From: Japin Li <japinli@hotmail.com>
To: Lakshmi N <lakshmin.jhs@gmail.com>
Cc: Amit Langote <amitlangote09@gmail.com>,
  "pgsql-hackers@lists.postgresql.org"
 <pgsql-hackers@lists.postgresql.org>,  andrew@dunslane.net
Subject: Re: Reject invalid databases in pg_get_database_ddl()
In-Reply-To: 
 <CA+3i_M8Mq7fr6mUspSa2rLik9+oY4sOeD1qsB_-dvnUB4NrYbg@mail.gmail.com>
	(Lakshmi N.'s message of "Thu, 16 Apr 2026 09:46:45 -0700")
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Hi, Lakshmi

On Thu, 16 Apr 2026 at 09:46, Lakshmi N <lakshmin.jhs@gmail.com> wrote:
> Hi Amit,
>
> On Thu, Apr 16, 2026 at 2:29=E2=80=AFAM Amit Langote <amitlangote09@gmail=
.com> wrote:
>
>  Hi,
>
>  On Thu, Apr 16, 2026 at 5:20=E2=80=AFPM Lakshmi N <lakshmin.jhs@gmail.co=
m> wrote:
>  > pg_get_database_ddl() is not checking for databases in an invalid stat=
e
>  > before producing ddl statements. This caused the function to emit
>  > CONNECTION_LIMIT =3D -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 =3D -2 and
>  your patch catches that at the top instead of down below near this
>  code:
>
>  /* CONNECTION LIMIT */
>  if (dbform->datconnlimit !=3D -1)
>  {
>      resetStringInfo(&buf);
>      appendStringInfo(&buf, "ALTER DATABASE %s CONNECTION LIMIT =3D %d;",
>                       quote_identifier(dbname), dbform->datconnlimit);
>      statements =3D lappend(statements, pstrdup(buf.data));
>  }
>
>  which, I guess, makes sense.
>
>  The comment is correct but could be more explicit:
>
>      /*
>       * Reject invalid databases: datconnlimit =3D -2 would be emitted as
>       * CONNECTION LIMIT =3D -2, which fails on replay.
>       */
>
> Thank you for reviewing! Please find the attached v2 addressing this.
>

Thanks for updating the patch.  Is it possible to cover this with a test ca=
se?

> Regards,
> Lakshmi=20
>
> [4. text/x-diff; v2-0001-Reject-pg_get_database_ddl-for-invalid-databases=
.patch]...

--=20
Regards,
Japin Li
ChengDu WenWu Information Technology Co., Ltd.