Re: Development of an extension for PostgreSQL and PostGIS

In order to get an LWGEOM from PostGIS you'll need to convert from the
serialized form (GSERIALIZED) which you can read all about in the
liblwgeom.h header. You'll be adding a hard dependency of course, but
hopefully you're OK with that.

If you're just hoping to build a compound type, as your example shows, you
can do that without a C extension, just read up on CREATE TYPE.

For an alternate example of an extension with a lighter dependency on
PostGIS, check out pgpointcloud, which has it's own structure for spatial
data (a point patch) and exchanges data with PostGIS via well-known-binary.
This removes the liblwgeom dependency, which means it's possible to compile
and use pgpointcloud without PostGIS installed, which is not entirely
uncommon.

P

On Mon, Aug 14, 2017 at 11:18 AM, Fabiana Zioti <fabi_zioti(at)hotmail(dot)com>
wrote:

> Hello.
>
> I will start developing an extension to PostgreSQL next to PostGIS using
> the C language.
>
> If my new type were:
>
>
> CREATE TYPE mytype (.., .., .., geom geometry);
>
> The creation of the structure in c, would be something like?
>
> #include "liblwgeom.h"
>
> Struct mytype
> {
> Int32 id;
> LWGEOM lwgeom;
>
> };
>
>
> In the extension I will create new data types for PostgreSQL, but I would
> like to use the geometric objects that the PostGIS extension offers, such
> as POINT, LINE, POLYGON, etc. In addition to their input functions (wkt-
> ST_GeomFromText ()), operators, index, etc.
>
> In this case just importing the liblwgeom library would be enough to
> develop an extension to PostgreSQL / PostGIS?
>
> Would you have any examples of such a project?
>
> Thanks in advance!!
>
>