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Re: [HACKERS] regressin failure on latest CVS

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Rocco Altier <RoccoA(at)Routescape(dot)com>
Cc: Michael Glaesemann <grzm(at)myrealbox(dot)com>,pgsql-patches(at)postgresql(dot)org, ohp(at)pyrenet(dot)fr
Subject: Re: [HACKERS] regressin failure on latest CVS
Date: 2005-07-23 18:51:16
Message-ID: 200507231851.j6NIpGv15183@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-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(at)candle(dot)pha(dot)pa(dot)us] 
> > Sent: Saturday, July 23, 2005 10:54 AM
> > To: Rocco Altier
> > Cc: Michael Glaesemann; pgsql-patches(at)postgresql(dot)org; 
> > pgsql-hackers(at)postgresql(dot)org; ohp(at)pyrenet(dot)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(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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