[postgis-devel] PgSQL Memory Stuff

[Nicklas Avén]

Thanks a lot Paul !!!

This makes things clearer for me :-)

Then I just would like to add freeing the bbox also for the point-case
in lwpoint_free.  (or what the name was)

Then we will get rid of "my" memory leak with the left bounding box that
I create.


But what about some earlier discussion/explanation you gave about the
difficulty to know if the pointer to the point-array in the
LWGEOM-representation is pointing directly to the stored version or a
copied version of the point-array? 

How is that handled?
Or did I miss understand something?  

Getting this things right makes things more fun.

Thanks again
Nicklas


On Tue, 2010-12-07 at 16:27 -0800, Paul Ramsey wrote:
> Nik,
> Here's an annotated version of one of your functions, none of this
> stuff is critical, since pgsql just cleans right up behind you, but in
> case you want to do it "right"...
> 
> 
> PG_FUNCTION_INFO_V1(LWGEOM_shortestline2d);
> Datum LWGEOM_shortestline2d(PG_FUNCTION_ARGS)
> {
> 	PG_LWGEOM *result;
> 	/* Detoast the actual PgSQL varlena structures, in our case PG_LWGEOM
> (soon to be GSERIALIZED) */
> 	PG_LWGEOM *geom1 = (PG_LWGEOM*)PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
> 	PG_LWGEOM *geom2 = (PG_LWGEOM*)PG_DETOAST_DATUM(PG_GETARG_DATUM(1));
> 	/* Build LWGEOM from the varlena (soon to be with lwgeom_from_gserialized) */
> 	LWGEOM *lwgeom1 = pglwgeom_deserialize(geom1);
> 	LWGEOM *lwgeom2 = pglwgeom_deserialize(geom2);
> 	LWGEOM *theline;
> 
> 
> 	if (lwgeom1->srid != lwgeom2->srid)
> 	{
> 		elog(ERROR,"Operation on two GEOMETRIES with different SRIDs\n");
> 		PG_RETURN_NULL();
> 	}
> 
> 	theline = lw_dist2d_distanceline(lwgeom1, lwgeom2, lwgeom1->srid, DIST_MIN);
> 	if (lwgeom_is_empty(theline))
> 		PG_RETURN_NULL();
> 
> 	/* Serialize the result back down from LWGEOM, but don't return right away */
> 	result = pglwgeom_serialize(theline);
> 	/* First free the LWGEOMs you used */
> 	lwgeom_free(lwgeom1);
> 	lwgeom_free(lwgeom2);
> 
> 	/* Then call free_if_copy on the *varlena* structures you originally
> get as arguments */
> 	PG_FREE_IF_COPY(geom1, 0);
> 	PG_FREE_IF_COPY(geom2, 1);
> 
> 	/* And now return */
> 	PG_RETURN_POINTER(result);
> }
> _______________________________________________
> postgis-devel mailing list
> postgis-devel at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-devel
>