pgis_geometry_union_finalfn()

Datum pgis_geometry_union_finalfn

(

PG_FUNCTION_ARGS

)

Definition at line 515 of file postgis/lwgeom_geos.c.

{
        CollectionBuildState *state;
        ListCell *l;
        LWGEOM **geoms;
        GSERIALIZED *gser_out;
        size_t ngeoms = 0;
        int empty_type = 0;
        bool first = true;
        int32_t srid = SRID_UNKNOWN;
        int has_z = LW_FALSE;
 
        if (PG_ARGISNULL(0))
                PG_RETURN_NULL(); /* returns null iff no input values */
 
        state = (CollectionBuildState *)PG_GETARG_POINTER(0);
        geoms = palloc(list_length(state->geoms) * sizeof(LWGEOM*));
 
        /* Read contents of list into an array of only non-null values */
        foreach (l, state->geoms)
        {
                LWGEOM *geom = (LWGEOM*)(lfirst(l));
                if (geom)
                {
                        if (!lwgeom_is_empty(geom))
                        {
                                geoms[ngeoms++] = geom;
                                if (first)
                                {
                                        srid = lwgeom_get_srid(geom);
                                        has_z = lwgeom_has_z(geom);
                                        first = false;
                                }
                        }
                        else
                        {
                                int type = lwgeom_get_type(geom);
                                empty_type = type > empty_type ? type : empty_type;
                                srid = (srid != SRID_UNKNOWN ? srid : lwgeom_get_srid(geom));
                        }
                }
        }
 
        /*
        ** Take our array of LWGEOM* and turn it into a GEOS collection,
        ** then pass that into cascaded union.
        */
        if (ngeoms > 0)
        {
                GEOSGeometry *g = NULL;
                GEOSGeometry *g_union = NULL;
                LWCOLLECTION* col = lwcollection_construct(COLLECTIONTYPE, srid, NULL, ngeoms, geoms);
 
                initGEOS(lwpgnotice, lwgeom_geos_error);
                g = LWGEOM2GEOS((LWGEOM*)col, LW_FALSE);
                if (!g)
                        HANDLE_GEOS_ERROR("Could not create GEOS COLLECTION from geometry array");
 
                g_union = GEOSUnaryUnion(g);
                GEOSGeom_destroy(g);
                if (!g_union)
                        HANDLE_GEOS_ERROR("GEOSUnaryUnion");
 
                GEOSSetSRID(g_union, srid);
                gser_out = GEOS2POSTGIS(g_union, has_z);
                GEOSGeom_destroy(g_union);
        }
        /* No real geometries in our array, any empties? */
        else
        {
                /* If it was only empties, we'll return the largest type number */
                if (empty_type > 0)
                        PG_RETURN_POINTER(
                            geometry_serialize(lwgeom_construct_empty(empty_type, srid, has_z, 0)));
 
                /* Nothing but NULL, returns NULL */
                else
                        PG_RETURN_NULL();
        }
 
        if (!gser_out)
        {
                /* Union returned a NULL geometry */
                PG_RETURN_NULL();
        }
 
        PG_RETURN_POINTER(gser_out);
}

References COLLECTIONTYPE, geometry_serialize(), CollectionBuildState::geoms, GEOS2POSTGIS(), HANDLE_GEOS_ERROR, LW_FALSE, lwcollection_construct(), LWGEOM2GEOS(), lwgeom_construct_empty(), lwgeom_geos_error(), lwgeom_get_srid(), lwgeom_get_type(), lwgeom_has_z(), lwgeom_is_empty(), and SRID_UNKNOWN.

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