Re: pl/python tracebacks

Here's a patch implementing traceback support for PL/Python mentioned in
http://archives.postgresql.org/pgsql-hackers/2010-12/msg01991.php. It's
an incremental patch on top of the plpython-refactor patch sent eariler.

Git branch for this patch:
https://github.com/wulczer/postgres/tree/tracebacks.

It's a variant of
http://archives.postgresql.org/pgsql-patches/2006-02/msg00288.php with a
few more twists.

For errors originating from Python exceptions add the traceback as the
message detail. The patch tries to mimick Python's traceback.py module
behaviour as close as possible, icluding interleaving stack frames with
source code lines in the detail message. Any Python developer should
instantly recognize these kind of error reporting, it looks almost the
same as an error in the interactive Python shell.

A future optimisation might be not splitting the procedure source each
time a traceback is generated, but for now it's probably not the most
important scenario to optimise for.

Cheers,
Jan

On 23/12/10 14:56, Jan Urbański wrote:
> Here's a patch implementing traceback support for PL/Python mentioned in
> http://archives.postgresql.org/pgsql-hackers/2010-12/msg01991.php. It's
> an incremental patch on top of the plpython-refactor patch sent eariler.

Updated to master.

On 27/01/11 22:58, Jan Urbański wrote:
> On 23/12/10 14:56, Jan Urbański wrote:
>> Here's a patch implementing traceback support for PL/Python mentioned in
>> http://archives.postgresql.org/pgsql-hackers/2010-12/msg01991.php. It's
>> an incremental patch on top of the plpython-refactor patch sent eariler.
>
> Updated to master.

Updated to master again.

On 06/02/11 20:12, Jan Urbański wrote:
> On 27/01/11 22:58, Jan Urbański wrote:
>> On 23/12/10 14:56, Jan Urbański wrote:
>>> Here's a patch implementing traceback support for PL/Python mentioned in
>>> http://archives.postgresql.org/pgsql-hackers/2010-12/msg01991.php. It's
>>> an incremental patch on top of the plpython-refactor patch sent eariler.
>>
>> Updated to master.
>
> Updated to master again.

Once more.

On Wed, Feb 9, 2011 at 4:10 AM, Jan Urbański <wulczer(at)wulczer(dot)org> wrote:
> On 06/02/11 20:12, Jan Urbański wrote:
>> On 27/01/11 22:58, Jan Urbański wrote:
>>> On 23/12/10 14:56, Jan Urbański wrote:
>>>> Here's a patch implementing traceback support for PL/Python mentioned in
>>>> http://archives.postgresql.org/pgsql-hackers/2010-12/msg01991.php. It's
>>>> an incremental patch on top of the plpython-refactor patch sent eariler.
>>>
>>> Updated to master.
>>
>> Updated to master again.
>
> Once more.

Alex Hunsaker is listed as the reviewer for this patch, but I don't
see a review posted. If this feature is still wanted for 9.1, can
someone jump in here?

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

On Fri, Feb 11, 2011 at 08:45, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Wed, Feb 9, 2011 at 4:10 AM, Jan Urbański <wulczer(at)wulczer(dot)org> wrote:
>> On 06/02/11 20:12, Jan Urbański wrote:
>>> On 27/01/11 22:58, Jan Urbański wrote:
>>>> On 23/12/10 14:56, Jan Urbański wrote:
>>>>> Here's a patch implementing traceback support for PL/Python mentioned in
>>>>> http://archives.postgresql.org/pgsql-hackers/2010-12/msg01991.php. It's
>>>>> an incremental patch on top of the plpython-refactor patch sent eariler.
>>>>
>>>> Updated to master.
>>>
>>> Updated to master again.
>>
>> Once more.
>
> Alex Hunsaker is listed as the reviewer for this patch, but I don't
> see a review posted.  If this feature is still wanted for 9.1, can
> someone jump in here?

Goodness... I picked up this patch the day before yesterday because
no-one was listed. That being said, if anyone else wants to beat me to
the punch of reviewing this, have at it! The more eyes the merrier!

