Niels Nes wrote:
> On Tue, Apr 07, 2009 at 02:00:36PM -0700, Yue Sheng wrote:
>>    Hi, we installed MonetDB on a Linux box, and did some
>>    comparison between MySQL and MonetDB. The result seems off by a
>>    large magnitude. Has anyone encountered similar problem please?
>>    Thanks.
>>
>>    For MonetDB:
>>
>>
>>    ql>select count(ins_key) from bigtable where ins_key = 15012;
>>    +---------+
>>    | L1 |
>>    +=========+
>>    | 1931541 |
>>    +---------+
>>    1 tuple
>>    Timer 260771.478 msec 1 rows
>>
>>    For MySQL:
>>
>>    select count(ins_key) from
>>    bigtable where ins_key=15012;
>>    +----------------+
>>    | count(ins_key) |
>>    +----------------+
>>    | 1931548 |
>>    +----------------+
>
> I see 2 problems one the performance diff, but the second (more
> important) is the difference in result.

I agree

>
> Could you send the schema and size of the table?

The performance difference is easily explained if you look
at the size of the underlying base table, if it is a cold
or hot run, non-indexed, etc.. Even assuming the table was
already memory resident, then automatic construction of
a (hash-) index to support this query will become visible.
All techniques a DBA and database application builder should
be familiar with when he embarks upon building his first
sizeable database and selects the engine geared best
towards his task.

In case a phenonemon is repetative in a lab-setting and can
not be explained using the schema, database properties, and the
query trace then it is worth investigating.
Comparison of systems or even understanding
the performance of an application on a single system can not
be replaced by a simple call like this to the community.

For those interested in performance evaluation and
comparison of systems my find the following tutorial
on this challenging task helpful
http://old-www.cwi.nl/htbin/ins1/publications?request=abstract&key=MaMa:EDBT:09

Martin Kersten

>
> Niels
>>    real 0m0.989s
>>    user 0m0.002s
>>    sys 0m0.003s
>>
>>
>>    Indices:
>>    MonetDB: None
>>    MySQL: index on ins_key
>>
>>    Thanks.
>
>> ------------------------------------------------------------------------------
>> This SF.net email is sponsored by:
>> High Quality Requirements in a Collaborative Environment.
>> Download a free trial of Rational Requirements Composer Now!
>> http://p.sf.net/sfu/www-ibm-com
>> _______________________________________________
>> MonetDB-users mailing list
>> MonetDB-users@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/monetdb-users
>
>


------------------------------------------------------------------------------
This SF.net email is sponsored by:
High Quality Requirements in a Collaborative Environment.
Download a free trial of Rational Requirements Composer Now!
http://p.sf.net/sfu/www-ibm-com
_______________________________________________
MonetDB-users mailing list
MonetDB-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/monetdb-users