| From: | Emre Hasegeli <emre(at)hasegeli(dot)com> |
|---|---|
| To: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> |
| Cc: | Kevin Grittner <kgrittn(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andreas Karlsson <andreas(at)proxel(dot)se>, Teodor Sigaev <teodor(at)sigaev(dot)ru>, Robert Haas <robertmhaas(at)gmail(dot)com>, Kevin Grittner <kgrittn(at)ymail(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Joe Conway <mail(at)joeconway(dot)com> |
| Subject: | Re: Floating point comparison inconsistencies of the geometric types |
| Date: | 2016-11-18 09:58:27 |
| Message-ID: | CAE2gYzxVxKNS7qU74UdHVZTmfXQjxMbFiXH5+16XFy90SRAbXA@mail.gmail.com |
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| Lists: | pgsql-hackers |
> To keep such kind of integrity, we should deeply consider about
> errors.
My point is that I don't think we can keep integrity together with the
fuzzy behaviour, or at least I don't have the skills to do that. I
can just leave the more complicated operators like "is a
point on a line" as it is, and only change the basic ones. Do you
think a smaller patch like this would be acceptable?
> That's a fate of FP numbers. Btree is uasble for such data since
> it is constructed using inequality operators but hash is almost
> unsuitable without rounding and normalization because of the
> nature of floating point numbers. Range scan on bree will work
> find but on the other hand equality doesn't work even on btree
> index from the same reason to the below.
Btree is very useful with floats. There is no problem with it.
> Again, FP numbers generally cannot match exactly each other. You
> have to avoid that.
Again, they do match very well. Floating point numbers are no magic.
They are perfectly deterministic.
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