I wish I could squeeze
the lime of my time to find
a few more hours

On Fri, Feb 11, 2011 at 11:22 AM, Alex Hunsaker <badalex(at)gmail(dot)com> wrote:
> On Fri, Feb 11, 2011 at 08:45, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> On Wed, Feb 9, 2011 at 4:10 AM, Jan Urbański <wulczer(at)wulczer(dot)org> wrote:
>>> On 06/02/11 20:12, Jan Urbański wrote:
>>>> On 27/01/11 22:58, Jan Urbański wrote:
>>>>> On 23/12/10 14:56, Jan Urbański wrote:
>>>>>> Here's a patch implementing traceback support for PL/Python mentioned in
>>>>>> http://archives.postgresql.org/pgsql-hackers/2010-12/msg01991.php. It's
>>>>>> an incremental patch on top of the plpython-refactor patch sent eariler.
>>>>>
>>>>> Updated to master.
>>>>
>>>> Updated to master again.
>>>
>>> Once more.
>>
>> Alex Hunsaker is listed as the reviewer for this patch, but I don't
>> see a review posted.  If this feature is still wanted for 9.1, can
>> someone jump in here?
>
> Goodness... I picked up this patch the day before yesterday because
> no-one was listed. That being said, if anyone else wants to beat me to
> the punch of reviewing this, have at it! The more eyes the merrier!

Sorry, I didn't see when you'd picked it up. I was just keeping an
eye on my wall calendar.

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

Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

>> Goodness... I picked up this patch the day before yesterday
>> because no-one was listed. That being said, if anyone else wants
>> to beat me to the punch of reviewing this, have at it! The more
>> eyes the merrier!
>
> Sorry, I didn't see when you'd picked it up. I was just keeping
> an eye on my wall calendar.

[OT]

FWIW, this is the sort of situation which caused me to suggest that
the web app somehow show the date of the last reviewer change when
it is past the "Last Activity" date. I don't really care whether it
would be in the Reviewers column or as a second line, in
parentheses, in the Last Activity column. I would find it useful
when managing a CF, anyway....

-Kevin

On Wed, Feb 9, 2011 at 02:10, Jan Urbański <wulczer(at)wulczer(dot)org> wrote:
> On 06/02/11 20:12, Jan Urbański wrote:
>> On 27/01/11 22:58, Jan Urbański wrote:
>>> On 23/12/10 14:56, Jan Urbański wrote:
>>>> Here's a patch implementing traceback support for PL/Python mentioned in
>>>> http://archives.postgresql.org/pgsql-hackers/2010-12/msg01991.php. It's
>>>> an incremental patch on top of the plpython-refactor patch sent eariler.
>>>
>>> Updated to master.
>>
>> Updated to master again.
>
> Once more.

In PLy_traceback fname and prname look like they will leak (well as
much as a palloc() in an error path can leak I suppose). Other than
that everything looks good. I tested plpython2 and plpython3 and
skimmed the docs to see if there was anything obvious that needed
updating. I also obviously looked at the added regression tests and
made sure they worked.

Marking as Ready.

On 12/02/11 04:12, Alex Hunsaker wrote:
> On Wed, Feb 9, 2011 at 02:10, Jan Urbański <wulczer(at)wulczer(dot)org> wrote:
>> On 06/02/11 20:12, Jan Urbański wrote:
>>> On 27/01/11 22:58, Jan Urbański wrote:
>>>> On 23/12/10 14:56, Jan Urbański wrote:
>>>>> Here's a patch implementing traceback support for PL/Python mentioned in
>>>>> http://archives.postgresql.org/pgsql-hackers/2010-12/msg01991.php. It's
>>>>> an incremental patch on top of the plpython-refactor patch sent eariler.
>>>>
>>>> Updated to master.
>>>
>>> Updated to master again.
>>
>> Once more.
>
> In PLy_traceback fname and prname look like they will leak (well as
> much as a palloc() in an error path can leak I suppose).

But they're no palloc'd, no? fname is either a static "<module"> string,
or PyString_AsString, which also doesn't allocate memory, AFAIK. proname
is also a static string. They're transferred to heap-allocated memory in
appendStringInfo, which gets pfreed after emitting the error message.

> Marking as Ready.

Thanks!

