The number of dimensions in this case is teh number of coordinates, if your
point has 2 (X & Y) then it is 2, not 0. If it is an XYZ point, then ndim = 3.
ndim does not reere to points @ 0, lines @ 1 & polygons @ 2, but the dimensions
of the coordinate space.
Cheers,
Brent Wood
--- On Mon, 7/28/08, Edward Bridges <[EMAIL PROTECTED]> wrote:
> From: Edward Bridges <[EMAIL PROTECTED]>
> Subject: [postgis-users] ndim vs. st_dimension and enforce_dims_coordinate
> constraint
> To: "PostGIS Users Discussion" <postgis-users@postgis.refractions.net>
> Date: Monday, July 28, 2008, 7:30 AM
> Hello,
>
> I have a table with a geometry column which the
> AddGeometryColumn stored
> procedure has created a check constraint like so:
> Check constraints:
> "enforce_dims_coordinate" CHECK
> (ndims(coordinate) = 0)
>
> So, this uses the internal function "ndims" to
> check the dimensionality
> of the input coordinate.
>
> However, I'm getting a discrepancy when inserting a
> point into this
> column since ndims and st_dimensions are returning
> conflicting
> (apparently) values:
>
> rover=# select * from st_dimension(
> ST_GeomFromText('POINT(1 1)'));
> st_dimension
> --------------
> 0
> (1 row)
>
> rover=# select * from ndims( ST_GeomFromText('POINT(1
> 1)'));
> ndims
> -------
> 2
> (1 row)
>
> It seems that the ndims function returns only 2, 3, or 4;
> can someone
> please explain why the differing values and how to insert
> data into a
> point-type geometry column (seems to work fine with
> polygon) without
> crossing the check constraint?
>
> Thanks,
> Ed
>
>
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