Datum  
pg_database_size_name(PG_FUNCTION_ARGS)
{
        int64           size = 0;
        Name            dbName = PG_GETARG_NAME(0);
        Oid                     dbOid = get_database_oid(NameStr(*dbName));  

        if (!OidIsValid(dbOid))  
                ereport(ERROR,  
                                (errcode(ERRCODE_UNDEFINED_DATABASE),
                                 errmsg("database \"%s\" does not exist",  
                                                NameStr(*dbName))));

        size = calculate_database_size(dbOid);

        if (Gp_role == GP_ROLE_DISPATCH)
        {  
                StringInfoData buffer;
                initStringInfo(&buffer);
                appendStringInfo(&buffer, "select sum(pg_database_size('%s'))::int8 from gp_dist_random('gp_id');", NameStr(*dbName));

                size += get_size_from_segDBs(buffer.data);  
        }

        PG_RETURN_INT64(size);
}