sql - unwrap postgresql array into rows

Question

What is the fastest way to unwrap array into rows in PostgreSQL? For instance,

We have:

a
-
{1,2}
{2,3,4}

And we need:

b
- 
1
2
2
3
4

I'm using:

select explode_array(a) as a from a_table;

where explode_array is:

create or replace function explode_array(in_array anyarray) returns setof anyelement as
$$
    select ($1)[s] from generate_series(1,array_upper($1, 1)) as s;
$$

Is there any better way?

Answer 1

Use unnest. For example:

CREATE OR REPLACE FUNCTION test( p_test text[] )
  RETURNS void AS
$BODY$
BEGIN
  SELECT id FROM unnest( p_test ) AS id;
END;
$BODY$
  LANGUAGE plpgsql IMMUTABLE
  COST 1;