Using unnest function on multi-dimensional array.

Hi,

Can anybody highlight how to use unnest function from postgres 8.4 on
multi-dimensional array?

Below is the sample table structure:

Table "public.multi_array_test"
Column | Type | Modifiers
---------+----------+-----------
id | integer |
user_id | bigint[] |

Sample data:

1 | {{3567559397,0},{3020933367,1},{2479094216,2},{3310282955,3}}

Regards,
Nimesh.