ST_Equals(empty, empty) returns false

[strk]

Empty isn't equal to self. Shouldn't it ?

[strk]

ST_orderingEquals has the same bug

[strk]

Gah, it has to do with $1 ~= $2 !!! Both are affected because both insist in requiring bounding box overlap for two geometries to be equal. Does the EMPTY bounding box overlap the EMPTY bounding box ?

Do voids touch ?

[strk]

Actually, ST_Equals uses && and ST_OrderingEquals uses ~=. That is overlaps and contains samebox.

Speaking of which... I'd use samebox for ST_Equals as well, and have samebox return TRUE for empty. They do have the same box !

[strk]

r8778 fixes ~= and thus ST_OrderingEquals.

ST_Equals is still broken.

[strk]

So, ST_Equals is broken only because of the use of && done by the SQL wrapper. _ST_Equals already returns true for 2 EMPTY parameters (no matter type and dimension).

I propose to switch ST_Equals to use ~= which means "same box". There should be no issue with floats vs. double as we always round boxes to float be them computed or cached. If we still don't it's a bug in our side which we want to fix.

[strk]

Politics took over science: ​http://postgis.refractions.net/pipermail/postgis-devel/2012-January/017743.html

At time of writing we have:

-0 regina
+0 pramsey
+1 strk
+1 chodgson

Unless Mark vetoes out the motion passed for EMPTY being equal to EMPTY.

[strk]

I've fixed ST_Equals to return TRUE (consistently with _ST_Equals) with r8886.