Unexpected memory usage for repeated inserts within plpgsql function

Hi Hackers,

I have been seeing memory usage increasing for a simple plpgsql function. Could you please take a look and check is it a bug?

The function definition is:

create function f() returns int as
$$DECLARE count int;
BEGIN
count := 1;
LOOP
count := count + 1;

begin

EXECUTE 'insert into test values(10)';

IF count > 1000000 THEN
EXIT;
END IF;
exception when others then

end;
END LOOP;

END$$
LANGUAGE plpgsql;

When I ran this function by "select f()", from top command, I could see memory usage (Resident memory) kept on increasing:

Then I used gdb to suspend the process each time insert was actually executed, and issued " (gdb) p MemoryContextStats(TopMemoryContext) ". From the server log, I saw only "SPI Proc" part of all the memory contexts was increasing:

My question: Is this problem as-designed?

Thank you for your time!!
Guangzhou