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