Re: Reject invalid databases in pg_get_database_ddl()

Hi Amit,

On Thu, Apr 16, 2026 at 2:29 AM Amit Langote <amitlangote09@gmail.com>
wrote:

> Hi,
>
> On Thu, Apr 16, 2026 at 5:20 PM Lakshmi N <lakshmin.jhs@gmail.com> wrote:
> > pg_get_database_ddl() is not checking for databases in an invalid state
> > before producing ddl statements. This caused the function to emit
> > CONNECTION_LIMIT = -2, which is invalid SQL that Postgres rejects.
> > A database row can be in this inconsistent state longer, for example
> > server crashed during a drop database.
> >
> > Attached patch to fix this issue by doing a database_is_invalid_form()
> > check early in pg_get_database_ddl_internal().
>
> Thanks for the report.
>
> Hmm, I see that the function will happily emit datconnlimit = -2 and
> your patch catches that at the top instead of down below near this
> code:
>
> /* CONNECTION LIMIT */
> if (dbform->datconnlimit != -1)
> {
>     resetStringInfo(&buf);
>     appendStringInfo(&buf, "ALTER DATABASE %s CONNECTION LIMIT = %d;",
>                      quote_identifier(dbname), dbform->datconnlimit);
>     statements = lappend(statements, pstrdup(buf.data));
> }
>
> which, I guess, makes sense.
>
> The comment is correct but could be more explicit:
>
>     /*
>      * Reject invalid databases: datconnlimit = -2 would be emitted as
>      * CONNECTION LIMIT = -2, which fails on replay.
>      */
>
Thank you for reviewing! Please find the attached v2 addressing this.

Regards,
Lakshmi