Re: PL/pgSQL, RAISE and error context

Hi

here is initial version of reduced patch. It is small code, but relative
big (although I expected bigger) change in tests.

if these changes are too big, then we have to introduce a plpgsql GUC
plpgsql.client_min_context and plpgsql.log_min_client. These GUC overwrite
global setting for plpgsql functions. I'll be more happy without these
variables. It decrease a impact of changes, but there is not clean what
behave is expected when PL are used together - and when fails PLpgSQL
function called from PLPerl. The context filtering should be really solved
on TOP level.

Regards

Pavel

2015-07-08 14:09 GMT+02:00 Merlin Moncure <mmoncure(at)gmail(dot)com>:

> On Wed, Jul 8, 2015 at 1:35 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> wrote:
> >
> >
> > 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.
> >
> > 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
>
> +1
>
> merlin
>