[postgis-users] ERROR: couldnt parse object in GEOMETRY

[Paul Ramsey]

The problem is you are treating the $ variables like perl variables. You 
cannot just dump them into a string and expect them to evaluate. You 
need to explicitly concatenate them into a string. So for example, to 
create a WKT representation of a point from two inputs, do this:

'POINT(' || $1 || ' ' || $2 || ')'

Michael O'Sullivan wrote:
> Hi all,
> 
> I am trying to create a function which takes two points as arguments and
> calls length_spheroid using the two points as LINESTRING data.
> 
> Can someone explain why
> 
> CREATE FUNCTION get_length (numeric, numeric, numeric, numeric) RETURNS
> double precision AS '
> SELECT length_spheroid(\'LINESTRING(-88.8869323730469
> 30.4190692901611,-95.3706970214844 28.9613304138184)\',
> \'SPHEROID("GRS_1980",6378137,298.257222101)\');
> ' LANGUAGE SQL;
> 
> works, but
> 
> CREATE FUNCTION get_length (numeric, numeric, numeric, numeric) RETURNS
> numeric AS '
> SELECT length_spheroid(\'LINESTRING($1 $2, $3 $4)\',
> \'SPHEROID("GRS_1980",6378137,298.257222101)\');
> ' LANGUAGE SQL;
> 
> does not?
> 
> When I try and use function arguments as the values to the LINESTRING
> definition, I get
> 
> "ERROR:  couldnt parse object in GEOMETRY"
> 
> I have tried enclosing the LINESTRING($1 $2, $3 $4) call with a 
> GeometryFromText call, but I still get GEOMETRY parse errors.
> 
> I have searched the mailing list archive and found a mail from a while 
> back indicating you couldn't create the LINESTRING objects in the server 
> - is that what is going on here?
> 
>  > The $60000 question: at the moment, you cannot do so within the
>  > database. I think a better bet would be for us to get a
>  > distance(<geometry>,<geometry>) function in there ASAP. What say you,
>  > Dave?
> 
>  >Ted Rolle wrote:
>  >>
>  >> How do I make a LINESTRING from two POINTs?  What I want to do is 
> get the
>  >> {length2d|length3d} of this LINESTRING to determine the distance 
> between
>  >> two points.
>  >>
>  >> Ted
> 
> 
> 
> thanks,
> 
> 
> Michael
>