Re: 8.3 vs HEAD difference in Interval output?

>>> On Mon, Sep 15, 2008 at 4:58 PM, in message
<20219(dot)1221515913(at)sss(dot)pgh(dot)pa(dot)us>,
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com> writes:
>> Unless I'm compiling stuff wrong, it seems HEAD is giving me
>> slightly different output on Intervals than 8.3 in the roundoff
>> of seconds. 8.3 was rounding to the nearest fraction of a second,
>> HEAD seems to be truncating.
>
> Yeah, that's surely because of the change to integer timestamps.
>
>> Am I interpreting this right? If so, shall I submit a patch
>> that rounds it to hundredths of a second (hundredths seems
>> hardcoded in the sprintf), or perhaps just silently add that
>> fix to the EncodeInterval patch I'm doing any for SQL Standard
>> and ISO intervals?
>
> This is not the only place where the float-timestamps code has
rounding
> behavior that doesn't appear in the integer-timestamps code. I
don't
> know if we want to buy into making them act the same ... after all,
> if they acted exactly the same, we'd not have bothered with writing
the
> integer code. In this example, rounding to hundredths doesn't seem
like
> a particularly good idea; it seems to me it should give you the
exact
> down-to-the-microsecond value.

I find the results on 8.3.3 with integer timestamps surprising:

ccdev=# select version();
version
------------------------------------------------------------------------------------------------------------------
PostgreSQL 8.3.3 on x86_64-unknown-linux-gnu, compiled by GCC gcc
(GCC) 4.1.2 20070115 (prerelease) (SUSE Linux)
(1 row)

ccdev=# select '1 year 2 mons 3 days 04:05:06.699999'::interval;
interval
--------------------------------------
1 year 2 mons 3 days 04:05:06.699999
(1 row)

ccdev=# select '1 year 2 mons 3 days 04:05:06.699999'::interval(1);
interval
----------------------------------
1 year 2 mons 3 days 04:05:06.70
(1 row)

ccdev=# select '1 year 2 mons 3 days 04:05:06.699999'::interval(2);
interval
----------------------------------
1 year 2 mons 3 days 04:05:06.70
(1 row)

ccdev=# select '1 year 2 mons 3 days 04:05:06.699999'::interval(3);
interval
----------------------------------
1 year 2 mons 3 days 04:05:06.70
(1 row)

ccdev=# select '1 year 2 mons 3 days 04:05:06.699999'::interval(4);
interval
----------------------------------
1 year 2 mons 3 days 04:05:06.70
(1 row)

ccdev=# select '1 year 2 mons 3 days 04:05:06.699999'::interval(5);
interval
----------------------------------
1 year 2 mons 3 days 04:05:06.70
(1 row)

ccdev=# select '1 year 2 mons 3 days 04:05:06.699999'::interval(6);
interval
--------------------------------------
1 year 2 mons 3 days 04:05:06.699999
(1 row)

-Kevin