Jan

On Sat, Feb 12, 2011 at 01:50, Jan Urbański <wulczer(at)wulczer(dot)org> wrote:
> On 12/02/11 04:12, Alex Hunsaker wrote:
>> In PLy_traceback fname and prname look like they will leak (well as
>> much as a palloc() in an error path can leak I suppose).
>
> But they're no palloc'd, no? fname is either a static "<module"> string,
> or PyString_AsString, which also doesn't allocate memory, AFAIK.

Yeah, I was flat out wrong about proname :-(.

As for fname, I must be missing some magic. We have:

#if PY_MAJOR_VERSION > 3
...
#define PyString_AsString(x) PLyUnicode_AsString(x)
....
PLyUnicode_AsString(PyObject *unicode)
{
PyObject *o = PLyUnicode_Bytes(unicode);
char *rv = pstrdup(PyBytes_AsString(o));

Py_XDECREF(o);
return rv;
}

PyString_AsString is used all over the place without any pfrees. But I
have no Idea how that pstrdup() is getting freed if at all.

Care to enlighten me ?

On 12/02/11 10:00, Alex Hunsaker wrote:
> On Sat, Feb 12, 2011 at 01:50, Jan Urbański <wulczer(at)wulczer(dot)org> wrote:
>> On 12/02/11 04:12, Alex Hunsaker wrote:
>>> In PLy_traceback fname and prname look like they will leak (well as
>>> much as a palloc() in an error path can leak I suppose).
>>
>> But they're no palloc'd, no? fname is either a static "<module"> string,
>> or PyString_AsString, which also doesn't allocate memory, AFAIK.
>
> Yeah, I was flat out wrong about proname :-(.
>
> As for fname, I must be missing some magic. We have:
>
> #if PY_MAJOR_VERSION > 3
> ...
> #define PyString_AsString(x) PLyUnicode_AsString(x)
> ....
> PLyUnicode_AsString(PyObject *unicode)
> {
> PyObject *o = PLyUnicode_Bytes(unicode);
> char *rv = pstrdup(PyBytes_AsString(o));
>
> Py_XDECREF(o);
> return rv;
> }
>
> PyString_AsString is used all over the place without any pfrees. But I
> have no Idea how that pstrdup() is getting freed if at all.
>
> Care to enlighten me ?

Ooops, seems that this hack that's meant to improve compatibility with
Python3 makes it leak. I wonder is the pstrdup is necessary here, but
OTOH the leak should not be overly significant, given that no-one
complained about it before... and PyString_AsString is being used in
several other places.

Jan

On lör, 2011-02-12 at 02:00 -0700, Alex Hunsaker wrote:
> PyString_AsString is used all over the place without any pfrees. But I
> have no Idea how that pstrdup() is getting freed if at all.

pstrdup() like palloc() allocates memory from the current memory
context, which is freed automatically at some useful time, often at the
end of the query. It is very common throughout the PostgreSQL code that
memory is not explicitly freed. See src/backend/utils/mmgr/README for
more information.

On lör, 2011-02-12 at 10:07 +0100, Jan Urbański wrote:
> > PLyUnicode_AsString(PyObject *unicode)
> > {
> > PyObject *o = PLyUnicode_Bytes(unicode);
> > char *rv = pstrdup(PyBytes_AsString(o));
> >
> > Py_XDECREF(o);
> > return rv;
> > }
> >
> > PyString_AsString is used all over the place without any pfrees. But
> I
> > have no Idea how that pstrdup() is getting freed if at all.
> >
> > Care to enlighten me ?
>
> Ooops, seems that this hack that's meant to improve compatibility with
> Python3 makes it leak. I wonder is the pstrdup is necessary here,

The result of PyBytes_AsString(o) points into the internal storage of o,
which is released (effectively freed) by the decref on the next line.
So you'd better make a copy if you want to keep using it.

On tor, 2010-12-23 at 14:56 +0100, Jan Urbański wrote:
> For errors originating from Python exceptions add the traceback as the
> message detail. The patch tries to mimick Python's traceback.py module
> behaviour as close as possible, icluding interleaving stack frames
> with source code lines in the detail message. Any Python developer
> should instantly recognize these kind of error reporting, it looks
> almost the same as an error in the interactive Python shell.

