Paul, Huh. What do you want to change = to? A real =? If you do remember for better or worse it will have impact on -- GROUP BY, ORDER BY
as the = operator I can only guess is baked in deeply into the PostgreSQL implementation of these (not sure how though). So if you ever change it to a true equality operator, I suspect these things may become as slow as molasses, and well I see no point of making it a 64-bit check because the only reason is to make it more of a true equality which it isn't anyway. People should just get out of that mindset. Thanks, Regina -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Paul Ramsey Sent: Friday, January 08, 2010 12:51 PM To: PostGIS Users Discussion Subject: Re: [postgis-users] st_equals strangeness Well, that brings us to the API level, no? Because operators have meanings in index (32-bit) terms. Should all our operators have 64-bit rechecks? Should some of them? Should '=' just get a special treatment, because we have such an in-grained understanding of what that symbol connotes, and other symbols be left as pure index ops? P On Fri, Jan 8, 2010 at 9:44 AM, Mark Cave-Ayland <[email protected]> wrote: > Paul Ramsey wrote: > >> More to the point, it's a float32 box, not a double64 box. Your two >> points are in fact different, waaaaaay down deep into the precision >> of their 64-bit double coordinates. So deep in fact that the human >> readable decimal representations don't show it (look at the hexewkb >> output, and you'll see the differences, you should be able to do >> that, points are small enough to eyeball in hex). >> >> So when the 32-bit box is extracted from the 64-bit doubles, the >> points are identical at that level of precision and = returns true, >> while st_equals working against the doubles does not. >> >> P > > Again, another demonstration as to why BOX2DFLOAT4s should never be > used for calculations and only for internal "within" checks :( > > > ATB, > > Mark. > > -- > Mark Cave-Ayland - Senior Technical Architect PostgreSQL - PostGIS > Sirius Corporation plc - control through freedom > http://www.siriusit.co.uk > t: +44 870 608 0063 > > Sirius Labs: http://www.siriusit.co.uk/labs > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
