Re: [CAUTION: SUSPECT SENDER] RE: BUG #19029: Replication Slot size keeps increasing while logical subscription works fine

Hi,

> Can you clarify which directory occupied the disk? Is it `pg_wal`?
> You told that "upto 35GB per slot", and 6 replication slots exist on your
system,
> so did the disk usage increase 210GB in total?

Under the pg_replslot folder, each replication slot's folder increased
simultaneously. There were 12 folders (two publications, six subscribers),
and the total size increase was about 420 GB).

> Thanks. If possible, can you share the script to emulate system
architecture and
> settings? It is very helpful to fully understand the shape of the system
and
> definitions.

I will share as much data as I can.

> So you did run both DDLs and DMLs on the publisher side right? Can you
also
> provide SQL commands you run on the system? It's very helpful if all SQLs
are
> written in the executable scripts or something.

This is a complex ERP setup and I may not be able to give you all the SQL
from the publisher side. All of these 62 tables are either master tables or
configuration tables, so only INSERTs, DELETEs and UPDATEs happen, nothing
else.

Thank you for your help. I sincerely hope this is a real issue and not a
stupid configuration error at my end effectively wasting your valuable time.

Thadeus Anand.

On Mon, Aug 25, 2025 at 1:35 PM Hayato Kuroda (Fujitsu) <
kuroda(dot)hayato(at)fujitsu(dot)com> wrote:

> Dear Thadeus,
>
> >
> The size on the disk keeps increasing. Last week, it went upto 35 GB per
> slot,
> then I had to put a 20GB limit on max_slot_wal_keep_size. After reaching
> the size,
> the subscriptions went inactive. Then I dropped the subscriptions and
> freed up
> the replication slots.
> >
>
> Can you clarify which directory occupied the disk? Is it `pg_wal`?
> You told that "upto 35GB per slot", and 6 replication slots exist on your
> system,
> so did the disk usage increase 210GB in total?
>
> >
> I cannot share the real data right now because I have dropped the
> subscriptions
> and publications altogether. I can create them again tonight (I am in
> India) and
> share the details tomorrow.
> >
>
> Thanks. If possible, can you share the script to emulate system
> architecture and
> settings? It is very helpful to fully understand the shape of the system
> and
> definitions.
>
> >
> What I had was a straightforward logical replication setup. We had two
> publications
> and six subscribing servers. Please also note that this setup was working
> fine
> with PostgreSQL 15. During May we upgraded to 17.5, and ran into a bug
> which is
> described in the following release notes section of 17.6
> >
>
> So you did run both DDLs and DMLs on the publisher side right? Can you also
> provide SQL commands you run on the system? It's very helpful if all SQLs
> are
> written in the executable scripts or something.
>
> Best regards,
> Hayato Kuroda
> FUJITSU LIMITED
>
>