Hi,The server parses the function into a form of bytecode which is then cached until the routine changes. In the past any routine change would invalidate cache for all routines and that sometimes can still happen but it is rare. The server then interprets the bytecode for every call to the function and yes, the function is executed every time unless you memoize the function ( if(function_input != @last_input) then @last_input = function_input; return @last_result := function(function_input); else return @last_result;On Tue, Mar 3, 2015 at 6:59 AM, Peter Laursen <peter_laursen@webyog.com> wrote:I really don't know if it should take 2, 5 or 60 seconds. The numbers surprise me (in the bad maner). There is an incredible overhead when wrapping this query in a function. I wonder if there is an invocation of the function for every iteration.-- PeterOn Tue, Mar 3, 2015 at 2:51 PM, Federico Razzoli <federico_raz@yahoo.it> wrote:SELECT 1 was .42. What I find amazing is not the absolute numbers (it's an old computer with desktop installed, etc) but the difference between the tests. If SELECT 1 takes .42, test 2 shouldn't take more than 1 min... do you agree?
Federico
--------------------------------------------
Mar 3/3/15, Justin Swanhart <greenlion@gmail.com> ha scritto:
Oggetto: Re: [Maria-discuss] stored programs
A: "Peter Laursen" <peter_laursen@webyog.com>
Cc: "Federico Razzoli" <federico_raz@yahoo.it>, "Maria Discuss" <maria-discuss@lists.launchpad.net>
Data: Martedì 3 marzo 2015, 14:28
You
probably have either a faster CPU or bigger cache on your
cpu. How long does benchmark select 1 take? You should
find it is faster on your system too, right?
--Justin
Sent from my iPhone
On Mar 3,
2015, at 6:18 AM, Peter Laursen <peter_laursen@webyog.com>
wrote:
Your 3rd test case takes
2:02 in MariaDB 10.1 and 2:13 in MySQL 5.6 on my system
(when otherwise idle) .
--
Peter
On Tue,
Mar 3, 2015 at 1:58 PM, Federico Razzoli <federico_raz@yahoo.it>
wrote:
I made
some quick test to show what I mean by "performance
problem". Note that I'm not saying the the first
and the second test cases should perform equally. But there
is too much difference - see the conclusion.
1)
MariaDB [test]> SELECT BENCHMARK(50000000, (SELECT
1));
+---------------------------------+
| BENCHMARK(50000000, (SELECT 1)) |
+---------------------------------+
| 0 |
+---------------------------------+
1 row in set (0.42 sec)
2)
DELIMITER ||
CREATE FUNCTION f()
RETURNS TINYINT
BEGIN
RETURN 1;
END ||
DELIMITER ;
MariaDB [test]> SELECT BENCHMARK(50000000, (SELECT
f()));
+-----------------------------------+
| BENCHMARK(50000000, (SELECT f())) |
+-----------------------------------+
| 0 |
+-----------------------------------+
1 row in set (2 min 5.70 sec)
3)
DELIMITER ||
CREATE FUNCTION f(x TINYINT)
RETURNS TINYINT
BEGIN
RETURN x;
END ||
DELIMITER ;
MariaDB [test]> SELECT BENCHMARK(50000000, (SELECT
f(1)));
+------------------------------------+
| BENCHMARK(50000000, (SELECT f(1))) |
+------------------------------------+
| 0 |
+------------------------------------+
1 row in set (3 min 35.20 sec)
-- Conclusions:
Times in seconds:
0.42
125.70
215.20
I don't know which ratio would be acceptable, but the
difference betweem a trivial query and a trivial function is
too high.
Also, the difference between 2) and 3) is that the function
in 3) accepts and returns a parameter. Again, the
performance difference seems to me too high.
Regards
Federico
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