[postgis-devel] PgSQL Memory Stuff

[Nicklas Avén]

I have been looking through the measure functions according to the
example below, (in 2D I think you have fixed most of it Paul, but not in
3d). 

I have two questions

question 1) In LWGEOM_mindistance2d for instance there is this 

	PROFSTART(PROF_QRUN)

and 

	PROFSTOP(PROF_QRUN);
        PROFREPORT("dist",geom1, geom2, NULL); 

I have just left it there earlier because I have had no idea what it is
for.
Can I just remove it? I see very few other functions have this profile
thing. Or is it of any use?


question 2) 

In the example below there is this null-return if the result is empty:

	if (lwgeom_is_empty(theline))
		PG_RETURN_NULL();

Should we care about freeing stuff in this case too. I guess it wouldn't
be anything wrong in doing it at least?

like:
if (lwgeom_is_empty(theline)) 
{
	
	lwgeom_free(theline);
	lwgeom_free(lwgeom1);
	lwgeom_free(lwgeom2);
	PG_FREE_IF_COPY(geom1, 0);
	PG_FREE_IF_COPY(geom2, 1);
	PG_RETURN_NULL();
}

As I understand it there should not be any problem freeing "theline"
with lwgeom_free even if it is empty in any way.



Thanks

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);
> }
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