Passing multiple values in single parameter - sql

Question

Let's say I have this function:
CREATE OR REPLACE FUNCTION test_function(character varaying)
RETURNS integer AS
$BODY$
DECLARE
some_integer integer;
begin
Select column2 from test_table where column1 in ($1) into some_integer;
end;
Return some_integer;
$BODY$
LANGUAGE plpgsql VOLATILE COST 100;
And I want to call it like this:
Select * from test_function ('data1', 'data2','data3');
Of course, it cannot be done this way, because Postgres tries to find function with this name and three parameter which doesn't exists.
I tried to put quotes around commas but in that case parameter is interpreted wrong: data1', 'data2','data3, like one string.
Is there a way to put multiple values in parameter so IN clause can recognized it?

Answer 1

(Your function wouldn't be created. RETURN after END is syntactical nonsense.)
A function with a VARIADIC parameter does exactly what you ask for:
CREATE OR REPLACE FUNCTION test_function(date, date, VARIADIC varchar[])
RETURNS SETOF integer
LANGUAGE sql AS
$func$
SELECT col1
FROM test_table
WHERE col3 > $1
AND col4 < $2
AND col2 = ANY($3)
$func$;
db<>fiddle here - demo with additional parameters
Old sqlfiddle
Call (as desired):
SELECT * FROM test_function('data1', 'data2', 'data3');
Using a simple SQL function, plpgsql is not required for the simple example. But VARIADIC works for plpgsql functions, too.
Using RETURNS SETOF integer since this can obviously return multiple rows.
Details:
Pass multiple values in single parameter
Return rows matching elements of input array in plpgsql function
VARIADIC parameter must be the last input parameter
Return rows matching elements of input array in plpgsql function