I think the traceback should go into the CONTEXT part of the error. The
context message that's already there is now redundant with the
traceback.

You could even call errcontext() multiple times to build up the
traceback, but maybe that's not necessary.

On 24/02/11 14:10, Peter Eisentraut wrote:
> On tor, 2010-12-23 at 14:56 +0100, Jan Urbański wrote:
>> For errors originating from Python exceptions add the traceback as the
>> message detail. The patch tries to mimick Python's traceback.py module
>> behaviour as close as possible, icluding interleaving stack frames
>> with source code lines in the detail message. Any Python developer
>> should instantly recognize these kind of error reporting, it looks
>> almost the same as an error in the interactive Python shell.
>
> I think the traceback should go into the CONTEXT part of the error. The
> context message that's already there is now redundant with the
> traceback.
>
> You could even call errcontext() multiple times to build up the
> traceback, but maybe that's not necessary.

Hm, perhaps, I put it in the details, because it sounded like the place
to put information that is not that important, but still helpful. It's
kind of natural to think of the traceback as the detail of the error
message. But if you prefer context, I'm fine with that. You want me to
update the patch to put the traceback in the context?

Jan

On Thu, Feb 24, 2011 at 9:03 AM, Jan Urbański <wulczer(at)wulczer(dot)org> wrote:
> On 24/02/11 14:10, Peter Eisentraut wrote:
>> On tor, 2010-12-23 at 14:56 +0100, Jan Urbański wrote:
>>> For errors originating from Python exceptions add the traceback as the
>>> message detail. The patch tries to mimick Python's traceback.py module
>>> behaviour as close as possible, icluding interleaving stack frames
>>> with source code lines in the detail message. Any Python developer
>>> should instantly recognize these kind of error reporting, it looks
>>> almost the same as an error in the interactive Python shell.
>>
>> I think the traceback should go into the CONTEXT part of the error.  The
>> context message that's already there is now redundant with the
>> traceback.
>>
>> You could even call errcontext() multiple times to build up the
>> traceback, but maybe that's not necessary.
>
> Hm, perhaps, I put it in the details, because it sounded like the place
> to put information that is not that important, but still helpful. It's
> kind of natural to think of the traceback as the detail of the error
> message. But if you prefer context, I'm fine with that. You want me to
> update the patch to put the traceback in the context?

I don't see a response to this question from Peter, but I read his
email to indicate that he was hoping you'd rework along these lines.

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

----- Original message -----
> On Thu, Feb 24, 2011 at 9:03 AM, Jan Urbański <wulczer(at)wulczer(dot)org>
> wrote:
> > On 24/02/11 14:10, Peter Eisentraut wrote:
> > Hm, perhaps, I put it in the details, because it sounded like the place
> > to put information that is not that important, but still helpful. It's
> > kind of natural to think of the traceback as the detail of the error
> > message. But if you prefer context, I'm fine with that. You want me to
> > update the patch to put the traceback in the context?
>
> I don't see a response to this question from Peter, but I read his
> email to indicate that he was hoping you'd rework along these lines.

I can do that, but not until Monday evening.

Jan

On lör, 2011-02-26 at 09:34 +0100, Jan Urbański wrote:
> ----- Original message -----
> > On Thu, Feb 24, 2011 at 9:03 AM, Jan Urbański <wulczer(at)wulczer(dot)org>
> > wrote:
> > > On 24/02/11 14:10, Peter Eisentraut wrote:
> > > Hm, perhaps, I put it in the details, because it sounded like the place
> > > to put information that is not that important, but still helpful. It's
> > > kind of natural to think of the traceback as the detail of the error
> > > message. But if you prefer context, I'm fine with that. You want me to
> > > update the patch to put the traceback in the context?
> >
> > I don't see a response to this question from Peter, but I read his
> > email to indicate that he was hoping you'd rework along these lines.
>
> I can do that, but not until Monday evening.

Well, I was hoping for some other opinion, but I guess my request
stands.

