Calling postgres function with multiple params - sql

Question

This is my sql function in postgresql:
FUNCTION test(year integer)
RETURNS SETOF json AS
$BODY$
SELECT ARRAY_TO_JSON(ARRAY_AGG(T))
FROM table t
WHERE year = $1;
$BODY$
This works quite good. But now I want specify more parameters and
I'd like to get a return with the condition if parameters are set. For example following function call:
test(year := 2014, location := 'Belo Horizonte')
How should the function look like and where to set conditions? Here is my (wrong) suggestion:
FUNCTION test(year integer, location text)
RETURNS SETOF json AS
$BODY$
SELECT ARRAY_TO_JSON(ARRAY_AGG(T))
FROM table t
IF $1 IS SET THEN
WHERE year = $1
ELSIF $2 THEN
UNION
WHERE location = $2
END IF;
$BODY$
A further challenge is a return of the function for this statements:
test(year := 1584)
-- should return all entries with year 1584
test(location := 'Cambridge')
-- should return all entries with location Cambridge
test(year := 1584, location := 'Cambridge')
-- should return all entries with year 2014 AND location Belo Horizonte
Thanks in advance!

Answer 1

You may try to do something like that, adding default values, and working with OR clauses
FUNCTION test(year integer DEFAULT -1, location text DEFAULT 'noLocation')
RETURNS SETOF json AS
$BODY$
SELECT ARRAY_TO_JSON(ARRAY_AGG(T))
FROM table t
WHERE ($1 = -1 OR year = $1)
AND ($2 = 'noLocation' OR location = $2);
$BODY$