Hi,
I am having some troubles using DWithin when the passed-in distance is 0. My
query should return all geometries that are within or within a given
distance of a rectangle. DWithin works fine as long as the distance not
equals 0. If so, no geometries are returned. If I choose a very small
distance it works somehow.
select AsText(the_geom) from points where ST_DWithin(the_geom,
ST_GeomFromText('POLYGON((-180 -90, 180 -90, 180 90, -180 90, -180 -90))',
4326), 0);
astext
--------
(0 rows)
select AsText(the_geom) from points where ST_DWithin(the_geom,
ST_GeomFromText('POLYGON((-180 -90, 180 -90, 180 90, -180 90, -180 -90))',
4326), 0.000000000000000000000000000000000000000000000000000001);
astext
-------------------------------
POINT(56.25 32.34375)
POINT(-45 47.8125)
POINT(-26.71875 -54.140625)
POINT(116.3671875 61.171875)
POINT(131.8359375 -21.796875)
(5 rows)
I am using version 1.3.3, so according to the manual [1] and this workshop
[2], ST_DWithin is just translated into a combination of ST_Expand, && and
ST_Distance. But if I make a query that looks like the definition of
ST_DWithin, the points are returned.
select AsText(the_geom) from points
where
the_geom && ST_Expand(GeomFromText('POLYGON((-180 -90, 180 -90, 180 90,
-180 90, -180 -90))', 4326), 0)
AND
GeomFromText('POLYGON((-180 -90, 180 -90, 180 90, -180 90, -180 -90))',
4326) && ST_Expand(the_geom, 0)
AND
ST_Distance(the_geom, GeomFromText('POLYGON((-180 -90, 180 -90, 180 90,
-180 90, -180 -90))', 4326)) <= 0;
astext
-------------------------------
POINT(56.25 32.34375)
POINT(-45 47.8125)
POINT(-26.71875 -54.140625)
POINT(116.3671875 61.171875)
POINT(131.8359375 -21.796875)
(5 rows)
Is this behaviour intented?
Thank you,
Tobias
[1]: http://www.postgis.org/documentation/manual-1.5/ST_DWithin.html
[2]: http://workshops.opengeo.org/postgis-spatialdbtips/click-analyze.html
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