Yes, that's true. Hadn't thought of that one...
On 29-Oct-07, at 5:29 AM, Obe, Regina wrote:
P,
So does that mean you can create a more efficent st_dwithin that
instead
of doing this
SELECT $1 && ST_Expand($2,$3) AND $2 && ST_Expand($1,$3) AND
ST_Distance($1, $2) < $3
Does this
SELECT $1 && ST_Expand($2,$3) AND $2 && ST_Expand($1,$3) AND
_ST_DWithin($1, $2, $3)
And the new _ST_Dwithin function would do exactly what distance does
except it would return a boolean and kick out a true as soon as it
finds
a point set where the distance is < $3; no need to wait to reach 0.
R
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Paul
Ramsey
Sent: Thursday, October 25, 2007 10:50 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] noding problem
Yes, that is all the magic there is to the "distance is faster"
assertion. Obviously it's only faster for cases where there are lots
of fully contained candidates that return immediately on the first
point test.
P
On 25-Oct-07, at 4:24 AM, Obe, Regina wrote:
Am I safe in saying that distance treats the case of distance() ==
0 as
a special case - e.g. you can't get lower than 0 for distance so
there
is no point in checking any further?
_______________________________________________
postgis-users mailing list
[email protected]
http://postgis.refractions.net/mailman/listinfo/postgis-users
-----------------------------------------
The substance of this message, including any attachments, may be
confidential, legally privileged and/or exempt from disclosure
pursuant to Massachusetts law. It is intended
solely for the addressee. If you received this in error, please
contact the sender and delete the material from any computer.
_______________________________________________
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
