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From Tim.Ham...@mcnichols.com
Subject Re: Problem with several one to many relationships in breadth
Date Tue, 20 Feb 2007 17:40:36 GMT
Hi Jeff,
Claudio and I are able to use 2.1.7 successfully - it stopped working in 
2.2 versions.  Bummer about there maybe not being a fix going forward - 
I've got a ton of queries that use this feature and of course I don't want 
to change any long-time stable code which I'd have to do to use a 
RowHandler.  Pending a fix, I guess we'll have to go back to using nested 
selects.

Regards,
Tim




"Jeff Butler" <jeffgbutler@gmail.com> 
02/20/2007 12:11 PM
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Re: Problem with several one to many relationships in breadth






Interesting....
 
In my tests, it fails in BOTH versions (2.1.7 and 2.3.0), but in different 
ways.  So something definitely changed.  In my test, 2.3.0 is closer to 
correct than 2.1.7 is.
 
But the important truth is that it does fail in both versions.
 
For now, I think a row handler is the best way to go forward with this.
 
I'll open a JIRA ticket with my test case, so everyone can see it.  No 
guarantees about a fix, but at least it will be logged.
 
Jeff Butler
 

 
On 2/20/07, Jeff Butler <jeffgbutler@gmail.com> wrote: 
I''m surprised by this (obviously).  I'll take a look.  It probably has to 
do with the new support for multiple result sets.
 
Jeff Butler


 
On 2/20/07, Claudio Iacovozzi <claudio.iacovozzi@googlemail.com > wrote: 
I tested my given example with iBatis 2.1.7.597 and it works! Ibatis 
creates the expected bean:
Agent1  --> List<Customer> {1:Customer1, 3:Customer2}
        --> List<Event> {1:housebreaking, 2:damage, 4:theft} 
 
Further tests with more depth (e.g. Custommer containing adresses) or 
breadth (Agent containing additional List of addresses) were also 
successful.
 
So Tim ist right and something in iBatis must have been changed. We 
currently use version 2.2.0.638 / 2.3.0.677.
 
=> so what's the best solution if we still want to use the newest version? 
Should we implement our own row handler and how can that be done? 
Or is it possible that the behaviour of 2.1.7.597 will be restored?
 
 
 


 
2007/2/19, Jeff Butler <jeffgbutler@gmail.com>: 
That's a good solution - then you could deal with object identity 
yourself.
 
Jeff Butler

 
On 2/19/07, Larry Meadors <lmeadors@apache.org > wrote: 
..or you could use a rowhandler.

Larry 



On 2/19/07, Jeff Butler <jeffgbutler@gmail.com > wrote: 
iBATIS groupBy support does not support two independant lists.  This would 
be a very difficult problem to solve and would require us to deal with 
object identity - which we don't deal with now. 
 
So with groupBy, you can have one and only one list that is automatically 
populated.  Other lists will need to be populated with a nested select.
 
Jeff Butler


 
On 2/19/07, Tim.Hammar@mcnichols.com < Tim.Hammar@mcnichols.com > wrote: 

Greetings Claudio, 

We too have this problem with the latest two releases.  If you use version 
2.1.7.597 you should have no problems - hopefully you have not implemented 
any new features like we had (and had to scramble to undo).  Versions 2.2 
and 2.3 will not handle what you are trying to do.  I have been so swamped 
that I have been unable to generate a test case and submit a bug report. 
Maybe your example will suffice. 

Regards, 
Tim Hammar 




"Claudio Iacovozzi" <claudio.iacovozzi@googlemail.com > 
02/19/2007 06:51 AM 

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Problem with several one to many relationships in breadth









We have a problem filling objects with several '1 to many
relationships' in breadth from one single SQL statement.

On page 40 of the iBatis Data Mapper Developer Guide the 'groupBy' 
construct is described as follows:
"Using this approach, you can solve any N+1 problem of any depth or 
breadth."

This just seems to work for any depth but NOT for any *breadth*.

Example:

An insurance agent contains a list of customers as well as a list of
insured events.

<resultMap class="agent" id="agent" groupBy="id" >
<result property="id" column="agentId" /> 
 <result property="firstName" column="agent_firstname" />
 <result property="lastName" column="agent_lastname" />
 <result property="events" resultMap="event" /> 
 <result property="customers" resultMap="customer" />
</resultMap>

<resultMap class="event" id="event" groupBy="id" >
 <result property="id" column="eventId" /> 
 <result property="title" column="title" />
</resultMap>

<resultMap class="customer" id="customer" groupBy="id" >
<result property="id" column="customerId" /> 
 <result property="firstName" column="customer_firstname" />
 <result property="lastName" column="customer_lastname" />
 <result property="street" column="street" /> 
 <result property="city" column="city" />
</resultMap>

- The used SQL statement:

<select id="getAgent" resultMap="agent" parameterClass="int"> 
SELECT a.agentId, a.FirstName as agent_firstname, a.LastName as
agent_lastname, b.eventId, b.title,
c.customerId, c.FirstName as customer_firstname, c.LastName as
customer_lastname, c.street, c.city

FROM insurance_agent a, agenteventlink ab, insured_event b, customer c 
WHERE a.agentId = ab.agentId
AND ab.eventId = b.eventId
AND b.customerId = c.customerId
AND a.agentId = #id#

ORDER BY a.agentId,  c.customerId
</select>

- The returned result set:
agentId,agent_firstname,agent_lastname,eventId,title,customerId,customer_firstname,customer_lastname



{1,Agent1,Smith,1,housebreaking,1,Customer1,Johnson}
{1,Agent1,Smith,4,theft,1,Customer1,Johnson}
{1,Agent1,Smith,2,damage,3,Customer2,Miller}


What we would like to achieve is getting a bean of type Agent, which 
contains two lists of all its customers and all its associated
insured events:

Agent1  --> List<Customer> {1:Customer1, 3:Customer2}
            --> List<Event> {1:housebreaking, 2:damage, 4:theft} 
 

But iBatis creates a bean like this:
Agent1  --> List<Customer> {1: Customer1, 1:Customer1, 3: Customer2}
           --> List<Event> {1:housebreaking, 2:damage, 4:theft} 


We want to avoid several SQL statements to get the necessary data (one
to get all events, and one to get all customers).

Any solution ?








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