| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Nikita Glukhov <n(dot)gluhov(at)postgrespro(dot)ru> |
| Cc: | Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Darafei Praliaskouski <me(at)komzpa(dot)net>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Fedor Sigaev <teodor(at)sigaev(dot)ru> |
| Subject: | Re: compress method for spgist - 2 |
| Date: | 2017-09-20 22:34:47 |
| Message-ID: | 5454.1505946887@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Nikita Glukhov <n(dot)gluhov(at)postgrespro(dot)ru> writes:
> On 20.09.2017 23:19, Alexander Korotkov wrote:
>> On Wed, Sep 20, 2017 at 11:07 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us
>> <mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us>> wrote:
>>> Maybe I'm missing something, but it appears to me that it's
>>> impossible for bbox->low.x to be NaN unless circle->center.x and/or
>>> circle->radius is a NaN, in which case bbox->high.x would also have been computed as a NaN,
>>> making the swap entirely useless.
> It is possible for bbox->low.x to be NaN when circle->center.x is and
> circle->radius are both +Infinity. Without this float-order-preserving
> swapping
> one regression test for KNN with ORDER BY index will be totally broken
> (you can
> try it: https://github.com/glukhovn/postgres/tree/knn).
If that's the reasoning, not having a comment explaining it is
inexcusable. Do you really think people will understand what
the code is doing?
regards, tom lane
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