Loop through a composite array in plpgsql - postgresql

Question

I want to define a composite array , initialize three elements of the array and then iterate over each of the elements in a loop. I need this loop and to iterate over it as a requirement for an issue that I have.
I have tried for several days to write the code and refer to several resources on net but this has not worked. Can someone help on it. Here is the code, even the first initialization is not working so I don't have code for rest of the requirement (to iterate after the initialization)
CREATE TYPE temp_n_inv_item AS (
name text,
supplier_id integer,
price numeric
);
CREATE OR REPLACE function temp_n_bulk_load2()
returns void
as
$$
declare
v_t temp_n_inv_item[];
BEGIN
v_t[1] := ARRAY ['Item1',1,10];
v_t[2] := ARRAY ['Item2',2,20];
v_t[3] := ARRAY ['Item3',3,30];
-- raise notice 'first array % ', v_t[1];
--raise notice 'first array % ', v_t[2];
--raise notice 'first array % ', v_t[3];
--iterate though each of the v_t array in a loop
null; --added as a temporary placeholder
END;
$$
language plpgsql;
--select temp_n_bulk_load2()
Regards,
DbuserN
UPDATE
Surprisingly, after posting the question, I saw one reference and assignment is now working but I try to change the return type to the array which is not working, (which is an additional issue), though assignment is fixed now as below, but the error the below gives is "ERROR: cannot return non-composite value from function returning composite type"
Revised code
:
CREATE OR REPLACE function temp_n_bulk_load2()
returns temp_n_inv_item
as
$$
declare
v_t temp_n_inv_item[];
BEGIN
v_t[1] := row ('Item1',1,10);
v_t[2] := row ('Item2',2,20);
v_t[3] := row ('Item3',3,30);
raise notice 'first array % ', v_t[1];
raise notice 'first array % ', v_t[2];
raise notice 'first array % ', v_t[3];
--iterate though each of the v_t array in a loop
null; --added as a temporary placeholder
return v_t;
END;
$$
language plpgsql;

Answer 1

PLpgSQL has special statement for iteration over array. For large arrays it is much more effective (is not too significant for small arrays):
create type tp as (a int, b int);
do $$
declare a tp[];
r record;
begin
/* composite array initialization */
a = array[(1,2),(3,4),(5,6)];
/* iterate over a array */
foreach r in array a
loop
raise notice '% % %', r, r.a, r.b;
end loop;
end;
$$;
NOTICE: (1,2) 1 2
NOTICE: (3,4) 3 4
NOTICE: (5,6) 5 6
DO
Don't afraid read a documentation.

Answer 2

Here you are creating array of data type you generated using
CREATE TYPE temp_n_inv_item AS (
name text,
supplier_id integer,
price numeric
);
So simply return array of data type as temp_n_inv_item[].
CREATE OR REPLACE FUNCTION adm.temp_n_bulk_load2()
RETURNS boolean AS
$BODY$
declare
v_t temp_n_inv_item[];
BEGIN
/*CREATE TYPE temp_n_inv_item AS (
name text,
supplier_id integer,
price numeric
);*/
v_t[1] := row ('Item1',1,10);
v_t[2] := row ('Item2',2,20);
v_t[3] := row ('Item3',3,30);
raise notice 'first array % ', v_t[1];
raise notice 'first array % ', v_t[2];
raise notice 'first array % ', v_t[3];
--iterate though each of the v_t array in a loop
//updated
FOR cnt in 1..(array_length(v_t,1))
LOOP
Raise notice ' array value % ', v_t[cnt];
END LOOP;
return true;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
Hope this will solve your problem.