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From Kris Rasmussen <kristapes...@yahoo.com>
Subject Re: n+1 is triggering multiple queries, 3?
Date Thu, 14 Jul 2005 06:15:10 GMT
Thanks Clinton,
 
I will look into this myself when I have more time. I wish there were a MySql Profiler or
something so that I could see what queries are actually being executed. Maybe I will step
into your code if I get a chance.
 
Kris

Clinton Begin <clinton.begin@gmail.com> wrote:
Kris,

This is the right list (user-java@ibatis.com).

Sorry nobody responded.  I had a quick look when you originally sent it, and I couldn't see
how it was possible that the groupBy or a nested resultMap could cause additional queries...

Perhaps someone else has thoughts?  If not, you might have to write an isolated unit test
and submit it through JIRA.

Cheers,
Clinton


On 7/9/05, Kris Rasmussen <kristapestry@yahoo.com> wrote:I have an n+1 mapping. When
I look at mysql health in the administrator it apears that 3 queries are being executed instead
of one. The first query gets executed when I retrieve the intial object via queryForObject.
The next two queries are being executed when I attempt to access the List which stores the
related objects from the main object. I am very curious what is going on since I don't know
how Ibatis could even know what query to execute to get the items later?
 
The following maps are used to retrive a single instance of classB with all of its classA
children stored in one of its properties which is of course a list.
 

<resultMap id="getClassAResult" class="classA">

... some basic properties

</resultMap>



<resultMap id="getClassBResult" class="classB">

<result property="primKey1" column="classB.primKey1"/>

<result property="primKey2" column="classB.primKey2"/>

... some more properties

</resultMap>



<resultMap id="getClassBWithClassAsResult" class="classB" extends="getClassBResult" groupBy="primKey1,primKey2">

<result property="classAs" resultMap="namespace.getClassAResult"/>

</resultMap>

 

and my select statement...

<select id="getClassBWithClassAs" parameterClass="keyClass" resultMap="getClassBWithClassAsResult">

SELECT classB.*,classA.* FROM classB ,classA

WHERE classB.primKey1=#primKey1# AND classB.primKey2=#primKey2# AND gallery_image.SiteId=#siteId#
AND gallery_image.BlockId=#blockId#

GROUP BY classB.primKey1,classB.primKey2,classA.primKey3

</select>



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