pgis_union_geometry_array()

Datum pgis_union_geometry_array

(

PG_FUNCTION_ARGS

)

Definition at line 367 of file postgis/lwgeom_geos.c.

References genraster::count, error_if_srid_mismatch(), geometry_serialize(), GEOS2POSTGIS(), gserialized_get_srid(), gserialized_get_type(), gserialized_has_z(), gserialized_is_empty(), HANDLE_GEOS_ERROR, LW_FALSE, lwgeom_construct_empty(), lwgeom_geos_error(), PG_FUNCTION_INFO_V1(), POSTGIS2GEOS(), SRID_UNKNOWN, ST_UnaryUnion(), and genraster::value.

Referenced by pgis_geometry_union_finalfn(), and ST_FrechetDistance().

{
        /*
        ** For GEOS >= 3.3, use the new UnaryUnion functionality to merge the
        ** terminal collection from the ST_Union aggregate
        */
        ArrayType *array;

        ArrayIterator iterator;
        Datum value;
        bool isnull;

        int is3d = LW_FALSE, gotsrid = LW_FALSE;
        int nelems = 0, geoms_size = 0, curgeom = 0, count = 0;

        GSERIALIZED *gser_out = NULL;

        GEOSGeometry *g = NULL;
        GEOSGeometry *g_union = NULL;
        GEOSGeometry **geoms = NULL;

        int srid = SRID_UNKNOWN;

        int empty_type = 0;

        /* Null array, null geometry (should be empty?) */
        if ( PG_ARGISNULL(0) )
                PG_RETURN_NULL();

        array = PG_GETARG_ARRAYTYPE_P(0);
        nelems = ArrayGetNItems(ARR_NDIM(array), ARR_DIMS(array));

        /* Empty array? Null return */
        if ( nelems == 0 ) PG_RETURN_NULL();

        /* Quick scan for nulls */
#if POSTGIS_PGSQL_VERSION >= 95
        iterator = array_create_iterator(array, 0, NULL);
#else
        iterator = array_create_iterator(array, 0);
#endif
        while( array_iterate(iterator, &value, &isnull) )
        {
                /* Skip null array items */
                if ( isnull )
                        continue;

                count++;
        }
        array_free_iterator(iterator);


        /* All-nulls? Return null */
        if ( count == 0 )
                PG_RETURN_NULL();

        /* One geom, good geom? Return it */
        if ( count == 1 && nelems == 1 )
                PG_RETURN_POINTER((GSERIALIZED *)(ARR_DATA_PTR(array)));

        /* Ok, we really need GEOS now ;) */
        initGEOS(lwpgnotice, lwgeom_geos_error);

        /*
        ** Collect the non-empty inputs and stuff them into a GEOS collection
        */
        geoms_size = nelems;
        geoms = palloc(sizeof(GEOSGeometry*) * geoms_size);

        /*
        ** We need to convert the array of GSERIALIZED into a GEOS collection.
        ** First make an array of GEOS geometries.
        */
#if POSTGIS_PGSQL_VERSION >= 95
        iterator = array_create_iterator(array, 0, NULL);
#else
        iterator = array_create_iterator(array, 0);
#endif
        while( array_iterate(iterator, &value, &isnull) )
        {
                GSERIALIZED *gser_in;

                /* Skip null array items */
                if ( isnull )
                        continue;

                gser_in = (GSERIALIZED *)DatumGetPointer(value);

                /* Check for SRID mismatch in array elements */
                if ( gotsrid )
                {
                        error_if_srid_mismatch(srid, gserialized_get_srid(gser_in));
                }
                else
                {
                        /* Initialize SRID/dimensions info */
                        srid = gserialized_get_srid(gser_in);
                        is3d = gserialized_has_z(gser_in);
                        gotsrid = 1;
                }

                /* Don't include empties in the union */
                if ( gserialized_is_empty(gser_in) )
                {
                        int gser_type = gserialized_get_type(gser_in);
                        if (gser_type > empty_type)
                        {
                                empty_type = gser_type;
                                POSTGIS_DEBUGF(4, "empty_type = %d  gser_type = %d", empty_type, gser_type);
                        }
                }
                else
                {
                        g = (GEOSGeometry *)POSTGIS2GEOS(gser_in);

                        /* Uh oh! Exception thrown at construction... */
                        if ( ! g )
                        {
                                HANDLE_GEOS_ERROR("One of the geometries in the set "
                                                  "could not be converted to GEOS");
                                PG_RETURN_NULL();
                        }

                        /* Ensure we have enough space in our storage array */
                        if ( curgeom == geoms_size )
                        {
                                geoms_size *= 2;
                                geoms = repalloc( geoms, sizeof(GEOSGeometry*) * geoms_size );
                        }

                        geoms[curgeom] = g;
                        curgeom++;
                }

        }
        array_free_iterator(iterator);

        /*
        ** Take our GEOS geometries and turn them into a GEOS collection,
        ** then pass that into cascaded union.
        */
        if (curgeom > 0)
        {
                g = GEOSGeom_createCollection(GEOS_GEOMETRYCOLLECTION, geoms, curgeom);
                if ( ! g )
                {
                        HANDLE_GEOS_ERROR("Could not create GEOS COLLECTION from geometry array");
                        PG_RETURN_NULL();
                }

                g_union = GEOSUnaryUnion(g);
                GEOSGeom_destroy(g);
                if ( ! g_union )
                {
                        HANDLE_GEOS_ERROR("GEOSUnaryUnion");
                        PG_RETURN_NULL();
                }

                GEOSSetSRID(g_union, srid);
                gser_out = GEOS2POSTGIS(g_union, is3d);
                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, is3d, 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);
}

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