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From:Øystein Grøvlen Date:June 16 2011 2:32pm
Subject:Re: Regression test returning different result each time it's run
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On 16/06/2011 16:10, Hiromichi Watari wrote:
> Hi Øystein,
> Thank you for your reply.
>
> I am using the same storage engine (Innob I believe) and repeating the test results
> in different output each time.

Hi,

By default, InnoDB statistics will vary slightly each time you start the 
server.  Hence, you will get different output. (See my blog 
http://oysteing.blogspot.com/2011/04/more-stable-query-execution-time-by.html 
for a discussion about this.)

By default, the select test uses the MyISAM storage engine which 
provides exact statistics.

In order to mask such row count differences, a test can use the 
replace_column command:

--replace_column 9 x
explain select ...


Hope this helps,

--
Øystein

>
> Hiromichi
>
>
> --- On Thu, 6/16/11, Øystein Grøvlen<oystein.grovlen@stripped> 
> wrote:
>
>> From: Øystein Grøvlen<oystein.grovlen@stripped>
>> Subject: Re: Regression test returning different result each time it's run
>> To: "Hiromichi Watari"<hiromichiwatari@stripped>
>> Cc: internals@stripped
>> Date: Thursday, June 16, 2011, 3:22 AM
>> On 15/06/2011 17:08, Hiromichi Watari
>> wrote:
>>> Hi,
>>>
>>> I'm running a regression test
>> (/mysql-test/t/select.test) on 5.5 server (LaunchPad rev
>> 3487) but each time I run the test I get different number of
>> rows in explain select statements.
>>> Is this normal behavior ?  Or am I missing
>> something ?
>>
>> The difference is in the estimated number of rows in table
>> t2.  This
>> number is provided by the storage engine.  Maybe you
>> are using a
>> different storage engine?
>>
>> Hope this helps,
>>
>> --
>> Øystein Grøvlen, Principal Software Engineer
>> MySQL Group, Oracle
>> Trondheim, Norway
>>
>>>
>>> Thanks,
>>> Hiromichi
>>>
>>> p.s. I start up the server first then issue the
>> following command,
>>>
>>> [hwatari@desktop-intel mysql-test]$ sudo
>> ./mysql-test-run.pl --extern socket=/tmp/mysql.sock
>> t/select.test
>>>
>>>
>>>
>> -------------------------------------------------------------------------
>>>
>>>
>>> ---
>> /usr/local/mysql-5.5-3487/mysql-test/r/select.result
>> 2011-05-03 15:00:59.000000000 +0300
>>> +++
>> /usr/local/mysql-5.5-3487/mysql-test/r/select.reject
>> 2011-06-15 17:09:43.126761202 +0300
>>> @@ -133,10 +133,10 @@
>>>     1
>> SIMPLE    t2
>> ref    fld3
>> fld3    30
>> const    1    Using where;
>> Using index
>>>     explain select fld3 from t2 ignore
>> index (fld3) where fld3 = 'honeysuckle';
>>>     id
>> select_type    table
>> type    possible_keys
>> key    key_len
>> ref    rows    Extra
>>> -1    SIMPLE
>> t2    ALL
>> NULL    NULL
>> NULL    NULL
>> 1199    Using where
>>> +1    SIMPLE
>> t2    ALL
>> NULL    NULL
>> NULL    NULL
>> 1209    Using where
>>>
>>>
>>
>>
>> --
>> MySQL Internals Mailing List
>> For list archives: http://lists.mysql.com/internals
>> To unsubscribe:    http://lists.mysql.com/internals?unsub=1
>>
>>


-- 
Øystein Grøvlen, Principal Software Engineer
MySQL Group, Oracle
Trondheim, Norway
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              • Regression test returning different result each time it's runHiromichi Watari15 Jun
                • Re: Regression test returning different result each time it's runØystein Grøvlen16 Jun
                  • Re: Regression test returning different result each time it's runHiromichi Watari16 Jun
                    • Re: Regression test returning different result each time it's runØystein Grøvlen16 Jun
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