On 26/02/11 16:10, Peter Eisentraut wrote:
> On lör, 2011-02-26 at 09:34 +0100, Jan Urbański wrote:
>> ----- Original message -----
>>> On Thu, Feb 24, 2011 at 9:03 AM, Jan Urbański <wulczer(at)wulczer(dot)org>
>>> wrote:
>>>> On 24/02/11 14:10, Peter Eisentraut wrote:
>>>> Hm, perhaps, I put it in the details, because it sounded like the place
>>>> to put information that is not that important, but still helpful. It's
>>>> kind of natural to think of the traceback as the detail of the error
>>>> message. But if you prefer context, I'm fine with that. You want me to
>>>> update the patch to put the traceback in the context?
>>>
>>> I don't see a response to this question from Peter, but I read his
>>> email to indicate that he was hoping you'd rework along these lines.
>>
>> I can do that, but not until Monday evening.
>
> Well, I was hoping for some other opinion, but I guess my request
> stands.

I looked into putting the tracebacks in the context field, but IMHO it
doesn't really play out nice. PL/Python uses a errcontext callback to
populate the context field, so the reduntant information (the name of
the function) is always there. If that callback would be removed, the
context information will not appear in plpy.warning output, which I
think would be bad.

So: the context is currently put unconditionally into every elog
message, which I think is good. In case of errors, the traceback already
includes the procedure name (because of how Python tracebacks are
typically formatted), which makes the traceback contain redundant
information to the context field. Replacing the context field with the
traceback is difficult, because it is populated by the error context
callback.

After thinking about it more I believe that the context field should
keep on being a one line indication of which function the message comes
from (and that's how it's done in PL/pgSQL for instance), and the detail
field should be used for the details of the message, like the traceback
that comes with it, and that's what the attached patch does.

While testing I noticed that this broke "raise plpy.Fatal()" behaviour -
it was no longer terminating the backend but just raising an error.
That's fixed in this version. This patch also fixes a place where
ereport is being used to report Python errors, which leads to losing the
original error. Incidentally, this is exactly the issue that made
diagnosing this bug:

http://postgresql.1045698.n5.nabble.com/Bug-in-plpython-s-Python-Generators-td3230402.html

so difficult.

Cheers,
Jan

=?UTF-8?B?SmFuIFVyYmHFhHNraQ==?= <wulczer(at)wulczer(dot)org> writes:
> I looked into putting the tracebacks in the context field, but IMHO it
> doesn't really play out nice. PL/Python uses a errcontext callback to
> populate the context field, so the reduntant information (the name of
> the function) is always there. If that callback would be removed, the
> context information will not appear in plpy.warning output, which I
> think would be bad.

> So: the context is currently put unconditionally into every elog
> message, which I think is good. In case of errors, the traceback already
> includes the procedure name (because of how Python tracebacks are
> typically formatted), which makes the traceback contain redundant
> information to the context field. Replacing the context field with the
> traceback is difficult, because it is populated by the error context
> callback.

> After thinking about it more I believe that the context field should
> keep on being a one line indication of which function the message comes
> from (and that's how it's done in PL/pgSQL for instance), and the detail
> field should be used for the details of the message, like the traceback
> that comes with it, and that's what the attached patch does.

To me, none of those arguments seem good. Traceback is the sort of
thing that belongs in errcontext, and arbitarily deciding that plpython
isn't going to play by the rules doesn't sit well here. I agree that
what you are showing is redundant with the current errcontext printout,
but the solution for that is to change the errcontext printout, not to
add redundant and inappropriate errdetail.

An example of the reasoning for this is the situation where a plpython
function calls back into SQL, and something there throws an ereport
(which might include an errdetail). It would be useful to include the
Python traceback in the errcontext stack, since there might be multiple
levels of Python function call within what PG sees as just a "plpython
function". But you can't get there with this approach.

regards, tom lane

On 01/03/11 20:15, Tom Lane wrote:
> =?UTF-8?B?SmFuIFVyYmHFhHNraQ==?= <wulczer(at)wulczer(dot)org> writes:
>> After thinking about it more I believe that the context field should
>> keep on being a one line indication of which function the message comes
>> from (and that's how it's done in PL/pgSQL for instance), and the detail
>> field should be used for the details of the message, like the traceback
>> that comes with it, and that's what the attached patch does.
>
> To me, none of those arguments seem good. Traceback is the sort of
> thing that belongs in errcontext, and arbitarily deciding that plpython
> isn't going to play by the rules doesn't sit well here. I agree that
> what you are showing is redundant with the current errcontext printout,
> but the solution for that is to change the errcontext printout, not to
> add redundant and inappropriate errdetail.
>
> An example of the reasoning for this is the situation where a plpython
> function calls back into SQL, and something there throws an ereport
> (which might include an errdetail). It would be useful to include the
> Python traceback in the errcontext stack, since there might be multiple
> levels of Python function call within what PG sees as just a "plpython
> function". But you can't get there with this approach.

