Обсуждение: Re: [GENERAL] date_part bug?

Hello!

On Thu, 17 Dec 1998, Tim Williams wrote:
> When I run the following set of statements in postgres v6.4 (built on
> Debian Linux):
>
> create table tmp (v1 date, v2 datetime);
> insert into tmp values ('06-01-1999', '06-01-1999');
> select date_part('month', v1) as m1, date_part('month', v2) as m2 from
> tmp;
>
> I see the following results:
>
> m1|m2
> --+--
>  5| 6
> (1 row)
>
> Why is date_part giving different results for date and date_time?  Why
> is it wrong for 'date'? Anybody seen this before?

   I tried this and it works pretty good for me on Solaris.
   It looks like an error in postgres on glibc2-based linux platform. It is
discussing now on pgsql-hackers list. The solution is not ready yet. I am
working on this with a good deal of help from other people...

Oleg.
----
  Oleg Broytmann     http://members.tripod.com/~phd2/     phd2@earthling.net
           Programmers don't die, they just GOSUB without RETURN.

Oleg Broytmann wrote:
  >> create table tmp (v1 date, v2 datetime);
  >> insert into tmp values ('06-01-1999', '06-01-1999');
  >> select date_part('month', v1) as m1, date_part('month', v2) as m2 from
  >> tmp;
  >>
  >> I see the following results:
  >>
  >> m1|m2
  >> --+--
  >>  5| 6
  >> (1 row)
...
  >   I tried this and it works pretty good for me on Solaris.
  >   It looks like an error in postgres on glibc2-based linux platform. It is
  >discussing now on pgsql-hackers list. The solution is not ready yet. I am
  >working on this with a good deal of help from other people...

Not all glibc2: I run glibc2 Debian Linux and do not see this problem.
I was wondering if it was libc5 that was giving trouble...

--
Oliver Elphick                                Oliver.Elphick@lfix.co.uk
Isle of Wight                              http://www.lfix.co.uk/oliver
               PGP key from public servers; key ID 32B8FAA1
                 ========================================
     "In the beginning was the Word, and the Word was with
      God, and the Word was God. The same was in the
      beginning with God. All things were made by him; and
      without him was not any thing made that was made."
                                John 1:1-3

> Not all glibc2: I run glibc2 Debian Linux and do not see this problem.
> I was wondering if it was libc5 that was giving trouble...

Not on my libc5-only machine (where I developed the code). We'll need to
get a reproducible case to be able to track it down. I'm guessing that
we are seeing float->int rounding problems, though I don't know why this
test query should show different results for the two columns.

What glibc2, compiler, and optimization level are you using? If you are
using anything above -O2 try backing down to that; if you are already
there then try -O0 and tell us what changes.

                      - Tom

postgres=> create table tmp (v1 date, v2 datetime);
CREATE
postgres=> insert into tmp values ('06-01-1999', '06-01-1999');
INSERT 901482 1
postgres=> select date_part('month', v1) as m1, date_part('month', v2)
as m2 from tmp;
m1|m2
--+--
 6| 6
(1 row)