Thread moved to hackers, with a patch. --------------------------------------------------------------------------- On Thu, Apr 1, 2021 at 09:46:58PM -0700, Bryn Llewellyn wrote: > Or am I misunderstanding something? > > Try this. The result of each “select” is shown as the trailing comment on the > same line. I added whitespace by hand to line up the fields. > > select interval '-1.7 years'; -- -1 years -8 mons > > select interval '29.4 months'; -- 2 years 5 mons 12 > days > > select interval '-1.7 years 29.4 months'; -- 8 mons 12 > days << wrong > select interval '29.4 months -1.7 years'; -- 9 mons 12 > days > > select interval '-1.7 years' + interval '29.4 months'; -- 9 mons 12 > days > select interval '29.4 months' + interval '-1.7 years'; -- 9 mons 12 > days > > As I reason it, the last four “select” statements are all semantically the > same. They’re just different syntaxes to add the two intervals the the first > two “select” statements use separately. There’s one odd man out. And I reason > this one to be wrong. Is there a flaw in my reasoning? > > Further… there’s a notable asymmetry. The fractional part of “1.7 years” is 8.4 > months. But the fractional part of the months value doesn’t spread further down > into days. However, the fractional part of “29.4 months” (12 days) _does_ > spread further down into days. What’s the rationale for this asymmetry? > > I can’t see that my observations here can be explained by the difference > between calendar time and clock time. Here I’m just working with non-metric > units like feet and inches. One year is just defined as 12 months. And one > month is just defined as 30 days. All that stuff about adding a month to > 3-Feb-2020 taking you to 3-Mar-2020 (same for leap years an non-leap years) , > and that other stuff about adding one day to 23:00 on the day before the > “spring forward” moment taking you to 23:00 on the next day (i.w. when > intervals are added to timestamps) is downstream of simply adding two > intervals. > -- Bruce Momjian <bruce@xxxxxxxxxx> https://momjian.us EDB https://enterprisedb.com If only the physical world exists, free will is an illusion.