Currently the traceback is added to the detail and the original
errdetail is preserved. So you'd get the detail line and the traceback
below it.

But OK, since there are more voices in favour of putting tracebacks in
the context field, I'll keep on looking for a solution.

Jan

=?UTF-8?B?SmFuIFVyYmHFhHNraQ==?= <wulczer(at)wulczer(dot)org> writes:
> Currently the traceback is added to the detail and the original
> errdetail is preserved. So you'd get the detail line and the traceback
> below it.

Hm? I'm talking about plpython_error_callback() and friends, which
AFAICS you haven't changed the behavior of at all. And it would
certainly be completely inappropriate to do what's said above for
an errdetail with a non-plpython origin.

regards, tom lane

On 01/03/11 20:35, Tom Lane wrote:
> =?UTF-8?B?SmFuIFVyYmHFhHNraQ==?= <wulczer(at)wulczer(dot)org> writes:
>> Currently the traceback is added to the detail and the original
>> errdetail is preserved. So you'd get the detail line and the traceback
>> below it.
>
> Hm? I'm talking about plpython_error_callback() and friends, which
> AFAICS you haven't changed the behavior of at all. And it would
> certainly be completely inappropriate to do what's said above for
> an errdetail with a non-plpython origin.

Not sure if I understand the problem. PL/Python sets
plpython_error_callback right after entering the function call handler,
so any elog thrown while the function is executing has a "PL/Python
function %s" context message. If plpython calls into SQL with SPI and
something there throws an elog(ERROR) with an errdetail, that detail is
saved inside the exception and a Python error is then thrown. If this
Python error reaches the top of the Python stack, the error reporting
code kicks in, extracts the saved errdetail value from the Python
exception, and then extract the stack trace and also adds it to the
errdetail.

So you end up with a context message saying "PL/Python function %s" and
a detail message with the saved detail (if it's present) *and* the
traceback. The problem is that the name of the function is already in
the traceback, so there's no need for the context *if* there's a
traceback present.

The problem I'm having is technical: since the callback is already set
when the code reaches the traceback-printing stage, you can't really
unset it. AFAICS the elog code calls *all* callbacks from
error_context_stack. So I can't prevent the context message from
appearing. If I make the traceback part of the context as well, it's
just going to appear together with the message from the callback.

Jan

On Mar 1, 2011, at 12:10 PM, Jan Urbański wrote:
> So you end up with a context message saying "PL/Python function %s" and
> a detail message with the saved detail (if it's present) *and* the
> traceback. The problem is that the name of the function is already in
> the traceback, so there's no need for the context *if* there's a
> traceback present.
>
> The problem I'm having is technical: since the callback is already set
> when the code reaches the traceback-printing stage, you can't really
> unset it. AFAICS the elog code calls *all* callbacks from
> error_context_stack. So I can't prevent the context message from
> appearing. If I make the traceback part of the context as well, it's
> just going to appear together with the message from the callback.

I remember going through a lot of pain getting this done "right"
in pg-python[pl/py].

SELECT it_blows_up();
ERROR: function's "main" raised a Python exception
CONTEXT: [exception from Python]
Traceback (most recent call last):
File "public.it_blows_up()", line 13, in main
three()
File "public.it_blows_up()", line 10, in three
return two()
File "public.it_blows_up()", line 7, in two
return one()
File "public.it_blows_up()", line 4, in one
raise OverflowError("there's water everywhere")
OverflowError: there's water everywhere

[public.it_blows_up()]

IIRC, I unconditionally print the "[public.it_blows_up()]" part iff it's
not an ERROR. If it is an ERROR, I let the traceback rendering part of the code
handle it on the PL's entry point exit. It was really tricky to do this because I
was rendering the traceback *after* the error_context_stack had been called.

