how to get the size of array?

Hello,

Is there a way that I can get the size of one array ?

For example, create table test (id varchar[]);
insert into test values('{}');
insert into test values('{1, 2, 3}');

I am looking for something like :  select sizeOf(id) as size from test;


so that I can get results like:
size
-------
0
3

Thanks a lot,
Ying