Re: PL/pgSQL, RAISE and error context

2015-07-08 8:35 GMT+02:00 Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>:

>
>
> 2015-07-07 18:15 GMT+02:00 Merlin Moncure <mmoncure(at)gmail(dot)com>:
>
>> On Tue, Jul 7, 2015 at 9:04 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)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(at)iki(dot)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.

Pavel

>
> 2. second issue is general suppressing context info for interactive client
> or for log.
>
> These issues should be solved separately, because solution for @2 doesn't
> fix @1, and @1 is too local for @2.
>
> So what we can do?
>
> 1. remove current plpgsql workaround - and implement client_min_context
> and log_min_context
> 2. implement plpgsql.min_context, and client_min_context and
> log_min_context
>
> @1 is consistent, but isn't possible to configure same behave as was before
>
> @2 is difficult in definition what plpgsql.min_context should to really
> do - and what is relation to client_min_context and log_min_context, but I
> can prepare configuration, that is fully compatible.
>
> Comments, any other ideas?
>
> Personally, I prefer @1 as general solution, that will work for all PL
>
> Regards
>
> Pavel
>
>
>
>
>> merlin
>>
>
>