On tis, 2011-03-01 at 21:10 +0100, Jan Urbański wrote:
> So you end up with a context message saying "PL/Python function %s"
> and a detail message with the saved detail (if it's present) *and* the
> traceback. The problem is that the name of the function is already in
> the traceback, so there's no need for the context *if* there's a
> traceback present.

I wouldn't actually worry about that bit of redundancy so much. Getting
proper context for nested calls is much more important.

On 01/03/11 22:12, Peter Eisentraut wrote:
> On tis, 2011-03-01 at 21:10 +0100, Jan Urbański wrote:
>> So you end up with a context message saying "PL/Python function %s"
>> and a detail message with the saved detail (if it's present) *and* the
>> traceback. The problem is that the name of the function is already in
>> the traceback, so there's no need for the context *if* there's a
>> traceback present.
>
> I wouldn't actually worry about that bit of redundancy so much. Getting
> proper context for nested calls is much more important.

Here's another version that puts tracebacks in the context field.

I did some tests with the attached test script, calling various of the
functions defined there and the error messages more or less made sense
(or at least were not worse than before).

Cheers,
Jan

On 02/03/11 22:28, Jan Urbański wrote:
> On 01/03/11 22:12, Peter Eisentraut wrote:
>> On tis, 2011-03-01 at 21:10 +0100, Jan Urbański wrote:
>>> So you end up with a context message saying "PL/Python function %s"
>>> and a detail message with the saved detail (if it's present) *and* the
>>> traceback. The problem is that the name of the function is already in
>>> the traceback, so there's no need for the context *if* there's a
>>> traceback present.
>>
>> I wouldn't actually worry about that bit of redundancy so much. Getting
>> proper context for nested calls is much more important.
>
> Here's another version that puts tracebacks in the context field.
>
> I did some tests with the attached test script, calling various of the
> functions defined there and the error messages more or less made sense
> (or at least were not worse than before).

I realized I did not update the patch state in the CF app when I added
this version, so I flipped it back to Ready for Committer now.

Tracebacks are a nice-to-have, so if we decide to drop this one due to
time constraints, I'd understand that. But fixing "raise plpy.Fatal()"
to actually cause a FATAL is something that should be extracted from
this patch and committed, even if the full patch does not make it.

Cheers,
Jan

On ons, 2011-03-02 at 22:28 +0100, Jan Urbański wrote:
> I did some tests with the attached test script, calling various of the
> functions defined there and the error messages more or less made sense
> (or at least were not worse than before).

Is that script part of the regression tests you added?

On sön, 2011-03-06 at 13:14 +0100, Jan Urbański wrote:
> But fixing "raise plpy.Fatal()"
> to actually cause a FATAL is something that should be extracted from
> this patch and committed, even if the full patch does not make it.

Um, what? I didn't find any details about this in this thread, nor a
test case.

On 07/03/11 13:53, Peter Eisentraut wrote:
> On ons, 2011-03-02 at 22:28 +0100, Jan Urbański wrote:
>> I did some tests with the attached test script, calling various of the
>> functions defined there and the error messages more or less made sense
>> (or at least were not worse than before).
>
> Is that script part of the regression tests you added?

No, the regression tests are a bit different. Maybe this script should
be part of them as well?

On 07/03/11 13:53, Peter Eisentraut wrote:
> On sön, 2011-03-06 at 13:14 +0100, Jan Urbański wrote:
>> But fixing "raise plpy.Fatal()"
>> to actually cause a FATAL is something that should be extracted from
>> this patch and committed, even if the full patch does not make it.
>
> Um, what? I didn't find any details about this in this thread, nor a
> test case.

