presto-hive/src/main/java/io/prestosql/plugin/hive/metastore/glue/GlueHiveMetastore.java/GlueHiveMetastore/listRoleGrants
class GlueHiveMetastore:    @Override
    public Set<RoleGrant> listRoleGrants(HivePrincipal principal)
    {
        if (principal.getType() == USER) {
            return ImmutableSet.of(new RoleGrant(principal.toPrestoPrincipal(), PUBLIC_ROLE_NAME, false));
        }
        return ImmutableSet.of();
    }