Thread: Support for XLogRecPtr in expand_fmt_string?
Hi, I wonder if we just should add a format code like %R or something similar as a replacement for the %X/%X notion. Having to type something like "(uint32) (state->curptr >> 32), (uint32)state->curptr" everywhere is somewhat annoying. Opinions? Andres -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
Andres Freund <andres@2ndquadrant.com> writes:
> I wonder if we just should add a format code like %R or something similar as a
> replacement for the %X/%X notion.
Only if you can explain how to teach gcc what it means for elog argument
match checking. %m is a special case in that it matches up with a
longstanding glibc-ism that gcc knows about. Adding format codes of our
own invention would be problematic.
> Having to type something like "(uint32)
> (state->curptr >> 32), (uint32)state->curptr" everywhere is somewhat annoying.
If we really feel this is worth doing something about, we could invent a
formatting subroutine that converts XLogRecPtr to string (and then we
just use %s in the messages).
regards, tom lane
On tis, 2012-07-03 at 19:35 +0200, Andres Freund wrote: > I wonder if we just should add a format code like %R or something similar as a > replacement for the %X/%X notion. Having to type something like "(uint32) > (state->curptr >> 32), (uint32)state->curptr" everywhere is somewhat annoying. Maybe just print it as a single 64-bit value from now on.
Peter Eisentraut <peter_e@gmx.net> writes:
> On tis, 2012-07-03 at 19:35 +0200, Andres Freund wrote:
>> I wonder if we just should add a format code like %R or something similar as a
>> replacement for the %X/%X notion.
> Maybe just print it as a single 64-bit value from now on.
That'd be problematic also, because of the lack of standardization of
the format code for uint64. We could write things like"message... " UINT64_FORMAT " ...more message"
but I wonder how well the translation tools would work with that;
and anyway it would at least double the translation effort for
messages containing such things.
regards, tom lane
On Tuesday, July 03, 2012 08:09:40 PM Tom Lane wrote: > Andres Freund <andres@2ndquadrant.com> writes: > > I wonder if we just should add a format code like %R or something similar > > as a replacement for the %X/%X notion. > Only if you can explain how to teach gcc what it means for elog argument > match checking. %m is a special case in that it matches up with a > longstanding glibc-ism that gcc knows about. Adding format codes of our > own invention would be problematic. Ah. Yes. That kills the idea. > > Having to type something like "(uint32) > > (state->curptr >> 32), (uint32)state->curptr" everywhere is somewhat > > annoying. > If we really feel this is worth doing something about, we could invent a > formatting subroutine that converts XLogRecPtr to string (and then we > just use %s in the messages). I think that would make memory management annoying. Using a static buffer isn't going to work very well either because its valid to pass two recptr's to elog/ereport/.... I think at that point the current state is not worth the hassle, sorry for the noise. Greetings, Andres -- Andres Freund http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services
Andres Freund <andres@2ndquadrant.com> writes:
> On Tuesday, July 03, 2012 08:09:40 PM Tom Lane wrote:
>> If we really feel this is worth doing something about, we could invent a
>> formatting subroutine that converts XLogRecPtr to string (and then we
>> just use %s in the messages).
> I think that would make memory management annoying. Using a static buffer
> isn't going to work very well either because its valid to pass two recptr's to
> elog/ereport/....
Hm. I was assuming that we could probably get away with the
static-buffer trick, but if you think not ...
One possibility is to make call sites that need this pass local-variable
buffers to the formatting subroutine:
char xrp_buffer[XLOGRECPTR_BUF_LEN];char xrp_buffer2[XLOGRECPTR_BUF_LEN];
ereport(...., format_xlogrecptr(xrp_buffer, xlogval1), format_xlogrecptr(xrp_buffer2, xlogval2));
but it may not be worth the trouble.
regards, tom lane
On tis, 2012-07-03 at 14:52 -0400, Tom Lane wrote: > Peter Eisentraut <peter_e@gmx.net> writes: > > On tis, 2012-07-03 at 19:35 +0200, Andres Freund wrote: > >> I wonder if we just should add a format code like %R or something similar as a > >> replacement for the %X/%X notion. > > > Maybe just print it as a single 64-bit value from now on. > > That'd be problematic also, because of the lack of standardization of > the format code for uint64. We could write things like > "message... " UINT64_FORMAT " ...more message" > but I wonder how well the translation tools would work with that; > and anyway it would at least double the translation effort for > messages containing such things. The existing uses of INT64_FORMAT and UINT64_FORMAT show how this is done: You print the value in a temporary buffer and use %s in the final string. It's not terribly pretty, but it's been done this way forever, including in xlog code, so there shouldn't be a reason to hesitate about the use for this particular case.
