Re: compress method for spgist - 2

Darafei Praliaskouski <me(at)komzpa(dot)net> writes:
> I have some questions about the circles example though.

> * What is the reason for isnan check and swap of box ordinates for circle? It wasn't in the code previously.

I hadn't paid any attention to this patch previously, but this comment
excited my curiosity, so I went and looked:

+ bbox->high.x = circle->center.x + circle->radius;
+ bbox->low.x = circle->center.x - circle->radius;
+ bbox->high.y = circle->center.y + circle->radius;
+ bbox->low.y = circle->center.y - circle->radius;
+
+ if (isnan(bbox->low.x))
+ {
+ double tmp = bbox->low.x;
+ bbox->low.x = bbox->high.x;
+ bbox->high.x = tmp;
+ }

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. Likewise for the Y case. There may be
something useful to do about NaNs here, but this doesn't seem like it.

> How about removing circle from the scope of this patch, so it is smaller and cleaner?

Neither of those patches would be particularly large, and since they'd need
to touch adjacent code in some places, the diffs wouldn't be independent.
I think splitting them is just make-work.

regards, tom lane