Re: [HACKERS] regressin failure on latest CVS - Mailing list pgsql-patches

Would you please try the attached patch and let me know if it fixes the
problem?  I avoided accumulating into a float8.

---------------------------------------------------------------------------

Rocco Altier wrote:
> This still does not fix the problem.
>
> I had done my patch to try to mimic the way 8.0 had handled the math
> with the remainders, but to carry it over another bucket (day).
>
> The problem that I see is that we are taking day_remainder and
> multiplying by USECS_PER_DAY.  Which is a double * int64, thus there is
> the precision loss there.
>
> I think initial division by the factor can't be helped, but repeatedly
> doing more floating point math on with it is causing the rounding error.
>
> Thanks,
>     -rocco
>
> > -----Original Message-----
> > From: Bruce Momjian [mailto:pgman@candle.pha.pa.us]
> > Sent: Saturday, July 23, 2005 10:54 AM
> > To: Rocco Altier
> > Cc: Michael Glaesemann; pgsql-patches@postgresql.org;
> > pgsql-hackers@postgresql.org; ohp@pyrenet.fr
> > Subject: Re: [HACKERS] regressin failure on latest CVS
> >
> >
> > Rocco Altier wrote:
> > > This patch fixes the interval regression on my AIX box
> > (kookaburra) by
> > > only doing integer math on the interval, instead of
> > float/double math.
> > >
> > > I think this is the correct way to handle this, since it's
> > an integer
> > > data type.
> > >
> > > I don't know if it will fix Olivier's problem, since I
> > wasn't able to
> > > reproduce it.
> > >
> >
> > I have changed the way I compute the remainder values --- instead of
> > using multiplication, I use division and then subtraction.
> > This should
> > fix your rounding problem.  Looking at your fix, I don't see
> > how adding
> > USECS changes things because the factor is already a float,
> > but I think
> > the problem was more the way I was computing the remainders.
> >
> > Patch attached --- let me know if it does not fix your problem.
> >
> > --------------------------------------------------------------
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: Don't 'kill -9' the postmaster
>

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
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Index: src/backend/utils/adt/timestamp.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/utils/adt/timestamp.c,v
retrieving revision 1.145
diff -c -c -r1.145 timestamp.c
*** src/backend/utils/adt/timestamp.c    23 Jul 2005 14:53:21 -0000    1.145
--- src/backend/utils/adt/timestamp.c    23 Jul 2005 18:45:56 -0000
***************
*** 2309,2327 ****
      result->time = span->time / factor;

      /* Compute remainders */
!     month_remainder = span->month / factor - result->month;
!     day_remainder = span->day / factor - result->day;

      /* Cascade fractions to lower units */
      /* fractional months full days into days */
      result->day += month_remainder * DAYS_PER_MONTH;
-     /* fractional months partial days into time */
-     day_remainder += (month_remainder * DAYS_PER_MONTH) - (int)(month_remainder * DAYS_PER_MONTH);

  #ifdef HAVE_INT64_TIMESTAMP
!     result->time += day_remainder * USECS_PER_DAY;
  #else
!     result->time += day_remainder * SECS_PER_DAY;
      result->time = JROUND(result->time);
  #endif

--- 2309,2328 ----
      result->time = span->time / factor;

      /* Compute remainders */
!     month_remainder = (span->month / factor - result->month);
!     day_remainder = (span->day / factor - result->day);

      /* Cascade fractions to lower units */
      /* fractional months full days into days */
      result->day += month_remainder * DAYS_PER_MONTH;

+     /* fractional months partial days into time */
  #ifdef HAVE_INT64_TIMESTAMP
!     result->time += (day_remainder + month_remainder * DAYS_PER_MONTH -
!                     (int)(month_remainder * DAYS_PER_MONTH)) * USECS_PER_DAY;
  #else
!     result->time += (day_remainder + month_remainder * DAYS_PER_MONTH -
!                     (int)(month_remainder * DAYS_PER_MONTH)) * SECS_PER_DAY;
      result->time = JROUND(result->time);
  #endif