PostgreSQL convert array returned from function to columns

Question

I have a function in PostgreSQL (PLPGSQL) that returns an array containing two elements. When I run a select statement calling the function, I get a column containing the a

Answer 1

You can't do that. A single array column could have, for example, one array with three elements and another with five elements. If you tried to expand those arrays into individual columns, you'd end up with two rows in a result set that have different numbers of columns and that is not allowed.

The closest thing available is unnest:

expand an array to a set of rows

but that gives you rows rather the columns you want.

Answer 2

can you use a subselect?

postgres=# select ar[1], ar[2] from (select string_to_array('a b c', ' ') ar) as sq;
 ar | ar 
----+----
 a  | b
(1 row)

This still requires you explicitly extract each column (like you already do). If there are more elements in the array than extracted, they will be lost, and if there are fewer, then the missing columns will just be NULL.

EDIT: I think I would wrap the whole thing in a subselect; the inner subselect generates the desired rows, with the outer select projecting the inner query into the desired columns:

SELECT subquery1.a, subquery1.b, subquery1.c, 
    myfunction_result[1], myfunction_result[2] 
FROM ( SELECT table1.a, table1.b, table1.c,
              MyFunction(table1.a, table1.b, table1.c) as myfunction_result
       FROM table1 INNER JOIN table2 using(b) 
       WHERE ... GROUP BY table1.a, table1.b, table1.c
) AS subquery1;

The inner and outer selects will properly correlate the table1 references.

Answer 3

select data[1] as id, data[2] as value from (SELECT 
string_to_array(rs,':') as data from unnest(string_to_array('1:234,2:400',',')) as rs) as foo

This will result as:

id|Value
--------
1 | 234
2 | 400