Re: [PATCH] Add recovery boundary WAL record for database and tablespace commands

Hi JoongHyuk,

Thanks for picking this up. Both reports have been open for years and
took me some time to understand why we need that.

One question. The 2019 report also mentions recovery_target_xid set
to the xid of DROP DATABASE, with recovery_target_inclusive = off.
With the patch I still get

FATAL: cannot connect to invalid database "db_dropped"

Do you plan to handle this case, or should the docs mention it?

Thanks,
Shihao

On Mon, Sep 7, 2026 at 1:21 AM JoongHyuk Shin <sjh910805(at)gmail(dot)com> wrote:

> CREATE/DROP DATABASE, ALTER DATABASE SET TABLESPACE
> and CREATE/DROP TABLESPACE change directories as their WAL is replayed,
> while recovery_target_time is only checked on commit and abort records.
> So a target set before such a command does not stop recovery before it,
> leaving a dropped database gone or an orphan directory.
> This was reported in [1] and again in [2].
>
> 0001 emits an XLOG2 record carrying a timestamp
> before the first irreversible record of each command
> and stops recovery before it when the timestamp is past the target.
> Stopping there loses nothing, as replaying the record has no effect.
>
> 0002 makes recovery_min_apply_delay wait on the record too.
> A delayed standby currently removes a dropped database's directory
> as soon as it reads the drop, long before the delay expires.
>
> [1]
> https://www.postgresql.org/message-id/flat/aac5c3e6-2805-ba06-143b-070478aa9434(at)loxodata(dot)com
> [2]
> https://www.postgresql.org/message-id/flat/43f0c3df-a23c-4159-9610-934d3dceb80c(at)pgbackrest(dot)org
>
> --
> JH Shin
>