Re: PL/pgSQL, RAISE and error context

On Fri, Apr 24, 2015 at 6:11 AM, Joel Jacobson <joel@trustly.com> wrote:
> Entering the discussion because this is a huge pain for me in my daily
> work as well.
>
> This is not a reply to any specific post in this thread, but my first
> message in the thread.
>
> I see a great value in providing both a GUC and a new RAISE syntax.
> The different benefits of the two are maybe obvious, but perhaps worth
> pointing out:
> GUC: Good because you don't have to change any existing code.
> RAISE syntax: Good because you can control exactly what message should
> be emitted or not be emitted at that line of code.
>
> I think preserving backwards compatibility is very important.
> Not changing the default is not a problem for me, as long as it can be
> overridden.
>
> Whatever the default behaviour is, I think the need expressed by all
> users in this thread boils down to any of these two sentences:
>
> "I want CONTEXT to be (DISPLAYED|SUPPRESSED) for (ALL|ONLY THIS LINE)
> RAISE (NOTICE|WARNING|ERROR)"
> OR
> "I don't want to change the default current behaviour of CONTEXT"
>
> So we basically need a boolean setting value, where:
> NULL means the default behaviour
> TRUE means DISPLAY CONTEXT
> FALSE means SUPPRESS CONTEXT
>
> And the (ALL|ONLY THIS) part translates into using,
> * a GUC to change behaviour for ALL lines of code,
> * or using the RAISE syntax to change the behaviour of ONLY THIS line of code.
>
> And then we have the different message levels, for which CONTEXT is
> sometimes desirable in some situations:
> * The RAISE syntax allows controlling any message level in a natural
> way, as the message level is part of the syntax.
> * Allowing the same control using GUC would mean the message level
> would need to be part of the GUC key name, which means either add
> multiple GUCs, one for each message level, or only allow controlling
> the most important one and ignore the possibly need to control the
> other message levels.
>
> If it would be possible to somehow combine multiple message levels in
> the same GUC, that would solve the latter problem.
>
> We already have comma separated values for many GUCs, so maybe we
> could use that approach here as well.
>
> It looks like adding these two GUCs would meet the demands of all users:
>
> suppress_context_messages (enum)
> display_context_messages (enum)
>
> This would allow doing something crazy as:
>
> suppress_context_messages = warning,error
> display_context_messages = notice

This is a very flexible proposal, but it's a tremendous amount of
machinery for what's really a very minor issue.  If we added two GUCs
for every comparably important issue, we'd have about 40,000 of them.

I suggest we add the RAISE syntax first, because everybody agrees on
that.  Then, we can argue about the other stuff.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company