Re: PL/pgSQL, RAISE and error context - Mailing list pgsql-hackers

On Wed, Jul 8, 2015 at 4:39 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote:
> 2015-07-08 8:35 GMT+02:00 Pavel Stehule <pavel.stehule@gmail.com>:
>>
>>
>>
>> 2015-07-07 18:15 GMT+02:00 Merlin Moncure <mmoncure@gmail.com>:
>>>
>>> On Tue, Jul 7, 2015 at 9:04 AM, Pavel Stehule <pavel.stehule@gmail.com>
>>> wrote:
>>> >> It doesn't have to if the behavior is guarded with a GUC.  I just
>>> >> don't understand what all the fuss is about.  The default behavior of
>>> >> logging that is well established by other languages (for example java)
>>> >> that manage error stack for you should be to:
>>> >>
>>> >> *) Give stack trace when an uncaught exception is thrown
>>> >> *) Do not give stack trace in all other logging cases unless asked for
>>> >
>>> > what is RAISE EXCEPTION - first or second case?
>>>
>>> First: RAISE (unless caught) is no different than any other kind of
>>> error.
>>>
>>> On Tue, Jul 7, 2015 at 9:42 AM, Heikki Linnakangas <hlinnaka@iki.fi>
>>> wrote:
>>> > On 07/07/2015 04:56 PM, Merlin Moncure wrote:
>>> >> It doesn't have to if the behavior is guarded with a GUC.  I just
>>> >> don't understand what all the fuss is about.  The default behavior of
>>> >> logging that is well established by other languages (for example java)
>>> >> that manage error stack for you should be to:
>>> >>
>>> >> *) Give stack trace when an uncaught exception is thrown
>>> >> *) Do not give stack trace in all other logging cases unless asked for
>>> >
>>> > Java's exception handling is so different from PostgreSQL's errors that
>>> > I
>>> > don't think there's much to be learned from that. But I'll bite:
>>> >
>>> > First of all, Java's exceptions always contain a stack trace. It's up
>>> > to you
>>> > when you catch an exception to decide whether to print it or not. "try
>>> > { ...
>>> > } catch (Exception e) { e.printStackTrace() }" is fairly common,
>>> > actually.
>>> > There is nothing like a NOTICE in Java, i.e. an exception that's thrown
>>> > but
>>> > doesn't affect the control flow. The best I can think of is
>>> > System.out.println(), which of course has no stack trace attached to
>>> > it.
>>>
>>> exactly.
>>>
>>> > Perhaps you're arguing that NOTICE is more like printing to stderr, and
>>> > should never contain any context information. I don't think that would
>>> > be an
>>> > improvement. It's very handy to have the context information available
>>> > if
>>> > don't know where a NOTICE is coming from, even if in most cases you're
>>> > not
>>> > interested in it.
>>>
>>> That's exactly what I'm arguing.  NOTICE (and WARNING) are for
>>> printing out information to client side logging; it's really the only
>>> tool we have for that purpose and it fits that role perfectly.  Of
>>> course, you may want to have NOTICE print context, especially when
>>> debugging, but some control over that would be nice and in most cases
>>> it's really not necessary.  I really don't understand the objection to
>>> offering control over that behavior although I certainly understand
>>> wanting to keep the default behavior as it currently is.
>>>
>>> > This is really quite different from a programming language's exception
>>> > handling. First, there's a server, which produces the errors, and a
>>> > separate
>>> > client, which displays them. You cannot catch an exception in the
>>> > client.
>>> >
>>> > BTW, let me throw in one use case to consider. We've been talking about
>>> > psql, and what to print, but imagine a more sophisticated client like
>>> > pgAdmin. It's not limited to either printing the context or not. It
>>> > could
>>> > e.g. hide the context information of all messages when they occur, but
>>> > if
>>> > you double-click on it, it's expanded to show all the context, location
>>> > and
>>> > all. You can't do that if the server doesn't send the context
>>> > information in
>>> > the first place.
>>> >
>>> >> I would be happy to show you the psql redirected output logs from my
>>> >> nightly server processes that spew into the megabytes because of
>>> >> logging various high level steps (did this, did that).
>>> >
>>> > Oh, I believe you. I understand what the problem is, we're only talking
>>> > about how best to address it.
>>>
>>> Yeah.  For posterity, a psql based solution would work fine for me,
>>> but a server side solution has a lot of advantages (less protocol
>>> chatter, more configurability, keeping libpq/psql light).
>>
>>
>> After some work on reduced version of "plpgsql.min_context" patch I am
>> inclining to think so ideal solution needs more steps - because this issue
>> has more than one dimension.
>>
>> There are two independent issues:
>>
>> 1. old plpgsql workaround that reduced the unwanted call stack info for
>> RAISE NOTICE. Negative side effect of this workaround is missing context
>> info about the RAISE command that raises the exception. We know a function,
>> but we don't know a line of related RAISE statement. The important is fact,
>> so NOTICE doesn't bubble to up. So this workaround was relative successful
>> without to implement some filtering on client or log side.
>
>
> I found a other issue of this workaround - it doesn't work well for nested
> SQL statement call, when inner statement invoke RAISE NOTICE. In this case a
> context is showed too.
>
> postgres=# insert into xx values(60);
> NOTICE:  <<<<<>>>>>>
> NOTICE:  trigger_func(before_ins_stmt) called: action = INSERT, when =
> BEFORE, level = STATEMENT
> CONTEXT:  SQL statement "INSERT INTO boo VALUES(30)"
> PL/pgSQL function hh() line 1 at SQL statement
>
> So filtering context for selected environment is not good idea. The result
> is fragmented context, where is not clear, what is missing.

not quite following you. Is this a problem with your proposed patch,
or a reason why your patch is the 'right' implementation?

merlin