Yes, my fault for sneaking it here without more introduction than this
comment several messages upthread:

"""
While testing I noticed that this broke "raise plpy.Fatal()" behaviour -
it was no longer terminating the backend but just raising an error.
That's fixed in this version. This patch also fixes a place where
ereport is being used to report Python errors, which leads to losing the
original error. Incidentally, this is exactly the issue that made
diagnosing this bug:

http://postgresql.1045698.n5.nabble.com/Bug-in-plpython-s-Python-Generators-td3230402.html

so difficult.
"""

So this in fact are three separate things, tracebacks, fix for
plpy.Fatal and a one-line fix for reporting errors in Python iterators,
that as I noticed has a side effect of changing the SQLCODE being raised
:( I think I'll just respin the tracebacks patch as 3 separate ones,
coming right up.

BTW, it's hard to test if raising plpy.Fatal actually causes a FATAL
elog, because that would terminate the backend running the tests, and I
though pg_regress treats this as an unconditional error (or am I mistaken?).

Jan

On 07/03/11 14:01, Jan Urbański wrote:
> On 07/03/11 13:53, Peter Eisentraut wrote:
>> On sön, 2011-03-06 at 13:14 +0100, Jan Urbański wrote:
>>> But fixing "raise plpy.Fatal()"
>>> to actually cause a FATAL is something that should be extracted from
>>> this patch and committed, even if the full patch does not make it.
>>
>> Um, what? I didn't find any details about this in this thread, nor a
>> test case.

> So this in fact are three separate things, tracebacks, fix for
> plpy.Fatal and a one-line fix for reporting errors in Python iterators,
> that as I noticed has a side effect of changing the SQLCODE being raised
> :( I think I'll just respin the tracebacks patch as 3 separate ones,
> coming right up.

Respun as three separate patches. Sorry for the confusion. BTW: looks
like plpy.Fatal behaviour has been broken for quite some time now.

Jan

On mån, 2011-03-07 at 14:19 +0100, Jan Urbański wrote:
> On 07/03/11 14:01, Jan Urbański wrote:
> > On 07/03/11 13:53, Peter Eisentraut wrote:
> >> On sön, 2011-03-06 at 13:14 +0100, Jan Urbański wrote:
> >>> But fixing "raise plpy.Fatal()"
> >>> to actually cause a FATAL is something that should be extracted from
> >>> this patch and committed, even if the full patch does not make it.
> >>
> >> Um, what? I didn't find any details about this in this thread, nor a
> >> test case.
>
> > So this in fact are three separate things, tracebacks, fix for
> > plpy.Fatal and a one-line fix for reporting errors in Python iterators,
> > that as I noticed has a side effect of changing the SQLCODE being raised
> > :( I think I'll just respin the tracebacks patch as 3 separate ones,
> > coming right up.
>
> Respun as three separate patches. Sorry for the confusion. BTW: looks
> like plpy.Fatal behaviour has been broken for quite some time now.

Committed 1 and 2.

Your traceback implementation in PLy_elog is now using two errdetail
calls in one ereport call, which doesn't work (first one wins). Please
reconsider that. Also, the comment still talks about the traceback
going into detail.

On 07/03/11 22:55, Peter Eisentraut wrote:
> On mån, 2011-03-07 at 14:19 +0100, Jan Urbański wrote:
>> On 07/03/11 14:01, Jan Urbański wrote:
>>> On 07/03/11 13:53, Peter Eisentraut wrote:
>>>> On sön, 2011-03-06 at 13:14 +0100, Jan Urbański wrote:
>>>>> But fixing "raise plpy.Fatal()"
>>>>> to actually cause a FATAL is something that should be extracted from
>>>>> this patch and committed, even if the full patch does not make it.
>>>>
>>>> Um, what? I didn't find any details about this in this thread, nor a
>>>> test case.
>>
>>> So this in fact are three separate things, tracebacks, fix for
>>> plpy.Fatal and a one-line fix for reporting errors in Python iterators,
>>> that as I noticed has a side effect of changing the SQLCODE being raised
>>> :( I think I'll just respin the tracebacks patch as 3 separate ones,
>>> coming right up.
>>
>> Respun as three separate patches. Sorry for the confusion. BTW: looks
>> like plpy.Fatal behaviour has been broken for quite some time now.
>
> Committed 1 and 2.
>
> Your traceback implementation in PLy_elog is now using two errdetail
> calls in one ereport call, which doesn't work (first one wins). Please
> reconsider that. Also, the comment still talks about the traceback
> going into detail.

Gah, will look at this and fix.

Jan