Question

Let’s say I’ve created a composite type in Postgresql:

CREATE TYPE custom_type AS
   (x integer
    y integer);

I need to use it in a function as an array:

...
DECLARE
customVar custom_type[];
BEGIN
....

My question is: how do I access custom_type’s specific components?

For example, I want to (re)assign ‘x’ for the third element in custom_type array…

Answer 1

postgres=> create type pt as (x int, y int);
CREATE TYPE

postgres=> create or replace function fx()
returns void as $$
declare a pt[] = ARRAY[(10,20),(30,40)]; declare xx pt;
begin
  for i in array_lower(a, 1) .. array_upper(a,1)
  loop
    xx = a[i]; xx.x := xx.x + 1; a[i] := xx; raise notice '%', a[i].x;
  end loop;
end;
$$ language plpgsql;
CREATE FUNCTION
postgres=> select fx();
NOTICE:  11
NOTICE:  31
 fx 
────

(1 row)

Significant limit for target of assign statement is possibility to refer only one level nested properties. This limit can be bypassed by auxiliary variables – it is not too friendly – and internal implementation is too simple, but it is fast and enough for typical stored procedure usage although it is not strong in comparison with generic programming languages.