Horton

Re: Infinite Interval

Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>

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From: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Joseph Koshakow <koshy44@gmail.com>, "Gregory Stark (as CFM)" <stark.cfm@gmail.com>, jian he <jian.universality@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-03-28T13:43:54Z
Lists: pgsql-hackers

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On Sun, Mar 26, 2023 at 1:28 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> I think you can take it as read that simple C test programs on modern
> platforms will exhibit IEEE-compliant handling of float infinities.
>

For the record, I tried the attached. It gives a warning at compilation time.

$gcc float_inf.c
float_inf.c: In function ‘main’:
float_inf.c:10:17: warning: division by zero [-Wdiv-by-zero]
   10 |  float inf = 1.0/0;
      |                 ^
float_inf.c:11:20: warning: division by zero [-Wdiv-by-zero]
   11 |  float n_inf = -1.0/0;
      |                    ^
$ ./a.out
inf = inf
-inf = -inf
inf + inf = inf
inf + -inf = -nan
-inf + inf = -nan
-inf + -inf = -inf
inf - inf = -nan
inf - -inf = inf
-inf - inf = -inf
-inf - -inf = -nan
float 0.0 equals 0.0
float 1.0 equals 1.0
 5.0 * inf = inf
 5.0 * - inf = -inf
 5.0 / inf = 0.000000
 5.0 / - inf = -0.000000
 inf / 5.0 = inf
 - inf / 5.0 = -inf

The changes in the patch are compliant with the observations above.

-- 
Best Wishes,
Ashutosh Bapat

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.