Re: Problem with zero year

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Re: Problem with zero year

От:
Tom Lane <tgl@sss.pgh.pa.us>
Дата:
Bruce Momjian  writes:
> The problem is that the 2-digit year check is for <=2 digits, not
> exactly two digits:
> ...
> This leads to some unexpected outputs:

> 	test=> select '1-1-0'::date;
> 	   date
> 	------------
> 	 2000-01-01

We've interpreted that like that since 7.4, without complaints; and
I think it was an intentional change then (since 7.3 doesn't accept it).
I do not recommend changing it.
		regards, tom lane

Problem with zero year

От:
Bruce Momjian <bruce@momjian.us>
Дата:
We added the following commit in 8.4:
/src/backend/utils/adt/datetime.c                                                                      tgl Reject year zero during datetime input, except when it's a 2-digit year (then it means 2000 AD).  Formerly we silently interpreted this as 1 BC, which at best is unwarranted familiarity with the implementation. It's barely possible that some app somewhere expects the old behavior, though, so we won't back-patch this into existing release branches.

The problem is that the 2-digit year check is for <=2 digits, not
exactly two digits:
   /*    * When processing a year field, mark it for adjustment if it's only one    * or two digits.    */   if (*tmask == DTK_M(YEAR))       *is2digits = (flen <= 2);

This leads to some unexpected outputs:
test=> select '1-1-0'::date;   date------------ 2000-01-01
test=> select '1-1-0 BC'::date;ERROR:  date/time field value out of range: "1-1-0 BC"LINE 1: select '1-1-0 BC'::date;               ^
test=> select '1-1-0 AD'::date;    date------------ 2000-01-01
test=> select '1-1-000'::date;ERROR:  date/time field value out of range: "1-1-000"LINE 1: select '1-1-000'::date;

I think the BC part is fine because that can't possibily be 2000 AD, but
having '0' interpreted as 2000 seems counter to the commit message text;
should the assignment be changed to:
   if (*tmask == DTK_M(YEAR))       *is2digits = (flen == 2);

--  Bruce Momjian          http://momjian.us EnterpriseDB                             http://enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +

Re: Problem with zero year

От:
Bruce Momjian <bruce@momjian.us>
Дата:
Tom Lane wrote:
> Bruce Momjian  writes:
> > The problem is that the 2-digit year check is for <=2 digits, not
> > exactly two digits:
> > ...
> > This leads to some unexpected outputs:
> 
> > 	test=> select '1-1-0'::date;
> > 	   date
> > 	------------
> > 	 2000-01-01
> 
> We've interpreted that like that since 7.4, without complaints; and
> I think it was an intentional change then (since 7.3 doesn't accept it).
> I do not recommend changing it.

OK, the release note text will be:
Reject year '0 BC' and years '000' and '0000' (Tom)  Previously these were interpreted as 1 BC.

--  Bruce Momjian          http://momjian.us EnterpriseDB                             http://enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +
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