Re: Error-safe user functions

From: Ted Yu <yuzhihong(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, Amul Sul <sulamul(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Corey Huinker <corey(dot)huinker(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Joe Conway <mail(at)joeconway(dot)com>, Nikita Glukhov <n(dot)gluhov(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Error-safe user functions
Date: 2022-12-24 09:51:10
Message-ID: CALte62yRJwVzp5CxRRsumXV-0Y1JBHZguRGFMQt2fgwH0nUusw@mail.gmail.com
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On Fri, Dec 23, 2022 at 1:22 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Ted Yu <yuzhihong(at)gmail(dot)com> writes:
> > In makeItemLikeRegex :
>
> > + /* See regexp.c for explanation */
> > + CHECK_FOR_INTERRUPTS();
> > + pg_regerror(re_result, &re_tmp, errMsg,
> > sizeof(errMsg));
> > + ereturn(escontext, false,
>
> > Since an error is returned, I wonder if the `CHECK_FOR_INTERRUPTS` call
> is
> > still necessary.
>
> Yes, it is. We don't want a query-cancel transformed into a soft error.
>
> regards, tom lane
>
Hi,
For this case (`invalid regular expression`), the potential user
interruption is one reason for stopping execution.
I feel surfacing user interruption somehow masks the underlying error.

The same regex, without user interruption, would exhibit an `invalid
regular expression` error.
I think it would be better to surface the error.

Cheers

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