Unnest arrays of different dimensions

Question

Is there a function or query that could return arrays of different dimensions as a set? For example, I would like to return the values

ARRAY[1]
ARRAY[2,3]
ARRAY[4,5,6]

as

1
2
3
4
5
6

Answer 1

Use unnest():

SELECT unnest(arr) AS elem
FROM (
 VALUES
   (ARRAY[1])
  ,(ARRAY[2,3])
  ,(ARRAY[4,5,6])
  ) t (arr);

Returns as requested.
More details:

• PostgreSQL unnest() with element number