 kB
>  3184 kB
>  1304 kB
>  1152 kB
>  896 kB
>  544 kB
>  528 kB
>  336 kB
>  336 kB
>  336 kB
>  304 kB
>  296 kB
>  288 kB
>  272 kB
>  248 kB
>
> And this is the database size reported by this query:
> SELECT pg_size_pretty(pg_database_size('mydb'));
>
>  pg_size_pretty
> ----------------
>  3539 MB
>
> I've read about LOBs but I don't seem to have any.
>
> Any idea where the space is being used?
>
> Thanks

--
Jerry Sievers
Postgres DBA/Development Consulting
e: postgres.consulting@comcast.net
p: 312.241.7800


pgsql-admin by date:

Previous
From: Luis
Date:
Subject: Re: Difference in the size of database size and relations
Next
From: Dev Kumkar
Date:
Subject: Scheduled Events