Re: [GENERAL] ISO week dates

Bruce Momjian escribió:

Maybe now would be an appropriate time to discuss the open questions in
the submitting email:

> > Brendan Jurd wrote:

> > > I have tried to implement these features with as little disruption to
> > > the existing code as possible.  I built on the existing date2iso*
> > > functions in src/backend/utils/adt/timestamp.c, and added a few
> > > functions of my own, but I wonder if these functions would be more
> > > appropriately located in datetime.c, alongside date2j and j2date?
> > >
> > > I'd also like to raise the topic of how conversion from text to ISO
> > > week dates should be handled, where the user has specified a bogus
> > > mixture of fields.  Existing code basically ignores these issues; for
> > > example, if a user were to call to_date('1998-01-01 2454050',
> > > 'YYYY-MM-DD J') the function returns 2006-01-01, a result of setting
> > > the year field from YYYY, then overwriting year, month and day with
> > > the values from the Julian date in J, then setting the month and day
> > > normally from MM and DD.
> > >
> > > 2006-01-01 is not a valid representation of either of the values the
> > > user specified.  Now you might say "ask a silly question, get a silly
> > > answer"; the user shouldn't send nonsense arguments to to_date and
> > > expect a sensible result.  But perhaps the right way to respond to a
> > > broken timestamp definition is to throw an error, rather than behave
> > > as though everything has gone to plan, and return something which is
> > > not correct.
> > >
> > > The same situation can arise if the user mixes ISO and Gregorian data;
> > > how should Postgres deal with something like to_date('2006-250',
> > > 'IYYY-DDD')?  The current behaviour in my patch is actually to assume
> > > that the user meant to say 'IYYY-IDDD', since "the 250th Gregorian day
> > > of the ISO year 2006" is total gibberish.  But perhaps it should be
> > > throwing an error message.

My thinking is that erroneous patterns should throw an error, and not
try to second-guess the user.  (IIRC this was being discussed in some
other thread not long ago).

--
Alvaro Herrera                                http://www.CommandPrompt.com/
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