ST_SnapToGrid doesn't snap

[geognu]

Hi.

Testing various ST_SnapToGrid options looks like snapping is not working for values < 0.5, e.g. running the query

UPDATE mytable SET the_geom=ST_SnapToGrid(the_geom, 1)

I get the results, whilst

UPDATE mytable SET the_geom=ST_SnapToGrid(the_geom, 0.0000001)

doesn't work at all, leaving the geometry untouched.

[robe]

Can you please state the version of PostGIS you are using and also provide sample data.

SELECT postgis_full_version();

[geognu]

fatt_poly_01 - data exported to shape after setting grid=0.0000001

[geognu]

fatt_poly_05 - data exported to shape after setting grid=0.5

[geognu]

fatt_poly_50 - data exported to shape after setting grid=50 (exxagerated for testing)

[geognu]

postgis_full_version POSTGIS="2.1.1 r12113" GEOS="3.3.8-CAPI-1.7.8" PROJ="Rel. 4.8.0, 6 March 2012" LIBXML="2.9.1"

Files attached

[pramsey]

I don't know how you're evaluating what "works" or not, but I can snap things just fine using 2.1

select st_astext(st_startpoint(st_exteriorring(st_geometryn(st_snaptogrid(geom,0.01),1)))) from fattibilita_poly_01;