how to manually cache the values of function calls in 10g - oracle

Question

I have the following code
CREATE OR REPLACE FUNCTION slow_function (p_in IN NUMBER)
RETURN NUMBER
AS
BEGIN
DBMS_LOCK.sleep(1);
RETURN p_in;
END;
/
CREATE OR REPLACE PACKAGE cached_lookup_api AS
FUNCTION get_cached_value (p_id IN NUMBER)
RETURN NUMBER;
PROCEDURE clear_cache;
END cached_lookup_api;
/
CREATE OR REPLACE PACKAGE BODY cached_lookup_api AS
TYPE t_tab IS TABLE OF NUMBER
INDEX BY BINARY_INTEGER;
g_tab t_tab;
g_last_use DATE := SYSDATE;
g_max_cache_age NUMBER := 10/(24*60); -- 10 minutes
-- -----------------------------------------------------------------
FUNCTION get_cached_value (p_id IN NUMBER)
RETURN NUMBER AS
l_value NUMBER;
BEGIN
IF (SYSDATE - g_last_use) > g_max_cache_age THEN
-- Older than 10 minutes. Delete cache.
g_last_use := SYSDATE;
clear_cache;
END IF;
BEGIN
l_value := g_tab(p_id);
EXCEPTION
WHEN NO_DATA_FOUND THEN
-- Call function and cache data.
l_value := slow_function(p_id);
g_tab(p_id) := l_value;
END;
RETURN l_value;
END get_cached_value;
-- -----------------------------------------------------------------
-- -----------------------------------------------------------------
PROCEDURE clear_cache AS
BEGIN
g_tab.delete;
END;
-- -----------------------------------------------------------------
END cached_lookup_api;
/
I want to pass two parameters "pi_value1" and "pi_value2" both of varchar2 to the function slow_function instead of "p_in". Is is possible to cache the results with two in parameters in oracle 10g .
the above code works fine with 1 parameter.
Please any one explain?

Answer 1

You'd need to create a two-dimensional array type to cache the values. Something along the lines of this (omitting the cache expiration code since that isn't changing)
CREATE OR REPLACE PACKAGE BODY cached_lookup_api
AS
TYPE t_pi_value2_tbl IS TABLE OF NUMBER
INDEX BY VARCHAR2(100);
TYPE t_cache IS TABLE OF t_pi_value2_tbl
INDEX BY VARCHAR2(100);
g_cache t_cache;
FUNCTION get_cached_value( p_pi_value1 IN VARCHAR2,
p_pi_value2 IN VARCHAR2 )
IS
BEGIN
RETURN g_cache(p_pi_value1)(p_pi_value2);
EXCEPTION
WHEN no_data_found
THEN
g_cache(p_pi_value1)(p_pi_value2) := slow_function( p_pi_value1, p_pi_value2 );
RETURN g_cache(p_pi_value1)(p_pi_value2);
END;
END;