Re: PL/pgSQL return value in after triggers

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: PL/pgSQL return value in after triggers
Date: 2012-01-02 04:37:46
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On mån, 2011-02-28 at 19:07 +0200, Peter Eisentraut wrote:
> PL/pgSQL trigger functions currently require a value to be returned,
> even though that value is not used for anything in case of a trigger
> fired AFTER. I was wondering if we could relax that. It would make
> things a bit more robust and produce clearer PL/pgSQL code. The
> specific case I'm concerned about is that a trigger function could
> accidentally be run in a BEFORE trigger even though it was not meant for
> that. It is common practice that trigger functions for AFTER triggers
> return NULL, which would have unpleasant effects if used in a BEFORE
> trigger.
> I think it is very uncommon to have the same function usable for BEFORE
> and AFTER triggers, so it would be valuable to have coding support
> specifically for AFTER triggers. We could just allow RETURN without
> argument, or perhaps no RETURN at all.

Here is a patch for that.

One thing that I'm concerned about with this is that it treats a plain
RETURN in a BEFORE trigger as RETURN NULL, whereas arguably it should be
an error. I haven't found a good way to handle that yet, but I'll keep

Attachment Content-Type Size
plpgsql-trigger-return.patch text/x-patch 9.6 KB

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