On 07.07.2012 01:03, Peter Eisentraut wrote: > On tis, 2012-07-03 at 14:52 -0400, Tom Lane wrote: >> Peter Eisentraut<peter_e@gmx.net> writes: >>> On tis, 2012-07-03 at 19:35 +0200, Andres Freund wrote: >>>> I wonder if we just should add a format code like %R or something similar as a >>>> replacement for the %X/%X notion. >> >>> Maybe just print it as a single 64-bit value from now on. >> >> That'd be problematic also, because of the lack of standardization of >> the format code for uint64. We could write things like >> "message... " UINT64_FORMAT " ...more message" >> but I wonder how well the translation tools would work with that; >> and anyway it would at least double the translation effort for >> messages containing such things. > > The existing uses of INT64_FORMAT and UINT64_FORMAT show how this is > done: You print the value in a temporary buffer and use %s in the final > string. It's not terribly pretty, but it's been done this way forever, > including in xlog code, so there shouldn't be a reason to hesitate about > the use for this particular case. That's hardly any simpler than what we have now. On 03.07.2012 21:09, Tom Lane wrote:> Andres Freund<andres@2ndquadrant.com> writes:>> I wonder if we just should add a formatcode like %R or something similar as a>> replacement for the %X/%X notion.>> Only if you can explain how to teach gcc what it means for elog argument>match checking. %m is a special case in that it matches up with a> longstanding glibc-ism that gcc knows about. Adding format codes of our> own invention would be problematic. One idea would be to use a macro, like this: #define XLOGRECPTR_FMT_ARGS(recptr) (uint32) ((recptr) >> 32), (uint32) (recptr) elog(LOG, "current WAL location is %X/%X", XLOGRECPTR_FMT_ARGS(RecPtr)); One downside is that at first glance, that elog() looks broken, because the number of arguments don't appear to match the format string. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com
On tor, 2012-07-12 at 10:13 +0300, Heikki Linnakangas wrote: > One idea would be to use a macro, like this: > > #define XLOGRECPTR_FMT_ARGS(recptr) (uint32) ((recptr) >> 32), > (uint32) > (recptr) > > elog(LOG, "current WAL location is %X/%X", > XLOGRECPTR_FMT_ARGS(RecPtr)); > I would rather get rid of this %X/%X notation. I know we have all grown to like it, but it's always been a workaround. We're now making the move to simplify this whole business by saying, the WAL location is an unsigned 64-bit number -- which everyone can understand -- but then why is it printed in some funny format?
On Fri, Jul 13, 2012 at 10:34:35PM +0300, Peter Eisentraut wrote: > On tor, 2012-07-12 at 10:13 +0300, Heikki Linnakangas wrote: > > One idea would be to use a macro, like this: > > > > #define XLOGRECPTR_FMT_ARGS(recptr) (uint32) ((recptr) >> 32), > > (uint32) > > (recptr) > > > > elog(LOG, "current WAL location is %X/%X", > > XLOGRECPTR_FMT_ARGS(RecPtr)); > > > I would rather get rid of this %X/%X notation. I know we have all grown > to like it, but it's always been a workaround. We're now making the > move to simplify this whole business by saying, the WAL location is an > unsigned 64-bit number -- which everyone can understand -- but then why > is it printed in some funny format? +1 -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. +
Bruce Momjian <bruce@momjian.us> writes:
> On Fri, Jul 13, 2012 at 10:34:35PM +0300, Peter Eisentraut wrote:
>> I would rather get rid of this %X/%X notation.
> +1
I'm for it if we can find a less messy way of dealing with the
platform-specific-format-code issue. I don't want to be plugging
UINT64_FORMAT into string literals in a pile of places.
Personally I think that a function returning a static string
buffer is probably good enough for this. If there are places
where we need to print more than one XLogRecPtr value in a message,
we could have two of them. (Yeah, it's ugly, but less so than
dealing with platform-specific format codes everywhere.)
regards, tom lane
On Jul 13, 2012, at 2:34 PM, Peter Eisentraut <peter_e@gmx.net> wrote: > I would rather get rid of this %X/%X notation. I know we have all grown > to like it, but it's always been a workaround. We're now making the > move to simplify this whole business by saying, the WAL location is an > unsigned 64-bit number -- which everyone can understand -- but then why > is it printed in some funny format? We should take care that whatever format we pick can be easily matched to a WAL file name. So a 64-bit number printed as16 hex digits would perhaps be OK, but a 64-bit number printed in base 10 would be a large usability regression. Personally, I'm not convinced we should change anything at all. It's not that easy to visually parse a string of many digits;a little punctuation in the middle is not a bad thing. ...Robert