Taken from postgis documentation
http://www.postgis.org/documentation/manual-1.3/ch06.html
ST_Equals(geometry, geometry)
Returns 1 (TRUE) if the given Geometries are "spatially equal". Use
this for a 'better' answer than '='. equals('LINESTRING(0 0, 10
10)','LINESTRING(0 0, 5 5, 10 10)') is true.
Actually the '=' operator is not overloaded for spatial query.
Have a look in lwpostgis.sql
[EMAIL PROTECTED]:~# grep OPERATOR /usr/local/pgsql/share/lwpostgis.sql
CREATE OPERATOR < (
CREATE OPERATOR <= (
CREATE OPERATOR = (
CREATE OPERATOR >= (
CREATE OPERATOR > (
CREATE OPERATOR CLASS btree_geometry_ops
OPERATOR 1 < ,
OPERATOR 2 <= ,
OPERATOR 3 = ,
OPERATOR 4 >= ,
OPERATOR 5 > ,
CREATE OPERATOR << (
CREATE OPERATOR &< (
CREATE OPERATOR <<| (
CREATE OPERATOR &<| (
CREATE OPERATOR && (
CREATE OPERATOR &> (
CREATE OPERATOR >> (
CREATE OPERATOR |&> (
CREATE OPERATOR |>> (
CREATE OPERATOR ~= (
CREATE OPERATOR @ (
CREATE OPERATOR ~ (
--david;
Quoting Picavet Vincent <[EMAIL PROTECTED]>:
Hi,
Considering two similar geometries, but different, an equality test with
the '=' operator returns true, whereas st_equals returns false.
In this case, st_equals behaviour seems right, but I would expect the
equality test with = to return false as well, since the geometries are
actually different.
Does someone have an explanation to this result ? Some kind of float
precision related issue ?
select st_geometryfromtext(
'LINESTRING(94525.0864578169 2403749.07413185,94521.0361656005
2403752.12944388,94519.5539334096
2403754.3019993,94517.5683187493 2403757.1772215,94512.295369653
2403767.3398906)'
)
= st_geometryfromtext(
'LINESTRING(94512.295369653 2403767.3398906,94520.7920704004
2403760.91556806,94524.3349180666
2403757.32391662,94525.0864578169 2403749.07413185)'
);
select st_equals(st_geometryfromtext('LINESTRING(94525.0864578169
2403749.07413185,94521.0361656005 2403752.12944388,94519.5539334096
2403754.3019993,94517.5683187493 2403757.1772215,94512.295369653
2403767.3398906)')
,st_geometryfromtext('LINESTRING(94512.295369653
2403767.3398906,94520.7920704004 2403760.91556806,94524.3349180666
2403757.32391662,94525.0864578169 2403749.07413185)'));
tested with :
"POSTGIS="1.3.3" GEOS="3.0.0-CAPI-1.4.1" PROJ="Rel. 4.6.0, 21 Dec 2007"
USE_STATS (procs from 1.3.2 need upgrade)"
"POSTGIS="1.1.6" GEOS="2.2.3-CAPI-1.1.1" PROJ="Rel. 4.5.0, 22 Oct 2006"
USE_STATS (procs from 1.3.2 need upgrade)"
Thanks for any explanation,
Vincent
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Jean David TECHER
www.davidgis.fr
06 60 46 85 05
04 99 77 16 87
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