sepgsql: Enforce db_procedure:{execute} permission.

To do this, we add an additional object access hook type,
OAT_FUNCTION_EXECUTE.

KaiGai Kohei

contrib/sepgsql/sql/misc.sql

@@ -3,3 +3,28 @@
 --
 
 LOAD '$libdir/sepgsql';		-- failed
+
+--
+-- Permissions to execute functions
+--
+CREATE TABLE t1 (x int, y text);
+INSERT INTO t1 (SELECT x, md5(x::text) FROM generate_series(1,100) x);
+
+SET sepgsql.debug_audit = on;
+SET client_min_messages = log;
+
+-- regular function and operators
+SELECT * FROM t1 WHERE x > 50 AND y like '%64%';
+
+-- aggregate function
+SELECT MIN(x), AVG(x) FROM t1;
+
+-- window function
+SELECT row_number() OVER (order by x), * FROM t1 WHERE y like '%86%';
+
+RESET sepgsql.debug_audit;
+RESET client_min_messages;
+--
+-- Cleanup
+--
+DROP TABLE IF EXISTS t1 CASCADE;