[postgis-devel] Developing External Functions Using PostGIS Types with postgis-devel

[Esteban Zimanyi]

Dear all

I have similar problems when building MobilityDB, a temporal extension of
PostGIS that takes care of the temporal aspects and fully delegates all
spatial functionality to PostGIS. I ended up adding a file PostGIS.h in
which I put all declarations of PostGIS functions that are not in
liblwgeom.h, e.g.,

extern void srid_is_latlong(FunctionCallInfo fcinfo, int srid);
....

but also the functions from the API that I call directly

extern Datum transform(PG_FUNCTION_ARGS);
extern Datum buffer(PG_FUNCTION_ARGS);
extern Datum centroid(PG_FUNCTION_ARGS);
...

Regards

Esteban


On Mon, Mar 25, 2019 at 12:06 PM Adam Dadvar <adam.dadvar at gmail.com> wrote:

> Hi All,
>
> I have been trying to develop a separate function that builds on top of
> the PostGIS types. Effectively what I'm trying to do is use
> MultiLineStrings as a network to compute a minimum spanning tree. The end
> of each line is a node in this case.
> I think I have a basic understanding of how your code-base works but I am
> having issues where functions that I think should be available in
> postgis-devel are not.
>
> I know that liblwgeom.h is included in the postgis-devel library which
> provides the basic types and some utility functions, but for example, I
> want to input a MultiLineString (LWMLINE in the C code) so I use
> PG_GETARG_GSERIALIZED_P(0), but this is not included in liblwgeom.h. For
> that I can write my own function that does that from PG_DETOAST_DATUM, but
> for other functions it gets much more complicated - in order to convert the
> GSERIALIZED object I can either write my own function (which would take a
> long time) or just use the lwgeom_from_gserialized function that has
> already been written, however this function is not included in
> postgis-devel and has a large number of dependencies.
>
> I could just copy all of the header files from the source code and include
> them in my file but I'd prefer to just be able to say that the file depends
> on postgis-devel and then it can be compiled (this file needs to be rolled
> out to AWS in future).
>
> I understand that the recommendation might just be to produce the MST
> function within the PostGIS code-base, which I'd be open to do. It just
> seems strange that the postgis-devel library is basically unusable if you
> want to use it to extend PostGIS. Does anyone have any pointers on how to
> proceed?
>
> All advice is appreciated,
> Adam Dadvar
> _______________________________________________
> postgis-devel mailing list
> postgis-devel at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/postgis-devel
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-devel/attachments/20190325/443e9dec/attachment.html>