INSERT while LOOPing - postgresql

Question

i'd like to insert some records into a table while looping. Records are passed as a varchar tab to a function ie.:
create function a(tab varchar[]) RETURNS void AS
$$
DECLARE
b varchar(20);
BEGIN
FOREACH b IN ARRAY tab
LOOP
INSERT INTO....;
END LOOP;
RETURN;
END;
$$
LANGUAGE plpgsql;
However, when executing there is the error:
ERROR: syntax error at or near "FOREACH"
LINE 1: FOREACH $1 IN ARRAY tab LOOP INSERT INTO x (c, ...
QUERY: FOREACH $1 IN ARRAY tab LOOP INSERT INTO x (c) VALUES ( $1)
CONTEXT: SQL statement in PL/PgSQL function " near line ...
********** ERROR **********
ERROR: syntax error at or near "FOREACH"
Does anybody know why and how to fix this?

Answer 1

FOREACH construct was added in 9.1. For earlier versions you can use unnest() function the following way:
CREATE FUNCTION a(tab varchar[]) RETURNS void AS
$$
DECLARE
b varchar(20);
BEGIN
FOR b IN SELECT unnest(tab)
LOOP
INSERT INTO x(c) VALUES (b);
END LOOP;
RETURN;
END;
$$ LANGUAGE plpgsql;

Answer 2

Since PostgreSQL 9.1 there is also a built-in way to loop through array slices:
FOREACH x SLICE 1 IN ARRAY $1
LOOP
RAISE NOTICE 'row = %', x;
END LOOP;
Where x must be a matching array type and ...
The SLICE value must be an integer constant not larger than the number of dimensions of the array
For 1-dimensional arrays just omit the SLICE part and x can be a simple type like you display in your question.

Answer 3

I want to add one thing, and that is that unnest unnests all levels of an array:
select * from unnest(ARRAY[ARRAY[1,2,3],Array[5,6,7]]);
unnest
--------
1
2
3
5
6
7
(6 rows)
If you want to loop through one level of a multi-dimensional array, you should loop through the following instead
FOR out_count IN
array_lower(in_transactions, 1) ..
array_upper(in_transactions, 1)
LOOP
-- Fill the bulk payments table
INSERT INTO bulk_payments_in(id, amount)
VALUES (in_transactions[out_count][1],
in_transactions[out_count][2]);
END LOOP;