Re: Question about pg_dump + pg_restore + pg_toast

Hi,

On 24/02/2025 10:19, Edwin UY wrote:
> Hi,
> 
> Checking one of the databases, we have the schema below with size as 
> below. I just rename it as abc, this is the one we want to dump and restore.
> 
>      schema_name     | schema_size
> --------------------+-------------
>   public             | 656 kB
>   pg_catalog         | 6608 kB
>   pg_toast           | 412 GB
>   information_schema | 104 kB
>   abc                | 187 GB
> 
> We are upgrading this database from v12 to v16 and we want to do a dump 
> of it in case we decided to do a restore from v16 to v12.
> SO, after the upgrade, in case we want to rollback to v12, we will do a 
> pg_dump using v16 and then using v12 pg_restore
> When we do the dump, does it take into consideration the size of 
> pg_toast as well? So it will be 412+187-GB :( ?
> 

Yes. They are part of the tables, so, sure, they will be dumped (at 
least for those in the "abc" schema).

> BTW, was pg_toast created automatically by PostgreSQL? Reading on 
> https://www.postgresql.org/docs/current/storage-toast.html <https:// 
> www.postgresql.org/docs/current/storage-toast.html>, there is no mention 
> of it.
> 

Yes, it is automatically added when a user creates a database.

Regards.


-- 
Guillaume Lelarge
Consultant
https://dalibo.com