Hi, bq. My new code returns 0.2 months for this, not zero Can you clarify (the output below that was 2 mons, not 0.2) ?
Thanks On Fri, Apr 2, 2021 at 4:58 PM Bruce Momjian <br...@momjian.us> wrote: > On Fri, Apr 2, 2021 at 02:00:03PM -0700, John W Higgins wrote: > > On Fri, Apr 2, 2021 at 11:05 AM Bruce Momjian <br...@momjian.us> wrote: > > While maybe there is an argument to fixing the negative/positive > rounding issue > > - there is no way this gets solved without breaking the current > implementation > > > > select interval '0.3 years' + interval '0.4 years' - interval '0.7 > years' + > > interval '0.1 years' should not equal 0 but it certainly does. > > My new code returns 0.2 months for this, not zero: > > SELECT interval '0.3 years' + interval '0.4 years' - > interval '0.7 years' + interval '0.1 years'; > ?column? > ---------- > 2 mons > > which is also wrong since: > > SELECT interval '0.1 years'; > interval > ---------- > 1 mon > > > Unless we take the concept of 0.3 years = 3 months and move to something > along > > the lines of > > > > 1 year = 360 days > > 1 month = 30 days > > > > so therefore > > > > 0.3 years = 360 days * 0.3 = 108 days = 3 months 18 days > > 0.4 years = 360 days * 0.4 = 144 days = 4 months 24 days > > 0.7 years = 360 days * 0.7 = 252 days = 8 months 12 days > > > > Then, and only if we don't go to any more than tenths of a year, does > the math > > work. Probably this should resolve down to seconds and then work > backwards - > > but unless we're looking at breaking the entire way it currently resolves > > things - I don't think this is of much value. > > > > Doing math on intervals is like doing math on rounded numbers - there is > always > > going to be a pile of issues because the level of precision just is not > good > > enough. > > I think the big question is what units do people want with fractional > values. I have posted a follow-up email that spills only for one unit, > which I think is the best approach. > > -- > Bruce Momjian <br...@momjian.us> https://momjian.us > EDB https://enterprisedb.com > > If only the physical world exists, free will is an illusion. > > > >
