Hi, Just to avoid ambiguity: the stored function is executed as byte code in each call, and the native function is called by the byte code for each call. --Justin On Tue, Mar 3, 2015 at 7:04 AM, Justin Swanhart <greenlion@gmail.com> wrote:
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.
-- Peter
On 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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