Re: compress method for spgist - 2

Nikita Glukhov <n.gluhov@postgrespro.ru> writes:
> On 20.09.2017 23:19, Alexander Korotkov wrote:
>> On Wed, Sep 20, 2017 at 11:07 PM, Tom Lane <tgl@sss.pgh.pa.us 
>> <mailto:tgl@sss.pgh.pa.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