ST_CollectionExtract()

Datum ST_CollectionExtract

(

PG_FUNCTION_ARGS

)

Definition at line 2916 of file lwgeom_functions_basic.c.

{
        GSERIALIZED *gser_in, *gser_out;
        LWGEOM *lwg_in = NULL;
        LWGEOM *lwg_out = NULL;
        int extype = 0;
 
        if (PG_NARGS() > 1)
                extype = PG_GETARG_INT32(1);
 
        /* Ensure the right type was input */
        if (!(extype == 0 || extype == POINTTYPE || extype == LINETYPE || extype == POLYGONTYPE))
        {
                elog(ERROR, "ST_CollectionExtract: only point, linestring and polygon may be extracted");
                PG_RETURN_NULL();
        }
 
        gser_in = PG_GETARG_GSERIALIZED_P(0);
        lwg_in = lwgeom_from_gserialized(gser_in);
 
        /* Mirror non-collections right back */
        if (!lwgeom_is_collection(lwg_in))
        {
                /* Non-collections of the matching type go back */
                if (lwg_in->type == extype || !extype)
                {
                        lwgeom_free(lwg_in);
                        PG_RETURN_POINTER(gser_in);
                }
                /* Others go back as EMPTY */
                else
                {
                        lwg_out = lwgeom_construct_empty(extype, lwg_in->srid, lwgeom_has_z(lwg_in), lwgeom_has_m(lwg_in));
                        PG_RETURN_POINTER(geometry_serialize(lwg_out));
                }
        }
 
        lwg_out = (LWGEOM*)lwcollection_extract((LWCOLLECTION*)lwg_in, extype);
 
        gser_out = geometry_serialize(lwg_out);
        lwgeom_free(lwg_in);
        lwgeom_free(lwg_out);
        PG_RETURN_POINTER(gser_out);
}

References LINETYPE, lwcollection_extract(), lwgeom_construct_empty(), lwgeom_free(), lwgeom_from_gserialized(), lwgeom_has_m(), lwgeom_has_z(), lwgeom_is_collection(), POINTTYPE, POLYGONTYPE, LWGEOM::srid, and LWGEOM::type.

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