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* The IYYY mess again
@ 2014-12-29 15:06 Tom Lane <tgl@sss.pgh.pa.us>
2014-12-29 17:13 ` Re: The IYYY mess again Steve Atkins <steve@blighty.com>
2014-12-29 19:00 ` Re: The IYYY mess again David G Johnston <david.g.johnston@gmail.com>
2014-12-29 22:41 ` Re: The IYYY mess again Bruce Momjian <bruce@momjian.us>
0 siblings, 3 replies; 6+ messages in thread
From: Tom Lane @ 2014-12-29 15:06 UTC (permalink / raw)
To: pgsql-docs
In bug #12367
http://www.postgresql.org/message-id/20141229031218.8013.51171@wrigleys.postgresql.org
we see yet another iteration of somebody trying to combine to_char's
IYYY specifier with regular Gregorian MM/DD fields.
It occurs to me that this is largely our own fault, because the fine
manual just defines IYYY as "ISO year". I'm sure the typical newbie
thought process is "that sounds like a standard year, I'll use that".
There is a warning against combining IYYY with MM/DD, but it's buried
in trivia far down the page.
I did a bit of googling and came across
http://en.wikipedia.org/wiki/ISO_week_date
in which this construct is called an "ISO week-numbering year".
Not having a copy of ISO 8601, I'm not sure if that's the standard's
terminology; but ISTM that if we consistently referred to the Ixxx
format specifiers as "ISO week-numbering foo" then this type of error
might become a little less attractive.
Objections, better ideas?
regards, tom lane
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* Re: The IYYY mess again
2014-12-29 15:06 The IYYY mess again Tom Lane <tgl@sss.pgh.pa.us>
@ 2014-12-29 17:13 ` Steve Atkins <steve@blighty.com>
2 siblings, 0 replies; 6+ messages in thread
From: Steve Atkins @ 2014-12-29 17:13 UTC (permalink / raw)
To: pgsql-docs
On Dec 29, 2014, at 7:06 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> In bug #12367
> http://www.postgresql.org/message-id/20141229031218.8013.51171@wrigleys.postgresql.org
> we see yet another iteration of somebody trying to combine to_char's
> IYYY specifier with regular Gregorian MM/DD fields.
>
> It occurs to me that this is largely our own fault, because the fine
> manual just defines IYYY as "ISO year". I'm sure the typical newbie
> thought process is "that sounds like a standard year, I'll use that".
> There is a warning against combining IYYY with MM/DD, but it's buried
> in trivia far down the page.
>
> I did a bit of googling and came across
> http://en.wikipedia.org/wiki/ISO_week_date
> in which this construct is called an "ISO week-numbering year".
>
> Not having a copy of ISO 8601, I'm not sure if that's the standard's
> terminology; but ISTM that if we consistently referred to the Ixxx
> format specifiers as "ISO week-numbering foo" then this type of error
> might become a little less attractive.
>
> Objections, better ideas?
I've seen this problem a few times on IRC too. An explicit warning / cross
reference on IYYY that the user almost certainly wants YYYY instead might
be even better.
Cheers,
Steve
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* Re: The IYYY mess again
2014-12-29 15:06 The IYYY mess again Tom Lane <tgl@sss.pgh.pa.us>
@ 2014-12-29 19:00 ` David G Johnston <david.g.johnston@gmail.com>
2014-12-29 19:12 ` Re: The IYYY mess again Tom Lane <tgl@sss.pgh.pa.us>
2 siblings, 1 reply; 6+ messages in thread
From: David G Johnston @ 2014-12-29 19:00 UTC (permalink / raw)
To: pgsql-docs
Tom Lane-2 wrote
> In bug #12367
> http://www.postgresql.org/message-id/
> 20141229031218.8013.51171@.postgresql
>
> There is a warning against combining IYYY with MM/DD, but it's buried
> in trivia far down the page.
Can we move this warning/notice into code? Basically warn/disallow
IYYY-MM-DD (and similar) as a valid format?
And why not make it an error. If someone really needed to output mixed
modes they would be able to concatenate the two halves together to get the
desired result so it isn't like we are making it impossible to accomplish -
but the typical mistake goes away.
David J.
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* Re: The IYYY mess again
2014-12-29 15:06 The IYYY mess again Tom Lane <tgl@sss.pgh.pa.us>
2014-12-29 19:00 ` Re: The IYYY mess again David G Johnston <david.g.johnston@gmail.com>
@ 2014-12-29 19:12 ` Tom Lane <tgl@sss.pgh.pa.us>
2014-12-29 19:25 ` Re: The IYYY mess again David Johnston <david.g.johnston@gmail.com>
0 siblings, 1 reply; 6+ messages in thread
From: Tom Lane @ 2014-12-29 19:12 UTC (permalink / raw)
To: David G Johnston <david.g.johnston@gmail.com>; +Cc: pgsql-docs
David G Johnston <david.g.johnston@gmail.com> writes:
> Tom Lane-2 wrote
>> There is a warning against combining IYYY with MM/DD, but it's buried
>> in trivia far down the page.
> Can we move this warning/notice into code? Basically warn/disallow
> IYYY-MM-DD (and similar) as a valid format?
