Horton

Re: Infinite Interval

Joseph Koshakow <koshy44@gmail.com>

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From: Joseph Koshakow <koshy44@gmail.com>
To: jian he <jian.universality@gmail.com>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-01-02T18:53:08Z
Lists: pgsql-hackers

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On Mon, Jan 2, 2023 at 1:21 PM Joseph Koshakow <koshy44@gmail.com> wrote:
>
> On Sat, Dec 31, 2022 at 12:09 AM jian he <jian.universality@gmail.com> wrote:
> > In float8, select float8 'inf' / float8 'inf' return NaN. Now in your patch  select interval 'infinity' / float8 'infinity'; returns infinity.
> > I am not sure it's right. I found this related post (https://math.stackexchange.com/questions/181304/what-is-infinity-divided-by-infinity).
>
> Good point, I agree this should return an error. We also need to
> properly handle multiplication and division of infinite intervals by
> float8 'nan'. My patch is returning an infinite interval, but it should
> be returning an error. I'll upload a new patch shortly.
>
> - Joe

Attached is the patch to handle these scenarios. Apparently dividing by
NaN is currently broken:
    postgres=# SELECT INTERVAL '1 day' / float8 'nan';
                         ?column?
    ---------------------------------------------------
     -178956970 years -8 mons -2562047788:00:54.775808
    (1 row)

This patch will fix the issue, but we may want a separate patch that
handles this specific, existing issue. Any thoughts?

- Joe

Commits

  1. Support +/- infinity in the interval data type.

  2. Avoid integer overflow hazard in interval_time().

  3. Guard against overflow in make_interval().

  4. Fix minmax-multi on infinite date/timestamp values

  5. Optimize various aggregate deserialization functions, take 2

  6. Remove dead code in DecodeInterval()

  7. Accept "+infinity" in date and timestamp[tz] input.

  8. Fix overflow hazards in interval input and output conversions.