From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
cc: Andrew Dunstan <andrew@dunslane.net>, Andres Freund <andres@anarazel.de>,
        Alexander Korotkov <aekorotkov@gmail.com>,
        Robert Haas <robertmhaas@gmail.com>,
        "David G. Johnston" <david.g.johnston@gmail.com>,
        Corey Huinker <corey.huinker@gmail.com>,
        Joe Conway <mail@joeconway.com>,
        Nikita Glukhov <n.gluhov@postgrespro.ru>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Error-safe user functions
In-reply-to: <20221210122013.swbpo63go6ty2fcn@alvherre.pgsql>
References: <20221210122013.swbpo63go6ty2fcn@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@alvh.no-ip.org>
	message dated "Sat, 10 Dec 2022 13:20:13 +0100"
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Date: Sat, 10 Dec 2022 09:20:27 -0500
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Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> On 2022-Dec-09, Tom Lane wrote:
>> ...  So I think it might be
>> okay to say "if you want soft error treatment for a domain,
>> make sure its check constraints don't throw errors".

> I think that's fine.  If the user does, say "CHECK (value > 0)" and that
> results in a soft error, that seems to me enough support for now.  If
> they want to do something more elaborate, they can write C functions.
> Maybe eventually we'll want to offer some other mechanism that doesn't
> require C, but let's figure out what the requirements are.  I don't
> think we know that, at this point.

A fallback we can offer to anyone with such a problem is "write a
plpgsql function and wrap the potentially-failing bit in an exception
block".  Then they get to pay the cost of the subtransaction, while
we're not imposing one on everybody else.

			regards, tom lane