> And why not make it an error. If someone really needed to output mixed
> modes they would be able to concatenate the two halves together to get the
> desired result so it isn't like we are making it impossible to accomplish -
> but the typical mistake goes away.
I would say no, and no. It's not at all unreasonable to want to print
"YYYY-MM-DD (IYYY-IDDD)" or something like that. And even if we think
it's dumb, it's not to_char()'s place to tell people they can't print
silly combinations. One could argue in fact that the only reason for
to_char() to live at all is to print "silly" combinations --- otherwise,
you might as well just cast your timestamp to text.
regards, tom lane
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* Re: The IYYY mess again
2014-12-29 15:06 The IYYY mess again Tom Lane <tgl@sss.pgh.pa.us>
2014-12-29 19:00 ` Re: The IYYY mess again David G Johnston <david.g.johnston@gmail.com>
2014-12-29 19:12 ` Re: The IYYY mess again Tom Lane <tgl@sss.pgh.pa.us>
@ 2014-12-29 19:25 ` David Johnston <david.g.johnston@gmail.com>
0 siblings, 0 replies; 6+ messages in thread
From: David Johnston @ 2014-12-29 19:25 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: pgsql-docs
On Mon, Dec 29, 2014 at 12:12 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> David G Johnston <david.g.johnston@gmail.com> writes:
> > Tom Lane-2 wrote
> >> There is a warning against combining IYYY with MM/DD, but it's buried
> >> in trivia far down the page.
>
> > Can we move this warning/notice into code? Basically warn/disallow
> > IYYY-MM-DD (and similar) as a valid format?
>
> > And why not make it an error. If someone really needed to output mixed
> > modes they would be able to concatenate the two halves together to get
> the
> > desired result so it isn't like we are making it impossible to
> accomplish -
> > but the typical mistake goes away.
>
> I would say no, and no. It's not at all unreasonable to want to print
> "YYYY-MM-DD (IYYY-IDDD)" or something like that. And even if we think
> it's dumb, it's not to_char()'s place to tell people they can't print
> silly combinations. One could argue in fact that the only reason for
> to_char() to live at all is to print "silly" combinations --- otherwise,
> you might as well just cast your timestamp to text.
>
>
>
I didn't suggest "YYYY-MM-DD (IYYY-IDDD)" should throw an error...we can
be more conservative/targeted than that.
Anyway, I get your point though you know as well as I do that
documentation isn't always the answer. The OP on this issue likely figured
he was using the correct format because up until today it was returning the
correct result. Its easy enough in hindsight to now look at the
documentation and see why he was wrong but it doesn't fix the fact that the
code now needs to be fixed when a format specification error would have
prevented this simple misunderstanding - strictly using IYYYY-MM-DD instead
of YYYY-MM-DD.
Anyway, on the documentation side splitting up the single large table into
separate "calendar" tables would make the distinction clearer and also
group like specifications together. I would go so far as to repeat those
items that can be used with more than one calendar and so make each table
self-sufficient. The wording change may further help but breaking out and
describing the nuances of the different calendar interpretations of a given
point-in-time would add a visual separation for the reader.
David J.
^ permalink raw reply [nested|flat] 6+ messages in thread
* Re: The IYYY mess again
2014-12-29 15:06 The IYYY mess again Tom Lane <tgl@sss.pgh.pa.us>
@ 2014-12-29 22:41 ` Bruce Momjian <bruce@momjian.us>
2 siblings, 0 replies; 6+ messages in thread
From: Bruce Momjian @ 2014-12-29 22:41 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: pgsql-docs
On Mon, Dec 29, 2014 at 10:06:09AM -0500, Tom Lane wrote:
> In bug #12367
> http://www.postgresql.org/message-id/20141229031218.8013.51171@wrigleys.postgresql.org
> we see yet another iteration of somebody trying to combine to_char's
> IYYY specifier with regular Gregorian MM/DD fields.
>
> It occurs to me that this is largely our own fault, because the fine
> manual just defines IYYY as "ISO year". I'm sure the typical newbie
> thought process is "that sounds like a standard year, I'll use that".
> There is a warning against combining IYYY with MM/DD, but it's buried
> in trivia far down the page.
>
> I did a bit of googling and came across
> http://en.wikipedia.org/wiki/ISO_week_date
> in which this construct is called an "ISO week-numbering year".
>
> Not having a copy of ISO 8601, I'm not sure if that's the standard's
> terminology; but ISTM that if we consistently referred to the Ixxx
> format specifiers as "ISO week-numbering foo" then this type of error
> might become a little less attractive.
>
> Objections, better ideas?
+1 for saying "ISO week-numbering year".
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
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-- links below jump to the message on this page --
2014-12-29 15:06 The IYYY mess again Tom Lane <tgl@sss.pgh.pa.us>
2014-12-29 17:13 ` Steve Atkins <steve@blighty.com>
2014-12-29 19:00 ` David G Johnston <david.g.johnston@gmail.com>
2014-12-29 19:12 ` Tom Lane <tgl@sss.pgh.pa.us>
2014-12-29 19:25 ` David Johnston <david.g.johnston@gmail.com>
2014-12-29 22:41 ` Bruce Momjian <bruce@momjian.us>
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