Re: Reject invalid databases in pg_get_database_ddl()

From: Amit Langote <amitlangote09(at)gmail(dot)com>
To: Hu Xunqi <huxunqi(dot)08(at)gmail(dot)com>
Cc: Euler Taveira <euler(at)eulerto(dot)com>, Lakshmi N <lakshmin(dot)jhs(at)gmail(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Andrew Dunstan <andrew(at)dunslane(dot)net>
Subject: Re: Reject invalid databases in pg_get_database_ddl()
Date: 2026-04-17 03:30:59
Message-ID: CA+HiwqGf_eQNK_bqJzL7YZvXKhpCWsbxxa6pwYVAhQLcPS0rAQ@mail.gmail.com
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Hi,

On Fri, Apr 17, 2026 at 11:49 AM Hu Xunqi <huxunqi(dot)08(at)gmail(dot)com> wrote:
> On Fri, Apr 17, 2026 at 10:16 AM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> + /*
> + * Reject invalid databases: datconnlimit = -2 would be emitted as
> + * CONNECTION LIMIT = -2, which cannot be executed.
> + */
>
> This comment looks a bit too centered on datconnlimit=-2, but the real issue is that an invalid pg_database row should not be deparsed into DDL. So, maybe rephrase like:
>
> /*
> * Reject invalid databases. Deparsing a pg_database row in invalid state
> * can produce SQL that is not executable, such as CONNECTION LIMIT = -2.
> */

I was trying to be precise about datconnlimit = -2 being the thing
that produces invalid SQL. But your version covers that with the "such
as CONNECTION LIMIT = -2" example, and it's closer to the original,
which was on the right track, just needed to be more precise. Let's go
with it.

--
Thanks, Amit Langote

Attachment Content-Type Size
v4-0001-Reject-invalid-databases-in-pg_get_database_ddl.patch application/octet-stream 1.7 KB

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